DE1514989A1 - Particle acceleration tube - Google Patents

Description

PATENT ADVOCATE DIPL.-ING. ERICH SCHUBERT

From · .: Patent attorney Dipl.-Ing. SCHUBERT, 3 »SiafM, EiMrMr Strato 227 PottfodiXtS

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Τ · Μ (μ: | H 71) 3 34 N

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PotttdMcfckantoft. KSU IM * 31, EtMn m <2

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Dwhdw iMk AG., Filialm twowt «. OhwkcwMn (MiM.)

November 17, 1965

Kü / St.

UNITED KINGDOM ATOMIC ENERGY AUTHORITY, Patents Branch, 11, Charles il Street, London SI I ₁ England

For this registration, the priority is taken from the claimed British Patent Application No. 47250/64 dated November 19, 1964.

article acceleration tube

The invention relates to linear particles. Particle acceleration tubes that are used for the Suitable for use with electrostatic accelerators, e.g. Van de Graaff-Typfr.

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Such tubes / generally consist of a large number of acceleration electrodes in the form of round ones Plates or bowls opposed to ring-shaped glass iaolators are sealed and separated by this. The electrodes have aligned holes through which the ion beam passes. The degree of effectiveness of an electrostatic generator as a particle accelerator is usually determined by the quality of the acceleration

pipe limited, which the maximum acceleration span ^ r that can be achieved. In particular, the phenomenon known as "electron charge" / occurs at soft unwanted electrons, which are generated for example by field emission from electrodes, back in the direction of the positive end of the pipe can be accelerated, where / * · X-rays are generated when they hit the acceleration electrodes./cTie Cleavages preceding the pipe or / never encounter an ion source component group. These x-rays ionize the high pressure gas surrounding the pipe, reducing the effective insulation while the electrons themselves have a charge or load on

Form generator to reduce d ^^ a ^ BWT

It has been proposed to consider the electron charge effect to be reduced by the fact that the B «ichl« unigun £ telelectrodes be inclined at an angle to the pipe axis in such a way that electric fields eee »dt

soft deflect the electrons in order to hit the electrodes hit before they are accelerated to energies,

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at which d ^^ X-ray generation Air Effective

Arrangement of this type is for example in the British

'"• si-

Patent Q67 963 described JSSE present invention

_aca »f # l an alternate arrangement aimed at the same purpose

is directed or aims

According to the invention, a linear / ^ particle acceleration tube / i which ^ has a plurality of spaced electrodes provided with recesses, a device for generating axially arranged transverse magnetic fields, which are arranged along and within the tube at a distance M and by essentially field-free Hegions are separated, these fields serving to deflect undesired electrons into the electrodes, but to give an accelerated particle beam the possibility of leaving the tube on a path essentially parallel to the tube axis.

In addition, according to the invention, an Ainearee / particle acceleration tube with a plurality of spaced-apart electrodes provided with recesses contains at least a group of four devices for generating axially arranged transverse magnetic fields arranged along and within the tube, these fields being separated from one another by generally field-free regions are separated and aligned in order to deflect a charged particle beam in a common diametrical plane, the two outer devices of the group of four being oriented in such a way that they deflect the beam in one diametrical direction, while the two inner devices of the group of four are oriented in such a way that ei ·

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deflect the beam in the opposite diametrical direction / '

Each such device preferably has a magnetic pole pair on, which is attached to one of these electrodes, and these pole pairs are pre-wired by permanent magnets educated.

The invention will now be exemplified on the basis of it reproducing drawing described in more detail, and iwar lelgt bcw. seigen

Flg. 1 shows a schematic longitudinal section

Accelerator tube according to the invention, dlt Figs. 2 and 3 each have a plan view and a partial cross section of a shell-shaped structure Electrode that rereehea ltt with a magnetic pole pair

Flg. 4 is a graphical representation, giving way to changes the lag β. a s ^ radiates selgt when tr the drilling traversed

Figs. 5 and 6 views corresponding to Dtn FIGS. 2 and 3 a further embodiment,

Fig. 7 tint view of this wtlttrta AutfUhruaftfor «

tnttprtchtnd dtr Flg. 1, while Flg. 8 tint graphic representation according to dtr

Flg. 4 for dittt wtltert execution forum

reproduces.

Flg. 1 itIgt tint Variety of tob electrodes, diotin Bet chi eunlger pipe form and tob Slngaagttade dt · Bthrt · fat? numbered with 1 bit 142 tlad. DIt leaves tiad la dtr

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in the usual way by means of ring-shaped glass-Ieolators arranged at a distance. In the case of the tube, three quartet or groups of four of permanent magnet pairs are used; the first group of four is in the cup-shaped electrodes 31, 36, 48 and 54 attached; the second in the electrodes, 65, 74, 84th and 94; and the third in electrodes 104, 114. 124 and 135. The two poles of each pole pair are marked old N (north) and S (south). £ s is orsiohtlioh, that the poles of the two outer pole pairs of each group of four, i.e. at electrodes 31 and 54, 65 and 94, 104 and 135 ^ In the opposite direction to the inner pole pairs of their in groups of four, i.e. at electrodes 36 and 48, 74 and 84, 114 and 124, are oriented.

In FIGS. 2 and 3, one of the electrodes listed above is shown in detail, while a pair differs from Has permanent magnets, their respective I and S PoIs are oriented as shown and which are within the Shell-shaped parts of an aluminum electrode B are moistened and over «in Uafangsjoch Y are bound. The ion beam go! wipe the poles through a recess A In dsr BlektrM hinduoh. The end pieces of the recess are enlarged, Form over flaps B su that support the excavation of the pipe, and dl · Pol · as well as da · Jooh Bind through «la · Almalnlua» flat · C covered, dl «a recess old the smooth Has dimensions like that in the electrode. Tue Cover plate C, dl as dl electrode B rounded laaten to * «Nd is highly polished, 1st Torgeeehen, ia dl · savgnlt · uai daa Stahljooh against the strong electrical field absuefalraaa,

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to which the electrode is exposed during operation.

Figures 2 and 3 are approximately to scale, the width of the recess A in this embodiment being 2 inches (approximately 51 mm). The sintered Ticonal-G permanent magnets are 1 inch (25 ₁ 4 mm) deep in the axial direction and provide a field of about 400 Gaui in the recess. The electrodes are spaced 1.1 inches (approximately 28 mm) apart through the annular insulators.

The pole pairs are arranged to generate transverse magnetic fields which deflect away from the recess area into the electrodes any electrons which tend to migrate back towards the input end without creating any substantial net deviation of the beam from its axial path . In Flg. 1 let the path of the ion beam shown by the solid line D. Assuming that the beam path runs axially on reaching the first pair of poles of the third group of four at the electrode 104, the localized field generated by this pair of poles deflects the beam by an angle <χ in red on one side of the tube. (Although the deflection in the plane of the paper is shown in fl. Since it is oriented in the opposite direction, it deflects the beam back again by the angle «c, so that it is parallel to the pipe axis, but offset from this, leaves the air.

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Similarly, at electrode 124, the beam is deflected back towards the axis and decreases at the Electrode 135 again takes a substantially axial path. (In reality, as shown in Fig. 4, the ray takes a path parallel to the, but slightly offset but axis.)

Although the deflected path is shown linear, forming an angle ° C with the axis it is actually parabolic because of the increasing energy of the beam. Thus, for example, the angle <* is below which beam reaches electrode 114, in fact somewhat smaller than the angle ° <at which it leaves the electrode 104. This effect is however through the Compensated for the fact that the pressure on the electrode 114 The deflection due to the increasing energy is similarly reduced, so that the beam leaving the electrode 114 continues to run essentially parallel to the axis.

The first and second groups of four behave similarly. It can be seen, however, that if dit Fol pairs of the second and third groups of four along tem Tube are arranged at approximately the same intervals, those of the first group of four are arranged as two successive pairs, namely relatively dloht

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jerttotf aukmiL · W * together. This ieft yrmsa; at the entrance end 4

Rohres the beam energy is relatively low and therefore 4 Beam is very sensitive to deflection fields. To tm prevent the beam from being deflected iu far from the axis

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are therefore the pole pairs (on electrodes 36 and 54) which move the beam on its parallel and axial path bring back, arranged relatively close to the deflection pole pairs 31 and 48, respectively.

Fig. 4 shows the calculated displacements around the tube axis for a proton beam entering the above described tube on an axial path with an energy

and.

▼ on 15 k * V enters «4« this leaves with 2 MeV. It; is it can be seen that the distance between the adjacent electrodes, which carry pole pairs, is that of the way of the exiting beam the very low heat storage of 0.064 mm is given. A uniform electric Field of 15 kV between adjacent electrodes 1-135 was established assumed in this calculation, with the practiced Electrodes for acceleration were not used. In the case of the present embodiment, the successive ones steer Groups of four emit the beam to opposite sides of the axis. This is not essential Meaning, and an alternative arrangement is shown in FIG.

For electrons that are emitted by the electrodes and run towards the entrance end of the tube, The distraction created by each fol pair is much greater (because of their low mass relative to the ions), and these are deflected into the electrodes before ele Energies have reached at which the X-ray generation takes effect. In the present pipe, which · to

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Ions are intended to have energies in the range from 1.5 to 6 To accelerate MeV, the pole pairs are no further apart than about ten electrodes, which is a corresponds to a maximum electron energy of about 400 keV before deflection by a pair of poles.

It can be seen that at the entrance end of the tube, electrons leaving the electrode 31 are likely could reach the ion source with an energy of about 1.2 MeV (with a total applied voltage of 6 MV) without to be distracted. Aue the reasons already mentioned, ™

namely the sensitivity of the ion beam at low energies (which applies in particular when the applied total voltage is reduced to 1.5 MV), however, the magnetic deflection of the electrons is not used in the present embodiment in this area. A corresponding degree of electron charge can be permitted, or alternatively, metal electron suppression systems can be used, such as the use of electrodes with recesses that are corrugated all around, around ^

Provide non-axial electric fields, as ·· In the associated German patent application S 99060 VIIIo / 21g (Attorney file 65 093) described did. In the present exemplary embodiment, the electrodes 1-30 have conventional ones non-corrugated round recesses whose Durohmesssr, wi shown, gradually decrease.

The electron deflection fields that are generated by the poly-hair are quietly effective in the dm

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In the two lobes B there is only one magnetic * Fringing field, and to prevent electrons from being charged along the tube over these lapos, successive electrodes will see those the pairs of poles carry (except for those immediately adjacent to the latter adjoining) gradually over an angle relative to the previous electrode rotated so that the total rotation • between adjacent electrodes that carry pairs of folios, 180 °. UIe protruding parts P of the turned Electrodes form a helix along the pipe so that there is no free optical path parallel to the axis the tabs B is present through between adjacent electrodes which carry pole pairs. This method (optical Covered by successive rotating electrodes) of the electron suppression in a pipe old lsppenfurmlg extended Auseparungen the form described tor enabling an effective evacuation can without Magnetic suppression can be applied and used in Pipes that only have low voltages should be sufficient need to work.

The electrodes 31 and 36 and 48 and 54 are too close together for the above method to be used. In these parts of the tube, the electrodes 33 and 34 and 50, 91 and 52 are rotated by 90 °, so that the parts of these electrodes together with the widened lobes of the adjacent electrodes provide a significant increase in optical visibility the puap impedans.

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Ea can be seen that, in the case of each cup-shaped electrode having a pair of poles, the cover plate C takes up approximately the area that a preceding cup-shaped electrode would take up in a conventional tube. If, therefore, similarly echalenfuraig electrodes were used consistently, the number of electrodes would have to be reduced by the number of attached pole pairs for a given total length in the present tube compared to a conventional tube without pairs of rows. Thus, for a given permissible voltage stress per insulator, the applied maximum voltage would have to be used. In the present exemplary embodiment, the Antahl of the electrodes (and therefore also of the insulators) characterized kept at the "conventional ¹¹ value, that the degree of cupped" Ttrtiefung twiechen in some of the electrodes each pair of poles is reduced. For example, one begins with the pole-carrying electrode 124, The electrodes 125-128 are deepened in roller-shaped bowls, the electrodes 129-133 are gradually less deepened, and the electrode 134, which precedes the closest pole-bearing electrode 135, is deepened at all Absusohlrasn insulators in an acceleration tube is desirable, but not of essential importance, since in particular the beam energy increases.

It is obvious that the first and alternate pole pairs of each group of four, for example those in the electrodes 104 and 114 in the third group of four, should generate high-intensity fields in order to sweep the beam in one direction

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parallel to the pipe axis, and that in a similar way the third and fourth pole pairs, i.e. those in the Electrodes 124 and 135, fields of the same strength generate madness. However, it is not essential that the third and fourth pair of poles generated fields are the same as those generated by the first and second pair of poles.

The pipe described above is up to 6 MV with no measurable Electron charge has been used.

Instead of using a single pair of magnetic poles w to generate each localized transverse magnetic field, the poles can be distributed over two or more adjacent electrodes. The latter arrangement has the advantage that, for generating a given deflection angle, the individual magnets can be weaker (since the field is applied over a greater length of the pipe), and thus the magnets can be narrower in the axial direction, thereby making use equally deeply recessed electrodes over the whole length mSglloh is made.

) Instead of using separate magnets,

which are connected via a yoke can also be Rlngmmgmete can be used, which are magnetized over a diameter. Figures 5 and 6 show one Ring magnet M, which is in a bowl-shaped »electrode B * attached and geechUtit ltt, wwbel by a cover plate the component group is held together by two lines R, dl duroh LOoher in the lord and south pole areas de Magnets are permanently guided and Flg. 7 shows «in Accelerator tube, which has eight such electrodes

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has groups that form two groups of four. In this tube, which is designed to work at up to 3 MeV, each magnet M consists of Ticonal-G and generates a PeId of about 100 Gauss. The recess A ¹ (Pig. 6) is 3.5 inches (about 89 mm) in diameter and the magnet is 0.375 inches (about 9.5 mm) thick in the axial direction.

In Flg. 7 1st the first group of four of pole pairs In the electrodes 17, 23, 30 and 38 and the second in the Electrodes 44, 50, 57 and 64 attached. In contrast to the Pig embodiment. 1 are the pole pairs of the two successive groups of four (marked with I and S)

oriented in such a way that they move electrons to the same side ^ deflect the pipe axis. This arrangement has the advantage that, apart from the first and last pole pairs (those sitting in electrodes 17 and 64), dl electrons encounter successive pairs of deflection fields that are oriented in the same direction, thereby ensuring it becomes that any electrons, which are insufficiently deflected by the first field, through the second world to get distracted. This is particularly useful where smaller fields are used, such as the present one Embodiment. FIG. 8 shows the calculated displacements around the pipe axis for a proton beam which Energy of 3 ke? enters and exits with 210 keV. Dl The latent displacement is approximately 0.125 mm and runs parallel to the pipe axis ·. Dl «proton beam deflection takes clearly increases as soon as the

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gradient is decreased. So is in Pig. 8 the relationship for an applied gradient of 3 kV between adjacent electrodes, which is the lowest Gradient that is likely to be used in practice.

From Pig. 7 it can be seen that the electrodes relative to the directions of movement of the protons and electrons In ₁ the opposite direction to the electrodes of the flg.

are sohal-like deepened. The in Flg. 7 shown Riohtung is more effective by removing the distracted J Electrons cause successive electrodes to strike, rather than the inner surfaces of the glass insulators I'm bombing.

With the exceptions mentioned below, these are Electrodes in Figure 7 to a standard 1.1 inch depth {% twa 2Θ am) shell-shaped, with the insulators I * separate them by 0.9 inches (about 23 mm), ti in the execution example according to FIG. 1, the inclusion has of ling magnets in eight of the electrodes, the distance between these and the adjacent electrodes see below Reduce. In the case of the present execution document, this is Difficulty overcome by the fact that the bowl-shaped « Deepening of the two electrodes attached to each magnet-bearing Electrode is changed on the concave part of the same. Each magnet-bearing electrode (for example, electrode 17) is recessed to a standard 1.1 inch (about 28 bi) depth, but becomes .64 inch (16.25 ») 4t through the magnet and the cover plate (which like dl « has a die of 0.085 inch (about 2.1 ma) accommodates

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leaving about 0.7 inches (about 17.8 mm). To thee balance, the next adjacent electrode (for example, electrode 18) will only be 0.7 inches (about 17.8 mm) cup-shaped deepened, and the next following electrode (for example electrode 19) is only 0.9 inches (about 23 ι bowl-shaped deepened. The pole thereof is the effective distance between electrodes 17 and 18, 18 and 19 and 19 and 20 not decreased to less than 0.7 inches (about 17.8 mm). The same arrangement will be made in the near future other magnet-carrying electrodes are used. "

In contrast to the embodiment according to Flg. 1 are the Recesses A 'not in the present execution game lobe-shaped expanded. The recesses of the eight magnet carriers | the electrodes have a diameter of 3.5 inches (about 89 mm), ι In order to achieve maximum pump speed, the Cut-outs for most of the remaining electrodes to be 4.375 inches (111.1 mm) expanded. The exception are the charging electrodes 69 and 70, which are 3.5 inches (about 89 mm) in diameter, and the starting electrodes that are known in Welee "

form a tapered entrance. In the latter case, electrode 2 has a 3 inch recess diameter (76.2 mm) ι the electrodes 3 to 7 have cutouts from 4.375 inches (111.1 mm) f the electrodes θ through 13 have recesses by 4.25 inches (about 108 msj) | and the electrode 14 to 16 have recesses of 4 * 125 inches (about 105 ■ *) ·

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Although the invention is related to acceleration ▼ on rays of ions has been described, they can auoh be used in tubes for the acceleration of electrons, since the transverse fields have a smaller deflection of the high-energy electron beam than from undesired locally emitted electrons.

The invention also relates to modifications of the la enclosed claim 1 umriseenen AuefUhrungsfora and Tor all also relates to seed inventions, the la individual - or in coabination in the complete description and drawing are disclosed.

Claims.

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Claims (7)

Claims 1. Linear particle acceleration tube, consisting of a large number of spaced apart, with recesses provided electrodes and with at least a quartet of devices, at a distance along and within the Tubes arranged for viewing axially localized ones Transverse magnetic fields, the feider being essential through la Field-free regions separated from one another and aligned "load over a charged particle beam in a common Dianetral plane deflect, the two tueeereη bodies de · quartet · are oriented in such a way that ei · den Deflect the beam in one dianetral direction, while dl both internal institutions of the quartet · so oriented. that they have the beam in the opposite dlaaetralrichtuiif turn. 2. Pipe according to claim 1, characterized in that each said device has a pair of magnetic poles which at one of the electrodes mentioned above. 909832/06 2 BADORIOINAL 15U989 3. Tube according to claim 2, characterized in that said magnetic pole pairs consist of permanent magnets exist. 4. Pipe according to claim 3, characterized in that that the permanent magnets are fastened within shell-shaped recessed parts of the electrodes mentioned. 5. Pipe according to claim 4, characterized in that the permanent magnets are ring magnets, the over one w be magnetized across the diameter. 6. Tube according to claim 1 to 5, characterized in that that successive quartets or groups of four are oriented in such a way that they send electrons to the same Deflect the side of the pipe axis. 7. Linear particle acceleration tube, consisting of a plurality of spaced apart, alt Recessed electrodes and old devices 'for generating axially localized transverse magnetic fields that spaced along and within the pipe and spaced apart by substantially field-free regions are separated, these fields being there to serve, undesirable To deflect electrons into the electrodes, but to give an accelerated particle beam the opportunity to to leave the tube on a path substantially parallel to the axis la. BADORiGINAL 909832/082