DE1904985A1 - Ion accelerator - Google Patents

Description

James David London Hedley Wood, -15 Waysbrook, Letchworth, Hertfordshire, E η g I-a η d

For this filing, the priority is taken from the UK Patent application no. 5556/68 from 2. Eebr. 1968; claimed.

Ion accelerator

Brief description of the invention

In the supply or supply circuit for an ion accelerator with an ion source and an ion 'extractor electrode', the supply circuit containing an excitation supply for the ion source and an energy supply for the extractor electrode, a negative feedback loop is provided which is switched so that through it the extractor electrode current controls the excitation supply output in such a way that the extractor current is "kept" constant. The exemplary embodiment described is a neutron generator tube with a plasma ion source which is excited or operated by a radio frequency feed ₀

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Background of the Invention ; ;

The invention relates to circuit arrangements or supply circuits for Iqnenbe accelerators, in particular for Neutron generators, in which deuterium and / or tritium ions extracted or withdrawn from a plasma and directed towards a target which contains deuterium and / or tritium * holds, be accelerated. A neutron generator tube of this: - genus is described in British Patent 1,088,088.

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Briefly summarized, in the aforementioned generator a plasma is generated in the ion source section of the "tube by a surrounding winding that is fed or excited by a radio frequency oscillator Plasma is intensified in the area of this recess by an axial magnetic field, which is derived or generated by a coaxial \ solenoid _.:

Positive ions are extracted or withdrawn from the plasma by a negative potential, which is fed or transmitted to an extractor electrode. A plasma boundary is formed, its perimeter being coupled or keyed to the edge of the boundary electrode. The ions are drawn into a beam, the profile of which depends on the electrical field configuration between this plasma boundary . and applied to the extractor potential is generated ^ ^ the Gestal or, shape the LE. _t ^, limitation and their effects are on the beam profile, of, plasma ion density and the value of the applied Sfcentials, ... :.: -V ,,, .. dependent. Opt imal-Be tr leb requires that the ion beam through ■ the extractor recess with a minimal interception /inter.peptipn/

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to prevent excessive heating or atomization or spraying of the extractor electrode. Once the ion beam has passed through the extractor recess, it is accelerated through a target shielding recess, namely by a large negative potential _{r applied to it,} and finally passes the field-free area inside a suppressor electrode in order to reach the target or . to hit or bounce the interceptor »

In such pipes, there is little interception of the Beam through the extractor electrode under normal operating conditions, which gives rise to an extractor current. If the catch is too large, the extractor temperature rises on, and absorbed gas is released into the pipe. This creates an unstable condition as below described in more detail wild, the one destroying the pipe can lead · This is particularly easy to do under Start or Start-up conditions if or during the extractor potential and the radio frequency energy delivery to the plasma progressively increased werdeho

It is an object of the invention to provide some form of delivery circuit which alleviates this problem or taken into account,

Summary of the invention

According to the invention, in a supply or supply circuit for a particle accelerator with an ion source and an ion extractor electrode, which circuit provides an excitation feed for the ion source and an energy supply for the extractor electrode contains a liegative feedback loop provided, which is connected so that they the extractor electrode long-term causes the excitation supply output to be controlled in such a directional sense that the extractor

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etrom is kept constant. The excitation feed can be a High or Be radio frequency supply or »supply source, the is able to excite or to excite a plasma ion source operate.

The invention also relates to a combination of an ion accelerator, which has an ion source and an ion extractor electrode, and a supply circuit for this ion accelerator, which circuit is an actuation or excitation aspiration for the ion source and an energy supply or supply source for the Contains extractor electrode, wherein according to the invention the circuit has a negative feedback loop which is connected so that it causes the extractor electrode current to control the excitation for the supply output in such a sense that the extractor current is kept constant. The ion source can be a plasma ion source, the excitation voltage a high-frequency or radio-frequency supply or delivery source . "-. -..... '"".-' -_ '■ r . ■ ■ - ... "; ■■■■ '_

The ion accelerator can be a sealed neutron generator tube wherein the ion source is capable of generating hydrogen isotope ions. .

Description of the drawing

The invention will now be based on it, for example reproducing drawing described in more detail, namely ..

Fig. 1 is an echematic representation of a neutron egg

- Producer pipe, which is in a Yersorgungskreis according to the invention, "

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Figo 2 is a graph showing the change of the extractor and tail stream with the Extractor voltage at constant RP energy shows while

Fig. 3 shows a graph showing the

Change of the total tube current with the extractor voltage illustrates when EF power is controlled in accordance with the invention.

Description of the Preferred Implementation Game B.

Pig. 1 shows a neutron generator tube of the type which is described in detail in British patent specification 1,088,088. It has an ion source part 1, which is surrounded by an EP winding 2 for exciting a plasma located therein, and a magnetic solenoid 3. At one end there is a backstop or a bullet trap 4 and at the other end a recessed limit electrode 5, beyond which an extractor electrode 6, - a shielding electrode 7, a ünterdrüokerelectrode 8 and a target 9 are arranged in succession. "The cross-section of the ion beam under normal working conditions is indicated approximately at 10. The gas pressure is kept constant by a replenisher controlled by a Pirani gauge, both of which are omitted from Pig. 1 for clarity, such as also a part of the pipe casing ₀ Pig. 1 also shows the supply circuit associated with the connections νόΐή

Typical preferred operating conditions for the pipe '^ are the following "-'. *"'■■-' ■ '■ -. "■:; ..- ■ -" - "■" - ■

Gas pressure (50/50 D / T-Gemiseh) (P) 1.2 χ 10 R3? Excitation energy. (W) _: 200 watts RF-Fr eq.uenz '·. 14 MHz - Magnetic field (H) if 90 gauss Extraction potential 4, S-JcV ": ': Extraction Trap Stream (ΐ _Ε ί - 0.1 mA Acceleration potential (v _T > 120 kY Total pipe flow ' (i _A ) 12 mA Target stream CI ₁ ) ^ 6 mA Suppressor voltage (V ₃ ) 440 Y T suppressor current (Ig) 6 mA Ion beam ^ diameter at the target. 2.8 cm Neutron output 10 '' hay

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Heutrons / ^ ek.

Hg. 2 illustrates a typical extractor control characteristic: for a constant EF excitation energy W. With increasing extract orp ο tent ial Vg., The interception current I _E initially rises to a peak value, which corresponds to the increasing ion extraction, which of A beam collection is accompanied by the extractor. Subsequently, the ion extraction increases further, but is associated with a repression of the piasia border into the ion source part of the tube, the effect of which is a ^ ₁ . _{sr is} denser beam focusing so that the beam lies through the extractor recess and the intercepting current drops. The stra% profile is at a low-;. Well defined interception at the extractor, and this in turn defines the ion beam diameter at the target.

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The effect of increasing the HF energy W exists therein, the entire characteristic or characteristic curve, such as. shown moving to the right · This effect is increased on Ion source plasma density, which tends to bring the plasma boundary forward into the extraction area and requires an increased extraction potential to meet the initial focus conditions restore and in this way reduce the interception current.

A number of such characteristics exist, corresponding to the range of possible RF energies, but at higher levels they are impossible to determine because of the instabilities created at higher values of I _E. The maximum continuously acceptable value of L is about 0.15 mA.

An increase beyond this initially causes sin Increase in the temperature of the extractor electrode and with long Duration of atomization of the same. Sputtered material is undesirable because conductive deposits may appear on the insulating material Wall of the pipe can form, with serious consequences for the high-voltage insulation, and less seriously, with regard to the interference of the ion source Efficiency.

The chain can be more serious and downright catastrophic positive feedback processes caused by temperature increases is produced as follows: ■

(I) Adsorbed grass is driven out of the extractor.

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(II) As a result of the finite or limited response time of the pressure control system, the gas pressure rises.

(III) As the pressure increases, the KP energy becomes more easily coupled to the ion source, and the plasma ' Ion density increases.

(IV) The characteristics of the Pig. 3 following takes

the interception to which a further increase in temperature of the extractor electrode follows.

(V) At the same time, the ion current increases after towards the target, "and if this is given the opportunity, ■ increase beyond the coolant system capacity, so it will cause rapid target gas expulsion and further pressure rises.

(VI) The electron flow towards the backstop increases also with the pressure, and another gas expulsion can result from this electrode.

If this sequence is not controlled, then the energy consumption on the extractor electrode can increase to such a point that the glass-metal seal is destroyed. Protection against this could be achieved by overcurrent tripping or ■■■ -. * Blocking in the various circuits, but this can lead to an unwelcome and unacceptable number of "trips". Any change in the pipe supply conditions can initiate this chain, and continuous control is important for long-term stable conditions. . _: '

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In the present invention, any increase in Interception current to reduce the HF energy » thereby reducing the degree of interception and on this Way, the above-described 'runaway chain' ^ / run-away chain / is prevented by Yorggang. Each Fig. 1 lets the capture stream I-g flow through a resistor E ^ and develop thereby a potential in this. This potential is compared with a reference potential, which of a supply source 11 is derived by a transistorized differential amplifier 1.2 herk & pmlleher type. The out · output of the amplifier 12 controls the Besehußwinkel one Thyristor-Steuerkrelses 13, which in the 50-Hertz * connection of the! ^ oscillator 14 is switched, and thus finally the JRF * energy that is supplied to the ion source. To a Stability "of the negative feedback loop thus formed to ensure that the sensitivity and the tentative constants are measured regulated in a manner familiar to those skilled in the art of negative feedback technology. The one you want The value of the interception current I-g is adjusted to Ae s value set by Eg ;, '

The supply circuit described above had a long-term stable operation of the Eohr, enabled »for example "an uncovered I2 ^ stunae» »operation. At JüTietotvörhanden ^ Being in the negative feedback loop "must" be a leäienungsper's on £ n permanent already eli # ft 'presence ».

Another iTorteil to? frfindwg can be seen in the fact that the extract electrode mis a real f * ew # r ^ i ^ det turn leajiia, ^ ie i »fig _f # 3 ^ e3? anj? ehauiißhife _f Jas potgstt34l kmm arbitrarily increased pdsr decreased 'to the IMD Ipnejistrpm the following jJeutronensusgÄRg mu best bees .. the necessary JMDS-imngieii in & gg Jp after _{_jpnenau§iif:>} gr | Len automatically inserted through the 'development circle, and the yiasmabegrenzwng is

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a rope area in "the correct position for the stable Formation of a Xon beam of the desired profile and thus j for a stable position on the iEargei; maintain.

Even if the invention was described with reference to a Feix-fcronen generator pipe * toei which a BF-. ELasina-Icmenquelle yerwendei; scird, irerjsi; ejit it see, aslQ they are also used in / lieutron generators or other healthreselileTiHiigexn wmxAen Jcann, to which an extrajrfcionelrfcrode is applied, as always the irrigation which is caused by the generation of the ionic excitation., dmrcii. For example, in the case of a Lieutron egg; or _: in which a PIG ion source is used, the extractor current can be induced, the node tension and thus the. Controlling the discharge or discharge current in the source, "eutron generators, in which such ion sources, also known as" Penning sources ¹ ", are used are, for example, in British patent specifications 976 664 and 980 947 and in ITukleonics, December 1960, pages 69 to 74 »described ·

The invention also relates to modifications of the embodiment outlined in the accompanying patent claim 1 . also refers to all ErfindungsmerloHEtle that pder in detail in combination ~~ especially - are disclosed in the specification and drawings ,.

Claims

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Claims (3)

PATENT Attorney DIPL-ING. ERICH SCHUBERT Won: (0271) 32409 Telegram address: Patschub, Siegen Postal check accounts: Cologne 106931, Essen 203 i2 - Bank accounts: Deutsche Bank AG., Abs .: Palentanwalt Dipl.-Ing. SCHUBERT, 59 Siegen, Eiserner Strasse 227. Branches in Siegen υ. Oberhausen (RhId.). Postfadi325 69 055 Kü / Schm Jan. 31, 1969 claims 1. Supply or supply circuit for an ion accelerator with an ion source and an ion extract electrode, this circuit having an excitation supply for the ion source and an energy supply for the extractor electrode , characterized in that this circuit has a negative feedback loop that is so is switched that the extractor electrode current causes " becomes, the excitation supply output in such a directional sense to control that the extractor flow is kept constant. 2o control circuit according to claim. 1, characterized in that the excitation supply is a radio frequency supply which is able to excite a plasma ion source. ¹ 3. Combination of an ion accelerator, the one Having an ion source and an ion extractor electrode, and a supply circuit for this ion accelerator, the circuit being an excitation supply for the ion source and contains a power supply for the extractor electrode, characterized in that the circuit has a negative feedback loop which is switched so that it causes the extractor electrode current, the excitation supply output to be controlled in such a direction that the extractor flow is kept constant. 909 8 36/100 7 4β - combination according to claim 5, characterized in that the ion source is a plasma ion source and the excitation power is a ¹ or high radio frequency supply. 5 ·. Combination according to claim 5 or 4, characterized that the ion accelerator is a sealed neutron generator tube and that the ion source is able to generate hydrogen isotope ions. 909 83t /