KR100447800B1 - Cold Cathode Ionization Gauge - Google Patents

Abstract

The present invention relates to a cold cathode ionization gauge. The high voltage generation and output current detector included in the cold cathode ionization gauge according to the present invention is connected to an output voltage adjusting unit for adjusting an output voltage introduced into a voltage distribution unit for outputting a high voltage, the voltage distribution unit, and an output voltage unit. Including an output current sensing unit for sensing the current, the sensed output current is characterized in that it is used to measure the degree of vacuum.

Description

Cold Cathode Ionization Gauge

The present invention relates to a cold cathode ionization gauge, and more particularly, to a high voltage generation and output current detector included in the cold cathode ionization gauge.

Measuring pressure in a vacuum system is just as important as creating a vacuum. I made a vacuum system, but if I can't figure out the specific degree of vacuum, I can't be frustrated, and I can't expect the development of vacuum composition and application technology.

The degree of vacuum handled by recent vacuum technology is one ten trillion of atmospheric pressure. It is reaching torr or less. Gauges for measuring low pressures have not yet been developed to cover this wide range of more than 15 digits, and only professional gauges for narrow areas have been developed.

There is no direct way of seeing gas molecules, but the pressure of the gas is generated because the molecules are in thermal motion, so the amount of gas molecules can be known by measuring the pressure. Pressure is defined as the force per unit area. The most basic method of measuring displacement by force is the basic vacuum measurement method. The method of measuring pressure is largely classified into a direct method and an indirect method.

Indirect measurement gauges are classified into Hot Cathode Ionization Gauges and Cold Cathode Ionization Gauges, which measure charge generation (ionization). In the hot cathode ionization gauge, gas molecules are dissociated or synthesized by high temperature filaments, and the sensitivity of the gauge is severely changed due to changes in work function due to contamination of the filaments, and the filaments are oxidized in a high pressure region. There is a problem. In order to overcome this problem, Penning's cold cathode ionization gauge is less quantitative than the hot cathode ionization gauge, but there is no filament oxidation problem, much less gas emission, and its structure is very simple for easy handling. Has the advantage.

The penning gauge uses a penning discharge to increase the ionization efficiency which is a problem in the cold cathode ionization gauge. 1A and 1B are diagrams showing the principle of the penning discharge. Referring to FIGS. 1A and 1B, the essence of the Penning discharge principle is that electrons move helically in a magnetic field, greatly increasing the flying distance, and furthermore, the Penning cell serves as a trap for trapping electrons. will be.

FIG. 2A is a diagram schematically illustrating a structure of a penning gauge, and FIG. 2B is a graph showing discharge characteristics of the penning gauge.

2A and 2B, the penning gauge has a structure in which two cathode plates are placed in parallel with a cylindrical anode disposed therebetween. Typically, a magnetic field of 0.05-0.5 T (500-5000 Gs) is perpendicular to the cathode plate and horizontal to the anode cylinder. Then, a voltage of 2-3 kV is applied between the anode and the cathode, and a permanent magnet is usually used as a magnet.

To In the pressure range of the degree of Torr, the discharge is caused by the long-emitted electrons from the cathode, and the discharge is entirely dependent on the space shift distribution by the electrons. This is because ions are insensitive to magnetic fields because of their high mass and are rapidly attracted to the cathode without staying in the cell. However, if the pressure is too high, the plasma is in a plasma (PLASMA) state in which the ion density and electron density are almost the same, and the discharge current is constant regardless of the pressure.

Once the discharge is trapped in the cell and stabilizes itself, there is a relationship between the pressure P and the discharge current i as shown in Equation 1 below.

,

It is experimentally known that i is the discharge current, P is the pressure, c and n are constants, and the exponent n is in the range of 1.1 to 1.2.

The reason why the penning gauge is less accurate than the hot cathode ionization gauge may be attributed to the fact that the discharge current i is not directly proportional to the pressure P, as shown in Equation 1 above. Also, care should be taken when the cathode of the penning gauge is contaminated with foreign matter such as carbon, so that the discharge characteristics are lost. In addition, the penning gauge is the same principle as the ion pump ~ It has a relatively large exhaust speed of about L / S and is not used for quantitative measurement of vacuum degree.

Cold cathode ionization gauge in Torr is quantitative but If the value is more than Torr, there is a problem of poor quantitation. This is due to structural problems and circuit problems. Among these, in the circuit problem, the conventional cold cathode ionization gauge used a method of detecting current by connecting the gauge header and the circuit directly or indirectly. That is, the detection circuit uses a method of obtaining a value using a linear circuit. When the linear circuit is used in this way, the quantitative property is inferior as described above. The reason for this is as follows. At a degree of vacuum of more than Torr, a very small amount of ions move enough to count the number of ions. Very small amounts of ions can be expressed as a current, and the current that can flow at this degree of vacuum is a very small current of almost 10 nA or less. In addition, since the change in current is not large, it is not easy to detect in a linear circuit.

The present invention has been made to overcome the above-mentioned problems of the prior art, the high voltage generation and output current detector included in the cold cathode ionization gauge for detecting a small current that is difficult to detect in the linear circuit using a log amplification circuit To provide.

1A and 1B show the principle of the penning discharge;

Figure 2a is a simplified view of the structure of the penning gauge.

Figure 2b is a graph showing the discharge characteristics of the penning gauge.

3 is a schematic block diagram of a high voltage generation and output current detector in accordance with one preferred embodiment of the present invention.

4A is a circuit diagram of a high voltage circuit unit according to an exemplary embodiment of the present invention.

Figure 4b is an exemplary view showing an implementation photograph of the high voltage circuit unit according to an embodiment of the present invention.

5A is a circuit diagram of a current limiter and an output voltage adjuster according to an exemplary embodiment of the present invention.

Figure 5b is an exemplary view showing an implementation photo of the current limiting unit and the output voltage adjusting unit according to an embodiment of the present invention.

6A is a circuit diagram of a high speed switching unit according to an exemplary embodiment of the present invention.

Figure 6b is an exemplary view showing an implementation photograph of the high speed switching unit according to an embodiment of the present invention.

7 is a circuit diagram of an output current sensing unit according to an exemplary embodiment of the present invention.

8 is a circuit diagram of a simplified output current sensing unit in accordance with a preferred embodiment of the present invention.

9 is a graph showing the relationship of the output current value to the output voltage value according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

101... High-voltage circuit section 103. Transformer

105... Power distribution unit 107. Output current detector

109... Current limiting 111. Output voltage regulator

113... High speed switching unit

In order to achieve the above objects, according to an aspect of the present invention, in the high voltage generation and output current detector included in the cold cathode ionization gauge, a voltage distribution unit for outputting a high voltage, the output voltage introduced into the voltage distribution unit An output voltage adjusting unit connected to the output voltage adjusting unit and the double voltage unit, the output current detecting unit detecting an output current, wherein the detected output current is used to measure a degree of vacuum; Can be provided.

In a preferred embodiment, the high voltage generation and output current detector may further include a transformer for transforming the output voltage drawn from the output voltage adjusting unit to output to the double voltage unit.

In another preferred embodiment, the high voltage generation and output current detector may further include a current limiting unit to block the output voltage when a current of more than a predetermined current is consumed.

In another preferred embodiment, the high voltage generation and output current detector may further include a high speed switching unit for switching the output voltage to the transformer at high speed.

In another preferred embodiment, the output current sensing unit includes a first integrator circuit including a first amplifier, a second integrator circuit including a second amplifier, and a first transistor into which the output current drawn into the first integrator circuit is introduced. And a current mirror including a second transistor into which the reference current drawn into the second integrator circuit is introduced, and a variable resistor connected to an output terminal of the first integrator circuit and an output terminal of the current mirror. It is done.

In another preferred embodiment, the output current sensing unit may further include a first capacitor connected to an input terminal of the first integrator circuit and a second capacitor connected to an input terminal of the second integrator circuit to block high frequency noise. Can be.

In another preferred embodiment, the output current may be calculated by the output voltage at the output of the first integrator circuit.

Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram schematically illustrating a high voltage generation and output current detector according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the high voltage generation and output current detector includes a high voltage circuit unit 101 including a double voltage unit 105 and a transformer 103 for outputting a high voltage, and an output connected to the front end of the transformer 103. A voltage regulator 111, a current limiting unit 109 connected to the front end of the output voltage regulator 111, a high speed switching unit 113 connected to the transformer 103 and the output current detection connected to the voltage distribution unit Section 107.

The high voltage generation and output current detectors receive a 4-bit signal from a controller (not shown) and generate outputs of 3300 Vdc, 2000 Vdc, 1500 Vdc, and 800 Vdc. It also protects against The current limiting unit 109 cuts off the output voltage when a current of 0.3 mA or more is consumed. The output voltage adjusting unit 111 adjusts the voltage value introduced into the transformer 103 according to the output signal selection signal and boosts the voltage through the transformer 103 and the double voltage unit 105. The output voltage detector 107 measures a current value output using a high voltage output and a resistor. In another embodiment of the present invention, the controller may further include an analog-to-digital converter (ADC), and the measured current value may be input to the ADC and processed digitally.

In another preferred embodiment of the present invention, the high voltage generation and output current detector may further include an output voltage detector (not shown) connected to the front end of the transformer 103. The output voltage detector may detect a voltage output.

Each component of the high voltage generation and output current detector will be described in detail with reference to the accompanying drawings.

4A is a circuit diagram of a high voltage circuit unit according to an exemplary embodiment of the present invention, and FIG. 4B is an exemplary view showing an implementation photograph of the high voltage circuit unit according to an exemplary embodiment of the present invention.

4A and 4B, the high voltage circuit unit 101 includes a transformer 103 and a double voltage unit 105 using a diode and a capacitor. In a preferred embodiment of the present invention, the core of the transformer 103 uses a TDK PQ2020 PC40, the primary coil is wound 18 times with a Lits line 0.06 × 9, the secondary coil uses a 0.2mm enamel wire 500 times evenly to boost the voltage to 18: 500 with respect to the primary voltage. Therefore, according to the configuration of the transformer 103 as described above, it is possible to obtain a desired output voltage by adjusting the magnitude of the voltage applied to the primary coil. Since the high voltage output stage is floating, current flows from ground to the -V stage. This current is applied to the output current detector 107. The output current sensed by the output current sensing unit 107 is used as an input in the degree of vacuum calculation by the controller via the ADC.

5A is a circuit diagram of a current limiter and an output voltage adjuster according to an exemplary embodiment of the present invention, and FIG. 5B is an exemplary view showing an implementation photograph of the current limiter and an output voltage adjuster according to an exemplary embodiment of the present invention. .

5A and 5B, in the current limiting unit 109, the current may be limited by the feedback signal of the 2N4401 transistor of Q7 501 and the resistance of the R7 503. Here, by changing the resistance value of the R7 (503) it is possible to enlarge and reduce the area of the current limit. The output voltage adjuster 111 may finely adjust the output voltage by combining fixed resistors R2, R3, R4, R5, and the like and variable resistors R23, R24, R25, R26, and the like. In addition, the output voltage adjusting unit 111 is configured to automatically adjust by receiving a feedback of the voltage output. When a 5V signal is applied to the output selection terminal, the transistor is turned "ON" to adjust the input voltage of the transformer 103, and a corresponding high voltage can be output through the high voltage output terminal. When not selected, the maximum voltage is output, so a selection signal must be applied to one terminal.

6A is a circuit diagram of a high speed switching unit according to an exemplary embodiment of the present invention, and FIG. 6B is an exemplary view showing an implementation photograph of the high speed switching unit according to an exemplary embodiment of the present invention.

6A and 6B, the high speed switching unit 115 switches the input power of the transformer 103 at high speed to increase the voltage. The 25 kHz frequency may be generated through the resistor and the capacitor of the 555 timer chip 601 of the fast switching unit 115. The generated frequency must be configured so that exactly 1: 1 inversion occurs, otherwise not only high voltage will be generated, but heat will also be generated in the switching element IRF 530 IC 603 even if it occurs. In order to remove such heat, a small fan may be installed in the IC 603. The cause of the heat is due to the occurrence of overload due to a short circuit of the input when the IRF 530 IC 603 is turned on at the same time. For the above reason, the waveform output from the 555 timer chip 601 should be set to exactly 50% duty ratio through a resistor and a capacitor. In order to stop the high voltage output, the input signal to the IRF 530 IC 603 may be turned off.

7 is a circuit diagram of an output current sensing unit according to an exemplary embodiment of the present invention.

Referring to FIG. 7, R1 701 and C2 703 constitute an integrator circuit, corresponding to U1 705, which is an OP AMP. C1 707 and C4 709 are used to block high frequency noise. The high voltage circuit unit 101 uses an SMPS power source, and since the frequency of the high voltage circuit unit 101 generates a frequency of 10 kHz or more, the C1 707 and C4 709 not only emit such high frequencies, It is a configuration to block the noise that is radiated and input.

R6 711 is a pull up resistor that distributes a negative voltage to stably supply -2.5V to the D1 713. When the voltage supplied to the D1 713 changes, the range of the current changes, so that the output voltage may change by several volts even with a slight current variation.

R7 713 and C3 715 constitute an integrator circuit, corresponding to U2 727 which is an OP AMP.

R2 717 and R3 719 resistors output voltage ( These are the components that determine the K factor of. Depending on the change in these values, the output voltage ( ) Range is determined. In addition, the resistance of R4 721 is a temperature resistance, and when a change of 1 ° C occurs, the value changes by 0.35%. It is configured to correct the output value according to the temperature change. R5 723 is a component for limiting the current flowing to Q1 725, which is a current mirror element.

The current mirror Q1 725 is configured to be connected to integrator circuits corresponding to OP AMP U1 705 and U2 727, respectively. Here, 0.7V (diode semiconductor characteristic) This is the component used to take advantage of the phenomenon that is turned on. remind Changes slightly even at 0.7V.

The OP AMPs U1 705 and U2 727 are for constructing an integrator circuit and are devices that generate a low offset current. If the offset current is large, the applied current is vulnerable to noise.

Output voltage ( ) May be derived as in Equation 2.

,

here, , n = 2.3, = 0.7v (threshold voltage), R1 and R2 are resistors, Is the current to detect, Is the reference current.

8 is a circuit diagram of a simplified output current sensing unit according to an exemplary embodiment of the present invention.

Referring to Figure 8, the output current is It flows out toward the high voltage circuit part based on this OP AMP U2. In addition, transistors Q1 and Q2 are pnp transistors. Equation 2 can be derived from the above simplified configuration, and the process is as follows.

first, and May be defined by equations (3) and (4).

Also, 'Can be derived as shown in Equation 5.

Equation (3) and equation (4) to the derived equation (5) to summarize the equation (6).

here, Therefore, Equation 6 may be expressed by Equation 7.

, Where n = 2.3

May be derived as shown in Equation 8.

therefore, Can be summarized as in Equation (9).

here, Is a constant, so if you substitute the constant K, Can be finally summed up in equation (10).

The output current value may be detected from Equation 10.

9 is a graph showing the relationship of the output current value to the output voltage value according to an embodiment of the present invention.

Referring to FIG. 9, it can be seen that the output current value of the logarithmic scale is proportional to the output voltage value. This is a result that can be derived from equation (10).

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

By the high voltage generation and the output current detector according to the present invention, it is possible to detect a very small current that is difficult to detect in the linear circuit using a log amplification circuit.

In addition, the cold cathode ionization gauge according to the present invention can be applied not only to ion pumps but also to other vacuum measurement techniques.

In addition, the present invention can be applied in various fields such as advanced material fabrication, surface analysis equipment, radiation accelerator, proton accelerator, nanoscience, military equipment as basic equipment of extreme vacuum technology and basic science and technology development.

In addition, the cold cathode ionization gauge technology according to the present invention may be the most fundamental technology to study the extreme technologies, such as atomic science, nanoscience, which are emerging recently.

Claims (7)

In the high voltage generation and output current detector included in the cold cathode ionization gauge, A double voltage unit for outputting a high voltage; An output voltage adjusting unit adjusting an output voltage introduced into the double voltage unit; And An output current sensing unit connected to the double voltage unit and sensing an output current Including, The sensed output current is used to measure the degree of vacuum High voltage generation and output current detector characterized by. The method of claim 1, A transformer for transforming an output voltage drawn from the output voltage adjusting unit and outputting the converted voltage to the double voltage unit High voltage generation and output current detector further comprises. The method of claim 1, Current limiter cuts off the output voltage when current above a certain current is consumed High voltage generation and output current detector further comprises. The method of claim 2, High speed switching unit for switching the output voltage to the transformer at high speed High voltage generation and output current detector further comprises. The method of claim 1, The output current detector A first integrator circuit comprising a first amplifier; A second integrator circuit comprising a second amplifier; A current mirror including a first transistor into which an output current drawn into the first integrator circuit is introduced, and a second transistor into which a reference current drawn into the second integrator circuit is introduced; And A variable resistor connected to an output terminal of the first integrator circuit and an output terminal of the current mirror High voltage generation and output current detector comprising a. The method of claim 5, The output current detector A first capacitor connected to an input terminal of the first integrator circuit to block high frequency noise; And A second capacitor connected to an input terminal of the second integrator circuit High voltage generation and output current detector further comprises. The method of claim 5, The output current is High voltage generation and output current detector, characterized in that calculated by the output voltage at the output terminal of the first integrator circuit.