US3691377A - Automatic control system for varying a d.c. high voltage for accelerating tube of electron microscope and the like - Google Patents

Automatic control system for varying a d.c. high voltage for accelerating tube of electron microscope and the like Download PDF

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Publication number
US3691377A
US3691377A US104418A US3691377DA US3691377A US 3691377 A US3691377 A US 3691377A US 104418 A US104418 A US 104418A US 3691377D A US3691377D A US 3691377DA US 3691377 A US3691377 A US 3691377A
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output
control circuit
voltage
high voltage
automatic control
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US104418A
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English (en)
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Isao Matsui
Yoshihisa Minamikawa
Shinjiro Katagiri
Teruo Nakahara
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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
    • H01J37/24—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

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  • ABSTRACT The discharge which occurs in an accelerating tube of an electron microscope is detected by a detector and a comparing circuit determines whether or not the value of the detected discharge is larger or smaller than a predetermined value at which a spark occurs to produce a high level signal or a low level signal, respectively.
  • the d. c. high voltage applied to respective accelerating electrodes in the accelerating tube is decreased or increased in response to said high level signal or said low level signal so as to suppress any undesired large discharge in the tube, and thereby prevent sparking therein.
  • PATENTEDSEP 12 m2 3,591 377 SHEET 2 or 3
  • FIG 2 COMPARlNG CIRCUIT I7 ow SHOT l8 s: ⁇ /O- E2 MULTI- -3 le [5 V'BRATOR FLIP-FLOP 23 20) '2 CKT an? S2 CHANGER VIBRATOR 3%
  • FIG 3 SIG SOURCE g A "x. l 30 3
  • This invention relates to an automatic control system for increasing the acceleration voltage for an electron microscope or the like which is particularly capable of preventing discharge in the accelerating tube thereof.
  • an electron microscope of the type wherein the electron beam is accelerated by a high accelerating voltage such as 650 KV-1MV
  • a high accelerating voltage such as 650 KV-1MV
  • a d. c. high accelerating voltage 100 KV or less is applied between each pair of adjacent ac celerating electrodes.
  • undesirable discharge often occurs therein.
  • One object of this invention is to provide an automatic control system for a high voltage accelerating generator, which prevents undesirable discharge from occurring in an accelerating tube of an electron microscope or the like.
  • Another object of this invention is to provide an automatic control system which automatically and accurately performs said aging method.
  • the automatic control system is so constructed that it employs detecting means for detecting discharge current, or an X-ray produced due to occurrence of the discharge, in the accelerating tube under application thereto of an increasing d. c. high voltage.
  • detecting means for detecting discharge current, or an X-ray produced due to occurrence of the discharge in the accelerating tube under application thereto of an increasing d. c. high voltage.
  • FIG. 1 is a schematic block diagram of one embodiment of this invention.
  • FIGS. 2 and 3 are schematic block diagrams showing construction of the main parts of said embodiment.
  • FIGS. 4 and 5 are waveform diagrams showing the relation between an accelerating voltage and discharge current in said embodiments.
  • FIG. 6 is a partial view of a modification of the invention using an X-ray monitor.
  • a d. c. high voltage Producing device 1 which comprises an a.c. variable power device 2, a high voltage transformer T, supplied at its primary with an a. c. variable voltage from the power device 2, a rectifying diode D and condenser C,, connected to the secondary of the transformer T, to produce a d. 0. high voltage.
  • the d. c. high voltage produced by said device 1 is smoothed by a smoothing resistor R, and smoothing condenser C, and then is applied through a voltage dividing resistor R to respective accelerating electrodes 6 which are provided in an accelerating tube 9 of an electron microscope 100.
  • AC. power is supplied to a filament 4 to heat the same from an a. c. power source 3 through a transformer T condensers C and a filament transformer T An electron beam emitted from the filament 4 is accelerated by each accelerating electrode 6.
  • a part of the accelerated electron beam passes through an aperture'of a condenser apertured plate 7 and is then focused by a condenser lens 8 and further is introduced into the objective part 10 of the electron microscope so that the beam is directed to a specimen in a known manner.
  • a bias voltage to adjust the electron beam current is applied to a Wehnelt electrode 5 through a variable resistor R connected between the neutral point of the filament transformer T 3 and the voltage dividing resistor R
  • a discharge current B is observed to increase in the accelerating tube while the accelerating voltage, namely, the d. c. high voltage A produced by the d. c. high voltage producing device, is increased as shown in the same FIG. 4 until at last a spark C of the discharge may occur as described in the foregoing description.
  • the condenser apertured plate 7 can be used as a detector for detecting the discharge in the tube. Namely, said plate 7 is secured to the enclosure wall of the tube 9 by an insulating member 101 and when the discharge occurs, the discharge current is taken out by said plate 7.
  • the discharge current from said plate 7 is applied to a variable resistor R whose output voltage is amplified by an amplifier 11 and the output voltage E, thereof is applied to a comparing circuit 12.
  • the comparing circuit 12 produces a high level signal S, when the value of the voltage E, is larger than a predetermined value and A low level signal S, when the value of the voltage E, is less than said predetermined value. Both signals S, and S are supplied to a voltage control circuit 13 for varying said d. 0. high voltage.
  • the high level signal S is produced, for example, when the discharge current reaches a value between 0.01 ,u.A 0.05 pA. This value is particularly significant since, if the discharge current exceeds this value, an undesired spark may easily occur, so that a decrease in the high accelerating voltage must be effected upon detection of a discharge of such value.
  • The. low level signal S is designed to be produced when the discharge does not exist. Once the low level signal is produced, it operates the voltage control circuit 13 by which said d. 0. high voltage is caused to increase gradually. Then when the discharge current becomes larger than said predetermined value, the high level signal S, is applied to the voltage control circuit 13 so that said d. c. high voltage is caused to decrease until the low level signal is again produced. Thus, the increase and decrease in the d. c. high voltage is alternately repeated. In this way, said (1. 0. high voltage D and the discharge current E vary as shown in FIG. 5 and the value of said d. c. high voltage D can be gradually increased up to a desired value F without any spark being generated. Therefore, the aging method is attained automatically in accordance with the present invention.
  • said comparing circuit 12 and said voltage control circuit 13 are constituted as shown in FIGS. 2 and 3.
  • FIG. 2 shows an example of said comparing circuit 12, wherein a differential amplifier 15 has a terminal 14 connected to the output terminal of the amplifier 11 and another terminal 16 connected to a source of constant voltage E,,.
  • a one-shot multivibrator 17 is connected between the output terminal of the differential amplifier l5 and a set terminal 18 of a flip-flop circuit 19.
  • a sign changer or inverter 20 and another one-shot multivibrator 21 are connected in series between the output terminal of the differential amplifier 15 and a reset" terminal 22 of the flip-flop circuit 19.
  • the high level signal S appears'at the output terminal 23 of the flip-flop circuit 19, while the low level signal S, appears at the other output terminal 23' of the flip-flop circuit 19.
  • Said voltage E represents the predetermined threshold value such as 0.0 l -0.05 uA which forms the basis for determining whether the discharge current exceedsthe predetermined maximum at which sparking occurs.
  • the differential amplifier 15 produces an output voltage proportional to the difference between E, and E, by which the one-shot multivibrator 17 is triggered and produces an output pulse which is applied to the set terminal 18 of the flip-flop circuit 19. Therefore, when the discharge current becomes larger than the predetermined threshold value, the flip-flop circuit 19 is brought into the set" state so that it produces the high level signal S, at the terminal 23.
  • the sign changer 20 inverts the polarity of the output signal of the amplifier 15, so that the one-shot multivibrator 21 is not operated.
  • the one-shot multivibrator 17 does not operate, but the sign changer 20 operates to invert the polarity of said output voltage.
  • the one-shot multivibrator22 is, therefore, triggered by the output of said sign changer 20 and produces an output pulse which is applied to the reset terminal 22 of the flipflop circuit 19. Therefore, when the discharge is prevented or suppressed, the flip-flop circuit 19 produces the low level signal S, at the terminal 23.
  • FIG. 3 shows an example of said voltage control circuit 13, wherein 24 is a first reference signal source whose output is applied to a positive terminal of a subtracting circuit 25 through a break contact 26 of a switch 37, while 24 is a second reference signal source whose output is applied to said positive terminal through a make contact 27 of the relay switch 37.
  • the polarities of both outputs of the first and second reference signal sources are opposite to each other.
  • a servomotor 29 is driven by the output of an amplifier 28 to which the output of the subtracting circuit 25 is applied, and this motor rotates clockwise or counterclockwise in response to the polarity of the output of the subtracting circuit 25.
  • a slide contact 30 is adapted to contact to secondary winding 31 of a slidack transformer 32 whose primary winding 34 is connected to an a. c. power source 35 and is movable along the secondary winding 31 by the servomotor 29 in such manner than an a. c. output voltage obtained between the output terminals 30 and 30 of the secondary winding of the transformer 32 is either increased or decreased in response to rotation of the servomotor 29 in either the clockwise or counterclockwise directions.
  • This a. c. output voltage between the terminals 30 and 30' is supplied to the transformer T,, so that the transformer 32 and the source 35 serve as the a. 0. variable power device 2 of the circuit of FIG. 1.
  • a feedback potentiometer 36 which generates a feed-back signal which is variable in response to rotation of the servomotor 29 in cooperation with slide movement of the slidable contact 30 on the secondary winding of the slidack transformer 32.
  • This feed-back signal is negatively fed back to a negative terminal of the subtracting circuit 25 which produces an output signal proportional to the difference between the first or second reference signal applied to the positive terminal and the feed-back signal applied to the negative terminal.
  • the break contact 26 closes and the make contact 27 opens so that an output of the first reference signal source 24 is applied to the subtracting circuit 25 and the servomotor 29 rotates to cause said d. c. high voltage to increase gradually.
  • the break" contact 26 opens and themake contact 27 closes so that said d. c. high voltage decreases.
  • the voltage control circuit 13 shown in FIG. 3 constitutes a so-called servomechanism and thereby said d. c. high voltage is caused to increase gradually as shown in FIG. 5.
  • a suitable X-ray monitor 7' can be substituted for said plate 7 as a discharge detector, as illustrated in FIG. 6.
  • this X-ray is used as the detectable indicator representative of the discharge occuring in the accelerating tube.
  • the large undesirable discharge accompanied by sparks in the accelerating tube can be prevented completely, the inside wall of the accelerating tube is safe from being destroyed and the photograph of an electron microscope image can be obtained without disturbance. Moreover, the aging method can be effected automatically, so that longtime manual control is avoided.
  • An automatic control system for controlling the cl. c. high accelerating voltage applied to an accelerating tube of an electron microscope and the like comprising an accelerating tube having an electron source for emitting an electron beam and a plurality of accelerating electrodes for accelerating the electron beam;
  • detector means for detecting discharge in the ac celerating tube and for producing an output signal representative of the for discharge level; comparing circuit means for producing a first signal when the output signal of said detector means is larger than a predetermined value and a second signal when the output signal is less than said predetermined value;
  • variable d. c. high voltage source for generating a variable d. c. high voltage
  • said detector means is a conductive plate disposed in said accelerating tube so as to derive a discharge current therefrom, said conductive plate having an electron beam passage therein through which said electron beam passes.
  • said comparing circuit means includes a differential amplifier having one input connected to the output of said detector means and a second input connected to a threshold voltage source, a first one-shot multivibrator and an inverter each connected to the output of said differential amplifier, a second one-shot multivibrator connected to the output of said inverter, and a flip-flop having a set input connected to the output of said first one-shot multivibrator and a reset input connected to the output of said second one-shot multivibrator.
  • variable d. 0. high voltage source includes an a. c. variable power device and rectifier means for rectifying the output of said power device, said power device including a transformer having a primary winding connected to a source of a. c. voltage and a secondary winding having a slideable center contact connected to said rectifier means, the position of said center contact being controlled by said voltage control circuit means.
  • said voltage control circuit means includes a servo system responsive to said first and second signals for adjusting the position of said center contact to progressively increase the level of said d. c. high voltage without generating sparks in said accelerating tube.
  • said detector means is an X-ray monitor disposed in the accelerating tube for detecting X-rays produced by a discharge therein.
  • said comparing circuit means includes a differential amplifier having one input connected to the output of said detector means and a second input connected to a threshold voltage source, a first one-shot multivibrator and an inverter each connected to the output of said differential amplifier, a second one-shot multivibrator connected to the output of said inverter, and a flip-flop having a set input connected to the output of said first one-shot multivibrator and a reset input connected to the output of said second one-shot mu]- tivibrator.
  • variable d. c. high voltage source includes an a. 0. variable power device and rectifier means for rectifying the output of said power device, said power device including a transformer having a primary winding connected to a source of a. c. voltage and a secondary winding having a slideable center contact connected to said rectifier means, the position of said center contact being controlled by said voltage control circuit means.
  • said voltage control circuit means includes a servo system responsive to said first and second signals for adjusting the position of said center contact to progressively increase the level of said (1. c. high voltage without generating sparks in said accelerating tube.
  • said voltage control circuit means comprises a servomechanism for controlling the d. c. high voltage.

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  • Analytical Chemistry (AREA)
  • Electron Sources, Ion Sources (AREA)
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US104418A 1970-01-16 1971-01-06 Automatic control system for varying a d.c. high voltage for accelerating tube of electron microscope and the like Expired - Lifetime US3691377A (en)

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Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3794878A (en) * 1972-12-11 1974-02-26 Ford Motor Co Electron beam regulator
US3868541A (en) * 1971-06-05 1975-02-25 Philips Corp Filament-current control unit in electron-beam apparatus
US3921078A (en) * 1971-04-20 1975-11-18 Jeol Ltd Breakdown protection for field emission electron gun
US3936756A (en) * 1971-04-30 1976-02-03 Nihon Denshi Kabushiki Kaisha Field emission electron gun having automatic current control
US4342060A (en) * 1980-05-22 1982-07-27 Siemens Medical Laboratories, Inc. Energy interlock system for a linear accelerator
US4347547A (en) * 1980-05-22 1982-08-31 Siemens Medical Laboratories, Inc. Energy interlock system for a linear accelerator
US4361812A (en) * 1978-12-04 1982-11-30 Radiation Dynamics, Inc. Voltage stabilized particle accelerator system and method
FR2533070A1 (fr) * 1982-09-13 1984-03-16 Elektrotekhnichesky Inst Installation a faisceau electronique pour traitement electrothermique de metaux
US4555666A (en) * 1979-03-29 1985-11-26 Martin Frederick W Energy-stable accelerator with needle-like source and focused particle beam
US4642461A (en) * 1983-11-30 1987-02-10 Hitachi, Ltd. Field emission type electron microscope using a multi-stage acceleration tube
US4675524A (en) * 1985-03-11 1987-06-23 Siemens Aktiengesellschaft Scanning particle microscope with diminished boersch effect
US5235188A (en) * 1990-08-10 1993-08-10 U.S. Philips Corporation Charged particle beam device
US5401973A (en) * 1992-12-04 1995-03-28 Atomic Energy Of Canada Limited Industrial material processing electron linear accelerator
US5440210A (en) * 1993-04-16 1995-08-08 University Of Chicago Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude
DE4433531A1 (de) * 1994-09-20 1996-03-21 Jeol Ltd Hochspannungs-Gleichstromgenerator
DE4433524A1 (de) * 1994-09-20 1996-03-21 Jeol Ltd Hochspannungs-Gleichstromgenerator
JP3310504B2 (ja) 1994-09-20 2002-08-05 日本電子株式会社 直流高電圧発生装置
CN103390532A (zh) * 2012-05-11 2013-11-13 西门子公司 操作用于产生微波辐射的设备的方法
US11899159B2 (en) * 2019-04-02 2024-02-13 Schlumberger Technology Corporation Regulated charged particle beam emitter systems and methods

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Publication number Priority date Publication date Assignee Title
CN103488233B (zh) * 2013-10-10 2015-01-21 中国科学院上海高等研究院 基于相关信号来调节数字电位器的方法、系统及电路
JP7034752B2 (ja) * 2018-02-15 2022-03-14 株式会社荏原製作所 昇圧方法、昇圧システム、昇圧装置および昇圧プログラム

Cited By (24)

* 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
US3936756A (en) * 1971-04-30 1976-02-03 Nihon Denshi Kabushiki Kaisha Field emission electron gun having automatic current control
US3868541A (en) * 1971-06-05 1975-02-25 Philips Corp Filament-current control unit in electron-beam apparatus
US3794878A (en) * 1972-12-11 1974-02-26 Ford Motor Co Electron beam regulator
US4361812A (en) * 1978-12-04 1982-11-30 Radiation Dynamics, Inc. Voltage stabilized particle accelerator system and method
US4555666A (en) * 1979-03-29 1985-11-26 Martin Frederick W Energy-stable accelerator with needle-like source and focused particle beam
US4342060A (en) * 1980-05-22 1982-07-27 Siemens Medical Laboratories, Inc. Energy interlock system for a linear accelerator
US4347547A (en) * 1980-05-22 1982-08-31 Siemens Medical Laboratories, Inc. Energy interlock system for a linear accelerator
FR2533070A1 (fr) * 1982-09-13 1984-03-16 Elektrotekhnichesky Inst Installation a faisceau electronique pour traitement electrothermique de metaux
US4642461A (en) * 1983-11-30 1987-02-10 Hitachi, Ltd. Field emission type electron microscope using a multi-stage acceleration tube
US4675524A (en) * 1985-03-11 1987-06-23 Siemens Aktiengesellschaft Scanning particle microscope with diminished boersch effect
EP0194570A3 (de) * 1985-03-11 1988-11-17 Siemens Aktiengesellschaft Raster-Korpuskularmikroskop mit verringertem Boersch-Effekt
US5235188A (en) * 1990-08-10 1993-08-10 U.S. Philips Corporation Charged particle beam device
US5401973A (en) * 1992-12-04 1995-03-28 Atomic Energy Of Canada Limited Industrial material processing electron linear accelerator
US5440210A (en) * 1993-04-16 1995-08-08 University Of Chicago Indirectly sensing accelerator beam currents for limiting maximum beam current magnitude
DE4433531A1 (de) * 1994-09-20 1996-03-21 Jeol Ltd Hochspannungs-Gleichstromgenerator
DE4433524A1 (de) * 1994-09-20 1996-03-21 Jeol Ltd Hochspannungs-Gleichstromgenerator
DE4433524C2 (de) * 1994-09-20 1999-01-28 Jeol Ltd Hochspannungs-Gleichstromgenerator
JP3310504B2 (ja) 1994-09-20 2002-08-05 日本電子株式会社 直流高電圧発生装置
CN103390532A (zh) * 2012-05-11 2013-11-13 西门子公司 操作用于产生微波辐射的设备的方法
DE102012207930A1 (de) * 2012-05-11 2013-11-14 Siemens Aktiengesellschaft Verfahren zum Betreiben eines Geräts zum Erzeugen einer Mikrowellenstrahlung
US9076624B2 (en) 2012-05-11 2015-07-07 Siemens Aktiengsellschaft Generating microwave radiation
CN103390532B (zh) * 2012-05-11 2016-05-11 西门子公司 操作用于产生微波辐射的设备的方法
US11899159B2 (en) * 2019-04-02 2024-02-13 Schlumberger Technology Corporation Regulated charged particle beam emitter systems and methods

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GB1338423A (en) 1973-11-21
JPS4922371B1 (enrdf_load_stackoverflow) 1974-06-07

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