EP0362944A1 - Ionenextraktions- und -beschleunigungseinrichtung in einer abgeschmolzenen Hochfluss-Neutronenröhre mit Hinzufügung einer Hilfselektrode zur Vorbeschleunigung - Google Patents

Ionenextraktions- und -beschleunigungseinrichtung in einer abgeschmolzenen Hochfluss-Neutronenröhre mit Hinzufügung einer Hilfselektrode zur Vorbeschleunigung Download PDF

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Publication number
EP0362944A1
EP0362944A1 EP89202462A EP89202462A EP0362944A1 EP 0362944 A1 EP0362944 A1 EP 0362944A1 EP 89202462 A EP89202462 A EP 89202462A EP 89202462 A EP89202462 A EP 89202462A EP 0362944 A1 EP0362944 A1 EP 0362944A1
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EP
European Patent Office
Prior art keywords
ion
electrode
extraction
acceleration
acceleration electrode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP89202462A
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English (en)
French (fr)
Inventor
Henri Societe Civile S.P.I.D. Bernardet
Xavier Societe Civile S.P.I.D. Godechot
Claude Societe Civile S.P.I.D. Lejeune
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SODERN SA
Koninklijke Philips NV
Original Assignee
SODERN SA
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by SODERN SA, Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical SODERN SA
Publication of EP0362944A1 publication Critical patent/EP0362944A1/de
Withdrawn legal-status Critical Current

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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
    • H05H3/00—Production or acceleration of neutral particle beams, e.g. molecular or atomic beams
    • H05H3/06—Generating neutron beams

Definitions

  • the invention relates to a device for extracting and accelerating the ions of a high flux sealed neutron tube in which an ion source supplies from an ionized gas an ion beam extracted and accelerated at high energy by means of an acceleration electrode and which, projected onto a target electrode produces therein a fusion reaction causing an emission of neutrons as a function of the high value of potential difference existing between said source and said target electrode.
  • Neutron tubes of the same kind are used in techniques for examining matter by fast neutrons, thermal epithermal or cold: neutronography, analysis by activation, analysis by spectrometry of inelastic scatterings or radiative captures, scattering of neutrons etc ...
  • the d (3 H , 4 He ) n fusion reaction delivering 14 MeV neutrons is usually the most used due to its large cross section for relatively low ion energies.
  • the number of neutrons obtained per unit of charge passing through the beam is always increasing as the energy of the ions directed towards a thick target is itself increasing and this largely at the beyond the energies of the ions obtained in the sealed tubes currently available and supplied by a THT not exceeding 250 kV.
  • the erosion of the target by ion bombardment is one of the most determining.
  • Erosion is a function of the chemical nature and structure of the target on the one hand, the energy of the incident ions and their density distribution profile on the impact surface on the other.
  • the target consists of a hydrurable material (Titanium, Scandium, Zirconium, Erbium etc ...) capable of fixing and releasing large quantities of hydrogen without significant disturbance of its mechanical strength; the total quantity set is a function of the target temperature and the hydrogen pressure in the tube.
  • the target materials used are deposited in the form of thin layers, the thickness of which is limited by problems of adhesion of the layer to its support.
  • One way to delay erosion of the target is, for example, to form the absorbent active layer from a stack of identical layers isolated from each other by a diffusion barrier. The thickness of each of the active layers is of the order of the depth of penetration of the deuterium ions coming to strike the target.
  • Another way of protecting the target and therefore of increasing the lifetime of the tube consists in acting on the ion beam so as to improve its density distribution profile on the impact surface. At a constant total ion current on the target, which results in a constant neutron emission, this improvement will result from a distribution as uniform as possible of the current density over the entire surface offered by the target to the ion bombardment. .
  • One of the main causes of the inhomogeneity of the ion bombardment density profile results from the range of high voltages (between 100 and 400 kV) which must be applied between the electrodes of the tube to obtain a high production efficiency. 14 MeV neutrons.
  • the application of these high voltages to the extraction of ions and then to their acceleration by means of ion optics according to the state of the art requires at the level of the emission zone of the source, the use of either a grid or a deep channel limiting the penetration of the electric field inside the ion source.
  • a grid of conventional design cannot be used due to thermal constraints, and the structure of the equipotential lines penetrating inside a deep emission channel results in a significant homogeneity defect in the beam.
  • the interface zone between the ionized gas and the ion beam which is extracted therefrom then presents a concave surface with variable radius of curvature which makes the beam emerging from the source convergent but not laminar of the core type. more halot. This results in an overdensity factor on impact of the beam axis on the target.
  • the object of the invention is to provide a means of modifying the shape of the equipotentials inside the channel, so as to remedy the aforementioned lack of homogeneity.
  • said device further comprises an extraction-pre-acceleration electrode disposed between said ion source and said acceleration electrode and polarized at a value intermediate between that of the ion source and that of the acceleration electrode so as to decouple the ion extraction function from the ion acceleration function and thus obtain that the ionized gas-ion beam interface has a controlled shape varying from ideal flatness to a slight curvature of substantially constant radius, minimizing spherical aberrations and making said beam substantially laminar.
  • the extraction-pre-acceleration electrode In order to maintain its screen efficiency as a fixation of the equipotentials in the extraction and acceleration spaces, several embodiments given below by way of nonlimiting examples are possible.
  • the orifices of the extraction-pre-acceleration electrode are provided with grids of great transparency and of great thickness.
  • the orientation of the large dimension of the solid section of said grid is chosen so that it is parallel to the beam.
  • the materials used are refractory, with low sputtering under ion bombardment and with good thermal conductivity (molybdenum, tungsten, pyrolitic carbon, etc.).
  • the emission ports of the ion source for the same source are multiple.
  • the orifices of the extraction-pre-acceleration electrode are of the same order of magnitude in dimensions and one thus obtains a multi-beam assembly, without interception of the ions: the small dimension of the orifices of the extraction-pre-acceleration electrode allows as for a grid to screen the penetration of potential.
  • FIG. 1 shows the main basic elements of a sealed neutron tube 11 containing a gaseous mixture under low pressure to be ionized such as deuterium-tritium and which comprises an ion source 1 and an acceleration electrode 2 between which there is a very high potential difference allowing the extraction and acceleration of the ion beam 3 and its projection on the target electrode 4 where the fusion reaction takes place resulting in an emission of neutrons at 14 MeV for example.
  • a sealed neutron tube 11 containing a gaseous mixture under low pressure to be ionized such as deuterium-tritium and which comprises an ion source 1 and an acceleration electrode 2 between which there is a very high potential difference allowing the extraction and acceleration of the ion beam 3 and its projection on the target electrode 4 where the fusion reaction takes place resulting in an emission of neutrons at 14 MeV for example.
  • the ion source 1 secured to an insulator 5 for the passage of the THT supply connector is a Penning type source for example, consisting of a cylindrical anode 6, of a cathode structure 7 to which is incorporated a magnet 8 with an axial magnetic field which confines the ionized gas 9 around the axis of the anode cylinder and whose lines of force 10 show a certain divergence.
  • An ion emission channel 12 is formed in said cathode structure opposite the anode.
  • FIG. 2a shows the profile of the density J of bombardment of the ions in any radial direction 0r, from the point of impact 0 of the central axis of the beam on the surface of the target electrode for standard ion optics at a single electrode.
  • the shape of this profile highlights the inhomogeneous nature of this beam whose very high density in the central part decreases quickly when one moves away from it.
  • erosion takes place as a function of the bombardment density and the entire layer of hydrurable material of thickness e deposited on a substrate S is saturated with a deuterium-tritium mixture.
  • the depth of penetration of the deuterium-tritium energy ions represented in dotted lines is effected over a depth which is a function of this energy.
  • the erosion of the layer is such that the penetration depth l2 is greater than the thickness e in the most bombarded part; a part of the incident ions is implanted in the substrate and very quickly the atoms of deuterium and tritium are in supersaturation.
  • the cylindrical anode 6 is brought to a higher potential of the order of 4 kV than that of the cathode 7 itself brought to a very high voltage of 250 kV for example, positive with respect to the envelope of the tube.
  • the plasma ions are extracted from the source by the extraction-acceleration electrode 2 brought to the potential 0 of the mass, through the emission channel 12 formed in the cathode which thus plays the role of emission electrode .
  • the ion beam 3 thus formed bombards the target 4 also grounded.
  • the high potential difference between the emission and extraction-acceleration electrodes causes a strong penetration of the equipotentials inside the emission orifice 12.
  • the emission meniscus at the ionized gas-beam interface The ions then appear as a concave surface with a variable local radius of curvature. This results in aberrations in the space of extraction of the ions from the beam, such that all of the ions do not all focus at the same point on the axis of the beam, but in a succession of points spread over a certain range ⁇ f, which causes the bombardment of the target to be non-uniform.
  • the idea of the invention shown diagrammatically in FIG. 3 consists in interposing between the source 1 and the acceleration electrode 2 an extraction-pre-acceleration electrode 13 brought to a potential close to that of the emission electrode, for example +235 kV.
  • the small potential difference of 15 kV between the two electrodes tends to greatly attenuate and even eliminate the effect of penetration of the equipotentials into the emission orifices.
  • the ions are then extracted in a direction parallel to the axis of the beam, that is to say perpendicular to the equipotentials theoretically forming almost planar and parallel surfaces between the electrodes.
  • the result is a flat or slightly spherical shape of the emission meniscus at the ionized gas-ion beam interface.
  • the beam from this interface is laminar, that is to say that at any point of its volume it is transmitted only one trajectory. This laminarity character is preserved when it is focused under the effect of the high potential difference between the extraction-pre-acceleration 13 and acceleration 2 electrodes; it is the same during its impact on the target.
  • the parallelism of the beam requires that the quantity of ions that the source can deliver is roughly equivalent to the quantity of ions that can extract and accelerate under these conditions the ionic optics itself constituted by the electrodes.
  • the set of two ion source-ion optical elements must be suitably adapted to each other, according to well-known physical laws. Such an adaptation condition results in a potential difference of a few tens of kV between the extraction-pre-acceleration electrode and the source for the usual currents available, for acceleration voltages greater than 200 kV.
  • One can for example as indicated on the fiqure 4 provide a grid 14 the pre-acceleration extraction electrode 13 in order to obtain an electrostatic screen effect. But under the action of ion bombardment, this grid will heat up, hence the need to give it a large thickness to improve its thermal conductivity and to make it from a refractory material.
  • the solid section of the grid will be oriented to minimize interception of ions and therefore will be parallel to the beam.
  • FIG. 5 Another solution shown diagrammatically in FIG. 5 consists in having multiple emission orifices 15 of a few millimeters in unit diameter at the level of the ion source 1 and in aligning them with corresponding orifices 16 formed in the extraction electrode -preacceleration 13. This avoids the interception of ions by this electrode and therefore its heating while retaining the benefit of the screen effect.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Particle Accelerators (AREA)
  • Electron Sources, Ion Sources (AREA)
EP89202462A 1988-10-07 1989-10-02 Ionenextraktions- und -beschleunigungseinrichtung in einer abgeschmolzenen Hochfluss-Neutronenröhre mit Hinzufügung einer Hilfselektrode zur Vorbeschleunigung Withdrawn EP0362944A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8813184A FR2637723A1 (fr) 1988-10-07 1988-10-07 Dispositif d'extraction et d'acceleration des ions dans un tube neutronique scelle a haut flux avec adjonction d'une electrode auxiliaire de preacceleration
FR8813184 1988-10-07

Publications (1)

Publication Number Publication Date
EP0362944A1 true EP0362944A1 (de) 1990-04-11

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EP89202462A Withdrawn EP0362944A1 (de) 1988-10-07 1989-10-02 Ionenextraktions- und -beschleunigungseinrichtung in einer abgeschmolzenen Hochfluss-Neutronenröhre mit Hinzufügung einer Hilfselektrode zur Vorbeschleunigung

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US (1) US5130077A (de)
EP (1) EP0362944A1 (de)
JP (1) JPH02144900A (de)
FR (1) FR2637723A1 (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6441569B1 (en) 1998-12-09 2002-08-27 Edward F. Janzow Particle accelerator for inducing contained particle collisions
CN105873350A (zh) * 2016-06-07 2016-08-17 中国工程物理研究院核物理与化学研究所 一种扫描微焦靶
CN105869693A (zh) * 2016-06-07 2016-08-17 中国工程物理研究院核物理与化学研究所 一种中子源
CN105848401A (zh) * 2016-06-07 2016-08-10 中国工程物理研究院核物理与化学研究所 一种等效微焦靶
CN105848402A (zh) * 2016-06-07 2016-08-10 中国工程物理研究院核物理与化学研究所 一种扫描靶

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3569756A (en) * 1964-08-18 1971-03-09 Philips Corp Ion source having a plasma and gridlike electrode
US3581093A (en) * 1968-04-23 1971-05-25 Kaman Sciences Corp Dc operated positive ion accelerator and neutron generator having an externally available ground potential target
US3664960A (en) * 1968-02-02 1972-05-23 Nat Res Dev Control circuit for neutron generator tube
NL7707357A (en) * 1977-07-04 1979-01-08 Philips Nv Anode for neutron generator ion source - has holes aligned to outlets in cathode converging beams on target
US4447773A (en) * 1981-06-22 1984-05-08 California Institute Of Technology Ion beam accelerator system
EP0230290A2 (de) * 1986-01-21 1987-07-29 Leybold Aktiengesellschaft Verfahren zum Herstellen von Extraktionsgittern für Ionenquellen und durch das Verfahren hergestellte Extraktionsgitter

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3015032A (en) * 1959-03-23 1961-12-26 Jersey Prod Res Co Radiation generating device
GB981297A (en) * 1963-01-14 1965-01-20 Atomic Energy Authority Uk Apparatus for carrying out a nuclear reaction
NL289180A (de) * 1965-03-11
JPS60170141A (ja) * 1984-02-13 1985-09-03 Toshiba Corp イオン源装置

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3569756A (en) * 1964-08-18 1971-03-09 Philips Corp Ion source having a plasma and gridlike electrode
US3664960A (en) * 1968-02-02 1972-05-23 Nat Res Dev Control circuit for neutron generator tube
US3581093A (en) * 1968-04-23 1971-05-25 Kaman Sciences Corp Dc operated positive ion accelerator and neutron generator having an externally available ground potential target
NL7707357A (en) * 1977-07-04 1979-01-08 Philips Nv Anode for neutron generator ion source - has holes aligned to outlets in cathode converging beams on target
US4447773A (en) * 1981-06-22 1984-05-08 California Institute Of Technology Ion beam accelerator system
EP0230290A2 (de) * 1986-01-21 1987-07-29 Leybold Aktiengesellschaft Verfahren zum Herstellen von Extraktionsgittern für Ionenquellen und durch das Verfahren hergestellte Extraktionsgitter

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Publication number Publication date
FR2637723A1 (fr) 1990-04-13
US5130077A (en) 1992-07-14
JPH02144900A (ja) 1990-06-04

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