JPS6166350A - Plasma focus device - Google Patents

Abstract

PURPOSE:To reduce fluctuation of X-ray strength by applying a means for stabilizing temperature of an insulator to a plasma focus device in which plasma is generated by creeping discharge of the insulator and making amount of gas adsorbed constant. CONSTITUTION:A plasma focus device is constructed by disposing a cylindrical anode 1 and a cathode 2 on a coaxial and insulating by an insulator 3 of glass etc, and accommodating them in a vessel 4 which is sealed by gas of neon and argon, and providing a fluid path 7 in the vicinity of the insulator 3 to circulate pure water and air and controlling the temperature of the insulator by a sensor such as a thermister. And high voltage pulse is provided between electrodes 1, 2 to generate plasma and to inject soft X-rays. Then, the temperature of the insulator 3 is stabilized to make the amount of gas adsorbed on the surface of the insulator 3 constant, and fluctuation of X-ray strength is largely reduced to improve reproduceability.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention involves filling a discharge tube including an anode and a cathode coaxially arranged with an insulator in between, and applying a high voltage between these coaxial electrodes. This relates to the improvement of a plasma focus device that applies pulses to generate plasma on the surface of an insulator and focuses it near the tip of a coaxial electrode to form high-temperature, high-density plasma. X-ray is 1
for example.

It is used as a radiation source in X-ray exposure equipment and other equipment used to manufacture submicron ICs (integrated circuits).

[Background of the invention]

Regarding the plasma focus device for this tumor.

J. W. Mather “Methods of Exp.
erin+mental Physics"Vol, 9.
Pt8. pp, 187-199 (1971),
It is described in Academic Press. The outline of the device is as follows. One end of the two cylindrical electrodes is insulated with an insulator such as glass, and the other end is left open, arranged coaxially and housed in the discharge tube. A discharge tube is generally filled with hydrogen, etc., but in order to generate X-rays, neon, argon, krypton, etc.
The capacitor is sealed at a pressure in the orr range, and a pulse voltage is applied from the charged capacitor to cause discharge. When a pulse voltage is applied, dielectric breakdown occurs on the surface of the insulator and plasma is generated.

The generated plasma receives force from the electric field between the electrodes and the strong annular magnetic field generated by the discharge current.

It travels toward the open end of the electrode, and when it passes the end of the electrode, it is focused on the central axis by the magnetic field of the current.

It forms high-temperature, high-density plasma and emits X-rays.

A plasma focus device with such a configuration.

The structure is simple and the range of energy that can be injected is wide.

Because the intensity of the X-rays it generates is strong, it has the potential to be an excellent source of X-rays.

However, this kind of plasma focus device.

When used as an xIQ source for an X-ray exposure device, the biggest problem is the lack of reproducibility of the X-ray output for each discharge. In particular, as described in the above-mentioned document (page 194, line 13 onwards), the reality is that the problem of initial discharge on the glass surface in a plasma focus device has hardly been studied.

[Purpose of the invention]

The purpose of the present invention is to generate plasma on the surface of an insulator,
This is focused or pinched to form high-temperature, high-density plasma, and the soft X-rays emitted by this high-temperature, high-density plasma are used in plasma X-ray sources. An object of the present invention is to provide a plasma focus device that can reduce fluctuations in X-ray intensity that occur each time a discharge occurs.

[Summary of the invention]

In order to achieve the above object, the present invention provides means for keeping the temperature of the insulator surface of the plasma focus device constant. By keeping the temperature of the insulator surface constant, the amount of gas adsorbed on the two surfaces is kept constant, and the density distribution of the plasma initially created by creeping discharge is made uniform and constant.

Improving the reproducibility of discharge 6 While investigating the cause of inhibiting the reproducibility of X-ray output from plasma focus discharge tubes, the present invention discovered that the cause was dependent on creeping discharge of the insulator. It was born out of that.

[Embodiments of the invention]

The following two embodiments of the present invention are shown in FIG.

This will be explained using a cross-sectional view of a plasma focus discharge tube.

In this discharge tube, two cylindrical anodes 1 and a cathode 2 surrounding them are arranged coaxially, and both electrodes are insulated by an insulator 3 made of glass or the like. These are container 4
The inside is filled with a gas such as neon, argon, or krypton at a pressure of 9.1 to 1 Torr. A capacitor 5 is connected between the anode 1 and the cathode 2 via a discharge switch 6. When the discharge switch 6 is short-circuited.

The voltage charged in the capacitor 5 is instantaneously applied between both electrodes, and discharge begins on the surface of the insulator 3, generating plasma. The ions and electrons of the generated plasma are
It receives force from the electric field and the annular magnetic field created by the discharge current in the space between the two electrodes, and travels along the electrodes toward the open end of the electrodes.

When it passes the edge of the electrode, it is pinched by the pressure of the magnetic field.

A hot spot of compressed high-temperature, high-density plasma is formed on the axis near the tip of the anode 1, and soft X-rays are emitted.

In the above configuration, first, the plasma created by the creeping discharge of the insulator 3 becomes a seed and ionizes the atoms existing in the space between the two electrodes one after another, and the plasma generated one after another is caused by the electric and magnetic fields. Focus by action. If the density distribution of the plasma initially created is uneven or the amount of plasma generated changes, the subsequent progress of the discharge will change, the focused plasma may shift from the axis, or the temperature and density of the plasma may change. fluctuates,
The intensity of the emitted X-rays will fluctuate. As a result of investigating the causes of fluctuations in X-ray intensity, the present invention found that it is possible to keep the amount of gas adsorbed on the surface of the insulator 3 constant.
It was discovered that this method has a remarkable effect on reducing fluctuations in X-ray intensity, and by controlling the temperature of the insulator 3 and regularizing the discharge time interval, it is possible to stabilize the X-ray output. be.

7 in FIG. 1 is an example of insulator temperature stabilization.
This is a fluid channel placed near the insulator 3, and a liquid or gas at a constant temperature is placed in this fluid channel 7.

Alternatively, the temperature of the insulator 3 is controlled by circulating a liquid having an appropriate boiling point. To achieve even higher stability, a sensor such as a thermistor is embedded in the temperature measurement groove 8 to determine the temperature of the insulator 3 and control the flow rate of the liquid or gas circulating in the fluid flow path 7. . As the liquid or gas to be circulated, pure water, air, Freon, liquid nitrogen, etc. can be used.

〔Effect of the invention〕

As described above, according to one aspect of the present invention, in a plasma focus device that first generates plasma by creeping discharge of an insulator, by stabilizing the temperature of the insulator and regularizing the time intervals of discharge, It is possible to significantly reduce fluctuations in the intensity of X-rays emitted from the plasma.

To give a specific example of the effect, the probability of obtaining an X-ray intensity stronger than a predetermined value when repeatedly discharging using neon as the filling gas was less than 50% when the present invention was not implemented. , by regularizing the temperature stabilization and discharge time intervals of the present invention under the same conditions, the improvement was over 80%.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the present invention. <Explanation of symbols>

Claims (4)

[Claims] (1) A discharge tube including an anode and a cathode arranged coaxially through an insulator is filled with gas, and a high voltage pulse is applied between the coaxial electrodes to generate plasma on the surface of the insulator. , in a plasma focus device that forms high-temperature, high-density plasma by focusing near the tip of a coaxial electrode.
A plasma focus device comprising means for stabilizing the temperature of the insulator. (2) The plasma focus device according to claim 1, wherein the high voltage pulse applied between the electrodes is a high voltage pulse applied at regular time intervals. (3) The insulator temperature stabilizing means includes a fluid flow path disposed near the insulator, and a fluid circulation means for circulating a fluid at a substantially constant temperature within the flow path. The plasma focus device according to claim 1 or 2, characterized in that it is a stabilizing means. (4) The insulator temperature stabilizing means includes a fluid flow path disposed near the insulator, a means for circulating fluid in the flow path, and a temperature sensor that detects the temperature of the insulator;
Claim 1: An insulator temperature stabilizing means comprising means for controlling the flow rate or temperature of the fluid flowing into the fluid flow path in accordance with the detected temperature.
The plasma focus device according to item 1 or 2.