US3138736A - Electron beam generator system - Google Patents

Electron beam generator system Download PDF

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Publication number
US3138736A
US3138736A US96935A US9693561A US3138736A US 3138736 A US3138736 A US 3138736A US 96935 A US96935 A US 96935A US 9693561 A US9693561 A US 9693561A US 3138736 A US3138736 A US 3138736A
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United States
Prior art keywords
diaphragm
aperture
cathode
electron beam
chamber
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US96935A
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English (en)
Inventor
Scheffels Wilhelm
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RTX Corp
Original Assignee
United Aircraft Corp
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Filing date
Publication date
Application filed by United Aircraft Corp filed Critical United Aircraft Corp
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Publication of US3138736A publication Critical patent/US3138736A/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
    • H01J37/02—Details
    • H01J37/04—Arrangements of electrodes and associated parts for generating or controlling the discharge, e.g. electron-optical arrangement or ion-optical arrangement
    • H01J37/06—Electron sources; Electron guns
    • H01J37/073—Electron guns using field emission, photo emission, or secondary emission electron sources
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
    • H01J3/02—Electron guns
    • H01J3/025—Electron guns using a discharge in a gas or a vapour as electron source
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2893/00—Discharge tubes and lamps
    • H01J2893/0061—Tubes with discharge used as electron source

Definitions

  • This invention relates to an electron beam generating system and, more particularly, relates to an improved generator system utilizing secondary emission effects for the irradiation of objects in air by high velocity electrons and for generating electron beams of high velocity and high flux density in a vacuum.
  • Electron beam generating systems utilizing secondary emission from a cathode under positive ion bombardment are known to the art.
  • the electron beam generator consists of a massive metal electrode for a cathode and diaphragm-type anode with a circular aperture therein.
  • the diaphragm forms a part of a beam generating chamber enclosing the cathode.
  • the diaphragm separates the generating chamber from the exterior (which may be air or a working chamber) but permits communication between the generating chamber and the exterior through the circular aperture.
  • the generating chamber may be evacuated to the desired working pressure by continuously evacuating the chamber.
  • the pump works against the gas leakage through the circular aperture and, thus, the aperture must be small to provide the flow resistance necessary to allow the pump to evacuate the chamber to the desired working pressure.
  • the cathode is biased to a high negative voltage with respect to the diaphragm anode.
  • a delayed gas discharge will take place between the diaphragm aperture and the cathode.
  • the ions formed in the discharge will be accelerated towards and will impinge upon the oathode, releasing electrons therefrom.
  • the electrons are accelerated by the electrostatic field betwen the cathode and the diaphragm anode and will pass through the aperture in a beam which can be used to irradiate objects in the beam path.
  • the diaphragm To obtain large flux densities in the electron beam, the diaphragm must be so shaped that a gas discharge of maximum intensity occurs over a large area of the cathode.
  • a circular aperture discharge over a large area of a cathode has been impossible to obtain.
  • the increasing of the aperture diameter to the desired size for the electrical effect has been precluded by the capacity of the evacuating apparatus. That is, the aperture diameter is limited to relatively small sizes by the capacity of the vacuum pump since the pump must exhaust the chamber while working against entry of gases through the aperture.
  • the gas discharge between the diaphragm and the cathode results in the erosion of the cathode. If the gas discharge extends over a fairly long period, the erosion will result in holes in the cathode which will become so deep that the resultant electrostatic field causes electron emergence over an undesirably large solid angle.
  • a cathode contained in an evacuated chamber.
  • a diaphragm forms a portion of a beam generating chamber enclosing the cathode and the diaphragm has an aperture therein communicating between the chamber interior and exterior.
  • the chamber is continuously evacuated by a vacuum pump to maintain the desired pressure in the chamber. As with the prior art, the pump works against the leakage through the aperture.
  • the aperture is formed in the shape of a long, narrow slit to distribute the gas discharge and the resultant ion bombardment over a large area of the cathode electrode.
  • the slit ensures uniformity of the path of the gas discharge and the discharge will not skip between different places on the cathode surface.
  • the total area of the slit-like aperture may be larger than a circular aperture for the same flow resistance, since, for molecular flow, the flow resistance is proportional to UK where R is the radius of a circular aperture.
  • the slit may be cut in the shape of a spiral, open loop, or the like.
  • the slit aperture provides a large electrical aperture without commensurate decrease in flow resistance and the pressure ditferential between the chamber and the ex terior (whether higher or lower in pressure than the chamber) may be had with conventional pumping equipment.
  • the chamber may be considered a pressure stage, the flow resistance through the aperture and the delivery capacity of the pump determining the evacuation pressure.
  • means are provided to slowly rotate the cathode about its vertical axis thereby to prevent erosion of the cathode surface in deep holes which would result in the emergence of the electrodes over an undesirably large solid angle.
  • the cathode and the diaphragm are fabricated as concentric hemispheres, domes or cylinders to allow irradiation of objects over a wide angle Without the necessity of providing a plurality of beam generators or the necessity of providing deflection fields for guidance of the electron .beam.
  • the total electron flux density may be controlled by varying the amount of gas entering the beam generating space.
  • such variation may be afforded by an iris positioned over the diaphragm slit which iris may be adjusted to open a variable portion of the diaphragm aperture.
  • a second diaphragm preferably having the same aperture configuration as that of the first dia- 3. phragm is provided.
  • the gas for formation of the discharges may then be introduced between the two diaphragms to initiate the gas-discharges as the gas flows into the beam.
  • generating chamber Both the generator chamber and the vacuum chamber may be continuously evacuated to the desired pressure. The electron beam will.
  • the gas for thedischarge may be introduced into the generator chamber and the vacuum at the exterior maintained by continuous pumping.
  • FIG. 1. is a cross sectioned view of an electron beam generator in accordance with the prior art
  • FIG- 2 is' a plan view' of' the aperture used in electron beam generators, of which FIG; 2a is an'aperturein accordancewith' the prior artand' FIGS. 2b and 2c are apertures in accordance with the present invention;
  • FIGS; 3-5 are plan views of alternative apertures in accordancewith the present invention.
  • FIG. 6 is a cross sectioned view of one embodimentof an electron beam generating system in accordance with the present invention.
  • FIG. 7 is across sectioned view' of another'embodiment ofian'electron beam generating system in accordance with the present invention.
  • FIG. 8 is a cross sectioned view of still anotherembodiment of an: electron beam generating system in accordancewith thepresent invention.
  • FIG. 9 is a cross sectioned view of still another embodiment ofthe present invention.
  • FIG; 1 there is shown an electron beam generating system in accordance with the prior art, comprising a massive metal electrode-1 which. serves as a cathode, emitting 'electrons' during bombardment by'positive ions.
  • a diaphragm 2 In front of thismetal electrode 1 is placed a diaphragm 2, having a circular aperture3.
  • the metal electrode 1 is biased at a potential of, say, 10O kv.,.
  • FIG. 2a shows the circular diaphragm aperture of'the diaphragm 2.
  • the diaphragm aperture is constructed as a long, narrow slit, whose linear extension will be seen from-FIG. 2b. Comparison of FIGS 2a and Z'bwill show immediately that the area of the slit is greater than that of the circular diaphragm aperture 3. In spite of this, no more gas enters the beam generating space 7 through the slit 8, than through the aperture 3", so that, if the same vacuum is applied, the same pressure will be produced in the chamber 7 in bothcases.
  • the slit 8 shown in FIG. 2b may be so shaped that it has, for example, the sinusoid or meandering appearance 9, as shown in FIG. 20. The end is thereby attained that the slit extends over a larger cathode surface area by comparison with the area of the slit opening.
  • the diaphragm opening may also have the shape of a spiral 10, as shown in FIG. 3.
  • the diaphragm aperture may likei wise take the form of an open loop 11 and 12, as shown in FIGS. 4 and 5, respectively.
  • the slit form shown in FIG. 5 yields a gas discharge more extended in one direction than in the other.
  • the gas discharge is distributed over the largest possible (square) surface whenmthe shape. shown iniFIG. 4 is employed.
  • FIG. 6 shows anelectron beam generator system in which the diaphragm, 2 is provided with a spiral diaphragm. aperture 10'.
  • the gas discharge in this case is distributed between electrodes 1'. and2. over' a larger area than in the case of the system. shown in' FIG. 1'.
  • the electromagnetic focusing system 31 is placed immediately behind this diaphragm. If-this systemadjoins air under atmospheric pressure, the. electron: beam generated by the system here shown will have the approximateappearance indicated by 32.
  • the diaphragm 2-" may, if desired, be: provided with means for cooling the diaphragm suchascoolant passages.
  • FIG. 7 shows an electron beam generator system in which the metal electrode 14' is formed of a tube into which the cylindrcal diaphragm 13 projects.
  • Thetube; 13 is provided with diaphragm apertures, which, for example, have the shape of the sinusoid or meander 9, shown in FIG. 2c.
  • Theelectron flux issuing from the diaphragm 13 is distributed' over a 360, angle. Consequently, with the set-up. shown in FIG. 7,. foils or fibers, for instance, placed inside the diaphragm tube. 13,.may be irradiated with electrons over the entire exposed area.
  • the electrode and diaphragm may extend over a smaller angle if the. 360 irradiation angle:is.unnecessary.
  • FIG. 8' shows an electron beam generator system. in which the metal electrode 22 is connected to the shaft23. This shaft is rotationallymounted between the twosealing rings 24 and 25 in the insulator 26.
  • the diaphragm 27' is provided with sinusoid aperture 9;, During operation, the metal electrode 22' rotates slowly about its vertical axis, thus avoiding deep penetration of the holes eroded in the electrode 22.
  • the slide 28, placed" in front of the .diaphragm27 serves to control the electron flux.
  • the electron generating space may also be fed with gas directly through the duct 6.
  • the diaphragm 15 and the space 16 may be omitted.
  • Thediaphragm apertures shown in FIGS. 20, 3, 4 and Scan be made in particularly simple and accurate manner by means of an electron beam focussed upon the diaphragm and moved along. the lines of said apertures.
  • An electron beam generator comprising a cold cathode, a diaphragm, means including said diaphragm for enclosing said cathode to form a generator chamber, said diaphragm being provided with a long, narrow slit aperture therethrough, means for continuously maintaining the generator chamber at a desired working pressure against the leakage through the aperture, and means for biasing the cold cathode negatively with respect to said diaphragm to cause a gaseous discharge therebetween and resultant ionic bombardment of the cathode surface, said slit distributing the bombardment over a large area of the cathode surface and simultaneously maintaining a high flow resistance to said leakage through said aperture.
  • An electron beam generator system according to claim 1 which includes means for moving said cathode with respect to said diaphragm.
  • An electron beam generator system which includes a focusing system, said system being positioned adjacent said diaphragm.
  • An electron beam generator system which includes a slide positioned adjacent said diaphragm, said slide being movable to selectively cover portions of said slit aperture.
  • An electron beam generator system in which said diaphragm separates said chamber from an evacuated space and which includes means for introducing gas into said chamber.
  • An electron beam generator system which includes a second apertured diaphragm positioned near said first diaphragm to define a space therebetween, said second diaphragm separating said space from an evacuated chamber, and means for introducing gas into said defined space.
  • An electron beam generator comprising a cold cathode, a diaphragm, means including said diaphragm for enclosing said cathode to form a generator chamber, said diaphragm being provided with a long narrow slit aperture therethrough, means for continuously maintaining the generator chamber at a desired Working pressure against the leakage through the aperture, means for biasing the cold cathode negatively with respect to said diaphragm to cause a gaseous discharge therebetween and resultant ionic bombardment of the cathode surface, said slit distributing the bombardment over a large area of the cathode surface and simultaneously maintaining a high flow resistance to said leakage through said aperture, and focussing means to focus the beam after its passage through the diaphragm into a high intensity beam.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Particle Accelerators (AREA)
  • Electron Beam Exposure (AREA)
US96935A 1960-04-16 1961-03-20 Electron beam generator system Expired - Lifetime US3138736A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEZ7940A DE1117781B (de) 1960-04-16 1960-04-16 Elektronenstrahlerzeugungssystem und Verfahren zur Herstellung der Blendenoeffnung des Elektronenstrahlerzeugungssystems

Publications (1)

Publication Number Publication Date
US3138736A true US3138736A (en) 1964-06-23

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US96935A Expired - Lifetime US3138736A (en) 1960-04-16 1961-03-20 Electron beam generator system

Country Status (5)

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US (1) US3138736A (enrdf_load_stackoverflow)
CH (1) CH400384A (enrdf_load_stackoverflow)
DE (1) DE1117781B (enrdf_load_stackoverflow)
GB (1) GB979622A (enrdf_load_stackoverflow)
NL (1) NL263646A (enrdf_load_stackoverflow)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3389240A (en) * 1964-09-25 1968-06-18 Welding Research Inc Electron beam welding apparatus

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2266218A (en) * 1939-05-08 1941-12-16 Krause Friedrich Electron microscope vacuum system
US2721972A (en) * 1952-08-04 1955-10-25 Rothstein Jerome High sensitivity ionization gauge
US2847597A (en) * 1955-11-25 1958-08-12 Sylvania Electric Prod Electron discharge device
US2887599A (en) * 1957-06-17 1959-05-19 High Voltage Engineering Corp Electron acceleration tube
US2975326A (en) * 1958-08-26 1961-03-14 Ferranti Ltd Cathode-ray tubes

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2266218A (en) * 1939-05-08 1941-12-16 Krause Friedrich Electron microscope vacuum system
US2721972A (en) * 1952-08-04 1955-10-25 Rothstein Jerome High sensitivity ionization gauge
US2847597A (en) * 1955-11-25 1958-08-12 Sylvania Electric Prod Electron discharge device
US2887599A (en) * 1957-06-17 1959-05-19 High Voltage Engineering Corp Electron acceleration tube
US2975326A (en) * 1958-08-26 1961-03-14 Ferranti Ltd Cathode-ray tubes

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Publication number Publication date
CH400384A (de) 1965-10-15
GB979622A (en) 1965-01-06
DE1117781B (de) 1961-11-23
NL263646A (enrdf_load_stackoverflow)

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