EP0340832B1 - Abgedichtete Hochfluss-Neutronenröhre - Google Patents

Abgedichtete Hochfluss-Neutronenröhre Download PDF

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Publication number
EP0340832B1
EP0340832B1 EP89201010A EP89201010A EP0340832B1 EP 0340832 B1 EP0340832 B1 EP 0340832B1 EP 89201010 A EP89201010 A EP 89201010A EP 89201010 A EP89201010 A EP 89201010A EP 0340832 B1 EP0340832 B1 EP 0340832B1
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EP
European Patent Office
Prior art keywords
tube
neutron tube
neutron
target
ion source
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.)
Expired - Lifetime
Application number
EP89201010A
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English (en)
French (fr)
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EP0340832A1 (de
Inventor
Serge Société Civile S.P.I.D. Cluzeau
Gérard Société Civile S.P.I.D. Verschoore
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 EP0340832A1 publication Critical patent/EP0340832A1/de
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Publication of EP0340832B1 publication Critical patent/EP0340832B1/de
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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

  • a sealed, high flux neutron tube with improved service life and reliability contains a deuterium-tritium gas mixture, in which an ion source provides a high energy beam projected onto a target to produce a fusion reaction therein. generating a neutron emission, said neutron tube comprising a first part and a second part separated by means of an acceleration electrode forming a screen between said parts, said first part containing the ion source brought to a positive potential and said second part containing the target brought to a negative potential with respect to the zero value of the potential of said acceleration electrode grounded by the external envelope of the tube of which it is integral.
  • High flux sealed neutron tubes are used in fast, thermal, epithermal or cold neutron examination techniques.
  • the tubes currently available have an insufficient lifetime at the level of the emission necessary to obtain their full effectiveness in the various nuclear techniques: neutronography, analysis by activation, analysis by ⁇ spectrometry of inelastic diffusions or radiative captures, neutron scattering. ..
  • T (d, n) 4He reaction delivering 14 MeV neutrons is usually the most used due to its large cross-section for relatively low deutron energies but any other reaction considered adequate can be used.
  • Another risk of initiating discharges in the gas results from the surface effect of the electrodes subjected to a high electric field. This effect is initiated by electric particles emitted from a part of the negative potential tube playing the role of cathode placed opposite another part of the positive potential tube and therefore behaving like an anode and which should not be confuse with parts of the tube having identical names such as for example the anode and the cathode of the ion source. These particles coming to strike other molecules of matter in the gas or on the electrodes can cause by secondary emission a certain amplification of the emission and thus arrive step by step to an electric current sufficiently important to establish a breakdown by rupture of qualities dielectric of the medium, either on the surface of the insulating parts of the tube, or through the gas space of the tube itself.
  • the resistance to breakdown on the surface of the insulators is markedly improved on the one hand by increasing the inter-electrode distances and by dividing the tube into two parts respectively constituting the anode and the cathode so as to reduce the potential by half in each part of the tube and on the other hand by giving the insulating parts a suitable inclination relative to the direction of the electric field (see for example the article entitled “Metal / ceramic X-ray tubes for non-destructive testing "by W.Harth et al. published in Philips Technical Review, vol.41, 1983/1984, N ° 1, pages 24-29).
  • the values of the cold emission current density calculated by the Fowler-Nordheim formula show, according to the surface conditions of the electrodes, a high amplification coefficient of this current density for a given potential difference. As a result, a small voltage variation can produce a strong growth or a sharp decrease in the current depending on the direction of this variation. Qualitatively, there is such a high sensitivity of the current to the voltage for all the parasitic phenomena leading to the existence of a current between the electrodes.
  • the object of the invention is to provide a neutron tube device supplied at voltages much higher than 200 kV and allowing, with satisfactory maintained reliability, the increase in the lifetime mentioned above.
  • the device of the invention is remarkable in that said positive and negative potentials are both of adjustable value.
  • the intensity of the ion beam is reduced by the possibility of doubling the potential difference between source and target without increasing the risks of initiation in the deuterium-tritium mixture by collision of the ions with the gas molecules, because the material separation of said neutron tube into two parts by means of said screen keeps unchanged the travel distances of the ions in each of said parts. It is remarkable that this arrangement allows a significant reduction in the critical value of the product p ⁇ d along the electric field lines joining the electrodes.
  • said external envelope and said ion source respectively constitute the cathode and the anode of said first part of the tube on the one hand
  • said target and said external envelope respectively constitute the cathode and the anode of said second part of the tube on the other hand.
  • Said cold emission currents thus developed in each of said parts of the tube by surface effect of the facing electrodes are assigned a high reduction factor of up to 106 depending on the nature and the surface condition of said electrodes, because the difference from potential required for the acceleration of the ion beam is distributed in halves between said first and second parts of the tube.
  • a deuterium-tritium neutron tube which comprises a first part containing an ion source and a second part containing a target, separated by an electrode of acceleration grounded by the outer envelope of the tube of which it is integral, the ion source being brought to a positive potential and the target to a negative potential.
  • the distribution of the overall potential difference of the tube can be asymmetrical between the two parts of the tube - either because of the applied potentials, or because of the geometric distances separating the electrodes - which gives the interesting possibility of varying the spaces of acceleration between the separating electrode and the ion source on the one hand and between this same electrode and the target on the other hand, so as to better control the focusing of the ion beam in order to improve the lifetime of the tube .
  • Figures 1 and 2 show respectively in longitudinal section, a first and a second variant of neutron tubes according to the prior art.
  • Figures 3 and 4 respectively show the same longitudinal section of a first and a second variant of neutron tubes according to the invention.
  • an envelope 1 contains a gaseous mixture of deuterium and tritium coming from a reservoir 2. This mixture is ionized in the ion source 3 brought to ground potential. An ion beam 4 is extracted therefrom by the acceleration electrode 5 secured to the target 6 and brought to the negative potential of very high voltage (-THT).
  • the wall part 7 opposite the acceleration space is necessarily made of an insulating material.
  • the path metallic sprays from the ion source delimits the zone 8 of this part of the wall exposed to metallization, which constitutes the major drawback of this first variant.
  • the ion source 9 is brought to a positive very high voltage potential + THT via the cable 10, the end of which is surrounded by the insulating sleeves 11 and 12 between which is provided a space intended to allow the circulation of an insulating cooling fluid.
  • the acceleration electrode 13 cooled at 14 by a liquid circuit is brought to ground potential which enables it to be made integral with the metal wall 15. This arrangement which avoids metal spraying on the insulating parts of the tube constitutes the nearest prior art.
  • the gaseous mixture of deuterium and tritium is supplied via a pressure regulator 16.
  • the gas pressure is controlled using an ionization pressure gauge 17.
  • the ion source 9 of the Penning type in the example described (but which could be of a different type without harming the invention) comprises an anode 18 to which the potential + THT is applied, two cathodes 19 and 20 brought to a same negative potential of the order of 5 kV relative to the anode 18 and a permanent magnet 21 creating an axial magnetic field and the magnetic circuit of which is closed by the ferromagnetic socket 22 which envelops the ion source 9.
  • the ion beam 23 extracted from the ion source passes through the suppressor electrode 24 and strikes the target 25 cooled at 26 by a circulation of a liquid.
  • Breakdown phenomena can occur in the enclosure of a gas tube under the effect of high voltage applied between the electrodes and whose initiation process in the case of the neutron tube of Figure 2 is as follows.
  • the envelope of the ion source 9 constituted by the magnetic circuit 22 is at a high positive potential relative to that of the envelope 15 of the tube brought to the zero potential of the mass.
  • the envelope 22 of the ion source will therefore play the role of an anode and the envelope 15 of the neutron tube will play the role of a cathode at the level of which a macroscopic electric field develops.
  • the micro-asperities presented on the surface of this cathode are capable, according to their geometry, of microscopically amplifying the value of this field; there is then the possibility of cold emission of electrons.
  • This electronic current also causes ionization of the molecules of the gas contained in the tube. This results in an avalanche effect which risks leading to an accidental short circuit, that is to say a breakdown between electrodes.
  • the amplification factor ⁇ can be estimated from curves according to the shape of the end of the microspheres (spherical, ellipsoidal) and their height h above the surface of the electrode.
  • ⁇ ⁇ 102 for a ratio h / r 102, r being the radius of a microasperity whose end is spherical in shape.
  • the cold emission current density J is given as a function of the microscopic field E for different values of the output work W varying from 1.6 to 5 eV.
  • the output work is 2.5 eV.
  • the macroscopic electric field is of the order of 2105 V / cm in the usual neutron tubes. If we accept an amplification factor of 102 caused by the existence of micro-roughness we find a cold emission current density of the order of 4 103 ⁇ A / ⁇ m2. For a macroscopic electric field of 105V / cm, that is to say reduced by half, the density of the cold emission current becomes approximately 3.10 ⁇ 3 ⁇ A / ⁇ m2, that is to say that it is reduced in a ratio close to 106. This considerable reduction practically eliminates the risks of original F-N breakdown between electrodes and thus ensures good reliability of the tube.
  • the device of the invention provides the best possible compromise between the lifetime and reliability of a neutron tube by making it possible to increase the acceleration voltage of the ion beam while maintaining the electric field values between acceptable values. the tube electrodes.
  • Figure 3 shows the diagram of a first variant of this device which is presented as two parts similar to the part of the tube of Figure 2 between the accelerator electrode 13 and the THT supply cable 10.
  • One of these parts always contains the ion source 18, 19, 20, 21 inside the envelope 15 while the other part contains the suppressor electrode 27 and the target 28 inside the envelope 15 ′.
  • These two parts are joined by their face having the acceleration electrode 13 which is common to them and therefore arranged symmetrically with respect to the median plane of this electrode.
  • the elements of the first part of the tube identical to those of Figure 2 are indicated by the same reference numbers.
  • the elements of the second part of the tube having a character of symmetry with respect to those of said first part are indicated by the same reference number assigned to the sign ′: thus 10 and 10 ′ for the cable, ... 22 and 22 ′ For the ferromagnetic socket.
  • the pressure regulator 16 and the ionization manometer 17 are carried over to the end of this second part of the tube comprising the target.
  • FIG. 2 allows the tube to be fed by means of a single positive polarity, ie + V.
  • FIG. 3 allows the use of a generator with two polarities + V transmitted to the ion source by the cable 10 and - V transmitted to the target by the cable 10 ′. These two polarities are referenced with respect to the mass to which the accelerator electrode 13 is attached, integral with the outer envelopes 15 and 15 ′.
  • the electric fields at the cathode 15 of the first part of the tube on the one hand and at the cathode 22 ′ of the second part of the tube on the other hand are maintained at values compatible with acceptable reliability, so that the potential difference regulating the acceleration is equal to 2V in order to increase the service life of the tube by reduction of the target current, as already mentioned above.
  • Such a mode of supply of the neutron tube making it possible to double the difference in the potential of acceleration of the ion beam thus offers the possibility of compensating for the reduction in the neutron emission which would have resulted only from the reduction of the target current.
  • the device of the invention has an additional advantage from the point of view of reliability by the fact that the reduction in the target current is obtained by a correlative reduction in the current of the ion source by means of a reduction in the operating pressure.
  • This same device also makes it possible to reduce sprays originating from the ion source, as well as those resulting from parasitic ionizations on the path of the beam.
  • the accelerating electrode 13 also plays the role of a "screen" between the ion source and the target, which appreciably reduces the possible paths of the ions in the gas and therefore further limits the risks of breakdown in the prospect of even greater reliability.
  • the symmetrical feeding mode of the neutron tube offers another interesting possibility which is to be able to vary the acceleration spaces between the two parts of the tube and thus to achieve an ion optic making it possible to improve the adjustment of the focusing of the beam. . This amounts to reacting to the electric field values in each part of the tube.
  • the envelope 1 which is cathode.
  • This envelope constituting the outer wall of the tube has a high radius of curvature and an electric field E1 is developed between this envelope and the envelope 11 of the ion source playing the role of anode.
  • the envelope 11 ′ of the target which is cathode.
  • This envelope has a radius of curvature smaller than that of the wall because it is inside the tube and an electric field E2 is developed between this envelope and the external envelope 1 ′ of the tube playing the role of anode.
  • a second variant of the device of the invention shown schematically in Figure 4 defines the geometry of the insulating walls of the neutron tube so as to minimize the effect of "flash-over" along said walls. This effect is manifested by successive secondary emissions which develop on the surface of the insulator from the impact of a particle coming to strike this surface. This results in a damaging surface effect for the insulation which can be counteracted by tilting the insulating surfaces at an angle to the electric field so that rebounding does not occur.
  • the geometry of the insulators can be different depending on the polarity.
  • the second part of the neutron tube containing the target is identical to that of FIG. 3.
  • the content of the ferromagnetic socket 11 is also identical to that of FIG. 3.
  • the insulating sleeves 12 ′ and 12 ⁇ which correspond in the active areas of the tube have their surfaces inclined at a certain angle relative to the direction of the ionic flow indicated by the arrow 29.
  • the sleeve 11 ⁇ of the cable 10 ⁇ supplying the THT anode has been designed to adapt to this arrangement.

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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)

Claims (5)

  1. Abgedichtete Hochfluß-Neutronenröhre mit einer gasförmigen Deuterium/Tritiummischung, in der die Ionenquelle (9) ein Bündel mit hoher Energie liefert, das auf ein Target (28) projiziert wird, um dort eine Fusionsreaktion zu erzeugen, die eine Neutronenemission auslöst, wobei die Neutronenröhre einen ersten Teil und einen zweiten Teil enthält, die durch eine Beschleunigungselektrode (13) voneinander getrennt sind, die einen Schirm zwischen diesen Teilen bildet, wobei der erste Teil die Ionenquelle auf einem positiven Potential und der zweite Teil das Target auf einem negativen Potential in bezug auf den Nullwert des Potentials der Beschleunigungselektrode enthält, die durch die externe Röhrenhülle an Masse gelegt wird, mit der sie verbunden ist, dadurch gekennzeichnet, daß die positiven und negativen Potentiale je einen regelbaren Wert haben.
  2. Neutronenröhre nach Anspruch 1, dadurch gekennzeichnet, daß die elektrischen Felder in den ersten und zweiten Teilen der Neutronenröhre sich auf unsymmetrische Weise durch die angelegten positiven und negativen Potentiale verteilt sind.
  3. Neutronenröhre nach Anspruch 1, dadurch gekennzeichnet, daß die elektrischen Felder in den ersten und zweiten Teilen der Neutronenröhre durch die geometrischen Abstände zum Trennen der Elektroden unsymmetrisch verteilt sind, die für den ersten Teil der Röhre die Kathode durch die externe Hülle (15) und die Anode für die Ionenquelle (9) und für den zweiten Teil der Röhre die Kathode durch das Target (28) und die Anode durch die externe Hülle (15') bilden.
  4. Neutronenröhre nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die ersten und zweiten Teile der Neutronenröhre in bezug auf einer Medianebene durch die Beschleunigungselektrode, die den Schirm bildet, symmetrisch angeordnet sind.
  5. Neutronenröhre nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Oberflächen der Isolierwände (12', 12''), die in jedem der ersten und zweiten Teile der Neutronenröhre miteinander übereinstimmen, eine geneigte Stellung in der gleichen Richtung in bezug auf die Richtung des Ionenbündels haben.
EP89201010A 1988-04-26 1989-04-20 Abgedichtete Hochfluss-Neutronenröhre Expired - Lifetime EP0340832B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8805510A FR2630576B1 (fr) 1988-04-26 1988-04-26 Dispositif d'amelioration de la duree de vie et de la fiabilite d'un tube neutronique scelle a haut flux
FR8805510 1988-04-26

Publications (2)

Publication Number Publication Date
EP0340832A1 EP0340832A1 (de) 1989-11-08
EP0340832B1 true EP0340832B1 (de) 1993-12-29

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EP89201010A Expired - Lifetime EP0340832B1 (de) 1988-04-26 1989-04-20 Abgedichtete Hochfluss-Neutronenröhre

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US (1) US5053184A (de)
EP (1) EP0340832B1 (de)
JP (1) JPH0213900A (de)
DE (1) DE68911741T2 (de)
FR (1) FR2630576B1 (de)

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Publication number Priority date Publication date Assignee Title
GB9825402D0 (en) 1998-11-19 1999-01-13 Pfizer Ltd Antiparasitic formulations
US6441569B1 (en) 1998-12-09 2002-08-27 Edward F. Janzow Particle accelerator for inducing contained particle collisions
HUP0500984A3 (en) 2001-09-17 2007-02-28 Lilly Co Eli Synergetic pesticidal formulations
US6975072B2 (en) * 2002-05-22 2005-12-13 The Regents Of The University Of California Ion source with external RF antenna
US7176469B2 (en) * 2002-05-22 2007-02-13 The Regents Of The University Of California Negative ion source with external RF antenna
PL2294582T3 (pl) 2008-05-02 2019-02-28 Shine Medical Technologies, Inc. Urządzenie i sposób wytwarzania izotopów medycznych
WO2012003009A2 (en) 2010-01-28 2012-01-05 Shine Medical Technologies, Inc. Segmented reaction chamber for radioisotope production
US10734126B2 (en) 2011-04-28 2020-08-04 SHINE Medical Technologies, LLC Methods of separating medical isotopes from uranium solutions
CN102226406B (zh) * 2011-05-10 2013-09-18 中铁十二局集团第一工程有限公司 超长超前锚杆施工方法
CA2869559C (en) 2012-04-05 2022-03-29 Shine Medical Technologies, Inc. Aqueous assembly and control method
CN111739674B (zh) * 2020-05-26 2022-08-05 中国原子能科学研究院 一种用于负高压加速的小型中子发生器的靶电极

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US2287619A (en) * 1939-06-09 1942-06-23 Kallmann Hartmut Israel Device for the production of slow neutrons
NL111344C (de) * 1955-06-14
US2985760A (en) * 1958-09-12 1961-05-23 High Voltage Engineering Corp Compact neutron source
DE1233068B (de) * 1963-11-27 1967-01-26 Kernforschung Gmbh Ges Fuer Neutronengenerator
NL289180A (de) * 1965-03-11
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
DE1816459B1 (de) * 1968-12-21 1970-06-25 Kernforschung Gmbh Ges Fuer Neutronengenerator
US3746859A (en) * 1970-04-22 1973-07-17 Atomic Energy Commission High intensity neutron source
NL7200001A (de) * 1972-01-03 1973-07-05
US3760225A (en) * 1972-06-06 1973-09-18 Atomic Energy Commission High current plasma source
US4119858A (en) * 1976-08-11 1978-10-10 Lawrence Cranberg Compact long-lived neutron source
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
NL7810299A (nl) * 1978-10-13 1980-04-15 Philips Nv Neutronengenerator met een trefplaat.

Also Published As

Publication number Publication date
DE68911741D1 (de) 1994-02-10
DE68911741T2 (de) 1994-06-30
FR2630576A1 (fr) 1989-10-27
EP0340832A1 (de) 1989-11-08
FR2630576B1 (fr) 1990-08-17
US5053184A (en) 1991-10-01
JPH0213900A (ja) 1990-01-18

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