US2797322A - Magnetic induction electron accelerator - Google Patents

Magnetic induction electron accelerator Download PDF

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Publication number
US2797322A
US2797322A US374930A US37493053A US2797322A US 2797322 A US2797322 A US 2797322A US 374930 A US374930 A US 374930A US 37493053 A US37493053 A US 37493053A US 2797322 A US2797322 A US 2797322A
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voltage
expansion
phase
condenser
electron
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Expired - Lifetime
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US374930A
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English (en)
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Arx Arnold Von
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BBC Brown Boveri AG Germany
BBC Brown Boveri France SA
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BBC Brown Boveri France SA
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H11/00—Magnetic induction accelerators, e.g. betatrons

Definitions

  • the present invention relates to electron accelerators and in particular to those of the magnetic induction type wherein electron streams are accelerated on a generally circular orbit within an evacuated tube under the combined influence of a magnetic field varying with time and which field has two components.
  • One component of the field known as the acceleration flux which passes through the tube inside of the orbit causes the electron stream to be accelerated.
  • the other component, known as the control flux passes through the tube at the orbit and functions to maintain the electron stream on the orbit.
  • the electrons are conducted out each time at the end of an acceleration period, for example, by an enlargement of the equilibrium circuit (expansion) out of the circular path passed through during the acceleration and, for example, for the production of X-ray radiation, they are directed to an anticathode.
  • the expansion is efiected mostly by changing the relationship between the magnetic flux accelerating the electrons and the control flux retaining the electrons on the circular path.
  • These two fluxes can be produced by a single exiter coil fed from alternating current mains.
  • a special coil expansion coil
  • the feeding of the expansion coil takes place by way of brief current impulses which are switched in at the desired moment.
  • the present invention relates to a device for production of expansion impulses for an induction accelerator workice ing in this way.
  • both the instant corresponding to the desired electron energy and also the inherent amplitude of the expansion impulse are adjusted.
  • any arbitrary electron energy can be attained between zero and its maximum value.
  • the device according to the invention contains an expansion coil which encompasses the acceleration flux of the induction accelerator and a condenser which is connected each time with the expansion coil over one of two thyratrons switched in parallel with opposite conducting direction.
  • Fig. 1 is a condensed schematic electrical diagram showing the general arrangement of the principal circuit components and their connection used to attain the objective;
  • Figs. 2 and 3 are graphs showing the variation with time of the voltage components involved as well as a plot of the expansion current pulses
  • Fig. 4 is a graph showing the variation with time of the two components of the voltage applied to the grid of one of the thyratrons
  • Fig. 5 is an electrical circuit diagram illustrating one suitable arrangement in accordance with the invention for obtaining the voltage pulses utilized to fire or ignite the thyratron tubes which control flow of current pulses to the expansion coil;
  • Fig. 6 is a vector diagram showing the phase relationship between the voltage components which make up the phase shifting device utilized in the invention.
  • Fig. 7 is a plot of the voltage curve used to control ignition of one of the thyratron tubes.
  • Fig. 1 which illustrates an application of the invention to a magnetic induction accelerator of conventional construction
  • the magnetic field structure thereof, indicated at 10 is made up of steel laminations of appropriate contour to produce a pair of cylindrical poles 11-11 separated by an air gap 12 and located concentrically along axis a-a, and a pair of concentric annular poles 13-13' facing one another and separated by air gap 14.
  • Yoke members'15 complete the magnetic circuit for a cyclically varying flux set up in the cylindrical and annular poles.
  • Poles 11-11 and 13-13' are surrounded by an annular winding which may as shown be split into two coil sections 16-16 connected in series for energization from a source of alternating current of suitable frequency as for example cycles/sec. applied to terminals 17.
  • An evacuated glass tube 18 rests in the air gap 14 between the poles 1313' and thereby surrounds the axial poles 11-11'.
  • an electron emissive cathode which can be of the thermionic type such as illustrated by the coiled filament 20, the axis of which is placed parallel to axis a-a.
  • the electron stream to be accelerated is produced at the cathode by energizing means actuated in timed relation with the time-varied alternating current input at terminals 17 to effect emission of an electron stream from the cathode at the begining of each half of the flux wave produced by such current.
  • the electron stream After the electron stream has been accelerated to its final velocity along the circular orbit k, which occurs when the magnetic flux approaches or reaches its peak value, it can be caused to impinge upon an anti-cathode 21 to produce X-rays, or the stream can be removed for other uses. Since an electron stream is injected at the beginning of each half of the magnetic flux cycle two electron streams will be produced for each complete flux cycle and these are accelerated in opposite directions around the orbit k in succession.
  • This invention is directed to an improved arrangement for removing the electron streams of opposite accelerating directions from the orbit k utilizing a coil L which is applied to the central poles 1111 and thus surrounds only the acceleration component of the flux produced by the winding 16-16.
  • Coil L is pulsed at a selected instant during the accelerating period of one electron stream and near the close of the accelerating period of the other electron stream and the effect of the pulsing is to upset the ratio between the accelerating and control flux components normally maintained during the accelerating phase to keep the electron stream moving around an orbit of substantially constant radius.
  • a condenser C is connected with the coil L through switching means comprising a pair of grid controlled gas discharge tubes V1V2 known as thyratrons arranged in parallel in back-to-front relation. Since these tubes will conduct current in one direction only, the baek-to-front connection enables one to discharge condenser C through coil L once in each half cycle in alternate directions by appropriate control over their grids as will be explained hereinafter in more detail.
  • these expansion pulses are produced by discharging condenser C through coil L first in one direction and then the other via thyratrons V1, V2 which are fired or ignited in alternation.
  • the condenser discharge process exhibits the form of a weakly damped oscillation as a result of losses existing in the circuit which is interrupted after its first half period because the thyratron permits current flow in only one direction.
  • Each discharge of condenser C thus produces a brief current impulse in the expansion coil L.
  • Fig. 2 shows that a first discharge of the condenser C over the coil L occurs by ignition of the thyratron V1 at the phase a1.
  • the voltage Uc at the condenser C has the value Ur.
  • the coil L shows a voltage U2 produced by the acceleration flux. Since the half period of the free oscillation is passed practically free of loss, the voltage differences a and b are almost equally large.
  • the voltage on the condenser remains at the value U3. Somewhat later, the voltage induced in the coil L also reaches the value U3.
  • the size of A is chosen according to the invention so that the amplitude of the expansion impulse for the first ray or electron stream obtains just the right value proportional to the control flow at the moment of the expansion.
  • the difference between the voltages U1 and U1. (oil) has to be proportional in this to the control flow, i. e. it must be proportional to sin a1.
  • Fig. 3 shows a period of the processes already depicted in Fig. 2, drawn on a larger scale. It can be seen from this, that for the value a, which should be proportional to sin on, apart from the proportionality factors there applies:
  • the grid voltage Uez for the thyratron V2 consists of the components )1 and f2. In this,
  • a device for the production of the grid voltage for the thyratron V2 is contained in the embodiment shownin Fig. 5.
  • the component fl is obtained as a sum, firstly the amount 2.00s a from the secondary side (S1+S2) of the transformer T1, secondly the amount 1 which, for its part, is produced to the peak value by the rectification of the amount cos a from the secondary winding S2 in the rectifier G1 and charge of the condenser C1, and thirdly the amoun ⁇ /2 sin (a,+45), which is produced to the peak value by the rectification of the amount ⁇ /l.sin (a,+45).sin (t-Ot +'y) from the winding S1 of the transformer T2 in the rectifier G2 and charge of the condenser C2.
  • a voltage is conducted whose amplitude E is changed by arbitrary adjustment of the phase shifter P to the desired value of a, according to the function:
  • the component in is obtainedby a combination of the resistance R2 effecting a phase shift, and of the condenser C3, from the amount 2.cos on of the secondary side (s,+s,) of the transformer T1.
  • the rectifier G4 prevents the occurrence of positive values of the component f2 forming on the resistance R3.
  • the phase shifter P through Whose activation the phase a, of the first expansion impulse and thereby the desired electron energy is adjusted in the first ray, is produced by the voltage conducted to the primary side of the transformer T2 as the sum of a voltage E1 with fixed phase and a voltage E2 of the same amplitude with variable phase (Fig. 6).
  • the phase angle of the voltage E2 has to be changed over a range of 180 if the phase a, of the expansion impulse is to be shifted in the range between 0 and 90.
  • the phase shifter supplies a voltage of the form:
  • a device for the production of the grid voltage for the thyratron V1 is also contained in the embodiment shown in Fig. 5.
  • the grid voltage appears as sum of the constant amount sin (a,+45), which is obtained from the winding s, of the transformer T2 by rectification in the rectifier G and charging of the condenser C4 to the peak value, and the amount which originates from the windings (s +s,) of the transformer T2.
  • said means for producing ex pansion pulses for effecting a removal of said electron streams from said orbit following their acceleration comprising, an expansion coil surrounding only said central core portion and which is inductively coupled with said main Winding so as to cause an alternating voltage to be induced therein, a condenser, first and second grid controlled gaseous discharge valves connected in parallel in back-to-front relation, means connecting said expansion coil, condenser and paralleled valves in series, and means producing grid voltages for effecting ignition of said valves in alternation in timed relation with the phase of said magnetic field wave to thereby discharge said condenser alternately in opposite directions through said expansion coil and change the ratio between said accelerating and control components of said magnetic r field thereby to remove said streams of electrons from said orbit, said means for producing the grid control voltage for said first valve associated with removal of the electron stream introduced at phase or equal to 0 comprising a phase shifting device fed from the same source as that feeding said main winding, a first
  • Induction type electron accelerator apparatus as defined inrclaim 1 wherein the grid element of said first valve is directly connected to one side of the secondary of said first transformer, the cathode element of said firstvalve is connected to the other side of the secondary of said first transformer through a condenser, and said condenser is bridged by a rectifier connected to a tap on said secondary.
US374930A 1952-08-19 1953-08-18 Magnetic induction electron accelerator Expired - Lifetime US2797322A (en)

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CH749851X 1952-08-19

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US (1) US2797322A (xx)
CH (1) CH304532A (xx)
DE (1) DE939890C (xx)
FR (1) FR1094864A (xx)
GB (1) GB749851A (xx)
NL (2) NL93826C (xx)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3975689A (en) * 1974-02-26 1976-08-17 Alfred Albertovich Geizer Betatron including electromagnet structure and energizing circuit therefor
US4577156A (en) * 1984-02-22 1986-03-18 The United States Of America As Represented By The United States Department Of Energy Push-pull betatron pair
US20090153279A1 (en) * 2007-12-14 2009-06-18 Schlumberger Technology Corporation Single drive betatron
US20100148705A1 (en) * 2008-12-14 2010-06-17 Schlumberger Technology Corporation Method of driving an injector in an internal injection betatron

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2480169A (en) * 1946-10-26 1949-08-30 Gen Electric Apparatus for imparting high energy to charged particles
US2535710A (en) * 1942-06-17 1950-12-26 Gen Electric Controller for magnetic induction accelerators
US2538718A (en) * 1946-08-06 1951-01-16 Bbc Brown Boveri & Cie Magnetic induction device for accelerating electrons
US2654838A (en) * 1947-09-06 1953-10-06 Bbc Brown Boveri & Cie Impulse circuit
US2754419A (en) * 1951-06-29 1956-07-10 Bbc Brown Boveri & Cie Magnetic induction accelerator

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2331788A (en) * 1942-01-20 1943-10-12 Gen Electric Magnetic induction accelerator
US2394070A (en) * 1942-06-02 1946-02-05 Gen Electric Magnetic induction accelerator
US2394072A (en) * 1943-09-10 1946-02-05 Gen Electric Electron accelerator control system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2535710A (en) * 1942-06-17 1950-12-26 Gen Electric Controller for magnetic induction accelerators
US2538718A (en) * 1946-08-06 1951-01-16 Bbc Brown Boveri & Cie Magnetic induction device for accelerating electrons
US2480169A (en) * 1946-10-26 1949-08-30 Gen Electric Apparatus for imparting high energy to charged particles
US2654838A (en) * 1947-09-06 1953-10-06 Bbc Brown Boveri & Cie Impulse circuit
US2754419A (en) * 1951-06-29 1956-07-10 Bbc Brown Boveri & Cie Magnetic induction accelerator

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3975689A (en) * 1974-02-26 1976-08-17 Alfred Albertovich Geizer Betatron including electromagnet structure and energizing circuit therefor
US4577156A (en) * 1984-02-22 1986-03-18 The United States Of America As Represented By The United States Department Of Energy Push-pull betatron pair
US20090153279A1 (en) * 2007-12-14 2009-06-18 Schlumberger Technology Corporation Single drive betatron
US7638957B2 (en) * 2007-12-14 2009-12-29 Schlumberger Technology Corporation Single drive betatron
US20100148705A1 (en) * 2008-12-14 2010-06-17 Schlumberger Technology Corporation Method of driving an injector in an internal injection betatron
US8362717B2 (en) 2008-12-14 2013-01-29 Schlumberger Technology Corporation Method of driving an injector in an internal injection betatron

Also Published As

Publication number Publication date
GB749851A (en) 1956-06-06
CH304532A (de) 1955-01-15
DE939890C (de) 1956-03-08
NL93826C (xx)
FR1094864A (fr) 1955-05-25
NL180627B (nl)

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