NZ793595A - Systems and methods for improved sustainment of a high performance frc with multi-scaled capture type vacuum pumping - Google Patents
Systems and methods for improved sustainment of a high performance frc with multi-scaled capture type vacuum pumpingInfo
- Publication number
- NZ793595A NZ793595A NZ793595A NZ79359517A NZ793595A NZ 793595 A NZ793595 A NZ 793595A NZ 793595 A NZ793595 A NZ 793595A NZ 79359517 A NZ79359517 A NZ 79359517A NZ 793595 A NZ793595 A NZ 793595A
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- NZ
- New Zealand
- Prior art keywords
- frc
- formation
- plasma
- confinement
- divertors
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Links
- 238000005086 pumping Methods 0.000 title claims abstract 4
- 230000004907 flux Effects 0.000 claims abstract 3
- 230000015572 biosynthetic process Effects 0.000 claims 25
- 238000005755 formation reaction Methods 0.000 claims 25
- 230000001264 neutralization Effects 0.000 claims 6
- 210000002381 Plasma Anatomy 0.000 claims 5
- 125000004429 atoms Chemical group 0.000 claims 3
- 150000002500 ions Chemical class 0.000 claims 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims 2
- 229910052719 titanium Inorganic materials 0.000 claims 2
- 239000010936 titanium Substances 0.000 claims 2
- 240000004841 Meum athamanticum Species 0.000 claims 1
- 229940035295 Ting Drugs 0.000 claims 1
- 239000002245 particle Substances 0.000 abstract 1
Abstract
Systems and methods that facilitate forming and maintaining FRCs with superior stability as well as particle, energy and flux confinement and, more particularly, systems and methods that facilitate forming and maintaining FRCs with elevated system energies and improved sustainment utilizing multi-scaled capture type vacuum pumping. aled capture type vacuum pumping.
Description
Systems and methods that facilitate forming and maintaining FRCs with superior stability as well as
particle, energy and flux confinement and, more particularly, s and methods that facilitate
g and maintaining FRCs with elevated system energies and improved sustainment utilizing
multi-scaled capture type vacuum pumping.
NZ 793595
SYSTEMS ANDMETHODS FOR ED SUSTAINMENTOFA HIGH PERFORMANCEFRC WITH
MULTI-SCALEDCAPTURETYPEVACUUM PUMPING
FIELD
The subject matter described herein s generally to magnetic plasma confinement
systems having a field reversed configuration (FRC) and, more particularly, more particularly, to
systems and methods that facilitate forming and maintaining FRCs with elevated system energies
and improved sustainment utilizing multi-scaled capture type vacuum g.
Aspects of the present invention are described herein and in New Zealand specification
753042, from which the present specification is divided. Reference may be made in the description
to t matter which is not in the scope of the appended claims but relates to subject matter
claimed in the parent specification. That subject matter should be readily identifiable by a person
skilled in the art and may assist putting into practice the invention as defined in the appended .
NZ 753042 is the national phase entry in New Zealand of PCT/ US2017/060255 shed
as WO2018/085798), the entire contents of which are incorporated by this reference as if fully set
forth herein in their ty.
BACKGROUND INFORMATION
The Field Reversed Configuration (FRC) belongs to the class of magnetic plasma
confinement topologies known as compact toroids (CT). It exhibits predominantly poloidal
magnetic fields and possesses zero or small self-generated toroidal fields (see M. Tuszewski, Nucl.
Fusion 28, 2033 (1988)). The attractions of such a configuration are its simple geometry for ease of
construction and maintenance, a natural unrestricted divertor for tating energy extraction and
ash removal, and very high β (β is the ratio of the average plasma pressure to the e magnetic
field pressure inside the FRC), i.e., high power density. The high β nature is advantageous for
economic operation and for the use of ed, aneutronic fuels such as D-He3 and p-B11.
The traditional method of forming an FRC uses the field-reversed θ-pinch technology,
producing hot, high-density plasmas (see A. L. Hoffman and J. T. Slough, Nucl. Fusion 33, 27
(1993)). A variation on this is the translation-trapping method in which the plasma created in a
theta-pinch “source” is more-or-less immediately ejected out one end into a confinement chamber.
The ating plasmoid is then d between two strong mirrors at the ends of the chamber (see,
for instance, H. , S. Okada, S. Sugimoto, and S. Goto, Phys. Plasmas 2, 191 (1995)). Once in
the confinement chamber, various heating and current drive methods may be applied such as beam
ion al or neutralized), rotating magnetic fields, RF or ohmic heating, etc. This separation
of source and confinement functions offers key engineering advantages for potential future fusion
reactors. FRCs have proved to be extremely robust, resilient to dynamic formation, translation, and
violent capture events. Moreover, they show a tendency to assume a preferred plasma state (see e.g.
H. Y. Guo, A. L. Hoffman, K. E. Miller, and L. C. Steinhauer, Phys. Rev. Lett. 92, 245001 (2004)).
Significant progress has been made in the last decade developing other FRC ion methods:
merging spheromaks with oppositely-directed helicities (see e.g. Y. Ono, M. Inomoto, Y. Ueda, T.
Matsuyama, and T. Okazaki, Nucl. Fusion 39, 2001 (1999)) and by driving current with rotating
magnetic fields (RMF) (see e.g. I. R. Jones, Phys. Plasmas 6, 1950 (1999)) which also provides
additional stability.
Recently, the collision-merging technique, proposed long ago (see e.g. D. R. Wells, Phys.
Fluids 9, 1010 (1966)) has been significantly developed further: two te theta-pinches at
opposite ends of a confinement chamber aneously generate two plasmoids and accelerate the
ids toward each other at high speed; they then collide at the center of the confinement
chamber and merge to form a compound FRC. In the construction and successful operation of one of
the largest FRC experiments to date, the conventional collision-merging method was shown to
produce stable, ived, high-flux, high temperature FRCs (see e.g. M. Binderbauer, H.Y. Guo,
M. Tuszewski et al., Phys. Rev. Lett. 105, 045003 (2010)).
FRCs consist of a torus of closed field lines inside a separatrix, and of an annular edge layer
on the open field lines just outside the separatrix. The edge layer coalesces into jets beyond the FRC
length, providing a natural divertor. The FRC gy coincides with that of a Field-Reversed-
Mirror plasma. However, a icant difference is that the FRC plasma has a β of about 10. The
inherent low internal ic field provides for a certain indigenous kinetic particle population, i.e.
particles with large larmor radii, comparable to the FRC minor radius. It is these strong c
effects that appear to at least partially contribute to the gross stability of past and present FRCs, such
as those produced in the collision-merging experiment.
Typical past FRC ments have been dominated by convective losses with energy
confinement y determined by particle transport. les diffuse primarily radially out of the
separatrix volume, and are then lost axially in the edge layer. Accordingly, FRC confinement
s on the properties of both closed and open field line regions. The particle diffusion time out
of the separatrix scales as τ⊥ ~ a2/D⊥ (a ~ rs/4, where rs is the central separatrix radius), and D⊥ is a
characteristic FRC diffusivity, such as D⊥ ~ 12.5 ρie, with ρie enting the ion gyroradius,
evaluated at an externally applied magnetic field. The edge layer particle confinement time τ∥ is
essentially an axial transit time in past FRC experiments. In steady-state, the balance n radial
and axial particle losses yields a separatrix density gradient length δ ~ (D⊥τ∥)1/2. The FRC particle
confinement time scales as (τ⊥τ∥)1/2 for past FRCs that have substantial density at the separatrix (see
e.g. M. TUSZEWSKI, “Field Reversed Configurations,” Nucl. Fusion 28, 2033 (1988)).
In light of the foregoing, it is, therefore, desirable to improve the sustainment of FRCs in
order to use steady state FRCs with elevated energy systems as a pathway to a reactor core for fusion
of light nuclei for the future generation of energy.
SUMMARY
The present embodiments provided herein are directed to systems and methods that facilitate
forming and maintaining FRCs with elevated system energies and improved sustainment utilizing
multi-scaled capture type vacuum pumping. According to an embodiment of the present disclosure, a
method for generating and maintaining a magnetic field with a field reversed configuration (FRC)
comprising forming an FRC about a plasma in a confinement chamber, injecting a ity of
neutral beams into the FRC plasma at an angle toward the mid-plane of the confinement chamber,
pumping neutralized gas molecules accumulating in first and second diametrically opposed divertors
coupled to the confinement chamber with first and second capture vacuum pumps positioned in the
first and second ors and comprising two or more sides with surfaces having a view of each
other and an open side, wherein the first and second capture vacuum pumps having a ng factor
more than four (4) times greater than a sticking factor of a flat plate defining an area equivalent to
the open side of the first and second capture pumps.
According to a further embodiment of the present disclosure, at least one of the two or more
sides of the first and second capture vacuum pumps comprising an array of individual capture
vacuum pumps.
According to a r embodiment of the present disclosure, each of the individual capture
vacuum pumps comprising two or more sides with surfaces having a view of each other and an open
side, wherein each of the individual capture vacuum pumps having a sticking factor greater than a
sticking factor of a flat plate defining an area lent to the open side of each of the individual
capture vacuum pumps.
According to a further ment of the present disclosure, the first and second capture
vacuum pumps having a sticking factor that is N times greater than a ng factor of a flat plate
ng an area equivalent to the open side of the first and second capture pumps, n N is
4<N<16.
According to a further embodiment of the present disclosure, the es of the flat plate and
the first and second vacuum pumps includes a film of titanium ted thereon.
ing to a further embodiment of the present disclosure, the method further sing
injecting compact toroid (CT) plasmas from first and second CT injectors into the FRC plasma at an
angle towards the mid-plane of the confinement chamber, wherein the first and second CT injectors
are diametrically opposed on opposing sides of the mid-plane of the confinement chamber.
According to a further ment of the present disclosure, a capture vacuum pump
comprises two or more sides with surfaces having a view of each other and an open side, wherein
capture vacuum pump having a sticking factor more than four (4) times greater than a sticking factor
of a flat plate defining an area equivalent to the open side of the capture pump.
According to a further embodiment of the present disclosure, at least one of the two or more
sides of the first and second capture vacuum pumps comprising an array of individual capture
vacuum pumps.
According to a further embodiment of the present disclosure, each of the individual capture
vacuum pumps comprising two or more sides with surfaces having a view of each other and an open
side, wherein each of the dual capture vacuum pumps having a sticking factor greater than a
sticking factor of a flat plate ng an area equivalent to the open side of each of the individual
capture vacuum pumps.
According to a r embodiment of the present sure, the first and second capture
vacuum pumps having a sticking factor that is N times greater than a sticking factor of a flat plate
defining an area lent to the open side of the first and second capture pumps, wherein N is
4<N<16.
According to a further embodiment of the present disclosure, the surfaces of the flat plate and
the first and second vacuum pumps includes a film of titanium deposited thereon.
According to a further embodiment of the present disclosure, a system for generating and
maintaining a magnetic field with a field reversed configuration (FRC) comprising a confinement
r, first and second diametrically opposed FRC formation sections coupled to the confinement
chamber and ing first and second capture vacuum pumps positioned within the first and second
divertors and comprising two or more sides with es having a view of each other and an open
side, wherein the first and second capture vacuum pumps having a sticking factor more than four (4)
times greater than a ng factor of a flat plate defining an area equivalent to the open side of the
first and second capture pumps, one or more of a plurality of plasma guns, one or more biasing
electrodes and first and second mirror plugs, n the plurality of plasma guns includes first and
second axial plasma guns operably coupled to the first and second ors, the first and second
formation sections and the confinement chamber, wherein the one or more biasing electrodes being
positioned within one or more of the confinement chamber, the first and second formation sections,
and the first and second outer ors, and wherein the first and second mirror plugs being position
between the first and second formation sections and the first and second divertors, a gettering system
coupled to the confinement chamber and the first and second divertors, a plurality of neutral atom
beam injectors d to the confinement chamber and angled toward a mid-plane of the
confinement chamber.
According to a further embodiment of the present disclosure, the system further comprising
first and second compact toroid (CT) injectors coupled to the confinement chamber at an angle
towards the mid-plane of the confinement chamber, n the first and second CT injectors are
diametrically opposed on opposing sides of the mid-plane of the confinement chamber.
The systems, methods, features and advantages of the example embodiments will be or will
become nt to one with skill in the art upon examination of the following figures and detailed
description. It is ed that all such additional methods, features and advantages be included
within this description, and be protected by the accompanying claims. It is also intended that the
claims are not limited to e the details of the example embodiments.
BRIEF DESCRIPTION OF THE FIGURES
The accompanying drawings, which are included as part of the present specification, illustrate
the presently e embodiments and, together with the general description given above and the
detailed description of the example embodiments given below, serve to explain and teach the
principles of the present invention.
Figure 1 illustrates particle confinement in the present FRC system under a high performance
FRC regime (HPF) versus under a conventional FRC regime (CR), and versus other conventional
FRC experiments.
Figure 2 illustrates the components of the present FRC system and the magnetic topology of
an FRC producible in the t FRC system.
Figure 3A illustrates the basic layout of the present FRC system as viewed from the top,
including the preferred arrangement of the l confinement vessel, formation section, divertors,
l beams, electrodes, plasma guns, mirror plugs and pellet injector.
Figure 3B illustrates the central confinement vessel as viewed from the top and showing the
neutral beams arranged at an angle normal to the major axis of symmetry in the central confinement
Figure 3C illustrates the central confinement vessel as viewed from the top and showing the
neutral beams arranged at an angle less than normal to the major axis of symmetry in the central
confinement vessel and directed to inject les toward the mid-plane of the central confinement
vessel.
Figures 3D and 3E illustrate top and perspective views, tively, of the basic layout of an
alternative embodiment of the present FRC system, including the preferred arrangement of the central
confinement , formation section, inner and outer divertors, neutral beams arranged at an angle
less than normal to the major axis of symmetry in the central confinement vessel, electrodes, plasma
guns and mirror plugs.
Figure 4 rates a schematic of the components of a pulsed power system for the
formation sections.
Figure 5 illustrates an isometric view of an individual pulsed power formation skid.
Figure 6 illustrates an isometric view of a formation tube ly.
Figure 7 illustrates a partial sectional ric view of neutral beam system and key
components.
Figure 8 illustrates an isometric view of the neutral beam arrangement on confinement
chamber.
Figure 9 illustrates a partial sectional isometric view of a preferred arrangement of the Ti and
Li gettering systems.
Figure 10 illustrates a partial sectional isometric view of a plasma gun installed in the
or chamber. Also shown are the associated magnetic mirror plug and a or electrode
assembly.
Figure 11 illustrates a preferred layout of an annular bias electrode at the axial end of the
confinement chamber.
Figure 12 illustrates the evolution of the excluded flux radius in the FRC system obtained
from a series of external diamagnetic loops at the two field reversed theta pinch formation sections
and magnetic probes embedded inside the l metal confinement chamber. Time is measured
from the instant of synchronized field reversal in the formation sources, and distance z is given
relative to the axial midplane of the machine.
Figures 13A, 13B, 13C and 13D illustrate data from a representative non-HPF, tained
discharge on the present FRC system. Shown as functions of time are (Figure 13A) excluded flux
radius at the midplane, (Figure 13B) 6 chords of ntegrated density from the ne CO2
interferometer, (Figure 13C) Abel-inverted density radial profiles from the CO2 interferometer data,
and (Figure 13D) total plasma temperature from pressure balance.
Figure 14 illustrates the excluded flux axial profiles at selected times for the same discharge
of the present FRC system shown in Figure 13A, 13B, 13C and 13D.
Figure 15 rates an isometric view of the saddle coils mounted outside of the
ement chamber.
Figures 16A, 16B, 16C and 16D illustrate the correlations of FRC lifetime and pulse length
of injected neutral beams. As shown, longer beam pulses produce longer lived FRCs.
Figures 17A, 17B, 17C and 17D illustrate the dual and combined effects of different
components of the FRC system on FRC performance and the attainment of the HPF regime.
Figures 18 A, 18B, 18C and 18D illustrate data from a representative HPF, tained
rge on the present FRC system. Shown as functions of time are (Figure 18A) excluded flux
radius at the midplane, (Figure 18B) 6 chords of line-integrated density from the midplane CO2
interferometer, (Figure 18C) Abel-inverted density radial profiles from the CO2 interferometer data,
and (Figure 18D) total plasma temperature from pressure balance.
Figure 19 illustrates flux confinement as a function of electron temperature (Te). It
represents a graphical representation of a newly established superior scaling regime for HPF
rges.
Figure 20 illustrates the FRC lifetime corresponding to the pulse length of non-angled and
angled injected neutral beams.
Figures 21A, 21B, 21C, 21D and 21E illustrate the pulse length of angled injected neutral
beams and the lifetime of FRC plasma parameters of plasma , plasma density, plasma
ature, and magnetic flux corresponding to the pulse length of angled ed neutral beams.
Figures 22A and 22B illustrate the basic layout of a compact toroid (CT) injector.
Figures 23A and 23B illustrate the central confinement vessel showing the CT injector
mounted thereto.
Figures 24A and 24B illustrate the basic layout of an alternative embodiment of the CT
injector having a drift tube coupled thereto.
Figure 25 illustrates an isometric view of the FRC plasma core and the confinement chamber
DC coils, and the path of charged particles flowing from the FRC plasma core.
Figure 26 illustrates an isometric view of a divertor.
Figure 27 is a graph illustrating the density of l gas accumulating in the inner and outer
divertors as a function of time during ion of the present FRC system.
Figure 28 illustrates an isometric view of an individual pump object in the form of an open
face cube and a flat plate lent in size to the open face of the cube.
Figure 29 is a graph illustrating the effective sticking factor of the square opening of a box
shaped pump object as a function of the depth/width ratio of the box for a given sticking factor for
flat surfaces that make up the box.
Figure 30 illustrates an isometric view of a self-similar surfaced capture pump sing an
open sided cube formed from sides comprising an array of individual pumps comprising an open
faced cube.
Figure 31 is a graph rating the increase in effective ng factor of a imilar
surfaced capture pump as a on of te scale levels of self-similarity.
Figure 32 illustrates isometric detail views showing the scale levels of self-similarity of a
self-similar surfaced capture pump.
It should be noted that the figures are not necessarily drawn to scale and that elements of
similar structures or functions are generally represented by like reference numerals for illustrative
purposes throughout the figures. It also should be noted that the figures are only intended to
tate the description of the various embodiments described herein. The s do not
necessarily describe every aspect of the teachings disclosed herein and do not limit the scope of the
claims.
DETAILEDDESCRIPTION
The present embodiments provided herein are directed to systems and methods that facilitate
forming and maintaining FRCs with superior stability as well as particle, energy and flux
confinement. Some of the present embodiments are directed to systems and methods that facilitate
forming and maintaining FRCs with improved nment utilizing multi-scaled capture type
vacuum pump.
Representative examples of the embodiments described herein, which examples utilize many
of these additional features and teachings both separately and in combination, will now be described
in further detail with reference to the attached drawings. This detailed description is merely intended
to teach a person of skill in the art further details for practicing preferred aspects of the present
teachings and is not intended to limit the scope of the invention. Therefore, combinations of es
and steps disclosed in the following detail description may not be ary to practice the invention
in the broadest sense, and are instead taught merely to particularly describe representative examples
of the present teachings.
Moreover, the various features of the representative examples and the dependent claims may
be combined in ways that are not specifically and itly enumerated in order to provide
additional useful embodiments of the present teachings. In addition, it is expressly noted that all
es disclosed in the description and/or the claims are intended to be disclosed separately and
independently from each other for the purpose of al disclosure, as well as for the purpose of
restricting the claimed subject matter ndent of the compositions of the features in the
embodiments and/or the claims. It is also expressly noted that all value ranges or tions of
groups of entities disclose every possible intermediate value or intermediate entity for the purpose of
original disclosure, as well as for the purpose of cting the d subject matter.
Before turning to the systems and methods that facilitate sustainment an FRC plasma
utilizing multi-scaled capture type vacuum pumping, a discussion of systems and methods for
forming and maintaining high performance FRCs with superior stability as well as superior particle,
energy and flux ement over conventional FRCs is provided. Such high mance FRCs
provide a pathway to a whole y of applications including compact neutron s (for medical
isotope production, nuclear waste remediation, materials research, neutron radiography and
tomography), compact photon sources (for chemical production and processing), mass separation
and enrichment systems, and reactor cores for fusion of light nuclei for the future generation of
energy.
Various ancillary systems and operating modes have been explored to assess whether there is
a superior confinement regime in FRCs. These efforts have led to breakthrough discoveries and the
pment of a High Performance FRC paradigm bed herein. In accordance with this new
paradigm, the present systems and s combine a host of novel ideas and means to dramatically
improve FRC confinement as illustrated in Figure 1 as well as provide stability control without
negative side-effects. As discussed in greater detail below, Figure 1 depicts particle confinement in
an FRC system 10 described below (see Figures 2 and 3), ing in accordance with a High
Performance FRC regime (HPF) for forming and maintaining an FRC versus operating in accordance
with a conventional regime CR for forming and maintaining an FRC, and versus particle
confinement in accordance with conventional s for forming and maintaining an FRC used in
other experiments. The present disclosure will outline and detail the innovative individual
components of the FRC system 10 and methods as well as their collective effects.
FRC System
Vacuum System
Figures 2 and 3 depict a schematic of the present FRC system 10. The FRC system 10
includes a l confinement vessel 100 surrounded by two diametrically opposed reversed-fieldtheta-pinch
formation sections 200 and, beyond the formation sections 200, two divertor chambers
300 to control neutral density and impurity contamination. The present FRC system 10 was built to
accommodate igh vacuum and operates at typical base pressures of 10-8 torr. Such vacuum
pressures require the use of double-pumped mating flanges between mating components, metal O-
rings, high purity interior walls, as well as l initial surface conditioning of all parts prior to
assembly, such as physical and chemical cleaning followed by a 24 hour 250 °C vacuum baking and
en glow discharge cleaning.
The reversed-field-theta-pinch formation sections 200 are standard field-reversed-thetapinches
(FRTPs), albeit with an advanced pulsed power formation system discussed in detail below
(see Figures 4 through 6). Each formation section 200 is made of standard opaque industrial grade
quartz tubes that feature a 2 millimeter inner lining of ultrapure quartz. The confinement chamber
100 is made of stainless steel to allow a multitude of radial and tangential ports; it also serves as a
flux conserver on the timescale of the experiments described below and limits fast magnetic
transients. Vacuums are created and maintained within the FRC system 10 with a set of dry scroll
roughing pumps, turbo molecular pumps and cryo pumps.
Magnetic System
The magnetic system 400 is illustrated in s 2 and 3. Figure 2, amongst other features,
illustrates an FRC magnetic flux and density contours (as functions of the radial and axial
nates) pertaining to an FRC 450 producible by the FRC system 10. These contours were
obtained by a 2-D resistive Hall-MHD numerical simulation using code developed to simulate
systems and methods corresponding to the FRC system 10, and agree well with measured
experimental data. As seen in Figure 2, the FRC 450 consists of a torus of closed field lines at the
interior 453 of the FRC 450 inside a separatrix 451, and of an annular edge layer 456 on the open
field lines 452 just outside the separatrix 451. The edge layer 456 coalesces into jets 454 beyond the
FRC , providing a natural divertor.
The main ic system 410 includes a series of quasi-dc coils 412, 414, and 416 that are
situated at particular axial positions along the components, i.e., along the confinement chamber 100,
the formation ns 200 and the divertors 300, of the FRC system 10. The dc coils 412, 414
and 416 are fed by quasi-dc switching power es and produce basic magnetic bias fields of
about 0.1 T in the confinement chamber 100, the formation sections 200 and the divertors 300. In
addition to the quasi-dc coils 412, 414 and 416, the main magnetic system 410 includes quasi-dc
mirror coils 420 (fed by switching supplies) between either end of the ement r 100 and
the adjacent formation sections 200. The quasi-dc mirror coils 420 provide magnetic mirror ratios of
up to 5 and can be ndently energized for equilibrium shaping l. In addition, mirror
plugs 440, are positioned between each of the formation sections 200 and divertors 300. The mirror
plugs 440 comprise compact quasi-dc mirror coils 430 and mirror plug coils 444. The quasi-dc
mirror coils 430 include three coils 432, 434 and 436 (fed by switching supplies) that produce
onal guide fields to focus the magnetic flux surfaces 455 towards the small diameter passage
442 passing through the mirror plug coils 444. The mirror plug coils 444, which wrap around the
small diameter passage 442 and are fed by LC pulsed power circuitry, produce strong magnetic
mirror fields of up to 4 T. The purpose of this entire coil arrangement is to tightly bundle and guide
the ic flux surfaces 455 and end-streaming plasma jets 454 into the remote chambers 310 of
the ors 300. Finally, a set of saddle-coil “antennas” 460 (see Figure 15) are located outside the
confinement chamber 100, two on each side of the mid-plane, and are fed by dc power supplies. The
saddle-coil antennas 460 can be configured to provide a quasi-static magnetic dipole or quadrupole
field of about 0.01 T for controlling rotational instabilities and/or electron current control. The
saddle-coil antennas 460 can flexibly provide magnetic fields that are either symmetric or
antisymmetric about the machine’s midplane, depending on the direction of the applied currents.
Pulsed power formation systems
The pulsed power ion systems 210 operate on a modified theta-pinch principle. There
are two systems that each power one of the formation sections 200. Figures 4 through 6 illustrate the
main building blocks and arrangement of the formation systems 210. The formation system 210 is
composed of a r pulsed power arrangement that consists of individual units (=skids) 220 that
each energize a sub-set of coils 232 of a strap assembly 230 (=straps) that wrap around the formation
quartz tubes 240. Each skid 220 is composed of capacitors 221, inductors 223, fast high current
switches 225 and associated r 222 and dump circuitry 224. In total, each formation system 210
stores between 350-400 kJ of capacitive energy, which provides up to 35 GW of power to form and
rate the FRCs. Coordinated ion of these components is achieved via a state-of-the-art
trigger and control system 222 and 224 that allows synchronized timing n the ion
systems 210 on each formation section 200 and minimizes ing jitter to tens of nanoseconds.
The advantage of this modular design is its flexible operation: FRCs can be formed in-situ and then
accelerated and injected (=static ion) or formed and accelerated at the same time (=dynamic
formation).
Neutral Beam Injectors
Neutral atom beams 600 are deployed on the FRC system 10 to e heating and current
drive as well as to develop fast particle pressure. As shown in Figures 3A, 3B and 8, the individual
beam lines comprising neutral atom beam injector systems 610 and 640 are located around the
central confinement chamber 100 and inject fast particles tangentially to the FRC plasma (and
perpendicular or at an angel normal to the major axis of symmetry in the central confinement vessel
100) with an impact parameter such that the target trapping zone lies well within the separatrix 451
(see Figure 2). Each injector system 610 and 640 is capable of injecting up to 1 MW of neutral beam
power into the FRC plasma with particle energies between 20 and 40 keV. The systems 610 and 640
are based on positive ion multi-aperture extraction sources and utilize geometric focusing, inertial
cooling of the ion extraction grids and differential pumping. Apart from using different plasma
sources, the systems 610 and 640 are primarily entiated by their physical design to meet their
respective mounting locations, yielding side and top ion capabilities. Typical components of
these l beam injectors are specifically illustrated in Figure 7 for the side injector s 610.
As shown in Figure 7, each individual neutral beam system 610 includes an RF plasma source 612 at
an input end (this is substituted with an arc source in systems 640) with a magnetic screen 614
ng the end. An ion optical source and acceleration grids 616 is d to the plasma source
612 and a gate valve 620 is positioned between the ion optical source and acceleration grids 616 and
a neutralizer 622. A deflection magnet 624 and an ion dump 628 are located between the neutralizer
622 and an aiming device 630 at the exit end. A cooling system comprises two cryo-refrigerators
634, two cryopanels 636 and a LN2 shroud 638. This flexible design allows for operation over a
broad range of FRC parameters.
An alternative configuration for the neutral atom beam injectors 600 is that of injecting the
fast particles tangentially to the FRC , but with an angle A less than 90° relative to the major
axis of symmetry in the central confinement vessel 100. These types of orientation of the beam
injectors 615 are shown in Figure 3C. In addition, the beam injectors 615 may be oriented such that
the beam injectors 615 on either side of the mid-plane of the l confinement vessel 100 inject
their particles towards the mid-plane. Finally, the axial position of these beam systems 600 may be
chosen closer to the mid-plane. These alternative injection embodiments facilitate a more central
fueling option, which provides for better coupling of the beams and higher trapping efficiency of the
injected fast particles. Furthermore, depending on the angle and axial position, this arrangement of
the beam injectors 615 allows more direct and ndent control of the axial elongation and other
characteristics of the FRC 450. For instance, injecting the beams at a shallow angle A relative to the
vessel’s major axis of symmetry will create an FRC plasma with longer axial extension and lower
temperature while picking a more perpendicular angle A will lead to an y shorter but hotter
plasma. In this fashion the injection angle A and location of the beam injectors 615 can be optimized
for different es. In addition, such angling and positioning of the beam injectors 615 can allow
beams of higher energy (which is generally more favorable for depositing more power with less
beam divergence) to be injected into lower magnetic fields than would otherwise be necessary to trap
such beams. This is due to the fact that it is the azimuthal component of the energy that determines
fast ion orbit scale (which becomes progressively r as the injection angle relative to the
’s major axis of symmetry is reduced at constant beam energy). Furthermore, angled injection
towards the mid-plane and with axial beam positions close to the ane improves beam-plasma
coupling, even as the FRC plasma shrinks or otherwise axially contracts during the injection period.
Turning to Figures 3D and 3E, another alternative configuration of the FRC system 10
includes inner divertors 302 in addition to the angled beam injectors 615. The inner divertors 302 are
oned between the formation sections 200 and the confinement chamber 100, and are configured
and operate ntially r to the outer divertors 300. The inner divertors 302, which e
fast switching magnetic coils n, are effectively inactive during the formation process to enable
the formation FRCs to pass through the inner divertors 302 as the formation FRCs translate toward
the mid-plane of the confinement chamber 100. Once the formation FRCs pass through the inner
ors 302 into the ement chamber 100, the inner divertors are activated to operate
substantially similar to the outer divertors and isolate the confinement chamber 100 from the
formation sections 200.
Pellet Injector
To provide a means to inject new particles and better control FRC le inventory, a 12-
barrel pellet injector 700 (see e.g. I. Vinyar et al., “Pellet Injectors Developed at PELIN for JET,
TAE, and HL-2A,” Proceedings of the 26th Fusion Science and Technology Symposium, 09/27 to
/01 (2010)) is utilized on FRC system 10. Figure 3 illustrates the layout of the pellet injector 700
on the FRC system 10. The cylindrical s (D ~ 1 mm, L ~ 1 – 2 mm) are injected into the FRC
with a velocity in the range of 150 – 250 km/s. Each individual pellet contains about 5×1019
hydrogen atoms, which is comparable to the FRC particle inventory.
ing Systems
It is well known that neutral halo gas is a serious problem in all confinement systems. The
charge exchange and recycling (release of cold impurity al from the wall) processes can have a
devastating effect on energy and particle confinement. In addition, any significant density of neutral
gas at or near the edge will lead to prompt losses of or at least severely curtail the lifetime of injected
large orbit (high ) particles (large orbit refers to particles having orbits on the scale of the FRC
topology or at least orbit radii much larger than the characteristic ic field gradient length
scale) – a fact that is detrimental to all energetic plasma applications, including fusion via auxiliary
beam heating.
Surface conditioning is a means by which the detrimental effects of neutral gas and impurities
can be controlled or reduced in a confinement system. To this end the FRC system 10 provided
herein employs um and Lithium deposition systems 810 and 820 that coat the plasma facing
surfaces of the confinement chamber (or vessel) 100 and divertors 300 and 302 with films (tens of
micrometers thick) of Ti and/or Li. The coatings are ed via vapor deposition ques.
Solid Li and/or Ti are ated and/or sublimated and sprayed onto nearby surfaces to form the
coatings. The sources are atomic ovens with guide nozzles (in case of Li) 822 or heated spheres of
solid with guide ing (in case of Ti) 812. Li evaporator systems typically e in a
continuous mode while Ti sublimators are mostly operated intermittently in between plasma
operation. Operating temperatures of these systems are above 600 °C to obtain fast tion rates.
To achieve good wall coverage, multiple strategically located evaporator/sublimator systems are
necessary. Figure 9 details a preferred arrangement of the gettering deposition systems 810 and 820
in the FRC system 10. The coatings act as gettering surfaces and effectively pump atomic and
molecular hydrogenic species (H and D). The coatings also reduce other typical impurities such as
carbon and oxygen to insignificant levels.
Mirror Plugs
As stated above, the FRC system 10 employs sets of mirror coils 420, 430, and 444 as shown
in Figures 2 and 3. A first set of mirror coils 420 is located at the two axial ends of the confinement
chamber 100 and is independently energized from the DC confinement, ion and divertor coils
412, 414 and 416 of the main magnetic system 410. The first set of mirror coils 420 primarily helps
to steer and axially contain the FRC 450 during merging and provides equilibrium shaping control
during sustainment. The first mirror coil set 420 produces nominally higher magnetic fields (around
0.4 to 0.5 T) than the central confinement field produced by the central confinement coils 412. The
second set of mirror coils 430, which includes three compact quasi-dc mirror coils 432, 434 and 436,
is located between the formation sections 200 and the divertors 300 and are driven by a common
switching power supply. The mirror coils 432, 434 and 436, together with the more compact pulsed
mirror plug coils 444 (fed by a capacitive power supply) and the physical constriction 442 form the
mirror plugs 440 that provide a narrow low gas tance path with very high magnetic fields
(between 2 to 4 T with rise times of about 10 to 20 ms). The most t pulsed mirror coils 444
are of compact radial dimensions, bore of 20 cm and similar length, compared to the meter-plusscale
bore and pancake design of the confinement coils 412, 414 and 416. The purpose of the mirror
plugs 440 is multifold: (1) The coils 432, 434, 436 and 444 tightly bundle and guide the magnetic
flux es 452 and end-streaming plasma jets 454 into the remote divertor chambers 300. This
assures that the t particles reach the divertors 300 appropriately and that there are continuous
flux surfaces 455 that trace from the open field line 452 region of the central FRC 450 all the way to
the divertors 300. (2) The physical ictions 442 in the FRC system 10, through which that the
coils 432, 434, 436 and 444 enable passage of the ic flux surfaces 452 and plasma jets 454,
provide an impediment to neutral gas flow from the plasma guns 350 that sit in the divertors 300. In
the same vein, the constrictions 442 prevent back-streaming of gas from the formation sections 200
to the divertors 300 thereby reducing the number of neutral particles that has to be introduced into
the entire FRC system 10 when commencing the startup of an FRC. (3) The strong axial mirrors
produced by the coils 432, 434, 436 and 444 reduce axial particle losses and thereby reduce the
parallel particle diffusivity on open field lines.
In the alternative uration shown in Figures 3D and 3E, a set of low profile necking
coils 421 are positions between the inner divertors 302 and the formations sections 200.
Axial Plasma Guns
Plasma streams from guns 350 mounted in the divertor chambers 310 of the divertors 300 are
ed to improve stability and l beam performance. The guns 350 are mounted on axis
inside the chamber 310 of the divertors 300 as illustrated in Figures 3 and 10 and produce plasma
flowing along the open flux lines 452 in the divertor 300 and towards the center of the confinement
chamber 100. The guns 350 e at a high density gas discharge in a washer-stack channel and
are ed to generate several kiloamperes of fully ionized plasma for 5 to 10 ms. The guns 350
include a pulsed magnetic coil that matches the output plasma stream with the desired size of the
plasma in the confinement chamber 100. The technical parameters of the guns 350 are characterized
by a channel having a 5 to 13 cm outer diameter and up to about 10 cm inner diameter and provide a
discharge current of 10-15 kA at 400-600 V with a gun-internal ic field of between 0.5 to 2.3
The gun plasma streams can penetrate the magnetic fields of the mirror plugs 440 and flow
into the formation section 200 and confinement chamber 100. The efficiency of plasma transfer
through the mirror plug 440 increases with sing distance between the gun 350 and the plug
440 and by making the plug 440 wider and shorter. Under reasonable conditions, the guns 350 can
each deliver approximately 1022 protons/s through the 2 to 4 T mirror plugs 440 with high ion and
on temperatures of about 150 to 300 eV and about 40 to 50 eV, respectively. The guns 350
provide significant refueling of the FRC edge layer 456, and an improved overall FRC particle
confinement.
To r increase the plasma density, a gas box could be ed to puff onal gas into
the plasma stream from the guns 350. This technique allows a several-fold increase in the injected
plasma density. In the FRC system 10, a gas box installed on the divertor 300 side of the mirror
plugs 440 improves the refueling of the FRC edge layer 456, formation of the FRC 450, and plasma
line-tying.
Given all the adjustment parameters discussed above and also taking into account that
operation with just one or both guns is possible, it is readily apparent that a wide spectrum of
operating modes is accessible.
Biasing odes
Electrical biasing of open flux surfaces can e radial potentials that give rise to
azimuthal E×B motion that provides a control mechanism, analogous to turning a knob, to control
rotation of the open field line plasma as well as the actual FRC core 450 via velocity shear. To
accomplish this control, the FRC system 10 employs various odes strategically placed in
various parts of the e. Figure 3 depicts g electrodes positioned at preferred locations
within the FRC system 10.
In principle, there are 4 classes of electrodes: (1) point electrodes 905 in the confinement
r 100 that make contact with ular open field lines 452 in the edge of the FRC 450 to
provide local charging, (2) annular odes 900 between the confinement r 100 and the
formation sections 200 to charge far-edge flux layers 456 in an azimuthally symmetric fashion, (3)
stacks of concentric electrodes 910 in the divertors 300 to charge multiple concentric flux layers 455
(whereby the ion of layers is controllable by adjusting coils 416 to adjust the divertor ic
field so as to terminate the desired flux layers 456 on the appropriate electrodes 910), and finally (4)
the anodes 920 (see Figure 10) of the plasma guns 350 themselves (which intercept inner open flux
surfaces 455 near the separatrix of the FRC 450). Figures 10 and 11 show some typical designs for
some of these.
In all cases these electrodes are driven by pulsed or dc power sources at voltages up to about
800 V. Depending on electrode size and what flux surfaces are intersected, currents can be drawn in
the kilo-ampere range.
Un-Sustained Operation of FRC System – Conventional Regime
The standard plasma formation on the FRC system 10 follows the well-developed reversedfield-theta-pinch
technique. A typical process for starting up an FRC commences by driving the
quasi-dc coils 412, 414, 416, 420, 432, 434 and 436 to steady state operation. The RFTP pulsed
power circuits of the pulsed power formation systems 210 then drive the pulsed fast reversed magnet
field coils 232 to create a temporary reversed bias of about −0.05 T in the formation sections 200. At
this point a predetermined amount of neutral gas at 9-20 psi is injected into the two formation
volumes defined by the quartz-tube chambers 240 of the (north and south) formation sections 200 via
a set of azimuthally-oriented puff-vales at s located on the outer ends of the formation sections
200. Next a small RF (~ hundreds of kilo-hertz) field is generated from a set of antennas on the
surface of the quartz tubes 240 to create pre-ionization in the form of local seed ionization regions
within the neutral gas columns. This is followed by ng a ringing modulation on the
current driving the pulsed fast reversed magnet field coils 232, which leads to more global preionization
of the gas s. Finally, the main pulsed power banks of the pulsed power formation
systems 210 are fired to drive pulsed fast reversed magnet field coils 232 to create a forward-biased
field of up to 0.4 T. This step can be time-sequenced such that the forward-biased field is generated
uniformly throughout the length of the formation tubes 240 (static formation) or such that a
consecutive peristaltic field modulation is achieved along the axis of the formation tubes 240
(dynamic formation).
In this entire ion process, the actual field al in the plasma occurs rapidly, within
about 5 μs. The multi-gigawatt pulsed power delivered to the forming plasma readily produces hot
FRCs which are then ejected from the formation sections 200 via ation of either a timesequenced
tion of the forward magnetic field (magnetic peristalsis) or temporarily increased
currents in the last coils of coil sets 232 near the axial outer ends of the formation tubes 210 (forming
an axial magnetic field gradient that points axially towards the confinement chamber 100). The two
(north and south) formation FRCs so formed and rated then expand into the larger diameter
confinement chamber 100, where the quasi-dc coils 412 produce a forward-biased field to control
radial expansion and e the equilibrium external magnetic flux.
Once the north and south formation FRCs arrive near the midplane of the confinement
chamber 100, the FRCs collide. During the collision the axial kinetic energies of the north and south
formation FRCs are largely thermalized as the FRCs merge ultimately into a single FRC 450. A
large set of plasma diagnostics are available in the confinement chamber 100 to study the equilibria
of the FRC 450. Typical operating conditions in the FRC system 10 produce compound FRCs with
separatrix radii of about 0.4 m and about 3 m axial extend. Further characteristics are external
magnetic fields of about 0.1 T, plasma densities around 5×1019 m-3 and total plasma temperature of
up to 1 keV. t any sustainment, i.e., no heating and/or current drive via neutral beam
injection or other auxiliary means, the lifetime of these FRCs is limited to about 1 ms, the indigenous
characteristic uration decay time.
Experimental Data of ained Operation – Conventional Regime
Figure 12 shows a l time evolution of the excluded flux radius, rΔΦ, which
approximates the separatrix radius, rs, to illustrate the dynamics of the pinch merging process
of the FRC 450. The two (north and south) individual plasmoids are produced simultaneously and
then accelerated out of the respective formation sections 200 at a supersonic speed, vZ ~ 250 km/s,
and collide near the midplane at z = 0. During the collision the plasmoids compress axially,
followed by a rapid radial and axial expansion, before eventually merging to form an FRC 450. Both
radial and axial cs of the merging FRC 450 are ced by detailed density profile
measurements and bolometer-based aphy.
Data from a representative un-sustained discharge of the FRC system 10 are shown as
ons of time in Figures 13A, 13B, 13C and 13D. The FRC is initiated at t = 0. The excluded
flux radius at the machine’s axial ane is shown in Figure 13A. This data is obtained from an
array of magnetic probes, located just inside the confinement r’s stainless steel wall, that
measure the axial magnetic field. The steel wall is a good flux conserver on the time scales of this
discharge.
Line-integrated densities are shown in Figure 13B, from a 6-chord CO2/He-Ne interferometer
located at z = 0. Taking into account vertical (y) FRC displacement, as measured by bolometric
tomography, Abel inversion yields the density rs of Figures 13C. After some axial and radial
sloshing during the first 0.1 ms, the FRC settles with a hollow y profile. This profile is fairly
flat, with substantial density on axis, as required by typical 2-D FRC equilibria.
Total plasma temperature is shown in Figure 13D, derived from pressure balance and fully
consistent with Thomson scattering and oscopy measurements.
Analysis from the entire excluded flux array indicates that the shape of the FRC separatrix
(approximated by the excluded flux axial profiles) evolves gradually from racetrack to elliptical.
This evolution, shown in Figure 14, is consistent with a gradual magnetic reconnection from two to a
single FRC. Indeed, rough estimates suggest that in this particular instant about 10% of the two
initial FRC magnetic fluxes ects during the collision.
The FRC length shrinks steadily from 3 down to about 1 m during the FRC lifetime. This
shrinkage, visible in Figure 14, suggests that mostly convective energy loss dominates the FRC
confinement. As the plasma pressure inside the separatrix decreases faster than the external
ic pressure, the magnetic field line n in the end regions compresses the FRC axially,
restoring axial and radial equilibrium. For the discharge discussed in Figures 13 and 14, the FRC
magnetic flux, le inventory, and thermal energy (about 10 mWb, 7×1019 particles, and 7 kJ,
respectively) decrease by y an order of magnitude in the first millisecond, when the FRC
equilibrium appears to subside.
Sustained Operation – HPF Regime
The examples in Figures 12 to 14 are characteristic of ng FRCs without any
sustainment. However, several techniques are deployed on the FRC system 10 to further e
FRC confinement (inner core and edge layer) to the HPF regime and sustain the configuration.
Neutral Beams
First, fast (H) neutrals are ed perpendicular to Bz in beams from the eight neutral beam
injectors 600. The beams of fast neutrals are ed from the moment the north and south
formation FRCs merge in the ement chamber 100 into one FRC 450. The fast ions, created
primarily by charge exchange, have betatron orbits (with primary radii on the scale of the FRC
topology or at least much larger than the characteristic magnetic field gradient length scale) that add
to the azimuthal current of the FRC 450. After some on of the discharge (after 0.5 to 0.8 ms
into the shot), a sufficiently large fast ion population significantly improves the inner FRC’s stability
and ement properties (see e.g. M.W. Binderbauer and N. Rostoker, Plasma Phys. 56, part 3,
451 (1996)). Furthermore, from a sustainment perspective, the beams from the neutral beam
injectors 600 are also the primary means to drive current and heat the FRC plasma.
In the plasma regime of the FRC system 10, the fast ions slow down primarily on plasma
electrons. During the early part of a discharge, typical orbit-averaged slowing-down times of fast
ions are 0.3 – 0.5 ms, which results in significant FRC heating, primarily of electrons. The fast ions
make large radial excursions e of the separatrix because the internal FRC magnetic field is
inherently low (about 0.03 T on average for a 0.1 T external axial . The fast ions would be
vulnerable to charge exchange loss, if the neutral gas density were too high outside of the separatrix.
Therefore, wall gettering and other techniques (such as the plasma gun 350 and mirror plugs 440 that
contribute, amongst other things, to gas control) deployed on the FRC system 10 tend to minimize
edge neutrals and enable the required build-up of fast ion current.
Pellet ion
When a significant fast ion population is built up within the FRC 450, with higher electron
atures and longer FRC lifetimes, frozen H or D s are injected into the FRC 450 from the
pellet injector 700 to sustain the FRC particle inventory of the FRC 450. The anticipated ablation
timescales are sufficiently short to provide a significant FRC particle source. This rate can also be
increased by enlarging the surface area of the injected piece by breaking the individual pellet into
smaller fragments while in the barrels or injection tubes of the pellet injector 700 and before entering
the confinement chamber 100, a step that can be achieved by sing the friction between the
pellet and the walls of the injection tube by tightening the bend radius of the last segment of the
injection tube right before entry into the confinement r 100. By virtue of varying the firing
sequence and rate of the 12 barrels (injection tubes) as well as the fragmentation, it is possible to
tune the pellet injection system 700 to provide just the desired level of particle inventory
sustainment. In turn, this helps maintain the internal kinetic pressure in the FRC 450 and sustained
operation and lifetime of the FRC 450.
Once the ablated atoms encounter significant plasma in the FRC 450, they become fully
ionized. The resultant cold plasma component is then collisionally heated by the indigenous FRC
plasma. The energy necessary to in a d FRC temperature is ultimately ed by the
beam ors 600. In this sense the pellet injectors 700 together with the neutral beam injectors 600
form the system that maintains a steady state and sustains the FRC 450.
CT or
As an alternative to the pellet injector, a compact toroid (CT) injector is provided,
mainly for fueling field-reversed configuration (FRCs) plasmas. The CT injector 720 comprises a
magnetized coaxial plasma-gun (MCPG), which, as shown in Figures 22A and 22B, includes coaxial
cylindrical inner and outer odes 722 and 724, a bias coil positioned internal to the inner
electrode 726 and an electrical break 728 on an end opposite the discharge of the CT injector 720.
Gas is injected h a gas injection port 730 into a space between the inner and outer electrodes
722 and 724 and a Spheromak-like plasma is generated rom by discharge and pushed out from
the gun by Lorentz force. As shown in Figures 23A and 23B, a pair of CT injectors 720 are coupled
to the confinement vessel 100 near and on opposition sides of the mid-plane of the vessel 100 to
inject CTs into the l FRC plasma within the confinement vessel 100. The discharge end of the
CT injectors 720 are ed towards the mid-plane of the confinement vessel 100 at an angel to the
longitudinal axis of the confinement vessel 100 similar to the neutral beam injectors 615.
In an alternative embodiment, the CT injector 720, as shown in Figures 24A and 24B,
includes a drift tube 740 sing an elongate cylindrical tube coupled to the discharge end of the
CT injector 720. As depicted, the drift tube 740 includes drift tube coils 742 positioned about and
axially spaced along the tube. A plurality of diagnostic ports 744 are depicted along the length of the
tube.
The advantages of the CT injector 720 are: (1) control and adjustability of particle
inventory per ed CT; (2) warm plasma is deposited (instead of cryogenic pellets); (3) system
can be operated in rep-rate mode so as to allow for continuous fueling; (4) the system can also
e some magnetic flux as the injected CTs carry embedded magnetic field. In an embodiment for
experimental use, the inner diameter of an outer electrode is 83.1 mm and the outer diameter of an
inner electrode is 54.0 mm. The surface of the inner electrode 722 is preferably coated with tungsten
in order to reduce impurities coming out from the ode 722. As depicted, the bias coil 726 is
mounted inside of the inner electrode 722.
] In recent experiments a supersonic CT translation speed of up to ~100 km/s was achieved.
Other typical plasma parameters are as s: electron density ~5×1021 m-3, electron temperature
~30-50 eV, and particle inventory of ~0.5–1.0×1019. The high kinetic pressure of the CT allows the
injected plasma to penetrate deeply into the FRC and deposit the les inside the separatrix. In
recent experiments FRC particle fueling has resulted in ~10-20% of the FRC particle inventory being
provide by the CT injectors successfully demonstrating fueling can readily be carried out without
ting the FRC plasma.
Saddle Coils
To achieve steady state current drive and maintain the ed ion current it is desirable to
prevent or significantly reduce electron spin up due to the electron-ion onal force (resulting
from collisional ion electron momentum transfer). The FRC system 10 utilizes an innovative
technique to e on breaking via an externally applied static magnetic dipole or quadrupole
field. This is accomplished via the external saddle coils 460 depicted in Figure 15. The transverse
applied radial magnetic field from the saddle coils 460 induces an axial electric field in the rotating
FRC plasma. The resultant axial electron current interacts with the radial magnetic field to produce
an hal breaking force on the electrons, Fθ=-σVeθ‹∣Br∣2›. For typical conditions in the FRC
system 10, the required applied magnetic dipole (or quadrupole) field inside the plasma needs to be
only of order 0.001 T to e adequate electron breaking. The corresponding external field of
about .015 T is small enough to not cause appreciable fast particle losses or otherwise negatively
impact confinement. In fact, the applied magnetic dipole (or quadrupole) field contributes to
suppress instabilities. In combination with tangential neutral beam injection and axial plasma
injection, the saddle coils 460 provide an additional level of control with regards to current
maintenance and stability.
Mirror Plugs
The design of the pulsed coils 444 within the mirror plugs 440 s the local generation
of high magnetic fields (2 to 4 T) with modest (about 100 kJ) capacitive energy. For formation of
magnetic fields typical of the present operation of the FRC system 10, all field lines within the
formation volume are passing h the ictions 442 at the mirror plugs 440, as suggested by
the magnetic field lines in Figure 2 and plasma wall contact does not occur. Furthermore, the mirror
plugs 440 in tandem with the quasi-dc divertor magnets 416 can be adjusted so to guide the field
lines onto the divertor electrodes 910, or flare the field lines in an end cusp configuration (not
shown). The latter improves stability and suppresses parallel electron thermal conduction.
] The mirror plugs 440 by themselves also contribute to neutral gas l. The mirror
plugs 440 permit a better utilization of the deuterium gas puffed in to the quartz tubes during FRC
formation, as gas back-streaming into the divertors 300 is significantly reduced by the small gas
conductance of the plugs (a meager 500 L/s). Most of the residual puffed gas inside the formation
tubes 210 is quickly ionized. In addition, the high-density plasma flowing through the mirror plugs
440 provides efficient neutral ionization hence an effective gas barrier. As a result, most of the
neutrals recycled in the ors 300 from the FRC edge layer 456 do not return to the confinement
chamber 100. In addition, the neutrals associated with the ion of the plasma guns 350 (as
discussed below) will be mostly confined to the divertors 300.
Finally, the mirror plugs 440 tend to improve the FRC edge layer confinement. With
mirror ratios confinement magnetic fields) in the range 20 to 40, and with a 15 m length
between the north and south mirror plugs 440, the edge layer particle confinement time τ∥ increases
by up to an order of magnitude. ing τ∥ readily increases the FRC particle confinement.
Assuming radial diffusive (D) particle loss from the separatrix volume 453 balanced by
axial loss (τ∥) from the edge layer 456, one obtains (2πrsLs)(Dns/δ) = (2πrsLsδ)(ns/τ∥), from which the
separatrix density gradient length can be rewritten as δ = (Dτ∥)1/2. Here rs, Ls and ns are separatrix
radius, separatrix length and separatrix y, tively. The FRC particle confinement time is
τN = [πrs2Ls<n>]/[(2πrsLs)(Dns/δ)] = (<n>/ns)(τ⊥τ∥)1/2, where τ⊥ = a2/D with a=rs/4. ally,
improving τ∥ leads to increased δ (reduced separatrix density gradient and drift parameter), and,
therefore, reduced FRC particle loss. The overall improvement in FRC particle confinement is
generally at less than tic because ns increases with τ∥.
A significant improvement in τ∥ also requires that the edge layer 456 remains grossly stable
(i.e., no n = 1 flute, firehose, or other MHD instability typical of open systems). Use of the plasma
guns 350 provides for this preferred edge stability. In this sense, the mirror plugs 440 and plasma
gun 350 form an ive edge control system.
Plasma Guns
The plasma guns 350 improve the stability of the FRC exhaust jets 454 by line-tying. The
gun plasmas from the plasma guns 350 are ted t azimuthal angular momentum, which
proves useful in controlling FRC rotational instabilities. As such the guns 350 are an ive
means to control FRC stability without the need for the older quadrupole stabilization technique. As
a result, the plasma guns 350 make it possible to take advantage of the beneficial effects of fast
particles or access the advanced hybrid c FRC regime as outlined in this disclosure. Therefore,
the plasma guns 350 enable the FRC system 10 to be operated with saddle coil currents just te
for electron breaking but below the threshold that would cause FRC instability and/or lead to
dramatic fast particle diffusion.
As mentioned in the Mirror Plug discussion above, if τ∥ can be significantly improved, the
supplied gun plasma would be comparable to the edge layer particle loss rate (~ 1022 /s). The
lifetime of the gun-produced plasma in the FRC system 10 is in the millisecond range. Indeed,
consider the gun plasma with density ne ~ 1013 cm-3 and ion temperature of about 200 eV, ed
between the end mirror plugs 440. The trap length L and mirror ratio R are about 15 m and 20,
respectively. The ion mean free path due to Coulomb collisions is λii ~ 6×103 cm and, since λiilnR/R
< L, the ions are confined in the gas-dynamic regime. The plasma confinement time in this regime is
τgd ~ RL/2Vs ~ 2 ms, where Vs is the ion sound speed. For ison, the classical ion confinement
time for these plasma parameters would be τc ~ 0.5τii(lnR + .5) ~ 0.7 ms. The anomalous
transverse diffusion may, in principle, shorten the plasma confinement time. However, in the FRC
system 10, if we assume the Bohm diffusion rate, the estimated erse confinement time for the
gun plasma is τ⊥ > τgd ~ 2 ms. Hence, the guns would provide significant refueling of the FRC edge
layer 456, and an improved overall FRC particle confinement.
Furthermore, the gun plasma streams can be turned on in about 150 to 200 microseconds,
which permits use in FRC start-up, translation, and merging into the confinement chamber 100. If
turned on around t ~ 0 (FRC main bank initiation), the gun plasmas help to n the present
cally formed and merged FRC 450. The combined particle inventories from the formation
FRCs and from the guns is te for neutral beam capture, plasma heating, and long sustainment.
If turned on at t in the range -1 to 0 ms, the gun plasmas can fill the quartz tubes 210 with plasma or
ionize the gas puffed into the quartz tubes, thus permitting FRC formation with reduced or even
perhaps zero puffed gas. The latter may require sufficiently cold formation plasma to permit fast
diffusion of the reversed bias magnetic field. If turned on at t < -2 ms, the plasma streams could fill
the about 1 to 3 m3 field line volume of the formation and confinement regions of the formation
sections 200 and confinement chamber 100 with a target plasma density of a few 1013 cm-3, sufficient
to allow neutral beam build-up prior to FRC arrival. The ion FRCs could then be formed and
translated into the resulting ement vessel plasma. In this way the plasma guns 350 enable a
wide variety of operating conditions and parameter regimes.
ical Biasing
Control of the radial electric field profile in the edge layer 456 is beneficial in various ways
to FRC stability and confinement. By virtue of the innovative biasing components deployed in the
FRC system 10 it is possible to apply a variety of deliberate butions of electric potentials to a
group of open flux es throughout the e from areas well outside the central confinement
region in the ement chamber 100. In this way radial electric fields can be ted across the
edge layer 456 just outside of the FRC 450. These radial electric fields then modify the hal
rotation of the edge layer 456 and effect its confinement via E×B velocity shear. Any differential
rotation between the edge layer 456 and the FRC core 453 can then be transmitted to the inside of the
FRC plasma by shear. As a result, controlling the edge layer 456 directly impacts the FRC core 453.
Furthermore, since the free energy in the plasma rotation can also be responsible for instabilities, this
technique es a direct means to control the onset and growth of instabilities. In the FRC system
, appropriate edge g provides an effective control of open field line transport and rotation as
well as FRC core rotation. The location and shape of the various provided electrodes 900, 905, 910
and 920 allows for control of different groups of flux surfaces 455 and at different and independent
potentials. In this way a wide array of different electric field urations and strengths can be
realized, each with different characteristic impact on plasma performance.
A key advantage of all these innovative biasing techniques is the fact that core and edge
plasma behavior can be affected from well outside the FRC , i.e. there is no need to bring any
physical components in touch with the central hot plasma (which would have severe implications for
energy, flux and particle losses). This has a major beneficial impact on performance and all potential
applications of the HPF concept.
Experimental Data – HPF Operation
Injection of fast particles via beams from the neutral beam guns 600 plays an important role
in enabling the HPF regime. s 16A, 16B, 16C and 16D illustrate this fact. Depicted is a set of
curves showing how the FRC lifetime correlates with the length of the beam pulses. All other
operating conditions are held constant for all discharges comprising this study. The data is averaged
over many shots and, therefore, represents typical behavior. It is y evident that longer beam
duration produces longer lived FRCs. Looking at this evidence as well as other diagnostics during
this study, it demonstrates that beams increase stability and reduce losses. The correlation between
beam pulse length and FRC me is not t as beam trapping becomes inefficient below a
certain plasma size, i.e., as the FRC 450 shrinks in physical size not all of the ed beams are
intercepted and trapped. Shrinkage of the FRC is primarily due to the fact that net energy loss (~ 4
MW about midway through the discharge) from the FRC plasma during the discharge is somewhat
larger than the total power fed into the FRC via the neutral beams (~2.5 MW) for the particular
experimental setup. Locating the beams at a on closer to the mid-plane of the vessel 100 would
tend to reduce these losses and extend FRC lifetime.
Figures 17A, 17B, 17C and 17D illustrate the effects of different components to achieve
the HPF regime. It shows a family of typical curves depicting the lifetime of the FRC 450 as a
function of time. In all cases a nt, modest amount of beam power (about 2.5 MW) is injected
for the full duration of each discharge. Each curve is representative of a different combination of
components. For example, ing the FRC system 10 without any mirror plugs 440, plasma guns
350 or gettering from the ing systems 800 results in rapid onset of rotational instability and loss
of the FRC topology. Adding only the mirror plugs 440 delays the onset of instabilities and
increases confinement. ing the combination of mirror plugs 440 and a plasma gun 350 further
reduces instabilities and increases FRC lifetime. Finally adding gettering (Ti in this case) on top of
the gun 350 and plugs 440 yields the best results – the resultant FRC is free of instabilities and
exhibits the longest lifetime. It is clear from this experimental demonstration that the full
combination of components produces the best effect and provides the beams with the best target
conditions.
As shown in Figure 1, the newly discovered HPF regime exhibits dramatically improved
transport behavior. Figure 1 illustrates the change in particle confinement time in the FRC system 10
between the tionally regime and the HPF regime. As can be seen, it has ed by well
over a factor of 5 in the HPF regime. In addition, Figure 1 details the particle confinement time in
the FRC system 10 relative to the particle confinement time in prior conventional FRC experiments.
With regards to these other machines, the HPF regime of the FRC system 10 has improved
confinement by a factor of between 5 and close to 20. Finally and most importantly, the nature of
the confinement scaling of the FRC system 10 in the HPF regime is dramatically different from all
prior measurements. Before the establishment of the HPF regime in the FRC system 10, various
cal scaling laws were derived from data to predict confinement times in prior FRC
experiments. All those scaling rules depend mostly on the ratio R2/ρi, where R is the radius of the
ic field null (a loose measure of the physical scale of the machine) and ρi is the ion larmor
radius evaluated in the externally applied field (a loose measure of the applied magnetic . It is
clear from Figure 1 that long confinement in conventional FRCs is only possible at large machine
size and/or high magnetic field. Operating the FRC system 10 in the conventional FRC regime CR
tends to follow those scaling rules, as indicated in Figure 1. However, the HPF regime is vastly
superior and shows that much better confinement is attainable t large machine size or high
magnetic fields. More importantly, it is also clear from Figure 1 that the HPF regime results in
improved confinement time with reduced plasma size as compared to the CR regime. Similar trends
are also visible for flux and energy confinement times, as bed below, which have sed by
over a factor of 3-8 in the FRC system 10 as well. The breakthrough of the HPF regime, therefore,
enables the use of modest beam power, lower magnetic fields and smaller size to sustain and
maintain FRC equilibria in the FRC system 10 and future higher energy machines. Hand-in-hand
with these improvements comes lower operating and construction costs as well as d
engineering complexity.
For r comparison, Figures 18A, 18B, 18C and 18D show data from a representative
HPF regime rge in the FRC system 10 as a function of time. Figure 18A depicts the excluded
flux radius at the mid-plane. For these longer timescales the conducting steel wall is no longer as
good a flux conserver and the magnetic probes internal to the wall are augmented with probes
outside the wall to properly account for magnetic flux diffusion through the steel. Compared to
typical performance in the conventional regime CR, as shown in s 13A, 13B, 13C and 13D,
the HPF regime operating mode exhibits over 400% longer me.
] A representative cord of the line integrated density trace is shown in Figure 18B with its
Abel inverted complement, the density contours, in Figure 18C. Compared to the conventional FRC
regime CR, as shown in s 13A, 13B, 13C and 13D, the plasma is more ent throughout
the pulse, indicative of very stable operation. The peak density is also slightly lower in HPF shots –
this is a consequence of the hotter total plasma temperature (up to a factor of 2) as shown in Figure
For the respective discharge illustrated in Figures 18A, 18B, 18C and 18D, the energy,
particle and flux confinement times are 0.5 ms, 1 ms and 1 ms, respectively. At a nce time of 1
ms into the discharge, the stored plasma energy is 2 kJ while the losses are about 4 MW, making this
target very suitable for neutral beam sustainment.
Figure 19 summarizes all advantages of the HPF regime in the form of a newly established
experimental HPF flux confinement scaling. As can be seen in Figure 19, based on measurements
taken before and after t = 0.5 ms, i.e., t < 0.5 ms and t > 0.5 ms, the flux confinement (and similarly,
particle confinement and energy confinement) scales with roughly the square of the electron
Temperature (Te) for a given separatrix radius (rs). This strong scaling with a positive power of Te
(and not a negative power) is completely opposite to that exhibited by conventional tokomaks, where
confinement is typically inversely proportional to some power of the on temperature. The
manifestation of this scaling is a direct consequence of the HPF state and the large orbit (i.e. orbits
on the scale of the FRC topology and/or at least the characteristic magnetic field gradient length
scale) ion population. entally, this new scaling substantially favors high operating
temperatures and enables relatively modest sized reactors.
With the advantages the HPF regime presents, FRC sustainment or steady state driven by
neutral beams is achievable, meaning global plasma parameters such as plasma thermal energy, total
le numbers, plasma radius and length as well as magnetic flux are sustainable at reasonable
levels without substantial decay. For comparison, Figure 20 shows data in plot A from a
representative HPF regime discharge in the FRC system 10 as a function of time and in plot B for a
projected representative HPF regime discharge in the FRC system 10 as a function of time where the
FRC 450 is ned without decay through the duration of the neutral beam pulse. For plot A,
l beams with total power in the range of about 2.5-2.9 MW were injected into the FRC 450 for
an active beam pulse length of about 6 ms. The plasma diamagnetic me depicted in plot A was
about 5.2 ms. More recent data shows a plasma netic lifetime of about 7.2 ms is achievable
with an active beam pulse length of about 7 ms.
As noted above with regard to Figures 16A, 16B, 16C and 16D, the correlation between
beam pulse length and FRC lifetime is not perfect as beam trapping becomes inefficient below a
certain plasma size, i.e., as the FRC 450 shrinks in physical size not all of the injected beams are
intercepted and trapped. age or decay of the FRC is primarily due to the fact that net energy
loss (- 4 MW about midway through the discharge) from the FRC plasma during the discharge is
somewhat larger than the total power fed into the FRC via the neutral beams (-2.5 MW) for the
particular experimental setup. As noted with regard to Figure 3C, angled beam injection from the
neutral beam guns 600 towards the ane improves beam-plasma coupling, even as the FRC
plasma shrinks or otherwise axially contracts during the injection period. In addition, appropriate
pellet fueling will maintain the ite plasma density.
Plot B is the result of simulations run using an active beam pulse length of about 6 ms and
total beam power from the neutral beam guns 600 of slightly more than about 10 MW, where neutral
beams shall inject H (or D) neutrals with particle energy of about 15 keV. The equivalent current
injected by each of the beams is about 110 A. For plot B, the beam injection angle to the device axis
was about 20°, target radius 0.19 m. Injection angle can be changed within the range 15° - 25°. The
beams are to be injected in the co-current ion azimuthally. The net side force as well as net
axial force from the l beam momentum injection shall be minimized. As with plot A, fast (H)
ls are injected from the neutral beam injectors 600 from the moment the north and south
formation FRCs merge in the confinement chamber 100 into one FRC 450.
The simulations that where the foundation for plot B use multi-dimensional hall-MHD
solvers for the ound plasma and equilibrium, fully kinetic Monte-Carlo based solvers for the
energetic beam components and all ring processes, as well as a host of coupled transport
equations for all plasma species to model interactive loss processes. The ort components are
empirically calibrated and extensively benchmarked against an experimental se.
As shown by plot B, the steady state diamagnetic me of the FRC 450 will be the length
of the beam pulse. However, it is important to note that the key correlation plot B shows is that when
the beams are turned off the plasma or FRC begins to decay at that time, but not before. The decay
will be similar to that which is observed in discharges which are not beam-assisted - probably on
order of 1 ms beyond the beam turn off time - and is simply a reflection of the characteristic decay
time of the plasma driven by the sic loss processes.
Turning to Figures 21A, 21B, 21C, 21D and 21E, ment results illustrated in the
figures indicate achievement of FRC sustainment or steady state driven by angled l beams, i.e.,
global plasma parameters such as plasma radius, plasma density, plasma temperature as well as
magnetic flux are sustainable at constant levels without decay in correlation with NB pulse duration.
For example, such plasma parameters are essentially being kept constant for ~5+ ms. Such plasma
performance, including the sustainment feature, has a strong correlation NB pulse duration, with
diamagnetism persisting even several milliseconds after NB termination due to the accumulated fast
ions. As illustrated, the plasma performance is only limited by the pulse-length constraints arising
from finite stored energies in the associated power supplies of many al systems, such as the NB
injectors as well as other system ents.
Multi-Scaled Capture Type Vacuum Pumps
As noted above with regard to Figures 3A, 3B, 3C, 3D, 3E and 8, the l atom beams
600 are deployed on the FRC system 10 to provide heating and current drive as well as to develop
fast particle re. The individual beam lines comprising neutral atom beam injector systems 600
are located around the central confinement chamber 100 and, as shown in Figures 3C, 3D and 3E, are
preferably angled to inject neutral particles s the mid-plane of the confinement chamber 100.
To ramp-up plasma temperatures and elevate system energies, the t FRC system 10 includes a
neutral beam injector (NBI) system 600 of elevated power and expanded pulse length, e.g., for
exemplary purposes only, power of about 20+ MW with up to 30 ms pulse length.
To further improve FRC sustainment and demonstrate FRC ramp-up to high plasma
temperatures and elevated system energies, the present FRC system 10 also includes multi-scaled
capture type vacuum pumps in the outer and inner divertors 300 and 302 to prevent the buildup of
neutralized gas in the divertors 300 and 302. As illustrated in Figure 25, through various
mechanisms, charged plasma particles (such as, e.g., hydrogen and deuterium) are lost, as indicated
by arrows A, from the interior or core 453 of the FRC plasma 450 to the open field line plasma.
From there, the charged particles flow, as indicated by arrows B, along the open magnetic field lines
452 out of the central confinement vessel 100 to each of the four divertors 300 and 302 on either side
of the confinement vessel 100.
Once in the divertors 300 and 302, the charged particles will hit surfaces within the divertor
chambers 310, such as, e.g., bias electrodes 910 in divertors 300 and 302 (Figures 3A, 3D, 10 and
26), become neutralized and come off as neutralized gas. Keeping the y of such neutralized gas
sufficiently low is necessary for FRC sustainment and ramp-up to high plasma atures and
elevated system energies e electrons in the plasma along the open field lines 452 will ionize
the neutral gas in the ors 300 and 302 and, thus, lose energy (cooling) in the process. Electrons
that are too cold cause excessive drag on and slow down energetic ions orbiting around the plasma
core of the FRC plasma 450. Below a predetermined neutral gas density, electron cooling from
ionization tends not to be significant.
To avoid a p of such neutralized gas in the divertors 300 and 302, the neutralized gas
must be pumped away to t the gas density level N from exceeding a predetermined maximum
level of Y, i.e., N < Y m-3. For example, in certain embodiments, this gas buildup cannot exceed the
density level N of 1018 m-3 (3x10-5 Torr pressure lent at 300K) in the inner divertors 302, and
2x1018 m-3 (6x10-5 Torr pressure equivalent at 300K) in the outer divertors 300. The level of
g required to prevent exceeding this maximum density/pressure limit is determined by the
rate of charged particles flowing into each of the four divertors 300 and 302. The level of pumping
required is analogous to pouring water into a leaky bucket having one or more holes. The faster
water is poured into the bucket, the higher the level to which the water level rises. While the bigger
the leak, i.e., the greater the size and or number of holes, the lower the level to which the water level
drops. With a big enough leak (i.e., a pump) the water level (i.e., particle density/pressure) can be
maintained below a water level limit (i.e., a predetermined particle density/pressure limit; e.g., about
1018 m-3) while water is poured into the bucket (i.e., charge particles flow into the divertors 300 and
302).
In ion of the present FRC system 10, as shown in Figure 27, all the charged plasma
particles flowing towards the divertors 300 and 302 are expected to initially flow into the two outer
divertors 300 with a maximum rate of about 1.25x1022 #/s, which in more familiar vacuum units is
about 400 /s. Embodiments of the present FRC system 10 are ured to change to
magnetic fields shortly after FRC ion, e.g., within about 5 milliseconds, to switch 75% of the
total particle flow from the outer divertors 300 to the inner divertors 302. For example, the initial
flow rate into the inner divertors 302 will be about 300 Torr-L/s. Within a short time, e.g., about 5-10
milliseconds, following the switching of particle flow from the outer divertors 300 to the inner
divertors 302, plasma confinement in the FRC 450 will improve such that the expected particle flow
rates tend to drop down 4 to 5 fold, e.g., down to about 60 Torr-L/s. A simple zero dimension
tion model showed that a combination of a 2 million L/s vacuum pump plus 15 m3 of
volumetric pumping (letting gas expand into an empty volume) was required in each of the four
divertors 300 and 302 to keep the hydrogen gas density below red maximum limits. Deuterium
es 1.5 n L/s worth of pumping.
To handle these particles loads while keeping the gas density low enough requires an
enormous amount of pumping. tional pumping solutions are unable to provide the necessary
amount of pumping within the constraints associated with the divertors 300 and 302 of the present
FRC system 10, which include but are not d to, for example, cost, as well as limited volumetric
space (e.g., about 15 m3) and surface area (e.g., about 10 m2) inside each divertor 300 and 302.
The cheapest way to pump particles such as, e.g., hydrogen and deuterium, is to use
Titanium films deposited onto the surfaces of the chambers 310 of the divertors 300 and 302 to cause
the particles to stick to the surfaces of the chambers 310 in the form a capture type vacuum pump
(discussed in further detail . About 2.2 L/cm2s of pumping is achievable at room temperature,
which corresponds to the probability of the hydrogen les sticking and being captured by the
film of 5%. This is called the sticking factor, which can range from 0 to 100%. Using a limited
surface area of about 10 m2 of area will only yield a total pump speed of 22,000 L/s at this sticking
factor. This pump speed is about 100 times less than what is required to handle the particles loads of
the present FRC system 10 while keeping the gas density below a predetermined maximum.
To meet the pumping needs of the present FRC system 10, a combination of two pumping
solutions is ed. First, a titanium film is deposited on to cryogenically cooled surfaces, e.g.,
surfaces that are cryogenically cooled to about 77K. Such cooling tends to increase the sticking
factor up to about 4 fold, e.g., from about 5% to about 20%. Second, the pumping surfaces are
configured into a ity of multi-scaled self-similar surfaces to r increase the sticking factor
about 3 to 4 fold, e.g., from about 20% to about 70%. With such ses in ng factor, a 100
fold increase in pump speed is achieved. For example, for hydrogen a pump speed of 2,400,000 L/s
is achieved and for deuterium a pump speed of 1,500,000 L/s is achieved using just 7.3 m2 of the
available surface area, which fits inside a 15m3 vacuum vessel of the divertors 300 and 302. These
pumps can handle the total amount of gas (capacity) ted from a plasma shot on the present
FRC system 10. The pump keeps 95% of its pump speed from this amount of gas, and can be
regenerated to 100% by depositing more titanium.
Capture Type Vacuum Pump
Gas molecules can be captured onto a surface of a flat plate 312 (Figure 28) by sticking to
the surface of the plate 312. The capture of gas molecules can happen via various physical ses
such as condensation, as well as physical or chemical adsorption onto surfaces that can be composed
of many different types of materials. Each time a gas molecule hits this surface it can be captured
with a ility of sticking between 0 to 100%. This probability of ng onto a flat surface from
a single hit to the surface is called the ng factor (SF). If the gas molecule doesn’t stick it will
typically leave that surface in a random direction according to the cosine law. The sticking factor of a
flat surface is independent of the size of the flat surface. However, a pump’s total pumping speed
does depend on the e area, sticking factor and average speed of the gas molecules, and is given
by formula (1):
The ive sticking factor, and hence pump speed, can be sed by combining two or
more es together such that the surfaces have views of each other. For example, as shown in
Figure 28, five flat square shaped walls 322, 324, 326, 328 and 325 can be combined to create five
sides of a cube 320 with one open side such that the al surfaces of the walls 322, 324, 326, 328
and 325 have a view of each other. A gas molecule entering into this cube 320 on the open side will
hit one of the five surfaces and stick with a probability SF. If the gas molecule doesn’t stick to the
surface it initially hits, the gas molecule can head back out of the open side of the cube 320 the gas
molecule just entered from or the gas molecule can hit one of the other four surfaces of the cube 320
it has a view of with yet another chance of sticking to a surface by a probability of SF. A gas
molecule can bounce around hitting the surfaces of the cube 320 many times before either sticking to
one of the surfaces or leaving out through the open side of the cube 320. This effectively ses
the probably of a gas molecule sticking to a surface in the cube 320 compared to a flat square surface
312 of the same size as the opening of the cube 320. The cube 320 effectively equates to a flat
surface 312, but has a higher effective SF than the flat surface 312 where the flat surface has the
same area as the open side of the cube 320.
When combining two or more surfaces together such that the surfaces have views of each
other, the resulting shape need not necessarily form the shape of a cube. The resultant shape can be
any shape having multiple surfaces that form more than just a flat surface such as an open sided
chamber, cavity or channel. For example, as shown in Figure 29, a box with a square opening like
the cube 320 shown in Figure 28 can be formed but with a depth that varies. Figure 29 provides a
plot of the ive SF of the square opening of the box as a function of the Depth/Width ratio of the
box for a given SF for flat surfaces that make up the box. A box with zero depth (Depth/Width = 0
too) is just a flat surface 312, so the effective SF will be the same as the given SF of the box’s flat
surfaces. Sample SFs for a flat surface are shown to include 0.05, 0.10, 0.20 and 0.50. For a
Depth/Width ratio of Depth/Width=1, the box 320(1) is a cube. Boxes 320(2), , 320(4) and
320(5) have Depth/Width ratios of 2:1, 3:1, 4:1 and 5:1, respectively.
In addition to the Width ratio being variable, the shape and the number of open sides
may vary. The open sides need not to be square, but can be any shape including, but not d to,
hexagonal, circular, rectangular, triangular, star, etc., as long as two or more internal es have a
view of each other. The shape also doesn’t have to be made of a number of discrete flat surfaces. It
can be a continuously curved surface like a hemisphere. To calculate the effective SF for the
here, the curved surface is assumed to be composed of an infinite number of infinitely small
flat surfaces.
Self-Similar Surfaced Capture Pumps
One can take a basic shape to build self-similar structures on many scale levels that will
dramatically increase the effective SF. For example, the individual pump object in the form of the
five sided cube 320 described above (Figures 28 and 29), can be assembled with a plurality of cubes
320 into a 10x10 array of cubes to form a panel or wall 330. The array of cubes panel 330 can then
be used to form the five (5) walls 342, 344, 345, 346 and 348 of a larger five (5) sided cube 340.
] This process can be replicated over and over again increasing the SF and hence pump’s
speed and capacity. For example, as illustrated in Figures 31 and 32, if a flat square plate 312 having
an SF of 5% is used to form a five sided cube 320, the SF of the opening of the cube 320 will
increase to 20%. The cube 320 can then be assembled with a plurality of cubes 320 in a 10x10 array
of cubes to form a “flat” square plane or wall 330 with a SF equal to 20%. If the array of cubes wall
330 having an SF of 20% is used to form a five sided cube 340, with sides 342, 344, 345, 346 and
348, the SF of the opening of the cube 340 will increase to 50%. The cube 340 can then be
assembled with a plurality of cubes 340 in a 10x10 array of cubes to form a “flat” square plane or
wall 360 with a SF equal to 50%. If the array of cubes wall 360 having an SF of 50% is used to form
a five sided cube 380, with sides 382, 384, 385, 386 and 388, the SF of the opening of the cube 380
will increase to 80%. This process can be repeated as d to reach an optimal SF level.
] As shown in Figure 26, a plurality of the larger boxes 380 are positioned about the interior
of the chamber 310 of the divertors 300 and 302.
SF doesn’t depend on size. The increase of SF associated with the cubes of the previous
example can achieved by cubes of the same size opening rather than making the opening larger.
Stated differently, by transitioning from configuration of the first cube 320 to the configuration of
third cube 380 while keeping the opening of the first and third cubes 320 and 380 the same size, a
four-fold increase in SF and, hence, pump speed is achieved relative to the SF of a flat plate
corresponding to the opening area. This is an example of discrete scale levels of self-similarity. The
first cube 320 is only a one scale cube, i.e., the internal surfaces of the walls of the cube 320
comprise flat surfaces. However, the internal surfaces of the walls of the second cube 340 are not flat
but rather include an array of the first cubes 320. Similarly, the al surfaces of the third cube 380
include an array of the second cubes 340.
] As far as increasing the pump’s SF, speed and capacity, there is no requirement that the
individual pump objects used to convert a flat e into a three (3) dimensional surface have to
have the same shapes or sizes. The dual pump s just have to have a shape that can
increase the SF relative to a flat plate corresponding to the opening of the individual pump objects. In
the examples provided above, a 10:1 ratio is used in the scale sizes of the self-similar cubes, but this
ratio can be anything. The number of scale , shape and size can be optimized per situation.
As was mentioned above, a combination of cryogenically cooled surfaces and self-similar
shapes are employed in the present FRC system 10 to achieve a ng factor of about 80% or
above. In n situations, the SF gets reduced down to 70% from some shields that prevent the
titanium from depositing out through the opening of the individual pumps.
] There are ways to lly produce these types of imilar structures. Titanium films
grown on cryogenically cooled (77K) surface under different pressures of argon will produce submicron
structures that t self-similarity and will increase sticking factor of the surface.
r, the self-similar structures, such as, e.g., cubes 320, 340 and 380, are purposely-engineered
self-similar structures that are not grown from deposited films but can be used in conjunction with
deposited films.
There are many other ways that gas can be trapped onto surfaces besides titanium coatings.
NEGs (Non-Evaporable Getters), cryogenically cooled activated charcoal, are two of the more
common.
NEGs (Non-Evaporable Getters) pumps are commonly used throughout particle
accelerators. These are made from alloy powders mixtures of Titanium, Vanadium, Aluminum,
Zirconium, and Iron.
Typically, this NEG powder is sintered into disks that are arranged spaced stacks, or onto
metallic heater ribbon, which are then bent into shapes. So they do employ shapes to increase the
sticking factor, but only at one scale level. They are not shaped into self-similar ures on multi
scale sizes. These NEG powders could be sintered into self-similar shaped structures to increase their
low sticking factors and hence pump speed without increasing the size of the pump. sed NEG
pump speed would help improve the vacuum performance of particle accelerators.
Activated charcoal cooled to 10K can capture Hydrogen gas and cooled further to 4K can
capture Helium gas. It is one of the few ways to pump Helium gas. It is used as a pump in fusion
devices such as Tokamaks and Neutral Beams. Adhering a powdered activated charcoal onto a milar
structure will increase the sticking factor and pump speeds.
According to an embodiment of the present disclosure, a method for generating and
maintaining a magnetic field with a field reversed uration (FRC) comprising forming an FRC
about a plasma in a confinement chamber, injecting a plurality of neutral beams into the FRC plasma
at an angle toward the mid-plane of the confinement chamber, pumping neutralized gas les
accumulating in first and second diametrically opposed divertors coupled to the confinement
chamber with first and second capture vacuum pumps positioned in the first and second divertors and
comprising two or more sides with surfaces having a view of each other and an open side, wherein
the first and second capture vacuum pumps having a ng factor more than four (4) times greater
than a sticking factor of a flat plate ng an area lent to the open side of the first and
second capture pumps.
According to a further embodiment of the present disclosure, at least one of the two or more
sides of the first and second capture vacuum pumps comprising an array of individual capture
vacuum pumps.
According to a further embodiment of the present disclosure, each of the individual capture
vacuum pumps sing two or more sides with surfaces having a view of each other and an open
side, wherein each of the individual capture vacuum pumps having a sticking factor greater than a
sticking factor of a flat plate defining an area equivalent to the open side of each of the individual
e vacuum pumps.
According to a further embodiment of the present sure, at least one of the two or more
sides of each of the dual capture vacuum pumps comprising a second array of individual
capture vacuum pumps.
According to a further ment of the present disclosure, each of the individual capture
vacuum pumps of the second array comprising two or more sides with surfaces having a view of
each other and an open side, wherein each of the individual capture vacuum pumps of the second
array having a sticking factor greater than a sticking factor of a flat plate ng an area equivalent
to the open side of each of the individual capture vacuum pumps of the second array.
According to a further embodiment of the present disclosure, the first and second capture
vacuum pumps having a sticking factor that is N times greater than a sticking factor of a flat plate
defining an area lent to the open side of the first and second e pumps, wherein N is
4<N<16.
According to a further embodiment of the present disclosure, the surfaces of the flat plate
and the first and second vacuum pumps includes a film of titanium deposited thereon.
] According to a further embodiment of the t disclosure, the method r includes
maintaining the FRC at or about a constant value without decay by injecting beams of fast neutral
atoms from neutral beam injectors into the FRC plasma at an angle towards the mid through plane of
the confinement chamber.
According to a further embodiment of the present disclosure, the method further comprising
generating a magnetic field within the confinement r with quasi dc coils extending about the
confinement chamber and a mirror magnetic field within opposing ends of the confinement chamber
with quasi dc mirror coils extending about the opposing ends of the confinement chamber.
According to a r embodiment of the t sure, the method further comprising
generating a magnetic field within the confinement chamber with quasi dc coils extending about the
ement chamber and a mirror magnetic field within opposing ends of the confinement chamber
with quasi dc mirror coils extending about the opposing ends of the confinement chamber.
According to a further ment of the present disclosure, forming the FRC includes
forming a formation FRC in opposing first and second formation sections coupled to the confinement
chamber and accelerating the formation FRC from the first and second formation sections towards
the mid h plane of the confinement chamber where the two formation FRCs merge to form the
According to a further embodiment of the present disclosure, forming the FRC includes one
of forming a formation FRC while accelerating the formation FRC towards the mid-plane of the
confinement chamber and forming a formation FRC then rating the formation FRC towards
the mid through plane of the confinement chamber.
According to a r ment of the present disclosure, accelerating the formation
FRC from the first and second formation sections towards the mid-plane of the confinement chamber
includes passing the ion FRC from the first and second formation sections through first and
second inner divertors coupled to te ends of the confinement chamber interposing the
confinement chamber and the first and second formation sections.
According to a further embodiment of the present disclosure, passing the formation FRC
from the first and second formation ns through first and second inner divertors includes
inactivating the first and second inner divertors as the formation FRC from the first and second
formation sections passes through the first and second inner ors.
ing to a further embodiment of the present sure, the method further comprising
guiding magnetic flux surfaces of the FRC into the first and second inner divertors.
According to a further embodiment of the present disclosure, the method further comprising
guiding magnetic flux surfaces of the FRC into first and second outer divertors coupled to the ends
of the ion ns.
According to a further embodiment of the t disclosure, the method further comprising
generating a magnetic field within the formation sections and the first and second outer divertors
with quasi-dc coils extending about the formation sections and ors.
According to a r embodiment of the t disclosure, the method further comprising
generating a magnetic field within the ion sections and first and second inner divertors with
quasi-dc coils extending about the formation sections and divertors.
According to a further embodiment of the present disclosure, the method r comprising
generating a mirror magnetic field between the first and second ion sections and the first and
second outer divertors with quasi-dc mirror coils.
According to a further embodiment of the present disclosure, the method further comprising
generating a mirror plug magnetic field within a constriction between the first and second formation
sections and the first and second outer divertors with quasi-dc mirror plug coils extending about the
iction between the ion sections and the divertors.
According to a further embodiment of the present disclosure, the method further comprising
generating a mirror magnetic field between the confinement chamber and the first and second inner
divertors with quasi-dc mirror coils and generating a necking magnetic field between the first and
second formation sections and the first and second inner divertors with quasi-dc low profile necking
coils.
According to a further ment of the present disclosure, the method further comprising
generating one of a magnetic dipole field and a magnetic pole field within the chamber with
saddle coils coupled to the chamber.
According to a further embodiment of the present disclosure, the method further sing
conditioning the internal surfaces of the chamber and the internal surfaces of first and second
formation sections, first and second divertors interposing the confinement chamber and the first and
second formation sections, and first and second outer divertors coupled to the first and second
formation sections with a gettering system.
] According to a further embodiment of the present disclosure, the gettering system includes
one of a Titanium deposition system and a Lithium deposition system.
According to a further embodiment of the present disclosure, the method further comprising
axially injecting plasma into the FRC from axially mounted plasma guns.
According to a further embodiment of the t disclosure, the method further comprising
controlling the radial electric field profile in an edge layer of the FRC.
According to a further embodiment of the present disclosure, controlling the radial electric
field profile in an edge layer of the FRC includes applying a distribution of electric potential to a
group of open flux surfaces of the FRC with g electrodes.
According to a further embodiment of the present disclosure, the method r comprising
injecting compact toroid (CT) plasmas from first and second CT injectors into the FRC plasma at an
angle towards the mid-plane of the confinement chamber, wherein the first and second CT injectors
are diametrically opposed on opposing sides of the mid-plane of the confinement chamber.
According to a r embodiment of the present disclosure, a capture vacuum pump
comprising two or more sides with es having a view of each other and an open side, wherein
e vacuum pump having a ng factor more than four (4) times greater than a sticking factor
of a flat plate defining an area equivalent to the open side of the capture pump.
According to a further ment of the present disclosure, at least one of the two or more
sides of the first and second capture vacuum pumps sing an array of individual capture
vacuum pumps.
According to a further embodiment of the t disclosure, each of the individual capture
vacuum pumps comprising two or more sides with surfaces having a view of each other and an open
side, wherein each of the individual e vacuum pumps having a sticking factor greater than a
sticking factor of a flat plate defining an area equivalent to the open side of each of the dual
capture vacuum pumps.
According to a further embodiment of the present disclosure, at least one of the two or more
sides of each of the individual capture vacuum pumps comprising a second array of dual
capture vacuum pumps.
According to a further embodiment of the present disclosure, each of the individual capture
vacuum pumps of the second array comprising two or more sides with surfaces having a view of
each other and an open side, wherein each of the individual capture vacuum pumps of the second
array having a sticking factor greater than a sticking factor of a flat plate defining an area equivalent
to the open side of each of the dual capture vacuum pumps of the second array.
According to a further embodiment of the present disclosure, the first and second capture
vacuum pumps having a sticking factor that is N times greater than a sticking factor of a flat plate
defining an area equivalent to the open side of the first and second capture pumps, n N is
4<N<16.
] According to a further embodiment of the present disclosure, the surfaces of the flat plate
and the first and second vacuum pumps includes a film of titanium deposited thereon.
According to a r embodiment of the present disclosure, a system for generating and
maintaining a magnetic field with a field reversed configuration (FRC) comprising a confinement
chamber, first and second diametrically opposed FRC formation sections coupled to the confinement
chamber and including first and second capture vacuum pumps positioned within the first and second
divertors and comprising two or more sides with surfaces having a view of each other and an open
side, wherein the first and second capture vacuum pumps having a ng factor more than four (4)
times greater than a sticking factor of a flat plate defining an area equivalent to the open side of the
first and second capture pumps, one or more of a plurality of plasma guns, one or more biasing
electrodes and first and second mirror plugs, wherein the plurality of plasma guns includes first and
second axial plasma guns operably coupled to the first and second divertors, the first and second
formation sections and the confinement chamber, wherein the one or more biasing electrodes being
positioned within one or more of the confinement chamber, the first and second formation sections,
and the first and second outer divertors, and wherein the first and second mirror plugs being position
between the first and second formation sections and the first and second divertors, a gettering system
coupled to the confinement chamber and the first and second divertors, a plurality of neutral atom
beam injectors d to the confinement chamber and angled toward a mid-plane of the
confinement chamber.
According to a further embodiment of the present disclosure, the system is configured to
generate an FRC and maintain the FRC without decay while the neutral beams are injected into the.
According to a further embodiment of the t disclosure, the first and second divertors
se first and second inner ors interposing the first and second formation sections and the
confinement chamber, and further sing first and second outer divertors coupled to the first and
second formation sections, wherein the first and second ion sections interposing the first and
second inner divertors and the first and second outer divertors.
] According to a further ment of the present disclosure, the system further sing
first and second axial plasma guns ly coupled to the first and second inner and outer divertors,
the first and second formation ns and the confinement chamber.
According to a further embodiment of the present disclosure, the system further sing
two or more saddle coils coupled to the confinement chamber.
According to a further embodiment of the present disclosure, the formation section
comprises modularized formation systems for generating an FRC and translating it toward a
midplane of the ement chamber.
ing to a further embodiment of the present disclosure, the biasing electrodes
includes one or more of one or more point electrodes positioned within the containment chamber to
contact open field lines, a set of annular electrodes between the ement r and the first
and second formation sections to charge ge flux layers in an azimuthally symmetric n, a
plurality of concentric stacked electrodes positioned in the first and second divertors to charge
multiple concentric flux layers, and anodes of the plasma guns to intercept open flux.
According to a r embodiment of the present disclosure, the system further comprising
first and second compact toroid (CT) injectors d to the confinement chamber at an angle
towards the mid-plane of the confinement chamber, n the first and second CT injectors are
diametrically opposed on opposing sides of the mid-plane of the confinement chamber.
The example embodiments provided herein, however, are merely intended as illustrative
examples and not to be limiting in any way.
All features, ts, components, functions, and steps described with respect to any
embodiment provided herein are intended to be freely combinable and substitutable with those from
any other embodiment. If a certain e, element, component, function, or step is described with
respect to only one embodiment, then it should be understood that that feature, element, component,
on, or step can be used with every other ment bed herein unless explicitly stated
otherwise. This paragraph therefore serves as antecedent basis and written support for the
introduction of claims, at any time, that combine features, elements, components, functions, and
steps from different ments, or that substitute features, elements, components, functions, and
steps from one embodiment with those of another, even if the following description does not
explicitly state, in a particular instance, that such combinations or substitutions are possible. Express
recitation of every possible combination and tution is overly burdensome, especially given that
the permissibility of each and every such ation and substitution will be readily recognized by
those of ordinary skill in the art upon reading this description.
In many instances entities are described herein as being coupled to other entities. It should
be understood that the terms “coupled” and “connected” (or any of their forms) are used
interchangeably herein and, in both cases, are generic to the direct coupling of two entities (without
any non-negligible (e.g., parasitic) intervening entities) and the indirect coupling of two entities (with
one or more non-negligible intervening entities). Where entities are shown as being directly coupled
together, or described as coupled together without description of any intervening entity, it should be
understood that those entities can be ctly coupled er as well unless the context clearly
dictates otherwise.
While the ments are susceptible to various modifications and alternative forms,
specific examples thereof have been shown in the drawings and are herein described in detail. It
should be understood, however, that these embodiments are not to be limited to the particular form
disclosed, but to the contrary, these embodiments are to cover all modifications, equivalents, and
alternatives falling within the spirit of the disclosure. Furthermore, any es, ons, steps, or
elements of the embodiments may be recited in or added to the claims, as well as negative limitations
that define the inventive scope of the claims by features, functions, steps, or elements that are not
within that scope.
Claims (20)
1. A method for generating and maintaining a magnetic field with a field reversed configuration (FRC) comprising the steps of: g an FRC about a plasma in a confinement chamber, ing a plurality of l beams into the FRC plasma at an angle toward the mid-plane of the confinement chamber, and pumping neutralized gas les accumulating in first and second diametrically opposed divertors d to the confinement chamber with first and second capture vacuum pumps positioned in the first and second divertors and comprising an open sided chamber including an end plate having a surface, two or more sides with surfaces facing each other and an open side, the two or more side plates being coupled to the end plate at a first end of the two or more side plates and extending to an opening defined by a second end of the two or more side plates, wherein the opening ng an area equivalent to the surface of the end plate, wherein the first and second e vacuum pumps having a sticking factor more than four (4) times greater than a sticking factor of a flat plate defining an area equivalent to the opening of the first and second capture pumps, wherein at least one of the two or more sides of the first and second capture vacuum pumps comprising an array of individual capture vacuum pumps, wherein each of the individual e vacuum pumps comprising an end plate having a surface and two or more side plates with surfaces facing each other and coupled to the end plate at a first end of the two or more side plates and extending to an opening defined by a second end of the two or more side plates an open side, wherein the opening defining an area equivalent to the surface of the end plate, wherein each of the individual capture vacuum pumps having a sticking factor greater than a sticking factor of a surface of a flat plate defining an area equivalent to the opening of each of the individual capture vacuum pumps.
2. The method of claim 1, n at least one of the two or more sides of each of the individual capture vacuum pumps comprising a second array of individual capture vacuum pumps.
3. The method of claim 2, wherein each of the individual capture vacuum pumps of the second array comprising an end plate having a surface and two or more side plates with surfaces facing each other and coupled to the end plate at a first end of the two or more side plates and extending to an opening defined by a second end of the two or more side plates, wherein the opening defining an area equivalent to the surface of the end plate, wherein each of the individual capture vacuum pumps of the second array having a sticking factor greater than a sticking factor of a surface of a flat plate defining an area equivalent to the opening of each of the dual capture vacuum pumps of the second array.
4. The method of claim 1, wherein the first and second e vacuum pumps having a sticking factor that is N times greater than a sticking factor of a flat plate ng an area equivalent to the open side of the first and second e pumps, wherein N is 4
5. The method of claim 1, wherein the surfaces of the flat plate and the first and second vacuum pumps includes a film of titanium deposited thereon.
6. The method of claim 4, wherein the surfaces of the flat plate and the first and second vacuum pumps includes a film of titanium deposited thereon.
7. The method of claim 1, further es maintaining the FRC at or about a constant value without decay by injecting beams of fast neutral atoms from neutral beam injectors into the FRC plasma at an angle towards the mid through plane of the confinement chamber.
8. The method of claim 4, further includes maintaining the FRC at or about a constant value without decay by ing beams of fast neutral atoms from neutral beam injectors into the FRC plasma at an angle towards the mid h plane of the confinement chamber.
9. The method of claim 5, further includes maintaining the FRC at or about a constant value without decay by injecting beams of fast neutral atoms from neutral beam ors into the FRC plasma at an angle towards the mid through plane of the confinement chamber.
10. The method of claim 7, further comprising the step of generating a magnetic field within the ement chamber with quasi dc coils extending about the confinement r and a mirror magnetic field within opposing ends of the confinement chamber with quasi dc mirror coils extending about the opposing ends of the confinement chamber.
11. The method of claim 8, r comprising the step of generating a magnetic field within the confinement r with quasi dc coils extending about the confinement chamber and a mirror magnetic field within opposing ends of the confinement chamber with quasi dc mirror coils extending about the opposing ends of the confinement chamber.
12. The method of claim 10, n the step of the forming the FRC includes forming a ion FRC in opposing first and second formation sections coupled to the confinement chamber and accelerating the formation FRC from the first and second formation sections towards the mid through plane of the confinement chamber where the two formation FRCs merge to form the FRC.
13. The method of claim 11, wherein the step of the forming the FRC includes forming a formation FRC in opposing first and second formation sections coupled to the confinement chamber and accelerating the formation FRC from the first and second ion sections towards the mid through plane of the confinement chamber where the two formation FRCs merge to form the FRC.
14. The method of claim 12, wherein the step of g the FRC includes one of forming a ion FRC while accelerating the formation FRC towards the mid through plane of the confinement chamber and forming a formation FRC then accelerating the formation FRC towards the mid through plane of the confinement chamber.
15. The method of claim 12, wherein the step of accelerating the formation FRC from the first and second formation sections towards the mid plane of the ement chamber includes passing the formation FRC from the first and second formation sections through first and second divertors d to opposite ends of the confinement chamber interposing the confinement chamber and a first end of the first and second formation sections.
16. The method of claim 15, wherein the step of passing the formation FRC from the first and second formation sections through first and second divertors includes vating the first and second ors as the formation FRC from the first and second formation ns passes through the first and second divertors.
17. The method of claim 15, further sing the step of guiding magnetic flux surfaces of the FRC into the first and second divertors.
18. The method of claim 14, further comprising the step of guiding magnetic flux surfaces of the FRC into third and fourth divertors coupled to a second end of the first and second formation sections.
19. The method of claim 18, further comprising the step of ting a magnetic field within the formation sections and the third and fourth divertors with quasi-dc coils extending about the formation sections and divertors.
20. The method of claim 17, further comprising the step of generating a magnetic field within the formation sections and first and second divertors with quasi-dc coils extending about the formation sections and divertors. m6 mg WA» mamamxip Mam ,méwmm wmfiwfi maxim “my. "d. meu ‘u‘z 9 3E N Wm {8m} “x ‘smg; :mwaugmaf‘; ggsggsiea WO 85798
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US62/418,119 | 2016-11-04 |
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NZ793595A true NZ793595A (en) | 2022-10-28 |
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