US2721949A - Betatron - Google Patents

Betatron Download PDF

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Publication number
US2721949A
US2721949A US192731A US19273150A US2721949A US 2721949 A US2721949 A US 2721949A US 192731 A US192731 A US 192731A US 19273150 A US19273150 A US 19273150A US 2721949 A US2721949 A US 2721949A
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Prior art keywords
electrons
betatron
guiding
field
injector
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Expired - Lifetime
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US192731A
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English (en)
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Gund Konrad
Berger Hans
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Individual
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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
    • H05H11/00—Magnetic induction accelerators, e.g. betatrons

Definitions

  • This invention is concerned with a betatron in which the electrons are injected as a narrow beam about azi muthally into the stabilizing guiding field region close to its inner border.
  • betatron refers to a device in which electrons are moved along approximately circular paths in a r magnetic guiding field and accelerated by means of a magnetic flux of increasing strength passing through said circular paths.
  • the device may therefore also be referred to as a magnetic induction accelerator.
  • the electrons which leave the acceleration system of the injector in the form of a narrow beam travel first transversely across the guiding field and, as far as they enter the deflection system, they are ejected therefrom, like from an inner injector, into the inner stabilizing guiding field region.
  • the injector may be spaced from the outer border of the guiding field so that it does not obstruct expansion of the equilibrium orbit after completion of the ⁇ acceleration for the purpose of casting the electrons into the outer space.
  • the injector may therefore be made of any desired and suitable size. There is sufficient space available for accommodating the means for supplying higher pre* acceleration voltages. Nevertheless, the electrons are caught in the inner stabilizing guiding field region, which is advantageous because in such case, by maintaining the guiding field constant during the period of securing the electrons, the acceleration vessel can be uniformly filled with electrons, making it possible to obtain an increase of the space charge.
  • a current which is variable as a function of time and of such intensity, character, and direction that the entire magnetic field within such coil changes as a function of time so that, as a reaction, the guiding eld remains constant, such reaction being based on the fact that the entire field of the betatron or accelerator, being fed from an electric oscillating circuit, must have a sinusoidal character.
  • a core made of a magnetic material with substantially rectangular magnetization curve said core being disposed axially of the betatron and bridging the air gap between the accelerating poles.
  • This core is magnetically saturated in every half-wave 0f the current source, in one or another direction, due to strong magnetization caused by the current in the exciter winding of the betatron and in its state of saturation does not disturb the relation of the betatron fields.
  • a reversal of field direction in the core takes place after a relatively low current intensity has been reached.
  • the rapid change of flux during the reversal of the magnetic field direction causes in the exciter winding the induction of an electromotive force which obstructs the increase of the exciter current and the result is that this current increases again only after the magnetic saturation in the core has again been restored.
  • the deflection system of course must not obstruct the electrons which already have been caught and revolve near the inner border of the guiding field.
  • the system therefore provides a generally S-shaped deflection condenser built so that at least its ejection opening projects into the inner stabilizing guiding eld region and its entrance opening is preferably placed radially more toward the inside than the ejection opening.
  • Fig. 1 shows a sectional view taken approximately along the dot-dash line 1-1 of Fig. 2;
  • Fig. 2 is a sectional plan view of the vacuum vessel shown in Fig. .1, illustrating the path of travel of the electrons.
  • Figs 3 toV 6 indicate in diagrammatic manner sectional views of means for controlling the flow of electrons.
  • the generally toroidal ceramic vacuum Vessel 1 with the sealing stub 2 and the electron exit stub 3 closed by a thin metal window is provided with the tubular extension@ closed by the ceramic plate 5, containing the injector which isthus disposed completely outside of the outer boundary of the stabilizing zone 6 of the guiding field.
  • the injector comprises a filament 7, the electrode S surrounding it, and the electrodes 9 and 10 forming a sofcalled electrostatic immersion lens.
  • The-action of lthe electrodes 9 and 1f) produces at a point spaced from the filament 7 an enlarged image of the filament, and the electron beam leaving the filament 7 will therefore be of a divergent form.
  • the electrons emerge from the injector in the form of a slightly divergent beam which enters into the outer stabilizing region of the guiding field.
  • the electrodes 9 and 10 are connected relative to the filament 7 at voltages of about +2.5 kv. and +7 kv.
  • the electrode 8 is connected to about the same potential as the filament only twice during every cycle of the betatron field and only for a short time, namely, about 10-4 seconds, whereas during the remaining time it is connected to a negative locking potential.
  • Ahead of the electrode 10 is disposed an acceleration electrode 11, to which is connected, e. g., a voltage of +60 kv.
  • Ahead of the ejection opening of this injector with a pre-acceleration system is disposed a deflection condenser consisting of the two plates 12 and 13, with the aid of which the direction of the electron beam can be easily adjusted.
  • the electrodes 9, 10 and 11, and also the plates 12, 13 are suitably made of soft iron, so that they magnetically shield the electron beam from the leakage field of the betatron, at least while it is still weak.
  • On the plates 12, 13 of the deiiection condenser voltages of a few hundred volts are sufficient to adjust the electron beam in the desired direction.
  • the electrode 13 of the deliection condenser is connected with the acceleration electrode 11, and lies therewith by way of the Contact spring 14 at the grounded inner coating 15.
  • the electrons in the injector by applying the proper voltage at its acceleration electrodes, are given a velocity which, at the guiding field intensity operating during the injection, corresponds to the gyratory velocity of the electrons along the path 16 close to the inner boundary circle 17, and that the guiding field is maintained constant during the injection. If such conditions prevail, the electrons traverse the guiding field approximately in the manner shown in Fig. 2, and enter the entrance opening of the defiection condenser 1.8 shortly before reaching the inner boundary circle 17.
  • the deflection condenser 18 comprises the grounded, generally S-shaped outer condenser plate 20 facing the equilibrium orbit 19, and the two inner arcuately shaped counterplates 21 and 22 connected against ground to voltages of about -10 kv. and +10 kv., the average width of the condenser being about l mm.
  • a small electrode 23 At its entrace is provided a small electrode 23, the purpose of which is to adjust, if necessary, the direction in which the electron beam enters the deflector.
  • the voltages at the electrodes 21-23 are suitably chosen so that the electron beam, while the guiding field is being maintained constant, travels through the deflector without great losses at the electrodes, and leaves it azimuthally.
  • pocket-shaped trapping cages 24 and 25 for the purpose of avoiding disturbances of the secured electrons by secondary electrons which are released by the electron beam at the electrode 20 or at the inner wall of the vacuum vessel during the process of securing, or shortly thereafter.
  • the injection voltage and the guiding field intensity which is maintained constant, are suitably brought into such a reciprocal relationship that the electrons leaving the deflector undergo relatively slight radial oscillations in order to uniformly fill the guiding field with electrons.
  • the filament 7 and the electrodes 8 and 9 are adjustably supported by the molybdenum pins 27 which are sealed in the ceramic end plate 5 and serve at the same time as voltage supply terminals.
  • the acceleration system and the detiector thus form a structural unit which can be tested, before being introduced into the vacuum vessel, in an auxiliary vessel which must be placed in a stationary magnetic field analogous to the guiding field of the betatron. After the testing, the system is inserted into the vacuum vessel 1 and connected therewith by means of a vacuum-tight seal 30.
  • the vessel is thereupon evacuated by way of the pump stub 2, then it is heated and the metal part of the injector is annealed by high frequency.
  • the brackets 28 and 29 are metallized within the guiding field at the sides facing the electron beam, and the corresponding metal coatings are connected with the metallic inside lining 15 of the vacuum vessel.
  • the brackets carry on their outside narrow silver strips forming the leads for the electrodes 21-23 of the deficctor.
  • the leads are insulated by means of mica against the metallic inside lining of the vacuum vessel and are metallically connected with the bushings 31-33.
  • the defiector 18 it is possible, by suitably dimensioning the defiector 18, to obtain not only the defiection of the electrons which have traversed the guiding field, but also a constriction of the electron beam and therewith greater security against subsequent collision of the electrons with the defiector after one or more revolutions.
  • the width of the deflector is small in relation to its length, all electrons of the beam gather in its first section in a focal point after the beam has traveled in this section along a circular arc across an angle a1 of 63.7.
  • the voltage at the electrode 21 it is possible to place this point in the middle between the plates 20 and 21 of the first section. If the first section of the defiector is of such length that the focal point, as can be seen in Fig.
  • the angle is the larger, the greater the intiuence of the magnetic field compared to that of the electric fields of the defiector.
  • a betatron having a generally circular evacuated vessel and apparatus for accelerating and stabilizing electrons describing within said vessel an equilibrium orbital path, said apparatus comprising a device for producing electrons and introducing said electrons into said vessel, said device comprising an electron gun disposed outside said equilibrium orbital path and forming an electron source and accelerator, and an electron deilector within said equilibrium orbital path forming with said gun an electron path intersecting said orbital path, said deilector comprising opposed electrodes, one of said electrodes having a surface opposed to the perimeter of said vessel.
  • a betatron according to claim l wherein said electrode having a surface opposed to the perimeter of said vessel is generally S-shaped providing a concave portion proximate to said accelerator and a convex portion remote therefrom as viewed in the direction of electron flow, said other opposed electrode having concave and convex portions opposed to those of said S-shaped electrode and also being generally S-shaped and comprising two electrically separated arcuate portions.
  • a betatron according to claim 2 comprising an auxiliary electrode adjacent to but electrically separated from the portion of said electrode disposed nearest said accelerator.
  • a betatron according to claim 2 comprising an electron trap disposed at that end of each of said S- shaped electrodes proximate to said accelerator.
  • a betatron according to claim 1 comprising common supporting means mounting said electron gun, ac# celerator and deflector as a unit, said supporting means having opposed metallized surfaces, the inner walls of said vessel having a metallized coating, and means electrically connecting said metallized surfaces and coating.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Particle Accelerators (AREA)
US192731A 1949-10-31 1950-10-28 Betatron Expired - Lifetime US2721949A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE288012X 1949-10-31

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US2721949A true US2721949A (en) 1955-10-25

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US (1) US2721949A (de)
CH (1) CH288012A (de)
GB (1) GB706186A (de)
NL (1) NL93283C (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2790902A (en) * 1954-03-03 1957-04-30 Byron T Wright Ion accelerator beam extractor
US2929951A (en) * 1958-04-28 1960-03-22 Finkelstein David Ion-stabilized electron induction accelerator
US2947896A (en) * 1959-02-09 1960-08-02 Gen Electric Electrostatic deflection and focusing system
US3031596A (en) * 1958-03-13 1962-04-24 Csf Device for separating electrons in accordance with their energy levels
US3325713A (en) * 1961-08-25 1967-06-13 Ceskoslovenska Akademie Ved Apparatus for injecting charged particles into the magnetic field of a cyclic particle accelerator
US3348089A (en) * 1963-07-29 1967-10-17 Ibm Cyclotron accelerator having the electrostatic field appearing across a nonlinear gap
US3678321A (en) * 1964-08-26 1972-07-18 Us Army Signal and noise separation utilizing zero crossing electron tube and circuit

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2193602A (en) * 1938-05-06 1940-03-12 Westinghouse Electric & Mfg Co Device for accelerating electrons to very high velocities
US2528541A (en) * 1945-11-01 1950-11-07 Standard Telephones Cables Ltd Electron discharge device
US2533859A (en) * 1943-07-14 1950-12-12 Bbc Brown Boveri & Cie Improved injection system for magnetic induction accelerators

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2193602A (en) * 1938-05-06 1940-03-12 Westinghouse Electric & Mfg Co Device for accelerating electrons to very high velocities
US2533859A (en) * 1943-07-14 1950-12-12 Bbc Brown Boveri & Cie Improved injection system for magnetic induction accelerators
US2528541A (en) * 1945-11-01 1950-11-07 Standard Telephones Cables Ltd Electron discharge device

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2790902A (en) * 1954-03-03 1957-04-30 Byron T Wright Ion accelerator beam extractor
US3031596A (en) * 1958-03-13 1962-04-24 Csf Device for separating electrons in accordance with their energy levels
US2929951A (en) * 1958-04-28 1960-03-22 Finkelstein David Ion-stabilized electron induction accelerator
US2947896A (en) * 1959-02-09 1960-08-02 Gen Electric Electrostatic deflection and focusing system
US3325713A (en) * 1961-08-25 1967-06-13 Ceskoslovenska Akademie Ved Apparatus for injecting charged particles into the magnetic field of a cyclic particle accelerator
US3348089A (en) * 1963-07-29 1967-10-17 Ibm Cyclotron accelerator having the electrostatic field appearing across a nonlinear gap
US3678321A (en) * 1964-08-26 1972-07-18 Us Army Signal and noise separation utilizing zero crossing electron tube and circuit

Also Published As

Publication number Publication date
GB706186A (en) 1954-03-24
NL93283C (de)
CH288012A (de) 1952-12-31

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