US2103303A - Device for producing electron rays of high energy - Google Patents

Description

Dec. 28, 1937. STEENBECK 2,103,303 1 DEVICE FOR PRODUCING ELECTRON RAYS OF HIGH ENERGY Filed March '4, 1936 2 Sheets-Sheet l Dec. 28, 1937. m. STEENBECK DEVICE F03 PRODUCING ELECTRON RAYS OF HIGH ENERGY J Sheets-Sheet 2 zgrfi Fi Mag}; 4, 1936 5 a a a r a J i 1 J5 common Source of Sihusoia/al b o/Eye Patented 28. 1937 UNITED STATES DEVICE non PRODUCING ELECTRON RAYS or men ENERGY Max Steenbeck, Berlin-Siemensstamit, Germany,

assignor to Siemens-Schuckertwerke Aktiengesellschaft, Berlin-Slemensstadt, Germany, a

corporation of Germany Application March 4,1936, Serial No. 67,184

y In Germany March 6, 1935 10 Claims. (Cl. 250 -27) wander within the field by following the forces My invention relates'to a device for producing electron rays of'great energy.

The object of my invention is to produce by very simple means, above all without the use of 5 high voltages, electron rays of greatenergy, for instance rays having a velocity corresponding to the application of several million volts.

It has hitherto beenproposed toemploy for this purpose a magnetic alternating field by which an electric eddy field is produced which imparts to the electron the required speed. In this case the arrangement is carried out in such a manner that the electron path encloses the magneticfield in' the same manner as the turns of the secondary winding of a-transformer encloses the transformer core as well as the flux traversing this core.

In a known arrangement of this type an annular highly exhausted discharge vessel encloses 20. the core of a three-legged transformer whose central core is provided'with an exciting winding connected to an industrial alternating voltage of the usual voltage and frequency. A glowing cathode which emits the electrons necessary for v the'radiation is arranged in the discharge vessel. Besides the alternating field also an additional magnetic field produced by permanent magnets cal , acts on the electrons, the magnetic field serving to'maintain the electrons circulating about the 30 transformer core in a certain plane determined by the discharge vessel,i.'e.. to prevent the elec- The invention relates substantially tothe gulding of the electrons within the eddy field insuch 45 a manner that they are not elected prematurely from the eddy field. Further features of the in.-

vention relate to the production of the electric eddy field as well as to the introduction of the electrons at the beginning of the acceleration 50 into the eddy field and to the release from the field at the end of the acceleration.

Of particular importance are the provisions made for stabilizing the electron path within the eddy field. In order, that the electron may take 55 up energy within the electric eddy field it must field, the centrifugal force increases with time;

of the field. If in this case the particular advantage' of the eddy field that the same charge may repeatedly follow one and the same line of force is tobe utilized the charges must, therefore, 5 revolve in succession about the central magnetic flux many times. In order that the electron may remain during its numerous revolutions 'on a circular path a force directed towards the center' of the circular path must annul the centrifugal force of the electron mass. Since the speed of the electron (and in the neighborhood of the velocity of light the electron mass) increases the longer the electron has been accelerated by the eddy m consequently, also the centripetal force must-be increased in proportion to time. The object of the invention is, therefore, to determine an electric or magnetic field which by the forces of'the field exerted onthe electron charge stabilizes the electron on a given circular ,path/ A stabilizing. or a guiding field must be provided such as is also the case with the above-mentioned known device, in which said field has been produced by permanent magnets of a given arrangement. In this case, this stabilization must also be still effective even if the rotating electron experiences interferences of whatever kind whether it begins its flight in the eddy field under false initial conditions (for instance with an initial velocity deviating from the desired direction) or whether the electron experiences during its numerous revolutions a collision with one of the residual gas molecules even present at the highest vacuum, which causes a sudden (small) change of the direction of flight and of the flying speed. These unavoidable interferences must be permissible within a certain definite magnitude without deviating the electron'considerably from the ideal desired path along which a completely undis- 4 turbed electron would revolve within the eddy field. Furthermore, a stabilizing field must, also compensate for its own faults. It would not help any to create a stabilizing field which would compensate for the above-mentionedinterferences of theelectrons only in the case of an entirely.

- ideal field, but the stabilizing field must be of such nature as to bring about the compensation even in the case of slight deviations from the ideal field (for instance slight deviations from the rotation symmetry) which deviations cannot be avoided in the case of the actual realization of the field.

The main object ,of the vguiding field consists in maintaining the' radius of the path at a con- 66 stant value. such that a circular path is described by an electron, the radius thereof remaining constant within a given time interval, although the centrifugal force increases with time. The centrifugal force of the revolving electron may be annulled by an electric field having field lines running radially outwardly or by a magnetic field whose lines of force are perpendicular to the plane of the path. In order to guide an 11 million volt electron along a circle of 5 cm. radius a radial electric field of about 2.10 volts/cm. would be necessary. The distance between the electrodes for this electric field should be of a sum-- cient magnitude in order to permit also disturbed electrons deviating somewhat from the desired path to freely fly. The distance should be of the order of 1 cm. Consequently, a voltage of some millions of volts between these electrodes would be necessary only to guide the electron along a circular path which voltage, therefore, would be of the same order of magnitude as the speed of the electrons themselves. Consequently, the entire method would not afiord any advantages at all. To guide an 11 million volt electron along a circle of 5 cm. radius, however, only a magnetic field of about 7000 gauss is necessary which may be easily created. The "guiding field which guides theelectron along -a circular path about the central magnetic flux must, consequently, be a magnetic field.

The arrangement in principle is as follows: A central iron leg carries the magnetic flux varying at spaced intervals and produces about itself the electric eddy field. The guiding field Hz is produced by two cylindrical pole pieces which enclose the central iron leg and, therefore, the central magnetic flux and which guide the electrons on circles about the magnetic flux. The guiding field should not, as already proposed, be produced by a permanent magnet, for if the revolving electrons are accelerated with time to a greater extent the radius of path would become greater and greater in the case of a constant intensity of the guiding field. In order that the radius of the path may remain constant the intensity of the guiding field H1 must. consequently, increase with time. Since the speed of the electrons depends only upon the central magnetic fiux, and since the relation between the speed of the electrons and the guiding field is also unequivocal in the case of the radius R of the path being maintained constant, the necessary intensity of the guiding field Hr must be only dependent upon the magnitude of the central flux. In order that the radius R of the path may remain constant the following condition must be fulfilled:

' as it would be if the guiding fieldH: would homog'eneously fill up the interior of the circular path in order that the radius R of the paths of electrons may remain unchanged (1:2 condition"). This condition holds good even within the range of the relativistic speeds. It also holds good as to the sign, 1. e., the central flux and the guiding field must increase in the same direction at the ratio 1:2, Assuming that the direction of the central fiux is positive an increase'in flux produces an eddy field revolving only in one direction. The guiding field must be then so directed that the electrons therein revolve in such a direction as to be accelerated by the eddy field.

Consequently, the field must be A guiding field directed in opposite direction would cause the electrons to revolve against the eddy field so that the motion of the electrons would be checked.

Owing to the fact that the central flux and the guiding field H1 must have the same direction and be proportional to each other both are excited by the same winding. The guiding field Hz with its air gap which substantially determines the magnetic resistance is proportional to the instantaneous value of the exciting current. In order that the flux be proportional to the guiding field the flux must, therefore, also be proportional to the exciting current. This is, however, not the case with closed iron cores owing to the non-linearity of the magnetic iron characteristic B=f(H), even within the unsaturated range. In order to bring about the proportionality, an air gap-whose magnetic resistance is great as compared to that of the remaining iron path and, therefore, ensures the proportionality between fiux and guiding field-is also provided in the iron leg.

In the accompanying drawings I have shown different forms of an arrangement by which the desired result may be accomplished. In these drawings Fig. 1 is a diagrammatic illustration, in sectional elevation, of a magnetic body designed to illustrate the general principle on which the invention is based.

Fig. 2 shows diagrammatically the pole elements for producing the guide field.

Fig. 3 shows an advantageous form of such pole elements.

Figs. 4 through 9 show each in transverse section difierent constructions of acceleration pole elements which are composed in several different ways of laminations and wires.

Fig. 10 shows in sectional elevation a practical construction according to the present invention, it being assumed that the pole element. there shown constitute portions of a magnetic body which in general principles is constructed as shown in Fig. 1, and

Fig. 10 shows in planview the form of the electron vessel 3| in Fig. 10.

Referring to Fig. 1, in this arrangement th same amperetums W produce the flux it in the central leg and the guiding field H: between the pole shoes P. Since the flux dz enclosed by the electron circular path R should correspond to a field having an average magnitude twice as great as the guiding field Hi, the air 'gap in the central leg must be made correspondingly smaller than that between the poles P of the guiding field.

The arrangement shown in Fig. 1, even though the 1:2 condition be properly fulfilled, would only be suitable if the electrons were and would remain undisturbed. Undisturbed are such electrons, for which the condition is fulfilled that they were produced with the speed zero on the circle R at the moment at which the guiding field passes through zero. I

That the arrangement shown in Fig. 1 is not yet suitable to stabilize also disturbed electrons on the desired circle R may be deduced when assuming that an electron revolvingon the circle R has a small speed component in the upward direction which it either already had from the moment it entered the eddy field or had acquired during the flight owing to a collision with a residual gas molecule. This speed component is 9,108,303 I sequently, the electron circular path to the pole not influenced in the above-mentioned homogeneous magnetic. field Hr, since it runs parallel to the lines of the magnetic field. Even if'this speedcomponent amounts to 10. cm/sec. (this corresponds to an energy of only about 9.10 9 volts) it causes the electrons within the 5.10 sec., during which they must remain in the magnetic field at an energization at 50 cycles, to be ejected 5 cm. from the plane of the desired cirale and, therefore, they strike the, wall of the discharge vessel. It is also possible that the speed components of the electrons in this direction resulting from the thermic disorder of their mo- .tion are still of a greater order of magnitude so should, therefore, be taken by means of repulsive forces to prevent such a faulty speed from ejecting an electron at any distance from the plane ofthe desired circle in the upward or downward .direction and to cause the faulty speed to bring about at most a huntingif possible attenuated-about the desired plane with smallest possible amplitudes.

This may be attained according to the invention by rendering the guiding field somewhat non-homogeneous so that it. decreases with increasing distance vfrom the axis. The lines of force are then bent-outwardly (Fig. 2) so that also radial components H: of the magnetic field are produced. In the case of symmetrical electrodes these radial components of the magnetic field disappear in the central plane M between the electrodes. In this case the radial field'components above. the central plane are directed from the insideto the outside, whereas those below the central plane are directed from the outside tothe inside.

So long as the electron flies on a circle in the central plane M it is not subjected to any changes, since the radial components of the magnetic field are not present in the central plane M. If now the electron possesses a speed component in the upward direction-s'ma ll as compared to the total speed- -and if the circular path of the electron displaces itself gradually .in the upward direction,

electrodynamic forces between the flying electron and the radial field components are now added to the forces hitherto considered alone between the flying electron and the axial field component. The force which the radial field component exerts on the electron is perpendicular to the (tangential) direction of flight of the electron and perpendicular to the radial field component: A force is in axial direction is, therefore, obtained (Fig. 2)

which acts in a downward direction in the case of the electron circular path being displaced in the upward direction,'. as this is proved by the righthand rule. The electron is, therefore, driven back into the central plane. Since within the zone below the central plane the direction of the radial field component is reversed as in the space above the. central plane, the action of the radial component consists in this case in a deviation of the electron in an upward direction that is to-say the electron is again driven back toward the central plane. Such a non-homogeneous field decreasing outwardly stabilizes, thereforc, the electron circular path in the central plane.

Reversely a magnetic field increasing outwardly and having radial components in opposition would cause upon a small deviation of the electron in the vice versa. Such a magnetic field attracts,

pieces or to the wall of the discharge vessel and is, therefore, unsuitable for stabilizing purposes.

Since the magnitude of the radial field component-as proved by the computationof such a potential field--is proportional to z'for small deviations z from the central plane (see Fig. 2) a field decreasing outwardly results in a repulsive force which is proportional to the deviation 2;

the electron performs, therefore, harmonic oscillations about the central plane. 7

Besides the faulty speed in the axial direction the guiding field must also compensate for minty but they have in this case a radial direction.

To prevent these disturbances the guiding field is rated according to the invention in such a manner that the condition of stabilization R (IE is fulfilled with an optimum as to the exclusion of deviations of the electron from the desired path in the case of l R (H! -1 an? "r (3) The guiding field should, therefore, decrease always to a lesser extent, preferably half as much, I

than indirectly proportional to this radius.

a This condition is to ,be considered in connection with the above-mentioned 1:2 conditionac cording to the Equation (1) i. e., that radius which encloses a field, whose mean value referred to the area of the circle ,is just twice as great as the field prevailing at the periphery should fall within a non-homogeneous field zone which fulfills the condition of the Equation (2) and preferably the condition of Equation (3)..

An essential feature of the invention is the design of the pole pieces, which must be such that the field produced therebetween has the abovementioned properties of stabilization. In Fig. 3 is shown a form of the invention based on the following considerations: If the two hyperbole branches l and 2 are caused to rotate about the axis a two hyperboloids are produced. The field created between the two hyperboloids decreases steadily outwardly. In the neighborhood of the axis the field is practically homogeneous, at a considerable distance Rfrom the axis where the hyperboloid contacts approximately with the asymptotes the field decreases practically with l/R. The expression R/H.dH/dR characteristic for the non-homogeneity of the field varies in this ing the case in which 3:0, the hyperbole. field. therefore, fulfills in all cases the condition of Equation (2) But'it does not at first fulfill the 1:2 condition of Equation (1) in any case whatever. That is tosay, in the pure hyperbola'field there does not exist a circle, whose area in average covers just twice as strong a field as that prevailing at the periphery; the inner field is always too weak. Consequently, in order to utilize the hyperboloid as stabilizing pole piece form, the inner field must be strengthened; for instance, by rendering the distance between-the pole pieces case from 0 on the axis to 1 at infinity; exceptinthe neighborhood of the axis smaller than is the case with hyperboloids. This may be ac- However, the inner pole pieces A and B owing to the stray field thereof disturb the hyperbola field proper in an undesired manner (see. Fig. 3) and the circular electron path must be, therefore, placed so far outwardly or the auxiliary pole pieces must be carried out with such a small radius that the electrons are not any longer substantially influenced by this stray field. However, this means a limitation of the greatest possible inner flux 2 which should on the other hand be rendered very strong in order to attain electrons of great energy. It is, therefore, necessary to prevent the stray flux from extending too far in the lateral direction. This may be accomplished if the central flux is not caused to pass through one air gap but if this air gap is subdivided into a large number of small air gaps which, of course, may be filled up with any non-magnetic material. Since, however, the stray flux spreads only over zones of the magnitude of the width of the air gap, only a much smaller distance of the revolving electron from the central pole pieces is necessary. The stray flux may be even practically eliminated if a space as formed by the lines of force of the undisturbed hyperbolic field is filled up with pulverized iron which is embedded in the form of a compressed pulverized iron core into an insulating material. In this case it is possible by the proper choice of the iron filling factor to obtain such an average permeability that the central magnetic fiux produced thereby satisfies the 1:2 condition. Consequently, the desired circle R of the electron may then be placed very close around the central flux and a very high electron end speed is obtained with the small circle R and the strong flux. The pole pieces must be extended so far outwardly as to be able to rely extensively upon the pure hyperbolic field in the vicinity of the desired circle.

Strictly speaking with laterally limited pole pieces the field lines are, of course, displaced further outwardly over the entire space than would he the case with the pure hyperbolic field. This may, however, be compensated for in the surrounding of the desired circle R; if the pole pieces are caused to move away from one another to a somewhat lesser extent for a short distance outwardly as is the case with hyperboloids. In this manner a zone is provided with a relatively stronger field, whose cross pressure of the field lines can again force back the field into the vicinity of the desired circle approximately into the zone of a pure hyperbola field. A small total diameter of the pole pieces not only reduces the dimensions of the apparatus but also the power required for setting up the field.

Besides the above-described features for the design of the pole pieces adiacent to the field space it is essential to the stabilization of the electrons during their fiight in the eddy field that the total arrangement be rotation symmetrical as far as possible with respect to the axis of the circular electron path. Only in the case of a rotation symmetry, the field lines of the eddy field serving to accelerate the electrons are concentric circles. For this purpose the central iron leg, which is made of laminations on account of the eddy currents, must be given a rotation symmetrical design. If the laminations were stacked as shown in Fig. 4, that is to say, not according to a rotation symmetrical distribution it would not be possible to avoid an unsymmetry wound lamination as shown'in Fig. '7 creates an approximately rotation symmetrical field. The latter, however, acts in its outer layers as a secondary winding having a relatively high turn voltage so that a very reliable insulation is necessary between the individual layers which again impairs the iron filling factor. Since the turn voltage is smaller and in the interior a very reliable insulation may be dispensed with, such a lamination reel (Fig. 7) may. nevertheless, be employed preferably for filling up the central hole (Fig. 8) which is necessary in an involute yoke (Fig. 5) for which purpose also a bundle of wires may be employed (Fig. 9). Of the high-grade types of iron permalloy is above all suitable, since it combines sudden saturation with very high permeabilities in the unsaturated state.

To provide a rotation symmetrical eddy field it does not sufiice to design the central iron leg rotation symmetrically. The magnetic fiux must, moreover, be such as to form also exteriorly as far as possible a rotation symmetrically closed circuit. This may be accomplished if the magnetic circuit of a straight cylindrical iron core-as is the case with induction coils-is closed on all sides by air. However, in this case the expanded stray field and the power which has only the purpose of setting up the stray field may give rise to trouble. Furthermore, such a stray field may easily be brought qut of symmetry by outer iron or also by metal masses. If, on the other hand, the magnetic circuit were closed by iron, access to the eddy field in the case of a complete rotation symmetry would be completely prevented, consequently it would be impossible to get also the generated rapid electrons out of the eddy field. In order to attain at all events an approximate rotation symmetry the closing of the magnetic circuit according to the invention is not effected by one end yoke, but at least by two, if possible by more yokes, in which case an adjustable air gap may be provided in each yoke in order to distribute the magnetic flux symmetrically.

Further features of the invention consist in.

60 netic fields of high intensity, i. e., just at the axially therewith. The circular electron path is indicated at 32. r

The glowing cathode may in this case have, for instance, the form of a wire ring which is disposed somewhat above or below the desired circle. It would also be possible to close this wire ring and to heat it by induction by the short circuit current created therein. This would be of advantage owing to the maintenance of a complete rotation symmetry and to theelimination of particular heating connections. Nevertheless this kind of heating is not preferable, since the magnetic field of the heating current disturbs the guiding field. The heating current field has the tendency to attract the electrons to the glowingcathode. The effect of the heating current and of the heating voltage drop' may, however, be completely suppressed in the case of a separately heated cathode if an alternating current of the same frequency and phase as the exciting current of the magnetic field is employed as heating current, as indicated in Fig. 10. In this case the heating voltage and heating current pass through zero together with the magnetic field and do not, therefore, interfere in the timeintervals in which the emission of the electrons from the glowing cathode is needed. The short circuit current heating works, however, with a current having the same frequency but not the same phase (owing to the ohmic current component in the heating filament).

Another way of introducing the electrons into the field consists in shooting an electron ray to which an acceleration has been imparted already outside the pole pieces into the eddy field. The shooting in of slow electrons into the eddy field in the immediate neighborhood of the passage of the magnetic field through zero 'is preferable,

since then the rotational voltage of the eddy field is greatest as compared to the electron energy, that is to say it might exert its stabilizing action already after a relatively small number of revolutions.

As soon as the speed of the electrons has attained approximately its maximum value the electrons must be caused bysome suitable disturbance of the stabilizingproperties of the guiding' field to leave the desired circle and to be ejected from the magnetic field. Such disturbances may be produced in a variety of ways. For instance, an additional interfering field could be set up rapidly, for instance, an electric field between a particular electrode and its surroundings by a properly time-controlled transient wave or by a magnetic interfering field through a properly controlled energization of a particular coil. It is, however, very much simpler to utilize a disturbance caused by saturation of the iron, since the latter occurs each time automatically with-.- out specific synchronization in the case of ma moment when the acceleration of the electrons v has come to an end.

If by the saturation of the iron the guiding field H: in the arrangement shown in Fig. 3 is caused to be increased only up to a certain maximum Consequently, the circular electron path expands. ,The expansion may be such that the circle expands up to the unstable point,'from which the magnetic field decreases with dH/dR.R/H l or to a further extent and, therefore, the circular electron path explodes.-

Such a saturation of the guiding field may be.

effected with an arrangement of the pole pieces as disclosed in Fig. 10. While in the central portion the fiux passesthrough cylindrical pole pieces l2, |3-with the exception of the air gaps and the compressedpulverized iron core L, the

cylindrical pole pieces P which produce the guiding field H: are provided with a restricted passage A. The entire fiux for the guiding field (inclusive of the stray field) passes through this restricted passage and by suitably dimensioning the restricted passage A it is possible to render, by proceeding from any given value of the guiding field, the fiux intensity in the restricted passage so high that the iron becomes'saturated at that point and, therefore, acts as an additional magnetic resistance for retarding or preventing afurther increase of the guiding field. The enlarged portions of the cylindrical pole pieces located beyond the restricted passage are in this case only under the influence of such a low flux intensity that here the high permeability of the iron is maintained. The surfaces of the pole pieces which determine the form of the guiding field remain magnetic .equipotential surfaces as in the case of lower guiding field intensities and cause the guiding field to drive back on the circular path even the electrons which have strayed away after the saturation of the iron has occurred.

Only the circular path itself expands with the above-mentioned results.

The guiding field windings F and the acceleration field windings W are preferably connected to a source of sinusoidal voltage and are not fed with sinusoidal current, which may be easier effected from an electrotechnical point of view.

Since after the saturation of the guiding field the flux of the guiding field does not increase any longer, but the total flux must continue to increase in a sinusoidal manner owing to the sinusoidal voltage applied, the central fiux now increases much more than before the saturation of the guiding field. However, this means that a saturation of the guiding. field expands the circular electron path in a twofold manner: Not

only the checked increase of the guiding field but also the electrical intensity of the eddy field increased by the increased central flux contribute to expand the circular path. This double utilization of the saturation of the iron permits- A in the cylindrical pole piece a particular field winding may be still accommodated which may be employed for correction in the case of small dimension faults of the stabilization conditions, since the ampere turns of the field winding enclose only the central fiux.

It may be further pointed out that the pole pieces of the central magnetic field and the cylindrical pole pieces for the guiding field may be brought separately into cooperation with the yoke or main body of the magnetic arrangement.

The system operates in the following manner. Let us assume that at a given instant the two magnetic fields pass through zero value and the cathode 33 is glowing. From this instant the intensities of the two fields increase.v The acceleration'field generated in the pole pieces l2, It acts upon the electrons emanating from the glowing cathode and moves them in the circular path 32. A deviation of the electrons from this path is prevented, by the efiect of the guide field which increases in intensity simultaneously with the acceleration field. While the field intensities of both fields increase, the electrons travel at higher and higher speeds on their circular path. 11' now the excitation of all pole pieces exceeds a given value, the guide field prevailing between the pole pieces l4, l5 attains its saturation value, while the acceleration field which prevails between pole pieces l2, l3 still increases in intensity. This disturbance of the previously existing ratio between the intensities of the two fields has the eiIect that the electrons fiy out of their circular path at a tangent. They impinge at their final speed upon the wall of vessel ii. The speed attained by them may be of such magnitude that it may readily correspond with electric potential differences-of the order of 10 to 20 million volts.

As will be noted from Fig. 10, which shows a plan view of discharge vessel 3|, an outlet nozzle 35 is provided in a manner known in that type. of vessel. The axis of this nozzle is tangentially located with respect to the outer circle of vessel 3| so that the electrons, radially deflected in the manner aforedescribed, are discharged therefrom in the form of an electron beam S. This beam may be used for instance for therapeutic irradiation by directing the beam against the portions of the human body under treatment.

The magnetic field necessary for the production of 10 to 20 million volt electrons accumulates,

when completely developed, an energy of about 1 kilowatt second. If it were excited at 50 cycles per second a reactive power of 50 tokva. (with a cos =0.1) is necessary, whereas when excited at 500 cycles per second about 500 to 1000 kva. are required. At least in the second case the inductive wattless power will be compensated for by a condenser lying in parallel relation to the magnetic winding in order to dispense with a large-sized generator. An oscillating circuit tuned to the operating frequency must, consequently, be provided.

Although the invention may be used for various purposes, for which electrons or high speed are necessary it is very essential to therapeutics.

I claim as my invention:

1. A device for generating electron rays of great energy by means or an electric eddy field produced by a magnet field varying with time. comprising a source of electrons, an evacuated vessel containing said source and constructed to provide a circular path for said electrons, means for producing a magnetic field varying with time for accelerating the electrons in a circular path and whose field axis coincides with the rotation axis or the electron stream, means for producing a guide field for the electron stream which varies similarly with time and which coaxially surrounds said acceleration field, said guide fieldproducing means being arranged so that the field intensity decreases outwardly with increasing radius of the electron path but at a rate not more than inversely proportional to the path radius increase, the means for producing said two fields being normally proportioned relatively to one another so that the guide field has always one-half the intensity of the accelerating field, and means for disturbing the relative intensities of said two fields whenthe electrons have attained the desired speed. l

2. A device for generating electron rays of great energy by means of an electric eddy field produced by a magnet field varying with time, comprising a source of electrons, an evacuated vessel containing said source and constructed to provide a circular path for said electrons, means for producing a magnetic field varying with time for accelerating the electrons in a circular path and whose field axis coincides with the rotation axis or the electron stream, means for producing a guide field for the electron stream which varies similarly with time and which coaxially surrounds said acceleration field, said guide fieldproducing means being arranged sothat the field intensity decreases outwardly with increasing radius oi the electron path approximately atan inverse ratio of .5:1, the means for producin said two fields being normally proportioned relatively to one another so that the guide field has always one-half the intensity of the accelerating field, and meansior disturbing the relative intensities of said two fields when the electrons have attained the desired speed.

3. A device for generating electron rays of great energyby means-oi an electric eddy field produced by a magnetgfield varying with time, comprising a source of electrons, an evacuated vessel containing said source and constructed to provide a closed circular path for said electrons, a magnetic body having two opposing pole elements disposed coaxially with said electron path and being spaced apart and carrying energizing windings adapted to produce a magnetic acceleration field varying with time. two further opposing pole elements on said magnetic body carrying energizing windings for producing a guide field for the circular electron stream and similarly varying with time, said-guide pole elements surrounding said accelerationpole elements rotation-symmetrically and being shaped so that the intensity of the guide field produced by them is always equal to halt the intensity of the acceleration field, said guide pole elements being also constructed so that the intensity oi their generated field decreases with increasing dhtsnce from the pole axis but not more than inversely P rtional to the electron path radius increase, and means for disturbing the relative intensities of said two fields when the have attained the desired speed. I

4. a device for generating electron rays of greatenergybymeansotsnelectriceddyfield produced by a magnet field varying withtime.

comprising a source of electrons, an evacuated vesselcontainingsaldsourcesndconstructedto provide a closed circular path iorssid electrons. a magnetic body having two pole elements disposed couially. withsaid electron path and being spaced apart and carrying energising windings adapted to produce smsgnetic acceloration field varying with time, two further op- 2g,

posing pole elements on said magnetic body carsaid acceleration field pole elements being bridged rying energizing windings for producing a guide field for the circular electron stream-and similarly' varying with time, said guide pole elements surrounding said acceleration pole elements rotation-symmetrically and being shaped so that the intensity of the guide field produced by them is always equal to half the intensity 'of the accelerationfield, said guide pole elements being also constructed so that the intensity of their generated field decreases with increasing distance from the-pole axis but not more than inversely proportional to the electron path radius increase, and means for disturbing the relative intensities of said two fields when the electrons have attained the desired speed, the opposing faces of said guide poles being shaped as hyperboloids within the range of the field produced by them.

5. A device for generating electron rays ofgreat energy by means of an electric eddy field produced by a magnet field varying ,with time,

comprising a source of electrons, an evacuated field for the circular electron-stream and similarly varying with time, said guide pole elements surrounding said acceleration pole elements rotation-symmetrically and being shaped so that the intensity of the guide field produced by them is always equal to half the intensity oi'the acceleration field, said guide pole elements being also constructed so that the intensity of their generated field decreases with increasing distance from the pole axis but not more than inversely proportional to the electron path radius increase, and means for disturbing the relative intensitia of said two fields when the electrons have attained the desired speed, the space between said acceleration field pole elements being bridged by an alternating series of air gaps and magnetic material.

,6. A device for generating electron rays of great energy by means of an electric eddy field produced by a magnet field varying with time, comprising a source of electrons, an evacuated vessel containing said source and constructed to provide a closed circular path for said electrons, a magnetic body having two opposing pole elements disposed coaxially with said electron path and being spaced apart and carrying ener gizing windings adapted to produce a-magnetic acceleration field varying'with time; two further opposing pole elements on said magnetic body carrying energizing windings for producing a guide field for the circular electron stream and similarly varying with time,,said guide pole elements surrounding said acceleration pole elements rotation-symmetrically and being shaped so that the intensity of the guide field produced Y by them is always equal to half the intensity of the acceleration field, said guide pole elements being also constructed so that the intensity of their generated field decreases with increasing distance from the pole axis but not more than inversely proportional to the electron path radius increase, and means for disturbing the relative intensities of said two fields when the electrons have attained the desired speed, the space between by a mass consisting of iron powder and an insulating binder.

7. A device for generating electron rays of great energy by means of an electric eddyfield produced by a magnet field varying with time, comprising a source of electrons, an evacuated vessel containing said source and constructed to provide a closed circular path for said electrons,

a magnetic body having-two opposing pole; elements disposed coaxially with said electron path and being spaced apart and carryingenergizing winding-s adapted to produce 'a'magnetic acceleration field varying with time, two further opposing pole elements on said magnetic body carrying energizingwindings for producing a guide field for the circular electron stream and similarly varying with time, said guide pole elements surrounding said acceleration pole elements rotation-symmetrically and being shaped so that the intensity of theguide field produced by them is always equal to half the intensity of the acceleration field, said guide pole elements being also constructed so thatl-the intensity of their generated, field decreases 'with increasing distance from the poleaxls but not more than'inversely proportional to the electron path radius increase, the magnetic body portion carrying the guide' field poles being suitably shaped to produce in said portlonby the field, generated in said guide poles, magnetic saturation when a desired fiux density is attained, the value of which is below that at which the acceleration pole elements become saturated;

8. A device for generating electron rays of great energy by means'of an electric eddy field produced by a magnet field varying with time, comprising a source of electrons, an evacuated vessel containing saidfsource and constructed to provide a closed circularpath for said electrons, a magnetic bodyvhaving two opposing pole elements disposed coaxially with said electron path and being spaced apart and carrying energizing windings adapted to produce a magnetic acceleration field varyingwith time, two further opposing pole elements on said magnetic body carryin'g energizing windings for producing a guide field for the circular electron stream and similarly varying with time, said guide pole elements surrounding said acceleration pole elements rotation-symmetrically and being shaped so that the intensity of the guide field produced by them is always equal to half the intensity of the acceleration field, said guide pole elements being also constructed so that the intensity of their generated field decreases with increasing distance from density therein exceeds a given value at which the acceleration pole'elements remain still unsaturated.

9. A device for generating electron rays of great energy by means of an electric eddy field produced by a magnet field varying with time, comprising a source of electrons, an evacuated vessel containing said source and constructed to provide a closed circular path for said electrons, a magnetic body having two opposing'pole elements disposed coaxially With said electron path and being spaced apart and carrying energizing windings adapted to produce a magnetic acceleration field varying with time, two further opposing pole elements on said magnetic body carrying energizing windings for producing a guide field for the circular electron stream and similarly varying withtime, said guide pole elements surrounding said acceleration pole elements rotation-symmetrically and being shaped so that the intensity of the guide field produced by them is always equal to half the intensity oi. the acceleration field, said guide pole elements being also constructed so that the intensity of their generated field decreases with increasing distance from the pole axis but not more than inversely proportional to the electron path ra-,

dius increase, and meets for disturbing the relative intensities of said two fields when the electrons have attained the desired speed, the magnet body outside of said two kinds of pole elements forming a return circuit for the opposing pole elements being in a plane located substantially in the rotation axis of the electron stream.

10. A device for generating electron rays of great energy by means of an electric eddy field produced by a magnet field varying with time, comprising a glow cathode serving as a source of electrons, an evacuated vessel containing said source and constructed to provide a closed circular path for said electrons, a magnetic body having two opposing pole elements disposed coaxially with said electron path and being spaced apart to accommodate said vessel between them and carrying energizing windings adapted to produce a magnetic acceleration field varying with time, two further opposing pole elements on said creases with increasing distance from the pole axis but not more than at an inverse ratio to said distance, means for disturbing the relative intensitles of said two fields, a common alternating voltage source for the energizing windings of said acceleration and guiding pole elements so as to .produce equal variations as to time in the fields produced by said elements, said glow cathode being connected to the same voltage source so that the cathode voltage and the magnetic fields attain their zero values at the same time.

MAX STEENIBECK.

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