US2265113A - Cyclotron - Google Patents

Cyclotron Download PDF

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Publication number
US2265113A
US2265113A US308301A US30830139A US2265113A US 2265113 A US2265113 A US 2265113A US 308301 A US308301 A US 308301A US 30830139 A US30830139 A US 30830139A US 2265113 A US2265113 A US 2265113A
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Prior art keywords
chamber
high frequency
electrodes
accelerating
transformer
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Expired - Lifetime
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US308301A
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English (en)
Inventor
Dick Max
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BBC Brown Boveri AG Germany
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Bbc Brown Boveri & Cie
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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
    • H05H13/00—Magnetic resonance accelerators; Cyclotrons

Definitions

  • the cyclotron is used to give electrically charged particles, for instance positive ions, a high velocity.
  • the energy of the particles accelerated by means of the cyclotron is about equivalent to the energy which the particles would acquire when passing through a static potential of several million volts.
  • the main advantage of the cyclotron when compared with an ordinary high voltage plant is that only voltages of about 40,000 to 80,000 volts, although in the form of a high frequency alternating voltage, are required in order to impart high velocities to the charge carriers.
  • the cyclotron in its known form consists primarily of an accelerating chamber arranged between the poles of a powerful magnet.
  • this chamber there are usually only two accelerating electrodes which are formed by a circular box divided along a die-meter into two halves. Each part of the box is connected to a pole of a high frequency generator and the device for creating the charge carriers is arranged in the centre of the space bounded by the box surfaces. Under the influence of the alternating electric field and the constant magnetic field the charge carriers travel along spiral paths with an outwardly increasing velocity. When the charge carriers have reached a certain maximum travel radius and acquired a corresponding energy then, by means of further devices, they are diverted out of the range of the magnetic field into the observation chamber, which in the usual way is also kept under a suitably high vacuum like the accelerating chamber.
  • the cyclotrons used up to the present still have various defects which prevent energies of more than 6 eMV (6 million electron volts) being produced. It has namely been found that the charge carriers can only make a certain number of revolutions without falling out of step, so that the maximum energy will be greater the higher the amplitude of the alternating voltages applied to the accelerating electrodes can be chosen. An increase in the peak value of the high frequency supply current is, however, accompanied by considerable difiiculties as regards the construction of the bushing insulators, so that at present not much more than 70,000 volts high frequency voltage can be safely used. Even if it is assumed that the question of the insulation could be solved,
  • the object of the present invention is therefore to construct a cyclotron which does not possess the disadvantages of the type hitherto used and which enables, with a considerably smaller high frequency power, such energies to be imparted to the charge carriers as have not been previously attained.
  • a further advantage is that the chamber can be made more cheaply and reliably because the bushing insulators need only be designed for lower voltages. This is achieved by providing inside the accelerating chamber means for a voltage transformation of the high frequency oscillation supplied to the accelerating electrodes, in such a manner that the amplitude of the high frequency voltage at the place where the leading-in insulators are situated in the chamber is considerably smaller than the amplitude of the high frequency voltage prevailing between the accelerating electrodes.
  • Fig. l a voltage transformation by means of a transformer located inside the chamber is employed, whilst in Fig. 2 the transformation is achieved by the aid of a Lecher wire system, which is connected to the high frequency generator and the accelerating electrodes in such a way that a voltage intersection point occurs at the bushing insulators.
  • Fig. 3 both these means are combined in order to obtain a double transformation.
  • Figs. 4 and 5 show two further embodiments of the invention whereby means are provided for adjusting the cyclotron circuit; whilst in Figs. 6 and 7 cooling arrangements for the electrodes are illustrated.
  • the wall of the accelerating chamber is shown in section, so that in the plan view the electrodes 17 inside the casing wall a are visible.
  • the primary winding 11. of the transformer which preferably consists of only one coil and is coupled as closely as possible with the secondary coil, is connected directly to the low ohmic conductors i which are supplied from the high frequency generator k.
  • the tubes of the high frequency generator, normally operating as a reverse rhythm end stage are connected to the high ohmic primary winding of the transformer m, the secondary coil of which is connected with the conductors i. It is obvious that with such a construction of the cyclotron extremely high voltages can be generated at the accelerating electrodes 1) without equally high voltages occurring at the bushing insulators. Furthermore the capacity of the insulators e and the conductor 1' is now only of minor importance so that inside the chamber for a resonance tuning of the secondary coil 9' with the effective capacity between the accelerating electrodes b, a weakly dampened oscillating circuit will be obtained in which high resonance voltages can be excited.
  • the power of the high frequency generator can therefore also be correspondingly reduced or with the same power, for reasons already stated, considerably higher energies are obtained for the accelerated charge carriers.
  • the construction used formerly also possesses further disadvantages because the coil used for the resonance tuning and arranged outtaken in one stage but in a double transformation.
  • the arrangement shown in Fig. 3 is particularly favourable where first a transformation by means of a Lecher wire system occurs in such a manner that a voltage intersection point exists at the bushing insulators.
  • the Lecher wire system that is to say the part c of the system inside the chamber, is connected with the primary winding )1. of the high frequency transformer, the secondary winding 0 of which in the mannerdescribed for Fig. 1, is connected to the electrodes and tuned to resonance.
  • the high frequency transformer side the chamber causes undesirable eddy currents in the surrounding metal parts, for instance in the iron masses of the electromagnets or in special metal casings, these resulting in a high loss factor.
  • the coil outside the chamber produces on account of its large dimensions relative ranged inside the chamber, it is an easy matter to construct the metal surfaces of the casing 'wall so that the eddy current losses are consid-- erably reduced and the radiation of high ire-- quency energy is also completely suppressed by such screens.
  • a most suitable ratio of transformation for the inside of the chamber is about 1': 30. This ratio of transformation results in a sufliciently low voltage at the insulators without the currents in the low ohmic conductors becoming too high. It is preferable that such a ratio of transformation should not be undercan also be constructed as an autotransformer in which the low ohmic primary coil 71. forms part of the high ohmic secondary coil 9'. As in Fig. 2, it is also possible with this alternative to provide the part i of the Lecher wire system outside the chamber with additional impedances f or to connect it to a Lecher wire system with a correspondingly different wave resistance, so that voltage loops with a high amplitude no longer occur.
  • tuning elements can be provided in the high frequency conductors outside the accelerating chamber by means of which the alternating voltage on the accelerating electrodes must be accurately adjusted both as regards its amplitude and its frequency, in order that the required synchronous travel of the charge carriers to be accelerated can be controlled with the alternating voltage. It is therefore also of great importance that the cyclotron circuit be correctly tuned because the final energy of the charge carriers depends on this adjustment.
  • the adjustment of the cyclotron circuit in the known arrangements is usually undertaken by means oi. additional variable coils, telescopic Lecher wires or capacities, which are arranged as near as possible to the bushing insulators of the chamber, so as to obtain a high resonance resistance for the cyclotron circuit.
  • the usual arrangement of these switch elements is, however, accompanied by several disadvantages which make the use of the cyclotron somewhat complicated.
  • the switch elements for regulating the impedance of the cyclotron circuit are, namely, under a high voltage and carry high frequency alternating voltages of several thousand volts, so that their operating handles must be particularly 'well insulated to enable them to be handled without danger.
  • the insulation of the regulating elements themselves involves considerable difiiculties if voltages of more than 100,000 volts are used in the chamber. With such high voltages it is absolutely necessary that these switch elements should have a certain size, so that no discharge to the atmosphere can occur.
  • Fig. 4 the accelerating chamber a is shown in plan, the cover plate being removed.
  • semi-circular accelerating electrodes b are connected as an auto-transformer which serves to transform the high frequency voltage so that only comparatively low voltages occur at the bushing insulators d.
  • the natural frequency of the cyclotron circuit is thus mainly determined by the mutual capacity of both electrodes 22 and the effective self-induction of the coil 0.
  • two metal pieces e are provided which by means of the regulating devices can be moved into or out of the coil field so that their self-inductance can be varied within certain limits.
  • the regulating devices f are arranged to pass through vacuum tight glands g so that the self-inductance 0 can also be adjusted when the cyclotron is in operation.
  • the glands are provided with a flexible membrane, preferably in the form of a compressible corrugated tube, the outer edge of which is fastened to the casing in a vacuum-tight manner, whilst the regulating element passes through the centre of the membrane, for instance by means of an air-tight flange.
  • a metal plate 71. is provided which through the supports i can be rotated by the spindle 1 arranged outside the chamber, so that the distance between h and the electrodes b can be varied.
  • the glands g also preferably consist of sections of corrugated tube.
  • two adjustable plates can be used, each of which is as sociated with an accelerating electrode. This enables the capacity of each accelerating electrode with respect to the casing to be adjusted independently of the other electrode, so that it is possible to fix the voltage distribution of both electrodes with respect to the casing as desired.
  • Such a. symmetrical arrangement is of course also possible with the device shown in Fig. 4. With such arrangements for regulating the voltage distribution it is Preferable to connect the middle point of the coil 0 to the casing.
  • the special advantage of locating the tuning element inside the accelerating chamber is that less space is required and the regulating device can be arranged within easy reach of the observer. From the electrical point of view the tuning elements described are also superior to those connected outside the chamber, because the insulation of external switch elements depends on the dielectric losses or the break down voltage of the air, whilst with internal switch elements the minimum distances are only limited by the auto-electronic effect which only becomes noticeable with field strengths of several hundred thousand volts per centimetre. It is also very favourable that high frequency radiation is prevented and that the construction is very safe in operation due to the possibility of a direct galvanic connection of the tuning elements with the cas- With a cyclotron it is also necessary to cool the accelerating electrodes inside the chamber by providing additional cooling means for this purpose.
  • cooling means isaccompanied by considerable difilculties because the accelerating electrodes in rhythm with a high frequency oscillation carry very high voltages of about 70,000 volts compared with the easing.
  • the cooling medium pipes for each accelerating electrode inside the high frequency leads themselves.
  • Each of the high frequency leads from the chamber consists of two concentric pipes, one of which serves for the ingoing and the other for the outgoing flow of cooling water.
  • the cooling medium circuit is branched off. from the high frequency conductors, this being accomplished by means of two comparatively involved flem'ble spiral tube pieces connected to each conductor and acting as choke coils for the high frequency.
  • both electrodes four such choke'coils are therefore necessary; these can, however, be arranged in pairs either interwound or in the form of concentric tubes or pipes.
  • these choke coils occupy a large amount of space if it is desired to avoid a powerfulhigh frequency shunt which absorbs valuable high frequency power.
  • these large choke coils also possess the disadvantage that they have a dampingeifect on th cyclotron circuit, this being caused by radiation or the undesirable increase in the capacity of the high frequency supply circuit.
  • Fig. 6 shows a constructional example where the branching off of the cooling circuit from the high frequency leads occurs outside the accelerating chamber, whilst in Fig. 7 the junction is inside the chamber.
  • a is the casing of the accelerating chamber in which the semi-circular accelerating electrodes b to be cooled, are arranged.
  • the course of the cooling medium inside the electrodes themselves is not shown in the drawing and can be arranged in a known manner.
  • the cooling trodes b through the concentrically arranged pipes c, d; the cooling water entering through the pipe c and leaving through the pipe d.
  • the pipe 0 together with the internal pip d is wound to form a self-inductance which is located inside the accelerating chamber.
  • the constructional example shown in Fig. 6 enables, in a very simple manner, the cooling medium to be supplied through one of the high frequency conductors e, whilst the other conductor 1 serves solely for the discharge of the cooling medium.
  • cooling arrangements only two simple pipe coils having relatively small dimensions and acting as choke coils, are required.
  • the distribution of the cooling medium for the two electrodes occurs in the manner illustrated in the pipe system of th high frequency transformer.
  • the ends of the pipe coil acting as choke coils and furthest removed from the pipe These high frequency choke coils in the cool-' ing medium circuit can be omitted if, as shown in Fig. 7, the centre point k of the secondary winding of the high frequency transformer is connected to the casing of thechamber and the incoming and outgoing flow of cooling medium occurs over this centre point.
  • the main advantage of this arrangement is that the high frequency conductors e, f can be coupled over a galvanically separated primary coil with the secondary coil and that the high frequency supply circuit for the purpose of further voltage transformation can possess inside the chamber sections of Lecher wires, so that greater freedom as regards electrical adjustment is obtained.
  • a cyclotron comprising a casing providing a chamber, opposed accelerating electrodes in said chamber and electric circuit elements passing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circult elements including a high frequency transformer inside said chamber, said transformer comprising an auto-transformer in which the primary coil is a part of the secondary coil. the primary of said transformer being directly connected to a Lecher wire system leading through the insulating bushings into said chamber, said system being closed by a voltage junction point in the vicinity of the insulating bushings, and the secondary of said transformer being directly connected to said accelerating electrodes.
  • a cyclotron comprising a casing providing a chamber, opposed accelerating electrodes in said chamber and electric circuit elements passing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circuit elements including a high frequency transformer inside said chamber, the primary of said transformer being directly connected to conductor elements passing into said chamber, the ends of the secondary of said transformer being directly connected to said accelerating electrodes, the electrical midpoint of the secondary being connected to the casing of said chamber, and the secondary coil being in resonance with the resultant capacity between the accelerating electrodes at the operating frequency.
  • a cyclotron comprising a casing providing a chamber, opposed accelerating electrodes in said chamber and electric circuit elements passing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circuit elements including a high frequency transformer-inside said chamber, the primary of said transformer being directly connected to conductor elements passing into said chamber, the secondary of said transformer being directly connected to said accelerating electrodes, at least one tuning element positioned inside said chamber, and means passing through the casing of said chamber for actuating said tuning element from outside the chamber.
  • a cyclotron comprising a casing providing a chamber, opposed accelerating electrodes in said chamber and electric circuit elements passing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circuit elements including a high frequency transformer inside said chamber, the primary of said ing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circuit elements including a high frequency transformer inside said chamber, the primary of said transformer being directly connected to conductor elements passing into said chamber, the secondary of said transformer being directly connected to said accelerating electrodes, at least one tuning element positioned inside said chamber, and means passing through a flexible member attached to the casing of said chamber for actuating said tuning element from outside the chamber.
  • a cyclotron comprising a casing providing a chamber, opposed accelerating electrodes in said chamber and electric circuit elements passing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circuit elements including a high frequency transformer inside said chamber, the primary of said transformer being directly connected to conductor elements passing into said chamber, the secondary of said transformer being directly connected to said accelerating electrodes, at least one metal plate in said chamber adjacent an accelerating electrode, and means passing through the casing of said chamber for altering the position of said plate with respect to the electrode from outside the chamber.
  • a cyclotron comprising a casing providing a chamber, opposed accelerating electrodes in said chamber and electric circuit elements passing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circuit elements including a high frequency transformer inside said chamber, the primary of said transformer being directly connected to conductor elements passing into said chamber, the secondary of said transformer being directly connected to said accelerating electrodes, at least a portion of said circuit elements being hollow and serving to conduct a cooling medium to and from the accelerating electrodes, the junction of the cooling medium supply and the hollow circuit elements being positioned at a point where the voltage on th circuit elements is substantially lower than the voltage on the electrodes.
  • a cyclotron comprising a casing providing a chamber, opposed accelerating electrodes in said chamber and electric circuit elements passing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circuit elements including a high frequency transformer inside said chamber, the primary of said transformer being directly connected to conductor elements passing into said chamber, the secondary of said transformer being directly connected to said accelerating electrodes, at least a portion of said circuit elements being hollow and serving to conduct a cooling medium to and from the accelerating electrodes, the junction of the cooling medium supply and the hollow circuit elements being positioned at a point outside the chamber where the voltage on the circuit elements is substantially lower than the voltage on the electrodes.
  • a cyclotron comprising a casing providing a chamber, opposed accelerating electrodes in said chamber and electric circuit elements passing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circuit elements including a high frequency transformer inside said chamber, the primary of said transformer being directly connected to conductor elements passing into said chamber, the secondary of said transformer being directly connected to said accelerating electrodes, at least a portion of said circuit elements being hollow and serving to conduct a cooling medium to and from the accelerating electrodes, the junction of the cooling medium supply and the hollow circuit elements being positioned in the immediate vicinity of the insulating bushings at a point where the voltage on the circuit elements is substantially lower than the voltage on the electrodes.
  • a cyclotron comprising a casing providing a chamber, opposed accelerating electrodes in said chamber and electric circuit elements passing into said chamber through insulating bushings and connecting said electrodes with a source of high frequency oscillating current, said circuit elements including a high frequency transformer inside said chamber, said transformer comprising an auto-transformer in which the primary coil is a part of the secondary coil, the primary of said transformer being directly connected to conductor elements passing into said chamber, and the secondary of said transformer being 111- rectly connected to said accelerating electrodes, said transformer coil being hollow and serving to conduct cooling medium to and from said accelerating electrodes, the cooling medium being supplied to and removed from said coil through hollow conductor members.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Particle Accelerators (AREA)
US308301A 1938-12-19 1939-12-08 Cyclotron Expired - Lifetime US2265113A (en)

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CH534047X 1938-12-19

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US (1) US2265113A (de)
CH (3) CH205250A (de)
DE (1) DE925538C (de)
FR (1) FR862497A (de)
GB (1) GB534047A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2531384A (en) * 1947-09-20 1950-11-28 Int Standard Electric Corp Polyphase cyclotron
US2630549A (en) * 1948-08-31 1953-03-03 Rca Corp High-voltage generator
US2642531A (en) * 1950-08-29 1953-06-16 Atomic Energy Commission Radio-frequency oscillator
US2660644A (en) * 1951-07-10 1953-11-24 Usco Power Equipment Corp High-voltage fuse
US2713635A (en) * 1949-12-19 1955-07-19 Leitz Ernst Gmbh Electron-cyclotron discharge apparatus

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE760346C (de) * 1940-10-18 1953-03-23 Siemens & Halske A G Zyklotronanordnung
US2701304A (en) * 1951-05-31 1955-02-01 Gen Electric Cyclotron

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2531384A (en) * 1947-09-20 1950-11-28 Int Standard Electric Corp Polyphase cyclotron
US2630549A (en) * 1948-08-31 1953-03-03 Rca Corp High-voltage generator
US2713635A (en) * 1949-12-19 1955-07-19 Leitz Ernst Gmbh Electron-cyclotron discharge apparatus
US2642531A (en) * 1950-08-29 1953-06-16 Atomic Energy Commission Radio-frequency oscillator
US2660644A (en) * 1951-07-10 1953-11-24 Usco Power Equipment Corp High-voltage fuse

Also Published As

Publication number Publication date
CH205250A (de) 1939-06-15
FR862497A (fr) 1941-03-07
DE925538C (de) 1955-03-24
CH209266A (de) 1940-03-31
CH209267A (de) 1940-03-31
GB534047A (en) 1941-02-26

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