JPS61153999A - Charged particle accelerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to charged particle accelerators, and in particular to high voltage accelerators for keeping the absolute value of a high voltage constant against changes in load current used in electron microscopes, etc. This invention relates to a charged particle accelerator equipped with a voltage detection resistor.

[Background of the invention]

The conventional charged particle accelerator is THIRTY-FIF'
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As described in the document titled ``Tron ()un'', a high voltage resistance cable was used to transmit high voltage from a high voltage generator to apply a high voltage to the electron beam accelerator. Cables with a specific resistance value of several MΩ are normally used.The reason for using a resistance cable is to attenuate abnormal surge voltages generated by discharge etc. by the filtering effect of the resistance value R and capacitance C of the resistance cable. This is to protect the high voltage generator and the multi-stage accelerator tube that accelerates charged particles from dielectric breakdown. Furthermore, the voltage ripple component of the DC high voltage generator is filtered by the resistance value R and capacitance C of the resistance cable. This is to reduce energy fluctuations of charged particles as much as possible by attenuating the energy fluctuations.Furthermore, the fluctuations due to voltage ripples are kept on the order of 10-? for an accelerating voltage of 200 to 100 kV.Stability of DC high voltage To do this, a high voltage detection resistor is connected to the high voltage output side, the voltage is detected, and the variation with respect to the reference voltage is amplified by an error amplifier for stabilization. In the device,
Voltage stability including voltage ripple component is 1x that voltage.
it)-' or less.

However, a drawback of this method is that the high voltage detection resistor is provided on the power supply side of the resistance cable. If the electron beam field is changed by, for example, 10 microns by adjusting the filament temperature or bias voltage, and if the resistance value of the resistance cable is 2 Mg, the voltage will drop by 20 V from the normal voltage on the load side. In this way, the accelerating voltage does not change each time the emission current is changed.In addition to normal image observation, when using an energy analyzer that is commonly used these days, it is necessary to adjust the device each time. As a result, basic performance deteriorates and adjustments must be made frequently during use, which is a problem.

In order to solve the above problems, a high voltage detection resistor was connected to the load side of the resistance cable, and consideration was given to keeping the accelerating voltage constant despite changes in emission current, and this has been put into practical use. There is.

FIG. 2 is a block diagram of such a conventional charged particle accelerator, and shows the case of an electron microscope with a relatively high acceleration voltage of 500 kV or more. In FIG. 2, a high voltage resistance cable 2 provided with a cable bushing 17 is provided in a high voltage tank 16a that houses a high voltage generator 1, and the resistance cable 2 is connected to a high voltage The high voltage detection resistor 5 is connected to one end of the voltage dividing resistor 4 that applies a high voltage to the accelerating electrode 3 in the tank 16b, and is also connected to one end of the high voltage detection resistor 5.
The other end is connected to a reference resistor 7 and an error amplifier 9 to which a reference voltage 8 is applied.

6 is an electron source.

In the case of a relatively large-scale device as shown in Fig. 2, it is possible to install the high voltage detection resistor 5 without worrying about space, but it is possible to install the high voltage detection resistor 5 without worrying about the space. In an electron microscope with a low voltage, it is difficult to make the charged particle accelerator side the center of gravity in order to maintain versatility, and it is physically impossible to provide the high voltage detection resistor 5 as in the conventional case. It was difficult and there were problems in practical implementation.

[Purpose of the invention]

The present invention has been made in view of the above, and its purpose is to connect and provide a high voltage detection resistor to the charged particle accelerator side of the high voltage resistance cable without making the device too sacred. The purpose of the present invention is to provide a charged particle accelerator that can perform the following tasks.

[Summary of the invention]

The present invention is characterized by a structure in which a high voltage detection resistor connected to the charged particle accelerator side of the high voltage resistance cable is integrated and enclosed within the insulator of the high voltage insulating container on the charged particle accelerator side. That's the point.

[Embodiments of the invention]

The present invention will be explained in detail below using the embodiment shown in FIG.

FIG. 1 is a longitudinal sectional view showing an embodiment of the charged particle accelerator of the present invention. In FIG. 1, a high voltage from a high voltage generator 1 is applied to multiple stages of accelerating electrodes 3 through a high voltage resistance cable 2 after being equally divided by a voltage dividing resistor 4. On the other hand, the high voltage detection resistor 5 is integrated and sealed within the insulator of the high voltage insulating container 10, and the material of the insulator of the high voltage insulating container 10 is an epoxy molding material. A multi-stage accelerator tube having a plurality of stages of insulating containers holding accelerating electrodes 3 stores a highly insulating gas such as 7 Leon 12.8 Fg in a high-voltage insulating container 10.
It is sealed inside and maintains high insulation properties. A cylindrical bushing is provided at the distal end of the resistance cable 2 and maintains insulation from the high voltage insulating container 10 by surface pressure.

A tungsten filament or LaBe electron source 6 is used as an electron source. The heating power of the electron source 6 is transmitted to the high voltage side inside the high voltage insulating container 10 by using a push/button transformer 11 which is high frequency coupled. The high voltage from the resistance cable 2 applied to the voltage shield electrode 12 inside the high voltage side of the high voltage insulating container 10 is connected via the spring 13 to the voltage dividing resistor 4 in the multistage accelerator tube. Connect to one end of the high voltage detection resistor 5. In this case, the high voltage detection resistors 5 may be arranged in series as shown in FIG. 1 or may be mounted in a spiral shape. The detection current flowing through the high voltage detection resistor 5 is converted into voltage by the reference resistor 7 on the error amplifier 9 side, and the voltage is stabilized by comparison with the reference voltage 8 applied to the error amplifier 9. For example, for 200 kv, I Xi O-'m
Keep it below in. Note that 14 is a shield electrode, and 15 is an insulating cylinder.

According to the embodiment of the present invention described above, when the electron beam dose from the electron source 6 is changed, a voltage drop due to the inherent resistance value of the resistance cable 2 does not occur, so that the specified voltage is always maintained as below. It is applied to the multi-stage accelerating tube as an accelerating voltage while maintaining the stability of 1×10"min. Therefore, even if the electron beam dose is changed, the voltage remains constant, so the electron beam is always accelerated with a constant energy. As a result, recently
In particular, it is possible to enable use in a highly stable state without degrading the characteristics of energy analyzers, etc., which are often employed as analysis functions.

In addition, when compared with the conventional example, since the high voltage detection resistor 5 is built into the insulator of the high voltage insulating container 10, the exclusive volume of the device is approximately 1/10, and the accelerating voltage is relatively low. 2
If it is possible to miniaturize a 00 to 300 kV electron microscope, it is possible to improve the basic performance without compromising the general-purpose ratio.

〔Effect of the invention〕

As explained above, according to the present invention, a high voltage detection resistor can be connected and provided on the charged particle accelerator side of a high voltage resistance cable without increasing the size of the device, thereby reducing versatility. This has the effect of making it possible to improve basic performance without having to do so.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of the charged particle accelerator of the present invention, and FIG. 2 is a configuration diagram of a conventional charged particle accelerator. DESCRIPTION OF SYMBOLS 1... High voltage generator, 2... High voltage resistance cable, 3... Accelerating electrode, 4... Voltage division resistor, 5...
... High voltage detection resistor, 6... Electron source, 10...
High voltage insulation container.
, 1 agent Patent attorney Hiroto Nagasaki ′″ −bu・′ (and 1 other person)

Claims (1)

[Claims] 1. Charged particles, in which a high voltage generator and an acceleration means for accelerating charged particles are connected by a high voltage resistance cable, and a high voltage detection resistor is connected to the high voltage resistance cable and provided on the charged particle accelerator side. A charged particle accelerator characterized in that the high voltage detection resistor is integrated and sealed within an insulator of a high voltage insulating container on the side of the charged particle accelerator.