WO2019244826A1 - Ionization vacuum gauge and control device - Google Patents

Ionization vacuum gauge and control device Download PDF

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Publication number
WO2019244826A1
WO2019244826A1 PCT/JP2019/023844 JP2019023844W WO2019244826A1 WO 2019244826 A1 WO2019244826 A1 WO 2019244826A1 JP 2019023844 W JP2019023844 W JP 2019023844W WO 2019244826 A1 WO2019244826 A1 WO 2019244826A1
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Prior art keywords
potential
grid
filament
power supply
electron emission
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PCT/JP2019/023844
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French (fr)
Japanese (ja)
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貴伸 佐藤
豊昭 中島
宮下　剛
万沙洋 福原
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株式会社アルバック
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Priority to JP2019554002A priority Critical patent/JP6772391B2/en
Publication of WO2019244826A1 publication Critical patent/WO2019244826A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L21/00—Vacuum gauges
    • G01L21/30—Vacuum gauges by making use of ionisation effects
    • G01L21/32—Vacuum gauges by making use of ionisation effects using electric discharge tubes with thermionic cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J41/00—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas; Discharge tubes for evacuation by diffusion of ions
    • H01J41/02—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas
    • H01J41/04—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas with ionisation by means of thermionic cathodes

Definitions

  • the present invention relates to a hot cathode type ionization gauge and a control device used for the gauge.
  • Ionization gauges that ionizes gas molecules and obtains pressure from the number of generated ions.
  • Ionization gauges include a cold-cathode type, in which a strong electric field is applied to the electrode surface to use an electron emitted into a vacuum by a tunnel effect, and a heat emitted from a heated filament. It is divided into a hot cathode type using electrons.
  • a typical example of the cold cathode type is a Penning vacuum gauge, and a typical type of the hot cathode type is a BA (Bayard-Alpert) ionization gauge.
  • Hot cathode ionization gauges typically capture filaments that emit electrons, a grid that accelerates and collects the electrons emitted from the filament, and collects ions of gas that has been ionized by the collision of the accelerated electrons. It has a collector and a case for accommodating them.
  • the potential of each part is, for example, ground potential in the case part, plus several tens V in the filament part, plus one hundred and several tens V in the grid part, and ground potential in the collector part.
  • the electrons emitted from the filament go to the grid, and when the acceleration energy of the electrons exceeds the ionization energy of the gas molecules, the gas molecules in the atmosphere are ionized.
  • the ionized gas molecules move to the lower potential collector.
  • the number of ions reaching the collector is calculated from the ion current flowing through the collector and the electron current (emission current) from the filament, and the pressure value is calculated from the number of ions.
  • Emission current from the filament is generally switched stepwise according to the pressure region.
  • the emission current is controlled to several mA in a pressure range of 0.1 to 0.01 Pa or less, and to about several ⁇ A in a pressure range exceeding the above (higher pressure side).
  • the emission current is switched, the potential of the filament temporarily fluctuates greatly, which may make it impossible to continue pressure measurement stably.
  • Patent Document 1 proposes a configuration in which a filament bias power supply is arranged between the filament and the ground potential.
  • an object of the present invention is to provide an ionization gauge and a control device capable of stably measuring pressure without requiring an additional power supply.
  • an ionization gauge includes a tracing stylus and a control unit.
  • the probe has an electron emission source, a grid, and a collector.
  • the control unit has a drive circuit, a grid power supply, an ion current detection circuit, and a potential limiting circuit.
  • the drive circuit includes a drive power supply for driving the electron emission source, and controls the drive power supply so that an emission current flowing between the electron emission source and the grid is constant.
  • the grid power source maintains the grid at a predetermined grid potential.
  • the ion current detection circuit detects an ion current flowing into the collector.
  • the potential limiting circuit is connected between the driving circuit and the grid power supply, and sets the potential of the electron emission source to a first potential higher than the potential of the collector and a second potential lower than the grid potential. Is maintained within a predetermined range.
  • the fluctuation range of the potential of the electron emission source is limited to a predetermined region between the collector potential and the grid potential, the electrons emitted from the electron emission source can reliably reach the grid. Thus, the pressure can be stably measured.
  • the potential limiting circuit includes a first voltage dividing resistor that divides the grid potential to the first potential, a second voltage dividing resistor that divides the grid potential to the second potential, and the driving circuit A first rectifier connected between the first voltage divider and a second rectifier connected between the drive circuit and the second voltage divider; Is also good.
  • the drive circuit includes a resistance element that generates a potential of the electron emission source from the emission current, and a current-voltage converter that controls the drive power supply so that a current flowing through the resistance element has a predetermined value. May be.
  • the ionization gauge may further include a calculation unit that calculates a pressure value based on the emission current and the ion current.
  • a control device is a control device for an ionization gauge having an electron emission source, a grid, and a collector, and includes a drive circuit, a grid power supply, an ion current detection circuit, a potential limiter, And a circuit.
  • the drive circuit includes a drive power supply for driving the electron emission source, and controls the drive power supply so that an emission current flowing between the electron emission source and the grid is constant.
  • the grid power source maintains the grid at a predetermined grid potential.
  • the ion current detection circuit detects an ion current flowing into the collector.
  • the potential limiting circuit is connected between the driving circuit and the grid power supply, and sets the potential of the electron emission source to a first potential higher than the potential of the collector and a second potential lower than the grid potential. Is maintained within a predetermined range.
  • the pressure can be measured stably without requiring an additional power supply.
  • FIG. 3 is a conceptual diagram of a filament drive circuit for explaining a factor of fluctuation of a filament potential.
  • FIG. 4 is a schematic diagram showing a potential barrier structure when overshoot occurs.
  • FIG. 4 is a schematic diagram illustrating a potential barrier structure when an undershoot occurs.
  • FIG. 5 is a schematic configuration diagram of an ionization gauge according to a comparative example.
  • FIG. 2 is a schematic diagram illustrating a potential barrier structure of the ionization gauge of FIG. 1.
  • FIG. 3 is a conceptual diagram of a filament drive circuit for explaining a factor of fluctuation of a filament potential.
  • FIG. 4 is a schematic diagram showing a potential barrier structure when overshoot occurs.
  • FIG. 4 is a schematic diagram illustrating a potential barrier structure when an undershoot occurs.
  • FIG. 5 is a schematic configuration diagram of an ionization gauge according to a comparative example.
  • FIG. 2 is a schematic diagram illustrating a potential barrier structure of the
  • FIG. 6 is a diagram showing one experimental result for explaining a difference in operation between the ionization gauge of FIG. 1 and the ionization gauge of FIG. 5.
  • FIG. 6 is a diagram showing another experimental result for explaining a difference in operation between the ionization gauge of FIG. 1 and the ionization gauge of FIG. 5.
  • FIG. 1 is a schematic configuration diagram showing an ionization gauge according to an embodiment of the present invention.
  • a description will be given taking a BA type hot cathode ionization gauge as an example.
  • the ionization gauge 100 of the present embodiment includes a tracing stylus 10 and a control unit 20 as a control device.
  • the tracing stylus 10 has a filament 11 as an electron emission source, a grid 12, a collector 13, and a case 14 accommodating them.
  • the control unit 20 includes a drive circuit 21 for driving the filament 11, a grid power supply 22 for maintaining the grid 12 at the grid potential, and an ion current detection circuit (ammeter) 23 for detecting an ion current flowing through the collector 13.
  • the filament 11 is made of a high melting point metal material such as tungsten.
  • the filament 11 is supported by the bottom of the case 14 and is electrically connected to a driving circuit 21 described later.
  • the filament 11 is configured to be maintained at a predetermined set potential (for example, +25 V) by the drive circuit 21 and to emit electrons (thermoelectrons) when a heating current is supplied from the filament heating power supply 211.
  • the grid 12 is formed of a metal wire wound in a coil shape.
  • the grid 12 is supported by the bottom of the case 14 and is electrically connected to a grid power supply 22.
  • the grid 12 is maintained at a predetermined grid potential (for example, +150 V) higher than the set potential of the filament 11 by the grid power supply 22.
  • the collector 13 is composed of a straight metal wire arranged at the axis of the grid 12.
  • the collector 13 is supported by the bottom of the case 14 and is connected to a ground potential via an ion current detection circuit 23.
  • the collector 13 is configured to be able to collect ions of gas molecules in the case 14 generated by collision with electrons traveling from the filament 11 to the grid 12.
  • the case 14 is made of a metal material and typically has a cylindrical shape.
  • the case 14 is attached to a peripheral wall portion, a bottom wall portion, or the like of the chamber 1 so that the inside thereof can communicate with the internal space of the chamber 1.
  • Case 14 is connected to the ground potential.
  • the drive circuit 21 includes a filament heating power supply 211 as a drive power supply, a resistance element 212 that generates a filament potential from an emission current flowing between the filament 11 and the grid 12, and a current-voltage converter 213.
  • the filament heating power supply 211 is a current source for heating the filament 11. Energy is given to the electrons by energizing the filament 11, and when the energy becomes higher than the work function of the filament material, the electrons are emitted from the filament 11 by an electric field applied to the outside of the filament 11.
  • the resistance value of the filament 11 is relatively low at normal temperature, and increases when the current is heated. At the start of filament driving, driving is performed from a state close to normal temperature, so that the resistance value is low at the initial stage of driving, and a large inrush current easily flows. As the temperature rises, the resistance value increases, and the flowing current stabilizes low.
  • the resistance element 212 is connected between the cathode of the filament heating power supply 211 and the ground potential.
  • the current-voltage converter 213 includes a negative feedback amplifier having a non-inverting input terminal connected to a predetermined reference voltage (ground potential in this example) and an inverting input terminal connected to the resistance element 212.
  • the current-voltage converter 213 controls the filament heating power supply 211 so that the current flowing through the resistance element 212 has a predetermined value.
  • the resistance value (R1) of the resistance element 212 is not particularly limited, but is, for example, several tens k ⁇ to several M ⁇ .
  • the resistance value (R1) is set so that the product of the emission current value and the resistance value (R1) becomes the ground-filament potential, that is, the set potential of the filament 11 (+25 V in this example).
  • the resistance value of the resistance element 212 may be variable.
  • the drive circuit 21 performs current-voltage conversion of the current flowing to the ground potential via the resistance element 212 with the current-voltage converter 213, and feeds back the current to the filament heating power supply 211. In this way, by applying feedback so that the ground terminal side of the resistance element 212 is always at the ground potential, the emission current of several ⁇ A can be controlled with high accuracy.
  • FIG. 2 shows a potential barrier structure during normal operation of the ionization vacuum gauge 100.
  • the filament 11 is subjected to an electrolytic gradient by the grid potential applied to the grid 12, and a large number of electrons emitted from the filament 11 move toward the grid 12. Some of the electrons pass through the low potential between the filament 11 and the case 14, follow tracks around the grid 12, and finally reach the grid 12.
  • the acceleration energy of the electrons is maximum near the grid 12, and when the electrons collide with the gas molecules in the atmosphere when they have the acceleration energy that maximizes the ionization cross section of the gas molecules in the atmosphere, the gas molecules are most efficiently ionized. I do.
  • the ionized gas molecules travel to the collector 13 whose gradient is steeper than the potential of the filament 11, recombine with the electrons supplied from the collector 13, and are measured by the ion current detection circuit 23 as an ion current.
  • the ionization gauge 100 further includes a pressure calculator 30 for calculating a pressure value based on the emission current and the ion current.
  • the output of the current-voltage converter 213 is referred to for the emission current, and the output of the ion current detection circuit 23 is referred to for the ion current.
  • the pressure calculator 30 measures the ion current that has reached the collector 13 and converts the number of ions into a pressure value as shown in the following equation (1).
  • P Ii / (S ⁇ Ie) (1)
  • P pressure (Pa)
  • Ii ion current
  • Ie emission current
  • S sensitivity.
  • the pressure value calculated by the pressure calculation unit 30 is displayed via the display unit M.
  • the ionization vacuum gauge 100 is configured to control the emission current from the filament 11 stepwise according to the pressure region.
  • the current range is switched to several mA in a pressure range of 0.1 Pa to 0.01 Pa or less, and to about several ⁇ A in a pressure range exceeding it.
  • the sensitivity coefficient S of the ionization gauge depends on the shape of the probe, it is constant at any pressure. In the low pressure region, the ion current Ii decreases in proportion to the pressure, and the signal is buried in the thermal noise in the amplifier circuit, making accurate measurement difficult. Therefore, it is necessary to increase the true ion current Ii for accurate measurement. Therefore, the emission current Ie is increased, and the ion current Ii is relatively increased. In a low pressure region, the ratio of gas molecules adsorbed to the grid electrode increases the rate of electron-excited desorption due to the emission current. As a result, the amount of gas molecules adsorbed to the grid electrode decreases and the electron-excited desorption increases. The error amount of the ion current Ii due to the desorbed ions is also reduced.
  • the control of the emission current is executed based on, for example, a control command from the pressure calculation unit 30 to the drive circuit 21 (for example, a command to set the resistance value of the resistance element 212).
  • the current flowing through the resistance element 212 is feedback-controlled using the current-voltage converter 213 so that the emission current from the filament 11 has a predetermined value, as described above.
  • the current flowing through the filament reaches a maximum value, the current becomes stable at a steady current value.
  • the current does not decay immediately.
  • the temperature of the filament 11 is higher than that in the steady state due to the inrush current, and the filament 11 is in a state where the emission current can easily flow.
  • the filament potential may be higher than the grid potential as shown in FIG. 4A for a short time (overshoot). In this case, the electrons cannot reach the grid 12 and the electrons that temporarily contribute to the ionization of the gas molecules disappear, so that the pressure indication indicates the minimum value.
  • undershoot may occur depending on the time constant of the drive circuit 21 for driving the filament 11 and the parasitic capacitance due to wiring and the like, and the potential of the filament 11 may be lower than the set potential (+25 V) as shown in FIG. 4B.
  • the acceleration energy of the electrons when reaching the grid 12 takes a large value, and the cross-sectional area of Coulomb scattering is proportional to the reciprocal of the kinetic energy, so that the ionization efficiency is reduced.
  • the ionization gauge 100 of the present embodiment adjusts the fluctuation range of the filament potential so that the potential of the filament 11 fluctuates only within a preset voltage range.
  • a potential limiting circuit 28 for limiting is provided. Hereinafter, the details of the potential limiting circuit 28 will be described.
  • the control unit 20 has a potential limiting circuit 28.
  • the potential limiting circuit 28 is connected between the driving circuit 21 and the grid power supply 22.
  • the potential limiting circuit 28 is configured to maintain the potential of the filament 11 in a predetermined range between a first potential V1 higher than the potential of the collector 13 and a second potential V2 lower than the potential of the grid 12. You.
  • the potential limiting circuit 28 includes a first voltage dividing resistor 281, a second voltage dividing resistor 282, a first rectifying element 283, and a second rectifying element 284.
  • the first voltage dividing resistor 281 and the second voltage dividing resistor 282 are respectively connected in parallel to the grid 12 between the anode of the grid power supply 22 and the ground potential, and connect the grid potential to the first potential V1. And a second potential V2 higher than the first potential V1.
  • Each of the first voltage dividing resistor 281 and the second voltage dividing resistor 282 may be composed of a fixed resistance element or a variable resistance element.
  • the magnitudes of the first potential V1 and the second potential V2 are not particularly limited, and can be appropriately set according to an allowable fluctuation range of the potential of the filament 11.
  • the first rectifying element 283 is connected between the driving circuit 21 (the cathode of the filament heating power supply 211) and the first voltage dividing resistor 281 and a current flows from the first voltage dividing resistor 281 to the driving circuit 21. Is a forward direction.
  • the second rectifying element 283 is connected between the driving circuit 21 (the cathode of the filament heating power supply 211) and the second voltage dividing resistor 282, and a current flows from the driving circuit 21 to the second voltage dividing resistor 282. Is a forward direction.
  • the first and second voltage dividing resistors 281 and 282 may be constituted by variable resistors, whereby the first and second potentials V1 and V2 can be arbitrarily adjusted.
  • the potential limiting circuit 28 includes a divided voltage (first and second potentials V1 and V2) formed by two resistors (first and second voltage dividing resistors 281 and 282), Using the two diodes (first and second rectifying elements 283 and 284), the potential fluctuation region of the filament 11 is fixed. Thereby, even when there is a large fluctuation in the filament current, the potential barrier of the filament 11 is forcibly formed, so that when the undershoot of the filament potential occurs, the overshoot is performed so as not to become lower than the first potential V1. When a shoot occurs, the potential can be prevented from being equal to or higher than the second potential V2.
  • the first potential V1 and the first potential V1 are set so that all the electrons emitted from the filament 11 reach the grid 12 in the shortest time and that the emitted electrons can obtain an acceleration energy higher than the ionization energy.
  • the second potential V2 By adjusting the second potential V2, the fluctuation of the pressure instruction can be minimized.
  • the emission current can be measured with high accuracy. Even if the emission current is reduced by any reason, the true value of the emission current measured by the high accuracy is substituted into the above equation (1). It is possible to indicate the pressure value. Furthermore, since the fluctuation of the pressure command value at the time of switching the filament current or at the time of starting can be reduced, there is an effect that the switching time and the starting time are shortened. Further, there is no need to add a new power supply system.
  • FIGS. 7 and 8 show the pressure indication value and the filament potential time when the emission current is switched from 10 ⁇ A to 1 mA for the ionization gauge 200 according to the comparative example shown in FIG. 5 and the ionization gauge 100 of the present embodiment. The changes are shown in comparison.
  • the first potential V1 and the second potential V2 in the potential limiting circuit 28 are set so that the lower limit of the filament 11 is +15 V and the upper limit is +35 V.
  • the potential of the filament 11 in the steady state was + 25V.
  • the fluctuation of the potential of the filament 11 is limited, so that the overshoot accompanying the switching of the emission current can be avoided.
  • the first potential V1 and the second potential V2 formed in the potential limiting circuit 28 are fixed, respectively.
  • the present invention is not limited to this. May be variably configured.
  • BA type ionization gauge (BA gauge) has been described as an example of the ionization gauge, but the present invention is similarly applied to other types of hot cathode type ionization gauges. It is possible.

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  • General Physics & Mathematics (AREA)
  • Measuring Fluid Pressure (AREA)

Abstract

The ionization vacuum gauge according to one embodiment of the present invention is provided with a gauge head and a control unit. The control unit has a drive circuit, a grid power source, an ionic current detection circuit, and a potential restriction circuit. The drive circuit includes a drive power source for driving an electron emission source, and controls the drive power source such that an emission current flowing between the electron emission source and the grid becomes constant. The grid power source maintains a grid at a prescribed grid potential. The ionic current detection circuit detects an ionic current flowing into a collector. The potential restriction circuit is connected between the drive circuit and the grid power source, and maintains the potential of the electron emission source within a prescribed range from a first potential that is higher than the potential of the collector to a second potential that is lower than the grid potential.

Description

電離真空計及び制御装置Ionization gauge and controller
　本発明は、熱陰極型の電離真空計及びこれに用いられる制御装置に関する。 The present invention relates to a hot cathode type ionization gauge and a control device used for the gauge.
　気体分子を電離させ、生成したイオンの数から圧力を求める電離真空計が知られている。電離真空計には、気体を電離させるための電子源に、電極表面に強電界を印加しトンネル効果で真空中に放出された電子を利用する冷陰極型と、加熱したフィラメントから放出される熱電子を利用する熱陰極型とに分けられる。冷陰極型としてはペニング真空計が、熱陰極型としてはＢ－Ａ型（Bayard-Alpert）電離真空計が代表的である。 電 There is known an ionization gauge that ionizes gas molecules and obtains pressure from the number of generated ions. Ionization gauges include a cold-cathode type, in which a strong electric field is applied to the electrode surface to use an electron emitted into a vacuum by a tunnel effect, and a heat emitted from a heated filament. It is divided into a hot cathode type using electrons. A typical example of the cold cathode type is a Penning vacuum gauge, and a typical type of the hot cathode type is a BA (Bayard-Alpert) ionization gauge.
　熱陰極電離真空計は、典型的には、電子を放出するフィラメントと、フィラメントから放出された電子を加速し捕集するグリッドと、加速した電子との衝突により電離した気体のイオンを捕集するコレクタと、これらを収容するケースとを有する。各部の電位は、例えば、ケース部分がグランド電位、フィラメント部分がプラス数十Ｖ、グリッド部分がプラス百数十Ｖ、コレクタ部分がグランド電位となっている。フィラメントから放出された電子はグリッドへ向かい、電子の加速エネルギーが気体分子のイオン化エネルギーを超えると、雰囲気中の気体分子をイオン化する。イオン化された気体分子は、電位の低いコレクタへ移動する。コレクタを流れるイオン電流とフィラメントからの電子電流（エミッション電流）からコレクタに到達したイオンの数が算出され、そのイオンの数から圧力値が算出される。 Hot cathode ionization gauges typically capture filaments that emit electrons, a grid that accelerates and collects the electrons emitted from the filament, and collects ions of gas that has been ionized by the collision of the accelerated electrons. It has a collector and a case for accommodating them. The potential of each part is, for example, ground potential in the case part, plus several tens V in the filament part, plus one hundred and several tens V in the grid part, and ground potential in the collector part. The electrons emitted from the filament go to the grid, and when the acceleration energy of the electrons exceeds the ionization energy of the gas molecules, the gas molecules in the atmosphere are ionized. The ionized gas molecules move to the lower potential collector. The number of ions reaching the collector is calculated from the ion current flowing through the collector and the electron current (emission current) from the filament, and the pressure value is calculated from the number of ions.
　フィラメントからのエミッション電流は、圧力領域に応じて段階的に切り替えられるのが一般的である。例えば、０．１～０．０１Ｐａ以下の圧力領域では数ｍＡ、上記を超える圧力領域（より高圧側）では数μＡ前後にエミッション電流が制御される。このエミッション電流が切り替えられたとき、フィラメントの電位が一時的に大きく変動し、これが原因で圧力測定を安定に継続することができないことがある。このようなフィラメント電位の変動を抑制するために、例えば特許文献１には、フィラメントバイアス電源をフィラメントとグランド電位との間に配置する構成が提案されている。 Emission current from the filament is generally switched stepwise according to the pressure region. For example, the emission current is controlled to several mA in a pressure range of 0.1 to 0.01 Pa or less, and to about several μA in a pressure range exceeding the above (higher pressure side). When the emission current is switched, the potential of the filament temporarily fluctuates greatly, which may make it impossible to continue pressure measurement stably. In order to suppress such a fluctuation of the filament potential, for example, Patent Document 1 proposes a configuration in which a filament bias power supply is arranged between the filament and the ground potential.
特開平１１－８３６６１号公報JP-A-11-83661
　しかしながら、特許文献１に記載の構成では、フィラメント電位の変動を抑制するためにフィラメントバイアス電源を別途設ける必要があるため、装置構成の複雑化、大型化、高コスト化を招くという問題がある。 However, in the configuration described in Patent Document 1, it is necessary to separately provide a filament bias power supply in order to suppress the fluctuation of the filament potential, so that there is a problem that the configuration of the device becomes complicated, large, and high in cost.
　以上のような事情に鑑み、本発明の目的は、追加の電源を必要とすることなく、圧力を安定に測定することができる電離真空計及び制御装置を提供することにある。 In view of the above circumstances, an object of the present invention is to provide an ionization gauge and a control device capable of stably measuring pressure without requiring an additional power supply.
　上記目的を達成するため、本発明の一形態に係る電離真空計は、測定子と、制御部とを具備する。
　前記測定子は、電子放出源と、グリッドと、コレクタとを有する。
　前記制御部は、駆動回路と、グリッド電源と、イオン電流検出回路と、電位制限回路とを有する。前記駆動回路は、前記電子放出源を駆動する駆動電源を含み、前記電子放出源と前記グリッドとの間に流れるエミッション電流が一定となるように前記駆動電源を制御する。前記グリッド電源は、前記グリッドを所定のグリッド電位に維持する。前記イオン電流検出回路は、前記コレクタに流入するイオン電流を検出する。前記電位制限回路は、前記駆動回路と前記グリッド電源との間に接続され、前記電子放出源の電位を前記コレクタの電位よりも高い第１の電位と前記グリッド電位よりも低い第２の電位との間の所定範囲に維持する。 In order to achieve the above object, an ionization gauge according to one embodiment of the present invention includes a tracing stylus and a control unit.
The probe has an electron emission source, a grid, and a collector.
The control unit has a drive circuit, a grid power supply, an ion current detection circuit, and a potential limiting circuit. The drive circuit includes a drive power supply for driving the electron emission source, and controls the drive power supply so that an emission current flowing between the electron emission source and the grid is constant. The grid power source maintains the grid at a predetermined grid potential. The ion current detection circuit detects an ion current flowing into the collector. The potential limiting circuit is connected between the driving circuit and the grid power supply, and sets the potential of the electron emission source to a first potential higher than the potential of the collector and a second potential lower than the grid potential. Is maintained within a predetermined range.
　上記電離真空計においては、電子放出源の電位の変動幅がコレクタ電位とグリッド電位との間の所定領域に限定されるため、電子放出源からの放出電子をグリッドへ確実に到達させることができ、これにより圧力を安定に測定することができる。 In the above ionization gauge, since the fluctuation range of the potential of the electron emission source is limited to a predetermined region between the collector potential and the grid potential, the electrons emitted from the electron emission source can reliably reach the grid. Thus, the pressure can be stably measured.
　前記電位制限回路は、前記グリッド電位を前記第１の電位に分圧する第１の分圧抵抗と、前記グリッド電位を前記第２の電位に分圧する第２の分圧抵抗と、前記駆動回路と前記第１の分圧抵抗との間に接続された第１の整流素子と、前記駆動回路と前記第２の分圧抵抗との間に接続された第２の整流素子と、を有してもよい。 The potential limiting circuit includes a first voltage dividing resistor that divides the grid potential to the first potential, a second voltage dividing resistor that divides the grid potential to the second potential, and the driving circuit A first rectifier connected between the first voltage divider and a second rectifier connected between the drive circuit and the second voltage divider; Is also good.
　前記駆動回路は、前記エミッション電流から前記電子放出源の電位を生成する抵抗素子と、前記抵抗素子に流れる電流が所定の値となるように前記駆動電源を制御する電流電圧変換器と、を有してもよい。 The drive circuit includes a resistance element that generates a potential of the electron emission source from the emission current, and a current-voltage converter that controls the drive power supply so that a current flowing through the resistance element has a predetermined value. May be.
　前記電離真空計は、前記エミッション電流と前記イオン電流とに基づいて圧力値を演算する演算部をさらに具備してもよい。 The ionization gauge may further include a calculation unit that calculates a pressure value based on the emission current and the ion current.
　本発明の一形態に係る制御装置は、電子放出源と、グリッドと、コレクタとを有する電離真空計用の制御装置であって、駆動回路と、グリッド電源と、イオン電流検出回路と、電位制限回路とを具備する。
　前記駆動回路は、前記電子放出源を駆動する駆動電源を含み、前記電子放出源と前記グリッドとの間に流れるエミッション電流が一定となるように前記駆動電源を制御する。
　前記グリッド電源は、前記グリッドを所定のグリッド電位に維持する。
　前記イオン電流検出回路は、前記コレクタに流入するイオン電流を検出する。
　前記電位制限回路は、前記駆動回路と前記グリッド電源との間に接続され、前記電子放出源の電位を前記コレクタの電位よりも高い第１の電位と前記グリッド電位よりも低い第２の電位との間の所定範囲に維持する。 A control device according to one embodiment of the present invention is a control device for an ionization gauge having an electron emission source, a grid, and a collector, and includes a drive circuit, a grid power supply, an ion current detection circuit, a potential limiter, And a circuit.
The drive circuit includes a drive power supply for driving the electron emission source, and controls the drive power supply so that an emission current flowing between the electron emission source and the grid is constant.
The grid power source maintains the grid at a predetermined grid potential.
The ion current detection circuit detects an ion current flowing into the collector.
The potential limiting circuit is connected between the driving circuit and the grid power supply, and sets the potential of the electron emission source to a first potential higher than the potential of the collector and a second potential lower than the grid potential. Is maintained within a predetermined range.
　以上述べたように、本発明によれば、追加の電源を必要とすることなく、圧力を安定に測定することができる。 As described above, according to the present invention, the pressure can be measured stably without requiring an additional power supply.
本発明の一実施形態に係る電離真空計を示す概略構成図である。It is a schematic structure figure showing the ionization vacuum gauge concerning one embodiment of the present invention. 上記電離真空計の通常駆動時の電位障壁構造を示す模式図である。It is a schematic diagram which shows the potential barrier structure at the time of the normal drive of the said ionization vacuum gauge. フィラメント電位の変動要因を説明するフィラメント駆動回路の概念図である。FIG. 3 is a conceptual diagram of a filament drive circuit for explaining a factor of fluctuation of a filament potential. オーバーシュート発生時の電位障壁構造を示す模式図である。FIG. 4 is a schematic diagram showing a potential barrier structure when overshoot occurs. アンダーシュート発生時の電位障壁構造を示す模式図である。FIG. 4 is a schematic diagram illustrating a potential barrier structure when an undershoot occurs. 比較例に係る電離真空計の概略構成図である。FIG. 5 is a schematic configuration diagram of an ionization gauge according to a comparative example. 図１の電離真空計の電位障壁構造を示す模式図である。FIG. 2 is a schematic diagram illustrating a potential barrier structure of the ionization gauge of FIG. 1. 図１の電離真空計と図５の電離真空計の作用の違いを説明する一実験結果を示す図である。FIG. 6 is a diagram showing one experimental result for explaining a difference in operation between the ionization gauge of FIG. 1 and the ionization gauge of FIG. 5. 図１の電離真空計と図５の電離真空計の作用の違いを説明する他の実験結果を示す図である。FIG. 6 is a diagram showing another experimental result for explaining a difference in operation between the ionization gauge of FIG. 1 and the ionization gauge of FIG. 5.
　以下、図面を参照しながら、本発明の実施形態を説明する。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
　図１は、本発明の一実施形態に係る電離真空計を示す概略構成図である。本実施形態では、Ｂ－Ａ型熱陰極電離真空計を例に挙げて説明する。 FIG. 1 is a schematic configuration diagram showing an ionization gauge according to an embodiment of the present invention. In the present embodiment, a description will be given taking a BA type hot cathode ionization gauge as an example.
［基本構成］
　本実施形態の電離真空計１００は、測定子１０と、制御装置としての制御部２０とを備える。 [Basic configuration]
The ionization gauge 100 of the present embodiment includes a tracing stylus 10 and a control unit 20 as a control device.
　測定子１０は、電子放出源としてのフィラメント１１と、グリッド１２と、コレクタ１３と、これらを収容するケース１４とを有する。
　制御部２０は、フィラメント１１を駆動する駆動回路２１と、グリッド１２をグリッド電位に維持するグリッド電源２２と、コレクタ１３を流れるイオン電流を検出するイオン電流検出回路（電流計）２３とを有する。 The tracing stylus 10 has a filament 11 as an electron emission source, a grid 12, a collector 13, and a case 14 accommodating them.
The control unit 20 includes a drive circuit 21 for driving the filament 11, a grid power supply 22 for maintaining the grid 12 at the grid potential, and an ion current detection circuit (ammeter) 23 for detecting an ion current flowing through the collector 13.
　フィラメント１１は、タングステン等の高融点金属材料で構成される。フィラメント１１は、ケース１４の底部に支持されるとともに、後述する駆動回路２１に電気的に接続される。フィラメント１１は、駆動回路２１によって所定の設定電位（例えば＋２５Ｖ）に維持されるとともに、フィラメント加熱電源２１１から加熱電流が供給されることによって、電子（熱電子）を放出することが可能に構成される。 The filament 11 is made of a high melting point metal material such as tungsten. The filament 11 is supported by the bottom of the case 14 and is electrically connected to a driving circuit 21 described later. The filament 11 is configured to be maintained at a predetermined set potential (for example, +25 V) by the drive circuit 21 and to emit electrons (thermoelectrons) when a heating current is supplied from the filament heating power supply 211. You.
　グリッド１２は、コイル状に巻回された金属線で構成される。グリッド１２は、ケース１４の底部に支持されるとともに、グリッド電源２２に電気的に接続される。グリッド１２は、グリッド電源２２によって、フィラメント１１の設定電位よりも高い所定のグリッド電位（例えば＋１５０Ｖ）に維持される。 The grid 12 is formed of a metal wire wound in a coil shape. The grid 12 is supported by the bottom of the case 14 and is electrically connected to a grid power supply 22. The grid 12 is maintained at a predetermined grid potential (for example, +150 V) higher than the set potential of the filament 11 by the grid power supply 22.
　コレクタ１３は、グリッド１２の軸心に配置された直線的な金属線で構成される。コレクタ１３は、ケース１４の底部に支持されるとともに、イオン電流検出回路２３を介してグランド電位に接続される。コレクタ１３は、フィラメント１１からグリッド１２に向かう電子との衝突により生成されたケース１４内の気体分子のイオンを捕集することが可能に構成される。 The collector 13 is composed of a straight metal wire arranged at the axis of the grid 12. The collector 13 is supported by the bottom of the case 14 and is connected to a ground potential via an ion current detection circuit 23. The collector 13 is configured to be able to collect ions of gas molecules in the case 14 generated by collision with electrons traveling from the filament 11 to the grid 12.
　ケース１４は、金属材料で構成され、典型的には円筒形状を有する。ケース１４は、その内部がチャンバ１の内部空間と連通可能にチャンバ１の周壁部や底壁部などに取り付けられる。ケース１４は、グランド電位に接続される。 The case 14 is made of a metal material and typically has a cylindrical shape. The case 14 is attached to a peripheral wall portion, a bottom wall portion, or the like of the chamber 1 so that the inside thereof can communicate with the internal space of the chamber 1. Case 14 is connected to the ground potential.
　駆動回路２１は、駆動電源としてのフィラメント加熱電源２１１と、フィラメント１１とグリッド１２との間を流れるエミッション電流からフィラメント電位を生成する抵抗素子２１２と、電流電圧変換器２１３とを有する。 The drive circuit 21 includes a filament heating power supply 211 as a drive power supply, a resistance element 212 that generates a filament potential from an emission current flowing between the filament 11 and the grid 12, and a current-voltage converter 213.
　フィラメント加熱電源２１１は、フィラメント１１を加熱するための電流源である。フィラメント１１を通電することで電子にエネルギーを与え、フィラメント材料の仕事関数以上のエネルギーになったときに、電子はフィラメント１１の外部に印加された電界により、フィラメント１１から放出される。フィラメント１１の抵抗値は、常温時は比較的低く、通電加熱されるとその抵抗値が高くなる。フィラメント駆動開始時は常温に近い状態からの駆動になるため、駆動初期は抵抗値が低く、大きな突入電流が流れやすい。温度の上昇とともに抵抗値も高くなり、流れる電流も低く安定する。 The filament heating power supply 211 is a current source for heating the filament 11. Energy is given to the electrons by energizing the filament 11, and when the energy becomes higher than the work function of the filament material, the electrons are emitted from the filament 11 by an electric field applied to the outside of the filament 11. The resistance value of the filament 11 is relatively low at normal temperature, and increases when the current is heated. At the start of filament driving, driving is performed from a state close to normal temperature, so that the resistance value is low at the initial stage of driving, and a large inrush current easily flows. As the temperature rises, the resistance value increases, and the flowing current stabilizes low.
　抵抗素子２１２は、フィラメント加熱電源２１１の陰極とグランド電位との間に接続される。電流電圧変換器２１３は、所定の基準電圧（本例ではグランド電位）に接続される非反転入力端子と、抵抗素子２１２と接続される反転入力端子とを有する負帰還増幅器で構成される。電流電圧変換器２１３は、抵抗素子２１２を流れる電流が所定の値となるようにフィラメント加熱電源２１１を制御する。 The resistance element 212 is connected between the cathode of the filament heating power supply 211 and the ground potential. The current-voltage converter 213 includes a negative feedback amplifier having a non-inverting input terminal connected to a predetermined reference voltage (ground potential in this example) and an inverting input terminal connected to the resistance element 212. The current-voltage converter 213 controls the filament heating power supply 211 so that the current flowing through the resistance element 212 has a predetermined value.
　抵抗素子２１２の抵抗値（Ｒ１）は特に限定されないが、例えば、数十ｋΩ～数ＭΩである。エミッション電流値と抵抗値（Ｒ１）との積が、グランド－フィラメント間電位、つまり、フィラメント１１の設定電位（本例では＋２５Ｖ）となるように抵抗値（Ｒ１）が設定される。エミッション電流の切り替えのため、抵抗素子２１２はその抵抗値が可変に構成されてもよい。駆動回路２１は、抵抗素子２１２経由でグランド電位へ流れる電流を電流電圧変換器２１３で電流－電圧変換して、フィラメント加熱電源２１１へフィードバックをかける。このように、抵抗素子２１２のグランド端子側が常にグランド電位になるようにフィードバックがかかるようにすることで、数μＡのエミッション電流を高精度に制御することができる。 抵抗 The resistance value (R1) of the resistance element 212 is not particularly limited, but is, for example, several tens kΩ to several MΩ. The resistance value (R1) is set so that the product of the emission current value and the resistance value (R1) becomes the ground-filament potential, that is, the set potential of the filament 11 (+25 V in this example). For switching the emission current, the resistance value of the resistance element 212 may be variable. The drive circuit 21 performs current-voltage conversion of the current flowing to the ground potential via the resistance element 212 with the current-voltage converter 213, and feeds back the current to the filament heating power supply 211. In this way, by applying feedback so that the ground terminal side of the resistance element 212 is always at the ground potential, the emission current of several μA can be controlled with high accuracy.
［基本的動作］
　電離真空計１００の通常駆動時の電位障壁構造を図２に示す。
　フィラメント１１には、グリッド１２に印加されたグリッド電位により、電解の勾配がかけられており、フィラメント１１から放出された多数の電子はグリッド１２へ向かって移動する。一部の電子は、フィラメント１１とケース１４間の電位の低い位置を通り、グリッド１２周囲の飛跡をたどり、最終的にはグリッド１２に到達する。電子の加速エネルギーはグリッド１２付近で最大となり、電子が雰囲気中の気体分子の電離断面積が最大となる加速エネルギーを持った際に雰囲気中の気体分子と衝突すると、気体分子が最も効率よくイオン化する。イオン化された気体分子はフィラメント１１の電位よりも勾配の急峻なコレクタ１３へ向かい、コレクタ１３で供給される電子と再結合し、イオン電流検出回路２３においてイオン電流として計測される。 [Basic operation]
FIG. 2 shows a potential barrier structure during normal operation of the ionization vacuum gauge 100.
The filament 11 is subjected to an electrolytic gradient by the grid potential applied to the grid 12, and a large number of electrons emitted from the filament 11 move toward the grid 12. Some of the electrons pass through the low potential between the filament 11 and the case 14, follow tracks around the grid 12, and finally reach the grid 12. The acceleration energy of the electrons is maximum near the grid 12, and when the electrons collide with the gas molecules in the atmosphere when they have the acceleration energy that maximizes the ionization cross section of the gas molecules in the atmosphere, the gas molecules are most efficiently ionized. I do. The ionized gas molecules travel to the collector 13 whose gradient is steeper than the potential of the filament 11, recombine with the electrons supplied from the collector 13, and are measured by the ion current detection circuit 23 as an ion current.
　電離真空計１００は、エミッション電流とイオン電流とに基づいて圧力値を演算する圧力演算部３０をさらに備える。エミッション電流は、電流電圧変換器２１３の出力が参照され、イオン電流は、イオン電流検出回路２３の出力が参照される。圧力演算部３０は、コレクタ１３に到達したイオン電流を計測し、そのイオン数を次式（１）に示すように圧力値に換算する。
　Ｐ＝Ｉi／（Ｓ×Ｉe）　…（１）
　ここで、Ｐは圧力（Ｐａ）、Ｉiはイオン電流（Ａ）、Ｉeはエミッション電流（Ａ）、Ｓは感度である。
　圧力演算部３０において算出された圧力値は、表示部Ｍを介して表示される。 The ionization gauge 100 further includes a pressure calculator 30 for calculating a pressure value based on the emission current and the ion current. The output of the current-voltage converter 213 is referred to for the emission current, and the output of the ion current detection circuit 23 is referred to for the ion current. The pressure calculator 30 measures the ion current that has reached the collector 13 and converts the number of ions into a pressure value as shown in the following equation (1).
P = Ii / (S × Ie) (1)
Here, P is pressure (Pa), Ii is ion current (A), Ie is emission current (A), and S is sensitivity.
The pressure value calculated by the pressure calculation unit 30 is displayed via the display unit M.
　電離真空計１００は、圧力領域に応じて、フィラメント１１からのエミッション電流を段階的に制御するように構成される。例えば、０．１Ｐａ～０．０１Ｐａ以下の圧力領域では数ｍＡに、それを超える圧力領域では数μＡ前後に、電流レンジが切り替えられる。 The ionization vacuum gauge 100 is configured to control the emission current from the filament 11 stepwise according to the pressure region. For example, the current range is switched to several mA in a pressure range of 0.1 Pa to 0.01 Pa or less, and to about several μA in a pressure range exceeding it.
　電離真空計の感度係数Ｓは測定子の形状に依存するため、いかなる圧力においても一定である。圧力の低い領域では、圧力に比例してイオン電流Ｉiが少なくなり信号が増幅回路内の熱雑音に埋もれ正確な測定が難しくなる。従って、正確に測定するには真のイオン電流Ｉiを増やす必要がある。そのため、エミッション電流Ｉeを増やし、相対的にイオン電流Ｉiを増やしている。また、圧力の低い領域では気体分子がグリッド電極に吸着する割合に対して、エミッション電流により電子励起脱離する割合が増加し、結果としてグリッド電極への気体分子の吸着量が減り、電子励起脱離イオンによるイオン電流Ｉiの誤差量も少なくなる。 感 度 Since the sensitivity coefficient S of the ionization gauge depends on the shape of the probe, it is constant at any pressure. In the low pressure region, the ion current Ii decreases in proportion to the pressure, and the signal is buried in the thermal noise in the amplifier circuit, making accurate measurement difficult. Therefore, it is necessary to increase the true ion current Ii for accurate measurement. Therefore, the emission current Ie is increased, and the ion current Ii is relatively increased. In a low pressure region, the ratio of gas molecules adsorbed to the grid electrode increases the rate of electron-excited desorption due to the emission current. As a result, the amount of gas molecules adsorbed to the grid electrode decreases and the electron-excited desorption increases. The error amount of the ion current Ii due to the desorbed ions is also reduced.
　逆に圧力の高い領域において、エミッション電流Ｉeが多すぎると、気体イオンによる空間電荷の影響を受け、正確なイオン電流Ｉiが測定できなくなるため、エミッション電流Ｉeの電流量を少なくする動作をさせている。これにより、フィラメント１１の耐久性を高めつつ、精度の高い圧力計測を安定して行うことが可能となる。エミッション電流の制御は、例えば、駆動回路２１に対する圧力演算部３０からの制御指令（例えば、抵抗素子２１２の抵抗値設定指令）に基づいて実行される。 Conversely, in a high pressure region, if the emission current Ie is too large, space ions are affected by gas ions, and accurate ion current Ii cannot be measured. Therefore, the operation of reducing the amount of emission current Ie is performed. I have. This makes it possible to stably perform highly accurate pressure measurement while increasing the durability of the filament 11. The control of the emission current is executed based on, for example, a control command from the pressure calculation unit 30 to the drive circuit 21 (for example, a command to set the resistance value of the resistance element 212).
［フィラメント電位の変動］
　一方、フィラメント加熱電源２１１とグランドとの間のインピーダンスが比較的高いため、フィラメント１１の駆動時やフィラメント電流レンジの切り替え時に、フィラメント１１に突入電流が流れてフィラメント電位が一時的に大きく変動してしまう場合がある。 [Variation in filament potential]
On the other hand, since the impedance between the filament heating power supply 211 and the ground is relatively high, when driving the filament 11 or switching the filament current range, an inrush current flows through the filament 11 and the filament potential temporarily fluctuates greatly. May be lost.
　すなわち、フィラメント加熱電源２１１は、上述のように、フィラメント１１からのエミッション電流が所定の値となるように、抵抗素子２１２に流れる電流を、電流電圧変換器２１３を用いてフィードバック制御される。フィラメントに流れる電流が最大値になると、定常電流値に安定していく。この際、図３に概念的に示すように、駆動回路２１には抵抗素子２１２と直列にコイルの寄生容量が存在するため、フィラメント１１に大きな突入電流が流れると、抵抗素子２１２を流れている電流はすぐには減衰しない。また、フィラメント１１も突入電流により、定常時よりも温度が高くなっており、エミッション電流を流しやすい状態になる。コイルの寄生容量とフィラメント１１の温度が定常時よりも高いことにより、短い間ではあるがフィラメント電位が、図４Ａに示すように、グリッド電位よりも高い電位になることがある（オーバーシュート）。この場合、電子はグリッド１２に到達することができなくなり、一時的に気体分子のイオン化に寄与する電子が無くなるため、圧力指示が最小値を示すことになる。 That is, as described above, the current flowing through the resistance element 212 is feedback-controlled using the current-voltage converter 213 so that the emission current from the filament 11 has a predetermined value, as described above. When the current flowing through the filament reaches a maximum value, the current becomes stable at a steady current value. At this time, as shown conceptually in FIG. 3, since a parasitic capacitance of a coil exists in series with the resistance element 212 in the drive circuit 21, when a large rush current flows through the filament 11, the current flows through the resistance element 212. The current does not decay immediately. Also, the temperature of the filament 11 is higher than that in the steady state due to the inrush current, and the filament 11 is in a state where the emission current can easily flow. Since the parasitic capacitance of the coil and the temperature of the filament 11 are higher than in the steady state, the filament potential may be higher than the grid potential as shown in FIG. 4A for a short time (overshoot). In this case, the electrons cannot reach the grid 12 and the electrons that temporarily contribute to the ionization of the gas molecules disappear, so that the pressure indication indicates the minimum value.
　また、フィラメント１１を駆動する駆動回路２１の時定数、配線などによる寄生容量によってはアンダーシュートを起こし、図４Ｂに示すように、フィラメント１１の電位が設定電位（＋２５Ｖ）よりも低くなる場合がある。この場合、グリッド１２に到達する際の電子の加速エネルギーが大きな値をとり、クーロン散乱の断面積が運動エネルギーの逆数に比例することから、イオン化効率が低下する。 In addition, undershoot may occur depending on the time constant of the drive circuit 21 for driving the filament 11 and the parasitic capacitance due to wiring and the like, and the potential of the filament 11 may be lower than the set potential (+25 V) as shown in FIG. 4B. . In this case, the acceleration energy of the electrons when reaching the grid 12 takes a large value, and the cross-sectional area of Coulomb scattering is proportional to the reciprocal of the kinetic energy, so that the ionization efficiency is reduced.
　このような問題を解消するため、図５に示す電離真空計２００のように、フィラメント電源２４を設置することにより、フィラメント１１の電位を担保する方法も考えられる。この方式だと、フィラメント１１から放出されたエミッション電流を高精度に測定するには、フィラメント加熱電源２１１の陰極とフィラメント電源２４との間に電流計２５を設置する必要がある。 解 消 In order to solve such a problem, a method of securing the potential of the filament 11 by installing a filament power supply 24 as in an ionization gauge 200 shown in FIG. With this method, it is necessary to install an ammeter 25 between the cathode of the filament heating power supply 211 and the filament power supply 24 in order to measure the emission current emitted from the filament 11 with high accuracy.
　しかし、電流計２５を用いると、μＡオーダーの電流を計測するには量産機器としてのコストメリットを考えると、電流検出用の内部抵抗には１０ｋΩ以上の抵抗値のものを使う必要があり、エミッション電流の電流量の変化によりフィラメント１１の電位が変化してしまう。また、フィラメント電源２４を別途設置することになるので、装置構成の複雑化、大型化、コストの上昇等が避けられない。さらに、フィラメント１１の電位の変動を回避するため、グリッド１２側に電流計２６を設置する場合も、電流計２６の内部抵抗として１０ｋΩ以上の抵抗値のものを用いる必要があり、エミッション電流量により、グリッド電位が変動してしまうため、高精度な測定には向かない。 However, when using the ammeter 25, it is necessary to use an internal resistance for current detection of a resistance value of 10 kΩ or more in consideration of the cost merit as a mass-produced device for measuring a current on the order of μA. The potential of the filament 11 changes due to a change in the amount of current. In addition, since the filament power supply 24 is separately provided, it is inevitable that the configuration of the apparatus becomes complicated, the size of the apparatus increases, and the cost increases. Further, even when the ammeter 26 is installed on the grid 12 side to avoid the fluctuation of the potential of the filament 11, it is necessary to use an internal resistance of the ammeter 26 having a resistance value of 10 kΩ or more. However, since the grid potential fluctuates, it is not suitable for highly accurate measurement.
　このような問題を解消するため、本実施形態の電離真空計１００は、図１に示すように、フィラメント１１の電位が予め設定された電圧範囲内でしか変動しないようにフィラメント電位の変動幅を制限する電位制限回路２８を備えている。以下、電位制限回路２８の詳細について説明する。 In order to solve such a problem, as shown in FIG. 1, the ionization gauge 100 of the present embodiment adjusts the fluctuation range of the filament potential so that the potential of the filament 11 fluctuates only within a preset voltage range. A potential limiting circuit 28 for limiting is provided. Hereinafter, the details of the potential limiting circuit 28 will be described.
［電位制限回路］
　図１に示すように、制御部２０は、電位制限回路２８を有する。電位制限回路２８は、駆動回路２１とグリッド電源２２との間に接続される。電位制限回路２８は、フィラメント１１の電位をコレクタ１３の電位よりも高い第１の電位Ｖ１と、グリッド１２の電位よりも低い第２の電位Ｖ２との間の所定範囲に維持するように構成される。 [Potential limiting circuit]
As shown in FIG. 1, the control unit 20 has a potential limiting circuit 28. The potential limiting circuit 28 is connected between the driving circuit 21 and the grid power supply 22. The potential limiting circuit 28 is configured to maintain the potential of the filament 11 in a predetermined range between a first potential V1 higher than the potential of the collector 13 and a second potential V2 lower than the potential of the grid 12. You.
　本実施形態において電位制限回路２８は、第１の分圧抵抗２８１と、第２の分圧抵抗２８２と、第１の整流素子２８３と、第２の整流素子２８４と、を有する。 In the present embodiment, the potential limiting circuit 28 includes a first voltage dividing resistor 281, a second voltage dividing resistor 282, a first rectifying element 283, and a second rectifying element 284.
　第１の分圧抵抗２８１及び第２の分圧抵抗２８２は、それぞれ、グリッド電源２２の陽極とグランド電位との間にグリッド１２に対して並列的に接続され、グリッド電位を第１の電位Ｖ１と、第１の電位Ｖ１よりも高い第２の電位Ｖ２とに分圧する。 The first voltage dividing resistor 281 and the second voltage dividing resistor 282 are respectively connected in parallel to the grid 12 between the anode of the grid power supply 22 and the ground potential, and connect the grid potential to the first potential V1. And a second potential V2 higher than the first potential V1.
　第１の分圧抵抗２８１及び第２の分圧抵抗２８２はそれぞれ、固定抵抗素子で構成されてもよいし、可変抵抗素子で構成されてもよい。第１の電位Ｖ１及び第２の電位Ｖ２の大きさは特に限定されず、許容されるフィラメント１１の電位の変動幅に応じて適宜設定可能である。 (1) Each of the first voltage dividing resistor 281 and the second voltage dividing resistor 282 may be composed of a fixed resistance element or a variable resistance element. The magnitudes of the first potential V1 and the second potential V2 are not particularly limited, and can be appropriately set according to an allowable fluctuation range of the potential of the filament 11.
　第１の整流素子２８３は、駆動回路２１（フィラメント加熱電源２１１の陰極）と第１の分圧抵抗２８１との間に接続され、第１の分圧抵抗２８１から駆動回路２１へ向かう電流の流れを順方向とするダイオードで構成される。第２の整流素子２８３は、駆動回路２１（フィラメント加熱電源２１１の陰極）と第２の分圧抵抗２８２との間に接続され、駆動回路２１から第２の分圧抵抗２８２へ向かう電流の流れを順方向とするダイオードで構成される。 The first rectifying element 283 is connected between the driving circuit 21 (the cathode of the filament heating power supply 211) and the first voltage dividing resistor 281 and a current flows from the first voltage dividing resistor 281 to the driving circuit 21. Is a forward direction. The second rectifying element 283 is connected between the driving circuit 21 (the cathode of the filament heating power supply 211) and the second voltage dividing resistor 282, and a current flows from the driving circuit 21 to the second voltage dividing resistor 282. Is a forward direction.
　第１及び第２の分圧抵抗２８１，２８２は可変抵抗器で構成されてもよく、これにより、第１及び第２の電位Ｖ１，Ｖ２を任意に調整することができる。 (1) The first and second voltage dividing resistors 281 and 282 may be constituted by variable resistors, whereby the first and second potentials V1 and V2 can be arbitrarily adjusted.
　電位制限回路２８は、上述のように、２つの抵抗（第１及び第２の分圧抵抗２８１，２８２）により形成される分圧電圧（第１及び第２の電位Ｖ１，Ｖ２）と、２つのダイオード（第１及び第２の整流素子２８３，２８４）とを用いてフィラメント１１の電位の変動領域を固定する。これにより、フィラメント電流の大幅な変動があった際でも強制的にフィラメント１１の電位障壁が形成されるため、フィラメント電位のアンダーシュートが起きた場合は第１の電位Ｖ１以下にならないように、オーバーシュートが起きた場合は第２の電位Ｖ２以上にならないようにすることができる。 As described above, the potential limiting circuit 28 includes a divided voltage (first and second potentials V1 and V2) formed by two resistors (first and second voltage dividing resistors 281 and 282), Using the two diodes (first and second rectifying elements 283 and 284), the potential fluctuation region of the filament 11 is fixed. Thereby, even when there is a large fluctuation in the filament current, the potential barrier of the filament 11 is forcibly formed, so that when the undershoot of the filament potential occurs, the overshoot is performed so as not to become lower than the first potential V1. When a shoot occurs, the potential can be prevented from being equal to or higher than the second potential V2.
　その結果、図６に示す電位障壁構造の様に、フィラメント１１の電位が一時的に変動した際でも、フィラメント１１から放出されたすべての電子がグリッド１２に到達する電位の範囲内（Ｖ２－Ｖ１に相当）に抑えられるようにフィラメント１１の移動範囲が固定される。このため、フィラメント電流の切り替わり時やフィラメント１１の起動時などにおいても、フィラメント１１への突入電流により電子が喪失しない電位にフィラメント電位を維持することができる。 As a result, like the potential barrier structure shown in FIG. 6, even when the potential of the filament 11 fluctuates temporarily, all the electrons emitted from the filament 11 fall within the potential range (V2-V1 The moving range of the filament 11 is fixed so as to be suppressed. Therefore, even when the filament current is switched or when the filament 11 is started, the filament potential can be maintained at a potential at which electrons are not lost due to the rush current to the filament 11.
　フィラメント１１から放出されたすべての電子が最短の時間でグリッド１２へ到達するように、また、放出された電子がイオン化エネルギー以上の加速エネルギーを得ることができるように、第１の電位Ｖ１と第２の電位Ｖ２とを調整することで、圧力指示の変動を最小限にとどめることができる。さらに、高精度にエミッション電流の測定が可能となり、万が一なんらかの原因により、エミッション電流が低下した場合においても、高精度に測定されたエミッション電流値を上記式（１）に代入することにより、真の圧力値を指示することが可能となる。更には、フィラメント電流の切り替え時や起動時での圧力指示値の変動を小さくすることができるので、切り替え時間や起動時間を短くする効果がある。また、新たに電源系を追加するコストも不要である。 The first potential V1 and the first potential V1 are set so that all the electrons emitted from the filament 11 reach the grid 12 in the shortest time and that the emitted electrons can obtain an acceleration energy higher than the ionization energy. By adjusting the second potential V2, the fluctuation of the pressure instruction can be minimized. Further, the emission current can be measured with high accuracy. Even if the emission current is reduced by any reason, the true value of the emission current measured by the high accuracy is substituted into the above equation (1). It is possible to indicate the pressure value. Furthermore, since the fluctuation of the pressure command value at the time of switching the filament current or at the time of starting can be reduced, there is an effect that the switching time and the starting time are shortened. Further, there is no need to add a new power supply system.
　図７及び図８に、図５に示した比較例に係る電離真空計２００及び本実施形態の電離真空計１００について、エミッション電流を１０μＡから１ｍＡへ切り替えたときの圧力指示値及びフィラメント電位の時間変化をそれぞれ比較して示す。 FIGS. 7 and 8 show the pressure indication value and the filament potential time when the emission current is switched from 10 μA to 1 mA for the ionization gauge 200 according to the comparative example shown in FIG. 5 and the ionization gauge 100 of the present embodiment. The changes are shown in comparison.
　本実施形態の電離真空計１００においては、フィラメント１１の変動範囲として下限が＋１５Ｖ、上限が＋３５Ｖとなるように、電位制限回路２８における第１の電位Ｖ１及び第２の電位Ｖ２をそれぞれ設定した。なお、本実施形態及び比較例ともに、フィラメント１１の定常時の電位は＋２５Ｖとした。 In the ionization gauge 100 of the present embodiment, the first potential V1 and the second potential V2 in the potential limiting circuit 28 are set so that the lower limit of the filament 11 is +15 V and the upper limit is +35 V. In both the present embodiment and the comparative example, the potential of the filament 11 in the steady state was + 25V.
　図７及び図８において実線で示すように、比較例に係る真空計２００ではフィラメントの突入電流によりオーバーシュートが起き、フィラメント電位がグリッド電位以上になったため、グリッド電極に電子が到達せず、圧力指示が極端に低い値になることが確認された。その後、アンダーシュートが起き、フィラメント電位がグランド電位まで低下し、エミッション電流が安定するまで、正確な圧力指示を行う事ができなかった。 As shown by a solid line in FIGS. 7 and 8, in the vacuum gauge 200 according to the comparative example, an overshoot occurs due to a rush current of the filament, and the filament potential becomes higher than the grid potential. The reading was confirmed to be extremely low. Thereafter, an undershoot occurred, the filament potential dropped to the ground potential, and an accurate pressure instruction could not be given until the emission current was stabilized.
　これに対して本実施形態の電離真空計１００においては、図７及び図８において破線で示すように、フィラメント１１の電位の変動が制限されるため、エミッション電流の切り替えに伴うオーバーシュートを回避でき、これにより電子がグリッド１２へ到達しない時間を発生させることなく、圧力値の指示を連続かつ安定に行うことができる。 On the other hand, in the ionization gauge 100 of the present embodiment, as shown by the broken lines in FIGS. 7 and 8, the fluctuation of the potential of the filament 11 is limited, so that the overshoot accompanying the switching of the emission current can be avoided. Thus, it is possible to continuously and stably indicate the pressure value without generating a time during which electrons do not reach the grid 12.
　以上、本発明の実施形態について説明したが、本発明は上述の実施形態にのみ限定されるものではなく種々変更を加え得ることは勿論である。 Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.
　例えば以上の実施形態では、電位制限回路２８において形成される第１の電位Ｖ１及び第２の電位Ｖ２をそれぞれ固定としたが、これに限られず、圧力の測定タイミングや条件に応じてこれらの電位が可変に構成されてもよい。 For example, in the above-described embodiment, the first potential V1 and the second potential V2 formed in the potential limiting circuit 28 are fixed, respectively. However, the present invention is not limited to this. May be variably configured.
　また、以上の実施形態では、電離真空計として、Ｂ－Ａ型電離真空計（Ｂ－Ａゲージ）を例に挙げて説明したが、他の型式の熱陰極型電離真空計にも同様に適用可能である。 Further, in the above embodiment, the BA type ionization gauge (BA gauge) has been described as an example of the ionization gauge, but the present invention is similarly applied to other types of hot cathode type ionization gauges. It is possible.
　１０…測定子
　１１…フィラメント
　１２…グリッド
　１３…コレクタ
　１４…ケース
　２０…制御部
　２１…駆動回路
　２２…グリッド電源
　２３…イオン電流検出回路
　２８…電位制限回路
　３０…圧力演算部
　１００…電離真空計
　２１１…フィラメント加熱電源
　２１２…抵抗素子
　２１３…電流電圧変換器
　２８１…第１の分圧抵抗
　２８２…第２の分圧抵抗
　２８３…第１の整流素子
　２８４…第２の整流素子 DESCRIPTION OF SYMBOLS 10 ... Probe 11 ... Filament 12 ... Grid 13 ... Collector 14 ... Case 20 ... Control part 21 ... Drive circuit 22 ... Grid power supply 23 ... Ion current detection circuit 28 ... Potential limiting circuit 30 ... Pressure calculation part 100 ... Ionization gauge 211 ... filament heating power supply 212 ... resistance element 213 ... current-voltage converter 281 ... first voltage divider 282 ... second voltage divider 283 ... first rectifier 284 ... second rectifier

Claims (5)

  1. 　電子放出源と、グリッドと、コレクタとを有する測定子と、
    　　前記電子放出源を駆動する駆動電源を含み前記電子放出源と前記グリッドとの間に流れるエミッション電流が一定となるように前記駆動電源を制御する駆動回路と、
    　　前記グリッドを所定のグリッド電位に維持するグリッド電源と、
    　　前記コレクタに流入するイオン電流を検出するイオン電流検出回路と、
    　　前記駆動回路と前記グリッド電源との間に接続され、前記電子放出源の電位を前記コレクタの電位よりも高い第１の電位と前記グリッド電位よりも低い第２の電位との間の所定範囲に維持する電位制限回路と
    　　を有する制御部と
    　を具備する電離真空計。     A probe having an electron emission source, a grid, and a collector;
    A drive circuit including a drive power supply for driving the electron emission source and controlling the drive power supply so that an emission current flowing between the electron emission source and the grid is constant;
    A grid power supply for maintaining the grid at a predetermined grid potential;
    An ion current detection circuit that detects an ion current flowing into the collector,
    The potential of the electron emission source is connected between the driving circuit and the grid power supply, and a potential of the electron emission source is set to a predetermined range between a first potential higher than the potential of the collector and a second potential lower than the grid potential. And a control unit having: a potential limiting circuit for maintaining; and an ionization gauge.
  2. 　請求項１に記載の電離真空計であって、
    　前記電位制限回路は、
    　前記グリッド電位を前記第１の電位に分圧する第１の分圧抵抗と、
    　前記グリッド電位を前記第２の電位に分圧する第２の分圧抵抗と、
    　前記駆動回路と前記第１の分圧抵抗との間に接続された第１の整流素子と、
    　前記駆動回路と前記第２の分圧抵抗との間に接続された第２の整流素子と、を有する
    　電離真空計。     The ionization gauge according to claim 1,
    The potential limiting circuit,
    A first voltage dividing resistor for dividing the grid potential to the first potential;
    A second voltage-dividing resistor that divides the grid potential into the second potential;
    A first rectifying element connected between the driving circuit and the first voltage dividing resistor;
    A second rectifying element connected between the driving circuit and the second voltage-dividing resistor.
  3. 　請求項１又は２に記載の電離真空計であって、
    　前記駆動回路は、前記エミッション電流から前記電子放出源の電位を生成する抵抗素子と、前記抵抗素子を流れる電流が所定の値となるように前記駆動電源を制御する電流電圧変換器と、を有する
    　電離真空計。     It is an ionization gauge according to claim 1 or 2,
    The drive circuit includes a resistance element that generates a potential of the electron emission source from the emission current, and a current-voltage converter that controls the drive power supply so that a current flowing through the resistance element has a predetermined value. Ionization gauge.
  4. 　請求項１～３のいずれか１つに記載の電離真空計であって、
    　前記エミッション電流と前記イオン電流とに基づいて圧力値を演算する演算部をさらに具備する
    　電離真空計。     The ionization gauge according to any one of claims 1 to 3, wherein
    An ionization gauge further comprising a calculation unit for calculating a pressure value based on the emission current and the ion current.
  5. 　電子放出源と、グリッドと、コレクタとを有する電離真空計用の制御装置であって、
    　前記電子放出源を駆動する駆動電源を含み、前記電子放出源と前記グリッドとの間に流れるエミッション電流が一定となるように前記駆動電源を制御する駆動回路と、
    　前記グリッドを所定のグリッド電位に維持するグリッド電源と、
    　前記コレクタに流入するイオン電流を検出するイオン電流検出回路と、
    　前記駆動回路と前記グリッド電源との間に接続され、前記電子放出源の電位を前記コレクタの電位よりも高い第１の電位と前記グリッド電位よりも低い第２の電位との間の所定範囲に維持する電位制限回路と
    　を具備する制御装置。     An electron emission source, a control device for an ionization gauge having a grid and a collector,
    A drive circuit that includes a drive power supply that drives the electron emission source, and controls the drive power supply so that an emission current flowing between the electron emission source and the grid is constant;
    A grid power supply for maintaining the grid at a predetermined grid potential;
    An ion current detection circuit that detects an ion current flowing into the collector,
    The potential of the electron emission source is connected between the driving circuit and the grid power supply, and a potential of the electron emission source is set to a predetermined range between a first potential higher than the potential of the collector and a second potential lower than the grid potential. And a potential limiting circuit for maintaining.
PCT/JP2019/023844 2018-06-18 2019-06-17 Ionization vacuum gauge and control device WO2019244826A1 (en)

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
CN112504553A (en) * 2020-12-07 2021-03-16 杭州盘古自动化系统有限公司 Ionization gauge emission current voltage-controlled constant current control circuit

Citations (4)

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Publication number Priority date Publication date Assignee Title
JPH01106211A (en) * 1987-10-20 1989-04-24 Tokuda Seisakusho Ltd Emission control device
JP2001215163A (en) * 2000-02-02 2001-08-10 Anelva Corp Ionization gage
JP2008537998A (en) * 2005-03-04 2008-10-02 インフィコン ゲゼルシャフト ミット ベシュレンクテル ハフツング Vacuum gauge
US20170010172A1 (en) * 2015-07-09 2017-01-12 Mks Instruments, Inc. Ionization Pressure Gauge With Bias Voltage And Emission Current Control And Measurement

Patent Citations (4)

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Publication number Priority date Publication date Assignee Title
JPH01106211A (en) * 1987-10-20 1989-04-24 Tokuda Seisakusho Ltd Emission control device
JP2001215163A (en) * 2000-02-02 2001-08-10 Anelva Corp Ionization gage
JP2008537998A (en) * 2005-03-04 2008-10-02 インフィコン ゲゼルシャフト ミット ベシュレンクテル ハフツング Vacuum gauge
US20170010172A1 (en) * 2015-07-09 2017-01-12 Mks Instruments, Inc. Ionization Pressure Gauge With Bias Voltage And Emission Current Control And Measurement

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112504553A (en) * 2020-12-07 2021-03-16 杭州盘古自动化系统有限公司 Ionization gauge emission current voltage-controlled constant current control circuit
CN112504553B (en) * 2020-12-07 2022-03-18 杭州盘古自动化系统有限公司 Ionization gauge emission current voltage-controlled constant current control circuit

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