JP3310504B2 - DC high voltage generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC high voltage generator used for an electron microscope or the like to generate an accelerating voltage for accelerating charged particles.

[0002]

2. Description of the Related Art In an electron microscope, an electron emitter is maintained at a high potential, and electrons emitted from the emitter are accelerated to irradiate a sample. The stability of the potential applied to the emitter is one of the important factors that affect the resolution of an electron microscope image. In an electron microscope, a high voltage generator is used to apply a high potential to an emitter. A high voltage generator widely used in an electron microscope is a device mainly including a Cockcroft-Walton circuit. A conventional high voltage generator for an electron microscope will be described with reference to FIG.

In FIG. 1, reference numeral 1 denotes an AC power supply of 3 kHz, and an AC voltage from the AC power supply 1 is boosted by a step-up transformer 2. The voltage obtained from the boosting transformer 2 is boosted and rectified by a balanced Cockcroft-Walton circuit (hereinafter, referred to as a CCW circuit) 3 composed of multi-stage rectifying elements and capacitors. The high voltage generated by the CCW circuit 3 is smoothed by the first filter column 4. The first filter column 4 is configured by connecting a parallel connection unit of a capacitor and a resistor in series in multiple stages. The output smoothed by the first filter column 4 is further smoothed by the second filter column 5 to reduce the fluctuation component.

[0004] The second filter column 5 is also constructed by connecting units in which capacitors and resistors are connected in parallel in multiple stages. Reference numeral 6 denotes a detection column for detecting a high voltage applied between the filament 7 and the ground, and is configured by connecting a parallel connection unit of a resistor and a capacitor in multiple stages. From the last unit of the detection column 6, a signal representing a high voltage applied between the filament 7 and the ground is extracted.

Reference numeral 8 denotes a reference power supply for generating a signal serving as a reference for a high voltage applied between the filament 7 and the ground.
A signal representing the difference between the signal from the reference power supply 8 and the signal from the detection column 6 is supplied to an error amplifier 9. The output signal from the error amplifier 9 is supplied to an amplitude adjuster 10. The amplitude adjuster 10 is a circuit for adjusting the peak value of the voltage supplied from the AC power supply 1 to the step-up transformer 2 so that the deviation becomes zero. The error amplifier 9
The frequency characteristic is selected so that only DC or low frequency components in the input signal are amplified to prevent oscillation.
Reference numeral 11 denotes a bias resistor for controlling an emission current.

First and second filter columns 4 and 5
The second filter column 5 is provided with a signal extraction terminal T2 in order to monitor the voltage applied to the filament 7 via. The signal extracted from the terminal T2 is amplified by an amplifier 12, and the output of the amplifier can be displayed on an oscilloscope 13. Amplifier 1
2 can be varied over a wide range from high frequencies to low frequencies.

In such a configuration, the AC voltage generated from the AC power supply 1 is supplied to the step-up transformer 2 via the amplitude adjuster 10. As a result, a boosted voltage is generated from the boost transformer 2, and this AC voltage is boosted and rectified by the CCW circuit 3 and output. This output is smoothed by the first filter column 4 and the second filter column 6. The high voltage smoothed by the two filter columns 4 and 5 is applied to the filament 7 via the bias resistor 11. The high voltage applied between the filament 7 and the ground is detected by the detection column 6. The difference signal between the detection signal from the detection column 6 and the signal from the reference power supply 8 is sent to the error amplifier 9, and the amplitude of the voltage sent from the AC power supply 1 to the boost transformer 2 based on the output signal of the error amplifier 9. Is adjusted by the amplitude adjuster 10. Therefore, a DC voltage corresponding to the output signal of the reference power supply 8 is applied between the filament 7 and the ground. As a result, the acceleration voltage of the electrons emitted from the filament 7 is specified by the reference power supply 8.

[0008]

The amplifier 12 has a frequency of 10 kHz.
After setting the amplifier 12 so as to selectively amplify a signal in the high frequency band from 1 kHz to 1 kHz, the output of the amplifier 12 is displayed on an oscilloscope 13. As shown in FIG. It was found that there was a variable component. That is, in this signal, a large value of noise from other circuits was present together with the ripple of the excitation frequency of 3 kHz.

Further, the amplifier 12 is operated at a frequency of 100 Hz to 10 H
After setting the amplifier 12 so as to amplify signals in both the intermediate frequency of z and the low frequency band from 10 Hz to 1 Hz, the output of the amplifier 12 is displayed on the oscilloscope 13, as shown in FIG. It became clear that there was a large fluctuation component. Since the signal extracting terminal T2 is provided in the last unit of the column 5 to divide and extract the voltage, the actual variation of the high voltage is, for example, about 10% of the variation displayed on the oscilloscope.
It is 0 to 110 times. In FIG. 2A, one scale on the horizontal axis represents 100 μs, and one scale on the vertical axis is 2 m.
V. In FIG. 2B, one scale on the horizontal axis represents 100 msec, and one scale on the vertical axis represents 2 mV.

In the conventional high voltage generator of the electron microscope, the fluctuation of the DC component of the high voltage generated from the high voltage generator is suppressed to a small value, but as described above, it is superimposed on the high voltage. It is clear that high frequency and intermediate frequency fluctuations are large, and that low frequency fluctuations are at a level that needs improvement, and that such fluctuations hinder the improvement of the resolution of electron microscope images. Became clear.

The present invention solves such a conventional problem,
It is an object of the present invention to provide a DC high voltage generator capable of remarkably removing fluctuation components in a high frequency and an intermediate frequency region superimposed on the high voltage.

Further, according to the present invention, in removing a fluctuation component of a high frequency and an intermediate frequency, a DC voltage capable of detecting a high voltage output from a part of a filter circuit without being affected by noise induced by a CCW circuit. It is intended to provide a voltage generator.

Still another object of the present invention is to provide a compact DC high voltage generator capable of detecting a change in high voltage output from a filter circuit without being affected by noise induced from a CCW circuit. I have.

Another object of the present invention is to provide a DC high voltage generator capable of remarkably removing a fluctuation component in a low frequency region superimposed on the high voltage.

Further, in the present invention, in removing a fluctuation component in a low frequency region, a DC voltage capable of detecting a high voltage output from a part of a filter circuit without being affected by noise induced by a CCW circuit. It is intended to provide a voltage generator.

Further, the present invention provides a DC high voltage generator capable of removing fluctuations in a low frequency region during high voltage output, in addition to removing fluctuation components of a high frequency and an intermediate frequency. It is intended to be.

Further, according to the present invention, the detection of the fluctuation component in the high frequency and intermediate frequency regions and the detection of the fluctuation component in the low frequency region are performed separately, so that the DC voltage which can efficiently detect the fluctuation components in each region is obtained. It is intended to provide a voltage generator.

[0018]

According to a first aspect of the present invention, there is provided a DC high-voltage generator comprising a Cockcroft-Walton circuit, an AC power source arranged on a low voltage side for supplying power to the Cockcroft-Walton circuit, and a Cockcroft-Walton circuit. A multi-stage filter column for smoothing the generated DC high voltage, a detection column for detecting the smoothed DC high voltage, and the DC component of the signal detected by the detection column matches the reference value. A circuit for controlling the power supplied to the Cockcroft-Walton circuit from the AC power supply, and one of the filter columns for extracting a signal representing a fluctuation component superimposed on the smoothed high voltage. And amplifies at least the signal of the high frequency or intermediate frequency component of the signal from the terminal. It is characterized in that it comprises a circuit for negative feedback to the filter column.

According to the first aspect of the present invention, at least a signal of a high frequency or an intermediate frequency component among signals obtained from terminals provided in one of the filter columns is amplified and negatively fed back to another filter column. As a result, the fluctuation components in the high frequency and intermediate frequency regions superimposed on the high voltage can be remarkably removed.

A DC high voltage generator according to claim 2 is
The apparatus according to claim 1, further comprising means for shielding the filter column having the terminal from the Cockcroft-Walton circuit. In this way, even if the filter column having the terminals is accommodated in the same insulating tank as the Cockcroft-Walton circuit, it is possible to prevent noise from being introduced into the detection signal by induction from the Cockcroft-Walton circuit.

According to a third aspect of the present invention, there is provided a DC high voltage generator.
2. The apparatus according to claim 1, wherein the Cockcroft-Walton circuit and the filter column receiving the negative feedback are contained in a first insulating tank, and the filter column having terminals and the detection column are contained in a second insulating tank. It is characterized by: By doing so, it is possible to prevent noise from being introduced into the detection signal due to induction from the Cockcroft-Walton circuit.

A DC high voltage generator according to claim 4 is
A Cockcroft-Walton circuit, an AC power source arranged on the low voltage side to supply power to the Cockcroft-Walton circuit, a filter column for smoothing a high voltage generated by the Cockcroft-Walton circuit, and a smoothed DC high voltage A circuit for controlling the power supplied from the AC power supply to the Cockcroft-Walton circuit so that the DC component of the signal detected by the detection column matches the reference value,
A circuit for amplifying at least a signal of a high frequency or intermediate frequency component among signals detected by the detection column and negatively feeding back to the filter column is provided.

According to the fourth aspect of the present invention, at least the signal of the high frequency or the intermediate frequency component among the signals detected by the detection column is amplified and negatively fed back to the filter column. And fluctuation components in the intermediate frequency region can be remarkably removed.

A DC high voltage generator according to claim 5 is
A Cockcroft-Walton circuit, an AC power source arranged on the low voltage side to supply power to the Cockcroft-Walton circuit, and a filter column for smoothing a DC high voltage generated by the Cockcroft-Walton circuit,
A detection column for detecting the smoothed DC high voltage, and controlling the power supplied from the AC power supply to the Cockcroft-Walton circuit so that the DC component of the signal detected by the detection column matches the reference value. And a terminal provided in the filter column for extracting a signal representing a fluctuation component superimposed on the smoothed high voltage, and an amplifier for amplifying a signal of a low frequency component among signals from the terminal. And a circuit for controlling power supplied to the Cockcroft-Walton circuit from the AC power supply based on an output signal from the amplifier so that a fluctuation component of a low frequency is removed from the smoothed DC high voltage. And based on the output signal from the amplifier,
Power supply to the Cockcroft-Walton circuit
Circuit for controlling power is supplied from AC power supply
The product of the AC power and the signal from the detection column is obtained from the amplifier.
And a circuit for dividing the output signal by the output signal .

According to the fifth aspect of the present invention, the power supplied from the AC power supply to the Cockcroft-Walton circuit is controlled based on at least the low frequency component signal among the signals obtained from the terminals provided in one of the filter columns. Therefore, the fluctuation component in the low frequency region superimposed on the high voltage can be remarkably removed.

A DC high voltage generator according to claim 6 is
6. The apparatus according to claim 5, wherein the circuit for controlling the power supplied from the AC power supply to the Cockcroft-Walton circuit based on the output signal from the amplifier converts the signal of the low frequency component amplified by the amplifier into the signal. It is characterized by including a circuit for negative feedback to the step-up transformer.

[0027] The DC high voltage generator according to claim 7 is
A Cockcroft-Walton circuit, an AC power source arranged on the low-voltage side to supply power to the Cockcroft-Walton circuit, a multi-stage filter column for smoothing a DC high voltage generated by the Cockcroft-Walton circuit, And a circuit for controlling the power supplied from the AC power supply to the Cockcroft-Walton circuit so that the DC component of the signal detected by the detection column matches the reference value. And first and second terminals provided in the first and second filter columns for extracting a signal representing a fluctuation component superimposed on the smoothed high voltage;
A circuit for amplifying at least a high frequency or intermediate frequency component signal among the signals from the first terminal and negatively feeding back to the third filter column; and a low frequency component for the signal from the second terminal. And an amplifier for amplifying the signal of the above, and the AC power supply is supplied to the Cockcroft-Walton circuit based on the output signal from the amplifier so that a fluctuation component of a low frequency is removed from the smoothed DC high voltage. It is characterized by including a circuit for controlling power.

According to a seventh aspect of the present invention, in addition to the configuration of the first aspect, a configuration for removing a low-frequency fluctuation component is provided.
With the added configuration, it is possible to simultaneously remove the fluctuation component in the high frequency and intermediate frequency regions and the fluctuation component in the low frequency region superimposed on the high voltage. In the invention of claim 7, as described in claim 8, as a filter column of the first and 2 can use the same filter column, in this manner, to reduce the number of filter column Can be.

A DC high voltage generator according to claim 9 is
A Cockcroft-Walton circuit, an AC power source arranged on the low voltage side to supply power to the Cockcroft-Walton circuit, and a filter column for smoothing a DC high voltage generated by the Cockcroft-Walton circuit,
A detection column for detecting the smoothed DC high voltage, and controlling the power supplied from the AC power supply to the Cockcroft-Walton circuit so that the DC component of the signal detected by the detection column matches the reference value. And a circuit for amplifying at least a high frequency or intermediate frequency component signal among the signals detected by the detection column and negatively feeding back to the filter column, and superimposed on the smoothed high voltage A terminal provided in the filter column for extracting a signal representing a fluctuation component, an amplifier for amplifying a low-frequency component signal among signals from the terminal, and a low-frequency signal from the smoothed DC high voltage. The AC power supply supplies a Cockcroft-Walton circuit based on the output signal from the amplifier so that the fluctuation component is removed. It is characterized in that it comprises a circuit for controlling that power.

According to a ninth aspect of the present invention, in the configuration of the fourth aspect, a configuration for removing a low-frequency fluctuation component is provided.
With the added configuration, it is possible to simultaneously remove the fluctuation component in the high frequency and intermediate frequency regions and the fluctuation component in the low frequency region superimposed on the high voltage.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a diagram showing an example of a DC high-voltage generator according to the present invention. In this figure, the same components as those in FIG.
Description is omitted. The CCW circuit 3 and the first filter column 4 are housed in a first insulating tank 14.
The second filter column 5, the detection column 6, and the filament 7 are accommodated in a second insulating tank 15. A terminal T2 for extracting a signal from the last stage of the second filter column 5 is connected to a high-frequency band amplifier 16, and a signal representing a fluctuation superimposed on the high voltage extracted from the terminal T2 is a high-frequency band. The signal is supplied to the amplifier 16. The output signal of the amplifier 16 is inverted and fed back to the final stage of the first filter column 4. The high frequency band amplifier 16 can selectively amplify a signal of a high frequency from 1 kHz to 400 kHz. Also,
The signal extracted from the terminal T2 is also supplied to an intermediate frequency band amplifier 17 for selectively amplifying the intermediate frequency band, and the output signal of the amplifier 17 is also inverted so that the final stage of the first filter column 4 Has been returned to.
The intermediate frequency band amplifier 17 can selectively amplify an intermediate frequency signal from 400 Hz to 1 kHz. The feedback ratios of the two amplifiers are appropriately selected so that the fluctuation is suppressed in each frequency domain.

In such a configuration, since the second filter column 5 is housed in the second insulating tank 15, the container of the second insulating tank 15 shields the second filter column 5 from the CCW circuit 3. . Therefore, when extracting signals from the second filter column 5, noise due to induction from the CCW circuit 3 is not mixed into those signals. Therefore, the fluctuation component superimposed on the high voltage generated from the high voltage generator can be detected without being affected by the noise. Here, the signal extracted from the final stage of the second filter column 5 is supplied to the high-frequency band amplifier 16, and the output signal of the amplifier 16 is inverted and sent to the final stage of the first filter column 4. Because of the feedback, the high frequency fluctuation component superimposed on the high voltage applied between the filament and the ground is suppressed. The signal extracted from the last stage of the second filter column 5 is supplied to the intermediate frequency band amplifier 17, and the output signal of the amplifier 17 is inverted and fed back to the final stage of the first filter column 4. Therefore, the fluctuation component of the intermediate frequency superimposed on the high voltage applied between the filament and the ground is also suppressed.

The terminal T2 of the second filter column 5
The signal extracted from the oscilloscope 13 is displayed by the oscilloscope 13. FIG. 4A shows a displayed waveform in a high frequency band of 1 kHz to 10 kHz. FIG. 4B shows the output signal waveform of the amplifier 12 in the range of 1 Hz to 100 Hz. The latter frequency band includes both the intermediate frequency region and the low frequency region.

As can be seen from these figures, the fluctuation components in the high frequency region included in the output can be reduced to 11% of the original value, and the fluctuation components in the middle and low frequencies are reduced. Was reduced to 4% of the value. In FIG. 4A, one graduation on the horizontal axis represents 100 μsec, and one graduation on the vertical axis represents 0.5 mV. In FIG. 4B, one scale on the horizontal axis represents 100 msec, and one scale on the vertical axis represents 0.2 mV.

In the embodiment described above, the terminal T for detecting the signal indicating the fluctuation component superimposed on the high voltage is used.
Although 2 is provided on the second filter column 5, it is possible to provide the terminal T2 on the first filter column 4.
In this modification, the output signals from the amplifiers 16 and 17 are negatively fed back to the second filter column 5.

FIG. 5 shows another example of the DC high voltage generator according to the present invention. In the apparatus of FIG. 5, the third filter column 18 has the first and second filter columns 4 and 4.
5 are provided in parallel. This third filter column 18 is housed in the second insulating tank 15. The third filter column 18 also has a configuration in which units in which capacitors and resistors are connected in parallel are connected in series in multiple stages.

A terminal T3 for detecting a signal indicating a fluctuation component superimposed on the smoothed high voltage is provided in the third filter column 18. The signal obtained from the terminal T3 is supplied to the high frequency band amplifier 16 and the intermediate frequency band amplifier 17. Amplifiers 16 and 17
The output signal from the second filter column 5 is inverted.
Is returned to the final stage.

The high voltage generator of FIG. 5 differs from the device already described with reference to FIG. 3 in the following points. The third filter column 18 detects the fluctuation component superimposed on the high voltage. The output signal from the third filter column 18 is supplied to amplifiers 16 and 17. The output signals of the amplifiers 16 and 17 are inverted and fed back to the second filter column 5. The output of the amplifier 9 is inverted, and the amplitude controller 1
0. The amplifier 9 can amplify only a signal in a low frequency range from 0.1 Hz to 100 Hz, for example.

The high frequency and intermediate frequency component signals are effectively extracted from the final stage of the second filter column 5, and the low frequency component signals are effectively extracted from the final stage of the third filter column 18. The capacity of the last stage capacitor of the second filter column 5 is selected to be smaller than the capacity of the last stage capacitor of the third filter column 18. More specifically, the capacity of the capacitor at the final stage of the third filter column 18 is set so that a low-frequency signal component can be taken out from the final stage of the third filter column 18 with a sufficient size.
7 times larger than the capacitance of the last stage capacitor. The feedback ratio of the amplifier in each band is set to an appropriate value so as to reduce the fluctuation in each band. When the DC high voltage generator described above is used for an electron microscope, it is effective in making the insulating tank compact.

FIG. 6 shows still another example of the DC high voltage generator according to the present invention. The difference between the high voltage generator shown in FIG. 6 and the device already described with reference to FIG. 3 is as follows. The detection column 6 detects the fluctuation component superimposed on the high voltage. An output signal from the detection column 6 is supplied to amplifiers 16 and 17. The output signals of the amplifiers 16 and 17 are inverted and fed back to the first filter column 4.

In the embodiment described with reference to FIGS. 5 and 6, a fluctuation component in a high frequency or intermediate frequency band superimposed on a high voltage can be removed very efficiently.

FIG. 7 shows still another example of the DC high voltage generator according to the present invention. In the apparatus shown in FIG. 7, the signal extracted from the terminal T2 provided in the last unit of the second filter column 5 is supplied to a low frequency band amplifier 19 for selectively amplifying a low frequency band. You. The output signal of the amplifier 19 is supplied to the amplitude adjuster 10 after being inverted. The amplifier 19 can selectively amplify a low-frequency signal from 0.1 Hz to 100 Hz, for example. Since the lower cut-off frequency is given by the filter column 5, the low-frequency band amplifier 19 has 0 Hz (DC).
An amplifier having a frequency band of １００100 Hz can be used.

The AC voltage generated from AC power supply 1 is modulated based on the signals from both amplifiers 9 and 19, and the amplitude is adjusted. If the amplitude of the AC voltage generated from the AC power supply 1 is “x” and the output signals from the amplifiers 9 and 19 are “y” and “z”, respectively, the amplitude of the AC voltage extracted from the amplitude adjuster 10 is , “X (y / z)”. In other words, the output signal y from the error amplifier 9
Is divided by the output signal z of the low-frequency band amplifier 19 in the amplitude adjuster 10, and further, the output amplitude x of the AC power supply 1
Is multiplied by (y / z) while passing through the amplitude adjuster 10.

In the configuration of FIG. 7 described above, since the second filter column 5 and the detection column 6 are accommodated in the insulating tank 15 different from the CCW circuit 3, noise due to induction from the CCW circuit may be mixed. And a fluctuation component superimposed on the high voltage can be detected.

The signal extracted from the final stage of the second filter column 5 without any noise mixed in this way is passed through the low frequency band amplifier 19 to the amplitude adjuster 10.
Supplied to The amplitude of the AC voltage output from the amplitude adjuster 10 is “x (y / z)” as described above.
Is represented by On the other hand, the low-frequency fluctuation component included in the output signal from the amplifier 9 shows the same change as the fluctuation component included in the output signal from the amplifier 19. Therefore, (y
/ Z) is removed. As a result, the low frequency fluctuation component superimposed on the high voltage applied between the filament and the ground is suppressed.

FIG. 8 shows a waveform of a signal obtained from the terminal T2 provided in the second filter column 5 displayed on the oscilloscope 13. FIG. 8 shows that 1 Hz to 100
3 shows a waveform in a low frequency band of Hz. In FIG. 8, one graduation on the horizontal axis indicates 200 msec, and one graduation on the vertical axis indicates 2 mV. While the amplitude of the fluctuation component in the conventional low frequency-intermediate frequency band is 9 mV as shown in FIG. 2B, in FIG.
It can be seen that it has been improved to 2 mV.

FIG. 9 shows still another example of the DC high voltage generator according to the present invention. The device shown in FIG. 9 differs from the device shown in FIG. 7 in the following points. That is, the output signal of the amplifier 19 is supplied to the error amplifier 9. The sum of the signal from the amplifier 19 and the signal from the detection column 6 is compared with a reference signal supplied to the error amplifier 9. The AC power supplies 20a and 20b supply an AC voltage of 3 kHz to the step-up transformer 2. The output signal of the error amplifier 9 is inverted and supplied to the step-up transformer 2.

Also in the present embodiment, a low frequency component of the signal showing the fluctuation component superimposed on the high voltage obtained from the terminal T2 is extracted through the amplifier 19, and supplied to the CCW based on the extracted signal. Since the amplitude of the AC voltage is controlled, a fluctuation component in a low frequency band superimposed on a high voltage can be sufficiently suppressed.

FIG. 10 shows still another example of the DC high voltage generator according to the present invention. The device shown in FIG. 10 basically has a structure in which the device shown in FIG. 3 and the device shown in FIG. 7 are combined. That is, terminals T2 and T3 are respectively provided in the last unit of the second filter column 5 and the third filter column 18, and the signal indicating the fluctuation component extracted from the terminal T2 is the same as that of the device shown in FIG. Similarly, the first filter column 4 via the high frequency band amplifier 16 and the intermediate frequency band amplifier 17
Returned to. The signal indicating the fluctuation component extracted from the terminal T3 is sent to the amplitude adjuster 10 via the low-frequency band amplifier 19, similarly to the apparatus shown in FIG.

In order to effectively extract high frequency and intermediate frequency component signals from the final stage of the second filter column 5 and to effectively extract low frequency component signals from the final stage of the third filter column 18, The capacity of the last stage capacitor of the second filter column 5 is selected to be smaller than the capacity of the last stage capacitor of the third filter column 18. More specifically, the capacity of the capacitor at the final stage of the third filter column 18 is set so that a low-frequency signal component can be taken out from the final stage of the third filter column 18 with a sufficient size.
7 times larger than the capacitance of the last stage capacitor. The feedback ratio of the amplifier in each band is set to an appropriate value so as to reduce the fluctuation in each band.

Further, the signal extracted from the final stage of the third filter column 18 is supplied to a low frequency band amplifier 19, and the output signal of the amplifier 19 is inverted and then supplied to the amplitude adjuster 10. Therefore, a low-frequency fluctuation component superimposed on a high voltage applied between the filament and the ground is also suppressed. The feedback ratio of each of the frequency band amplifiers is adjusted so that the fluctuation in each band becomes small.

With such a configuration, FIG.
DC high voltage generator shown in the above, the fluctuation component in the low frequency band superimposed on the high voltage applied between the filament and the ground, the fluctuation component in the intermediate frequency band, the fluctuation component in the high frequency band, all It can be suppressed over a frequency band.

FIG. 11 shows still another example of the DC high voltage generator according to the present invention. The device shown in FIG. 11 basically has a structure in which the device shown in FIG. 5 and the device shown in FIG. 7 are combined. In this embodiment, the signal extracted from the terminal T3 provided in the third filter column 18 is sent to the high frequency band amplifier 16, the intermediate frequency band amplifier 17, and the low frequency band amplifier 19. High frequency band amplifier 16 and intermediate frequency band amplifier 1
7 is fed back to the second filter column 5,
Since the output signal of the low-frequency band amplifier 19 is sent to the amplitude adjuster 10, the DC high-voltage generator shown in FIG. 11 uses a variable component in the low-frequency band superimposed on the high voltage applied between the filament and the ground. In addition, both the fluctuation component in the intermediate frequency band and the fluctuation component in the high frequency band can be suppressed over all frequency bands.

FIG. 12 shows still another example of the DC high voltage generator according to the present invention. The device shown in FIG. 12 basically has a structure in which the device shown in FIG. 6 and the device shown in FIG. 7 are combined. In the present embodiment, the signal indicating the fluctuation component extracted from the detection column 6 is output from the high frequency band amplifier 16 and the intermediate frequency band amplifier 17 to the first filter column 4 and provided to the second filter column 5. Since the signal indicating the fluctuation component extracted from the terminal T2 is fed back to the amplitude adjuster 10 via the low frequency band amplifier 19, the fluctuation in the low frequency band superimposed on the high voltage applied between the filament and the ground. Component, and the fluctuation component in the intermediate frequency band,
Variation components in high frequency bands can also be suppressed over all frequency bands.

The above-described embodiment is merely an example of the present invention, and the present invention can be modified and implemented. For example, in the above-described embodiment, when detecting a signal representing a high voltage output from the filter column and a fluctuation component thereof, the detection column and the terminal are provided so that noise due to induction from the CCW circuit is not mixed into the detection signal. The filter column is housed in a separate tank from the insulating tank in which the CCW circuit is housed, but if the CCW circuit and other filter columns are shielded by a shield plate, the CCW circuit and other filter columns can be housed. You may make it accommodate in the same insulating tank. However, CC
When the W circuit and the other filter column are housed in the same insulating tank, it is necessary to secure the insulation distance between the CCW circuit and the other filter column in the insulating tank. 2 in the above embodiment
It is larger than the sum of the volumes of the individual insulating tanks. In other words, the high voltage generator in the electron microscope according to the above-described embodiment having two insulating tanks is advantageous in making the insulating tank portion compact.

Furthermore, the above-described embodiment is an example in which the present invention is used to generate an accelerating voltage for an electron microscope. However, a DC high voltage generator according to the present invention is an The present invention can be similarly applied to a case where a DC high voltage is generated in a beam device.

[0057]

According to the present invention described above, a high frequency or intermediate frequency fluctuation component superimposed on a high voltage generated from a high voltage generator can be remarkably removed. Therefore, when the DC high voltage generator according to the present invention is used as a high voltage generator for an electron microscope, the resolution of an electron microscope image can be improved in each stage.

Further, according to the present invention, a low-frequency fluctuation component superimposed on the high voltage can be sufficiently removed. Therefore, if the DC high-voltage generator according to the present invention is used in an electron microscope, electron This can greatly contribute to improving the resolution of a microscope image.

Further, according to the present invention, the fluctuation component can be sufficiently removed from all of the high frequency, intermediate frequency, and low frequency components superimposed on the high voltage. If the voltage generator is used for an electron microscope, it can greatly contribute to improving the resolution of an electron microscope image.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a conventional high voltage generator of an electron microscope.

FIG. 2 is a diagram for explaining a ripple in an output voltage of a conventional high voltage generator of an electron microscope.

FIG. 3 is a diagram showing an example of an embodiment of the present invention.

4 is a diagram for explaining a ripple in an output voltage in the device shown in FIG.

FIG. 5 is a diagram showing another example of the embodiment of the present invention.

FIG. 6 is a diagram showing another example of the embodiment of the present invention.

FIG. 7 is a diagram showing another example of the embodiment of the present invention.

FIG. 8 is a diagram showing another example of the embodiment of the present invention.

FIG. 9 is a diagram showing another example of the embodiment of the present invention.

FIG. 10 is a diagram showing another example of the embodiment of the present invention.

FIG. 11 is a diagram showing another example of the embodiment of the present invention.

FIG. 12 is a diagram showing another example of the embodiment of the present invention.

[Explanation of symbols]

1, 20: AC power supply 2: Step-up transformer 3: Balanced cockcroft-Walton circuit 4: First filter column 5: Second filter column 6: Detection column 7: Filament 8: Reference power supply 9: Error amplifier 10: Amplitude adjustment 11: Bias resistor 12: Error amplifier 13: Oscilloscope 14: First insulating tank 15: Second zetene tank 16: High frequency band amplifier 17: Intermediate frequency band amplifier 18: Third filter column 19: Low frequency band amplifier T1, T2, T3: Signal extraction terminals

Continuation of the front page (56) References JP-A 2-31058 (JP, U) JP-A 60-160089 (JP, U) JP-A 60-14692 (JP, U) JP-A 5-11792 (JP U.S. Pat. No. 3,491,377 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 7/10 H01J 37/248

Claims (9)

(57) [Claims] 1. A Cockcroft-Walton circuit, an AC power source arranged on a low-voltage side for supplying power to the Cockcroft-Walton circuit, and a plurality of filter columns for smoothing a DC high voltage generated by the Cockcroft-Walton circuit And a detection column for detecting the smoothed DC high voltage, and the power supplied from the AC power supply to the Cockcroft-Walton circuit so that the DC component of the signal detected by the detection column matches the reference value. A circuit for controlling, a terminal provided in one of the filter columns for extracting a signal representing a fluctuation component superimposed on the smoothed high voltage, and at least a high frequency or intermediate signal among signals from the terminal. A circuit for amplifying the signal of the frequency component and performing negative feedback on the other filter columns; High-voltage generator. 2. A DC high voltage generator according to claim 1, further comprising means for shielding the filter column having the terminal from the Cockcroft-Walton circuit. 3. The Cockcroft-Walton circuit according to claim 1,
The DC high-voltage generator according to claim 1, wherein the filter column and the detection column each including the terminal are accommodated in a second insulating tank. 4. A Cockcroft-Walton circuit, an AC power source disposed on the low voltage side for supplying power to the Cockcroft-Walton circuit, a filter column for smoothing a high voltage generated by the Cockcroft-Walton circuit, and a smoothing unit. A detection column for detecting the detected DC high voltage, and for controlling the power supplied from the AC power supply to the Cockcroft-Walton circuit so that the DC component of the signal detected by the detection column matches the reference value. A direct current high voltage generator comprising: a circuit; and a circuit for amplifying at least a signal of a high frequency or intermediate frequency component among signals detected by the detection column and negatively feeding back to the filter column. 5. A Cockcroft-Walton circuit, an AC power source disposed on the low voltage side for supplying power to the Cockcroft-Walton circuit, a filter column for smoothing a DC high voltage generated by the Cockcroft-Walton circuit, and a smoothing circuit. A detection column for detecting the converted DC high voltage, and for controlling the power supplied from the AC power supply to the Cockcroft-Walton circuit so that the DC component of the signal detected by the detection column matches the reference value. And a terminal provided in the filter column for extracting a signal representing a fluctuation component superimposed on the smoothed high voltage, and an amplifier for amplifying a low frequency component signal among signals from the terminal. Output from the amplifier so that low-frequency fluctuation components are removed from the smoothed DC high voltage. And a circuit for controlling the power supplied to the Cockcroft Walton circuit from the AC power supply based on the item, based on the output signal from the amplifier
From the AC power supply to the Cockcroft-Walton circuit.
The circuit for controlling the supplied power is
The product of the supplied AC power and the signal from the detection column is
Provide a circuit for dividing by the output signal from the amplifier.
And a DC high voltage generator. 6. A circuit for controlling power supplied from the AC power supply to the Cockcroft-Walton circuit based on an output signal from the amplifier, the circuit comprising: a low-frequency component signal amplified by the amplifier; The direct-current high-voltage generator according to claim 5, further comprising a circuit for performing negative feedback. 7. A Cockcroft-Walton circuit, an AC power source disposed on the low-voltage side for supplying power to the Cockcroft-Walton circuit, and a plurality of filter columns for smoothing a high DC voltage generated by the Cockcroft-Walton circuit. And a detection column for detecting the smoothed DC high voltage, and the power supplied from the AC power supply to the Cockcroft-Walton circuit so that the DC component of the signal detected by the detection column matches the reference value. A control circuit; first and second terminals provided on first and second filter columns for extracting a signal representing a fluctuation component superimposed on the smoothed high voltage; Amplifying at least a high-frequency or intermediate-frequency component signal among the signals from the first terminal, A circuit for negatively feeding back the signal, an amplifier for amplifying a low frequency component signal of the signal from the second terminal, and a low frequency fluctuation component is removed from the smoothed DC high voltage. A DC high-voltage generator including a circuit for controlling power supplied from the AC power supply to the Cockcroft-Walton circuit based on an output signal from the amplifier. 8. The DC high voltage generator according to claim 7 , wherein the same filter column is used as said first and second filter columns. 9. A Cockcroft-Walton circuit, an AC power source disposed on the low voltage side for supplying power to the Cockcroft-Walton circuit, a filter column for smoothing a DC high voltage generated by the Cockcroft-Walton circuit, and a smoothing circuit. A detection column for detecting the converted DC high voltage, and for controlling the power supplied from the AC power supply to the Cockcroft-Walton circuit so that the DC component of the signal detected by the detection column matches the reference value. A circuit for amplifying at least a high frequency or intermediate frequency component signal among the signals detected by the detection column and negatively feeding back to the filter column; and a fluctuation superimposed on the smoothed high voltage. A terminal provided on the filter column for extracting a signal representing a component; An amplifier for amplifying a signal of a low frequency component among the signals, and the AC power supply based on an output signal from the amplifier so as to remove a low frequency fluctuation component from the smoothed DC high voltage. A DC high-voltage generator including a circuit for controlling power supplied to a Cockcroft-Walton circuit.