US3810025A - Field emission type electron gun - Google Patents

Field emission type electron gun Download PDF

Info

Publication number
US3810025A
US3810025A US00245232A US24523272A US3810025A US 3810025 A US3810025 A US 3810025A US 00245232 A US00245232 A US 00245232A US 24523272 A US24523272 A US 24523272A US 3810025 A US3810025 A US 3810025A
Authority
US
United States
Prior art keywords
emitter
electrode
transformer
voltage
circuit
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
US00245232A
Other languages
English (en)
Inventor
R Aihara
S Ota
N Kobayashi
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.)
Jeol Ltd
Original Assignee
Jeol Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from JP3140571A external-priority patent/JPS5334708B1/ja
Priority claimed from JP6907071A external-priority patent/JPS5227992B2/ja
Application filed by Jeol Ltd filed Critical Jeol Ltd
Priority to US409918A priority Critical patent/US3921078A/en
Application granted granted Critical
Publication of US3810025A publication Critical patent/US3810025A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • H01J37/24—Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for
    • H01J37/241—High voltage power supply or regulation circuits
    • 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
    • H01J3/021—Electron guns using a field emission, photo emission, or secondary emission electron source
    • 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
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/20—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for electronic equipment

Definitions

  • Patent 11 1 FIELD EMISSION TYPE ELECTRON GUN Inventors: Ryuzo Aihara; Susumu Ota;
  • ABSTRACT This invention relates to a field emission type electron gun capable of protecting the emitter tip from damage when electrical breakdown occurs in the gun chamber.
  • the preferred embodiments incorporate circuitry for decreasing the impedance between the emitter and its associated electrode when electrical breakdown occurs.
  • This invention relates to a field emission type electron gun capable of protecting the emitter tip from damage when electrical breakdown occurs in the gun chamber.
  • the advantage of a field emission type electron gun in electron microscopes and the like as compared with the ordinary thermionic emission'type electron gun, is that it is possible to obtain a high current electron beam forming a microspot.
  • the emitter is very easily damaged due to electrical breakdown caused by a deterioration in the gun chamber vacuum or other phenomena, resulting in the generation of an unusually strong electric field in the vicinity of the emitter tip. As a result the tip is overheated due to large current during vacuum arc discharge. This inevitably results in a change in shape in the emitter tip which then becomes useless.
  • a field emission electron gun comprises a circuit for preventing an unusually high potential difference between the emitter and an electrode spaced near the emitter resulting from an electrical breakdown between that electrode and the grounded anode.
  • the preferred means of preventing the unusually high potential difference is to provide a circuit between the emitter and electrode which has a reduced impedance at the time of breakdown and preferably a circuit to increase impedance between the high voltage source and the emitter when breakdown occurs.
  • FIGS. 1(a) and (b) are schematic diagrams of a con- ,ventional field emission type electron gun.
  • FIG. 2 is a diagrammatic circuit of one embodiment according to the invention.
  • a gun chamber 1 contains a filament 2 heated by an A.C. current source 3 through an insulating'transformer 4, an emitter 5 attached to the filament 2, first electrode '6 for producing a strong electric field (for example, about lO' volt/cm) in the vicinity of the emitter tip and an anode 7 maintained at ground potentiaLA voltage source 8 supplies a voltage so as to create a constant orpulsed potential difference between the emitter 5 and the first electrode 6, in order a to draw electrons from said emitter tip.
  • Another volt age source 9 maintains the emitter at a high negative DC. potential in order to accelerate the emitted electrons.
  • Z10 and Z11 represent the impedances of sources 8 and 9 (FIG. 1(a)) respectively, and Z12 the impedance between the two sources.
  • the protection circuit 13 is arranged in parallel with voltage supply source 8, said circuit comprising a thyratron 14, a variable DC. voltage source 15 for adjusting the firing voltage of the thyratron 14, and a coupling condenser 16.
  • FIG. 3 illustrates another embodiment according to this invention in which an on-off switch 17 is provided in place of protection circuit 13.
  • This particular embodiment is very effective when electrical breakdown is predetermined as, for example, when applying the so-called conditioning technique whereby electrical breakdown between the first electrode and the anode is caused by setting the output voltage of voltage source 9 slightly higher than the regular working output voltage, in order to improve the withstand voltage in the gun chambenln this case, switch 17 is switched on during the conditioning" operation, and switched off during regular operation;
  • FIG. 4 illustrates yet another embodiment of the invention in which an additional electrode 18, hereinafter referred to as the second electrode, is provided between the first electrode 6 andthe anode 7.
  • the potential applied to the second electrode 18 is determined by a DC. voltage source 19 and the voltage source 9.
  • the output voltage of the voltage source 19 is almost the same as that of source 8 if the output of source 8 is DC, and is almost the same as. the pulse height of the output of source 8 if the output of source 8 is pulse.
  • the output voltage of source 19 is much smaller than the output voltage of source 9. Accordingly, electrical breakdown between the second electrode 18 and the anode 7 almost always occurs before the occurrence of breakdown between the second electrode 18 and the first electrode 6.
  • protection circuit 13 comprising a silicon symmetric switch (8.8.8.) 20, thereby decreasing the impedance between the two electrodes and, in so doing, prevents the reoccurrence of electrical breakdown since the potential fluctuation of said electrodes and the emitter 5 are about the same.
  • An additional advantage of this embodiment is the fact that the range of the protection circuit firing voltage is much wider than that of the protection-circuit decause, in the case of the embodiment shown in FIG. 2, it is necessary to adjust the firing voltage in accordance with the output voltage of voltage source 8 which has to be varied every time the emitter is exchanged. In the case of this embodiment, however, the relevant voltage source is source 19 which is seldom varied. Hence, in the case of this embodiment, there is almost no necessity to adjust the firing voltage of protection circuit 13. For this reason, it is possible to utilize a simple S.S.S. 20 switching device in place of the more complicated thyratron and its associated circuit.
  • FIG. The embodiment illustrated in FIG. is substantially the same as that illustrated in FIG. 4.
  • an insulation column 21 containing an insulating transformer 4, a high voltage source 22 and a filter circuit consisting of a resistor 23 and capacitors 24 is connected to gun chamber circuit 25 by high voltage cable 26.
  • the potential at the junction of balancing resistors 27 and 28 is used instead of the potential of the emitter 5, and protection circuit 13 which, in this case, incorporates a surge voltage protection tube 29 is connected between said junction and the second electrode 18.
  • this particular embodiment is very effective when electrical breakdown is predetermined as mentioned in the explanation of the embodiment shown in FIG. 3.
  • FIG. 6 illustrates an embodiment designed to further reduce E by increasing the impedance Z31 during discharge in addition to decreasing the impedance Z30.
  • circuit 32 consisting of a transformer 33, balancing resistors 34, 35, 36 and 37 and a high order resistor 38 capable of withstanding the high voltage output of source 22.
  • the two ends of the resistor 38 are connected to the junction of resistors 36 and 37 and the junction of resistors 34 and 35, respectively.
  • the embodiment When there is no discharge, the embodiment functions the same way as the embodiment shown in FIG. 5. If electrical breakdown occurs between the second electrode 18 and the anode 7, the amount. of discharge current flowing through high order resistor 38 is very much reduced, and the potential difference between the emitter 5 and the first electrode 6 is not so large.
  • Voltage source 8 consisting of an A.C. voltage source 40, insulating transformer 41, a pulse generator 39, a transformer 42 and a high order resistor 43 generates a pulse voltage which is applied to electrode 6 through transformer 42.
  • the discharge current due to the stray capacity of transformer 41 flows through resistor 43.
  • FIG. 7 illustrates a practical embodiment of the present invention in which function and operation is substantially the same as the embodiments shown in FIGS. 5 and 6.
  • pulse generator 39, insu lating transformer 41, and D.C. voltage source 19 etc. are all housed in insulation column 21.
  • the potential at the center tap of the output winding of transformer-4 is used instead of the potential at center tap of the input winding of transformer 33.
  • the function of resistor 44 is the same as that of resistor 43 in FIG. 6.
  • FIG. 8 illustrates an embodiment for D.C. field emission operation corresponding to the embodiment shown in FIG. 7.
  • the function of resistor '45 is the same as that of resistors 44 and 38.
  • FIG. 9 illustrates an embodiment designed to increase the impedance 231 inductively instead of resistively as in the case of the embodiments shown in FIGS.
  • circuit 32 which has a fairly high inductance; whereas, under normal operat ing conditions, the inductance of circuit 32 is cancelled out by the coils and is, therefore, zero.
  • the pulse signals generated by pulse generator 39 are transmitted to the input winding of the transformer 42 and capacitor CN+1 via the transmission line consisting ofcoils L21 L2N, L31 L3N and capacitors C1 CN without loss.
  • resistor 51 connected across the output winding of transformer 42 compensates for the sag in the pulse voltage applied between the emitter 5 and the first electrode 6.
  • the filament heating current is D.C. rectified by rectification circuit 52. Even if A.C. current is used for heating the filament, there is practically no loss in circuit 32, because coils L11, LIN and coils L31, L3N have the same inductance and are unidirectionally wound.
  • a field emission type electron gun device comprising:
  • a high voltage source for supplying negative high potential to said emitter in order to accelerate said electron beam
  • a voltage source for generating a potential difference between said electrode and said emitter in order to generate a strong electric field in the vicinity of said emitter tip
  • a protection means for preventing the generation of an unusually high potential difference between said emitter and said electrode comprising a switching circuit for rapidly decreasing the impedance of said protection means in the event that the voltage between said emitter and said electrode increases beyond the firing voltage of the switching circuit, and
  • means for heating the emitter comprising a first and second isolation transformer, the secondary of the first transformer being in series with the primaryof the second transformer, the primary of the first transformer being connected to an AC voltage supply, the secondary of the second transformer being in series with the emitter of the electron gun,
  • a field emission type electron gun device comprismg:
  • a high voltage source for supplying negative high potential to said emitter in order to accelerate said electron beam
  • a voltage source for generating a potential diffen ence between said first electrode and said emitter in order to generate a strong electric field in the vicinity of said emitter tip
  • a DC voltage source for supplying a potential to said secondary electrode
  • a protection means for preventing the generation of an unusually high potential difference between said second electrode and said emitter comprising a switching circuit for rapidly decreasing the impedance of said protection means in the event that the voltage between said emitter and said second electrode increases beyond the firing voltage of the switching circuit, and
  • means for heating the emitter comprising a first and second isolation transformer, the secondary of the first transformer being in series with the primary of the second transformer, the primary of the first transformer being connected to an AC. voltage supply, the secondary of the, second transformer being in series with the emitter of the electron gun, the high voltage supply being connected to the circuit between the said first and second transformers and the emitter being connected through a high value resistor to the circuit between said first and second transformers.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Particle Accelerators (AREA)
  • Electron Sources, Ion Sources (AREA)
US00245232A 1971-04-20 1972-04-18 Field emission type electron gun Expired - Lifetime US3810025A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US409918A US3921078A (en) 1971-04-20 1973-10-26 Breakdown protection for field emission electron gun

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP3087671 1971-04-20
JP3140571A JPS5334708B1 (enExample) 1971-05-11 1971-05-11
JP6907071A JPS5227992B2 (enExample) 1971-09-07 1971-09-07

Publications (1)

Publication Number Publication Date
US3810025A true US3810025A (en) 1974-05-07

Family

ID=27287125

Family Applications (1)

Application Number Title Priority Date Filing Date
US00245232A Expired - Lifetime US3810025A (en) 1971-04-20 1972-04-18 Field emission type electron gun

Country Status (2)

Country Link
US (1) US3810025A (enExample)
FR (1) FR2133915B1 (enExample)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3921078A (en) * 1971-04-20 1975-11-18 Jeol Ltd Breakdown protection for field emission electron gun
US4134032A (en) * 1976-05-12 1979-01-09 Pioneer Electronic Corporation Audio signal discriminator circuit
US4740705A (en) * 1986-08-11 1988-04-26 Electron Beam Memories Axially compact field emission cathode assembly
US5070282A (en) * 1988-12-30 1991-12-03 Thomson Tubes Electroniques An electron source of the field emission type
US5173635A (en) * 1990-11-30 1992-12-22 Motorola, Inc. Bi-directional field emission device
US5173634A (en) * 1990-11-30 1992-12-22 Motorola, Inc. Current regulated field-emission device
EP0703595A1 (en) * 1994-09-22 1996-03-27 Motorola, Inc. Field emission device arc-suppressor

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2928301C2 (de) * 1979-07-13 1983-12-29 Leybold-Heraeus GmbH, 5000 Köln Anordnung zur Leistungssteuerung eines Hochspannungs-Elektronenstrahlerzeugers

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2083205A (en) * 1933-10-11 1937-06-08 Schlesinger Kurt Safety means for television tubes
US2428616A (en) * 1943-11-02 1947-10-07 Philco Corp Electrical protective device
US2828417A (en) * 1954-11-12 1958-03-25 Monroe Calculating Machine Clamping circuit means
US2829282A (en) * 1956-05-17 1958-04-01 Itt Pulse generator
US3267321A (en) * 1962-03-28 1966-08-16 Sylvania Electric Prod Electron discharge device having cathode protective means within the envelope
US3461391A (en) * 1965-08-02 1969-08-12 Industrial Nucleonics Corp Electronic signal amplitude limiter
US3502933A (en) * 1968-07-29 1970-03-24 Connector Corp Kinescope socket with spark gap

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2083205A (en) * 1933-10-11 1937-06-08 Schlesinger Kurt Safety means for television tubes
US2428616A (en) * 1943-11-02 1947-10-07 Philco Corp Electrical protective device
US2828417A (en) * 1954-11-12 1958-03-25 Monroe Calculating Machine Clamping circuit means
US2829282A (en) * 1956-05-17 1958-04-01 Itt Pulse generator
US3267321A (en) * 1962-03-28 1966-08-16 Sylvania Electric Prod Electron discharge device having cathode protective means within the envelope
US3461391A (en) * 1965-08-02 1969-08-12 Industrial Nucleonics Corp Electronic signal amplitude limiter
US3502933A (en) * 1968-07-29 1970-03-24 Connector Corp Kinescope socket with spark gap

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Smith, CRT Arcing, Electro Optical Systems Design, Nov. 1971, cover and pp. 14 18. *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3921078A (en) * 1971-04-20 1975-11-18 Jeol Ltd Breakdown protection for field emission electron gun
US4134032A (en) * 1976-05-12 1979-01-09 Pioneer Electronic Corporation Audio signal discriminator circuit
US4740705A (en) * 1986-08-11 1988-04-26 Electron Beam Memories Axially compact field emission cathode assembly
US5070282A (en) * 1988-12-30 1991-12-03 Thomson Tubes Electroniques An electron source of the field emission type
US5173635A (en) * 1990-11-30 1992-12-22 Motorola, Inc. Bi-directional field emission device
US5173634A (en) * 1990-11-30 1992-12-22 Motorola, Inc. Current regulated field-emission device
EP0703595A1 (en) * 1994-09-22 1996-03-27 Motorola, Inc. Field emission device arc-suppressor

Also Published As

Publication number Publication date
FR2133915A1 (enExample) 1972-12-01
DE2219393B2 (de) 1975-11-20
DE2219393A1 (de) 1972-11-02
FR2133915B1 (enExample) 1976-08-06

Similar Documents

Publication Publication Date Title
US2299571A (en) Harmonic transmission system
US3567995A (en) Current stabilizer circuit for thermionic electron emission device
US3810025A (en) Field emission type electron gun
EP0497517A1 (en) Process of seasoning a vacuum tube for emitting x-rays
US3238415A (en) Electric arc control circuit
US2419428A (en) Power supply fob electron
US2254214A (en) Safety circuit for cathode ray tubes
US2447804A (en) Electron beam focusing circuit
US3921078A (en) Breakdown protection for field emission electron gun
US2059219A (en) Slope wave generator
US2219194A (en) Magnetic focusing of cathode ray tubes
US2462903A (en) Oscillator generator
US2052413A (en) Power supply system
US2023453A (en) Circuit for discharge tubes
US1896534A (en) Electrical system
US1696177A (en) System of distribution
US2130441A (en) Power supply system
US2226996A (en) Television receiver
US1872293A (en) Transformer
US1873952A (en) Method and apparatus for suppressing harmonics in direct current systems
US2644917A (en) Regulated high-voltage power supply system
US3119931A (en) Circuit means for coupling an x-ray device to a control supply apparatus
US2076368A (en) High frequency power supply system
US2404624A (en) Voltage regulator for electron discharge devices
US2201873A (en) Electric valve converting system