JPS61153936A - Plasma x-ray generator - Google Patents

Abstract

PURPOSE:To enable repeated usage by employing liquid metal as a target then dripping through a tubing from above a vacuum container while providing a liquid metal sump on the bottom of the vacuum container while balancing the pressure and collecting the liquid metal. CONSTITUTION:A tubing 2 is arranged above a vacuum container 1 to feed liquid metal or mercury to be employed as a target from a sump 3. While a Piezo element 10 is arranged near the tip of the tubing 2 then vibrated to drip the mecury droplet 9. Furthermore, a sump 8 is arranged on the bottom of the container 1 such that the height of liquid metal will be balanced through the tubing 71 thus to constitute a plasma X-ray generator. Then plasma production beam or laser pulse 81 is irradiated synchronously with production of the droplet 9 thus to produce X-ray. Consequently, a system enable of repeated usage while feeding/collection of target material is facilitated can be obtained.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a laser or charged particle beam that generates tL.
*Relating to a plasma X-ray generator that obtains X-rays from a plasma.

[Technical background of the invention and its problems]

By irradiating a target with focused laser light or a charged particle beam, high-temperature, high-density plasma can be generated at once. If this plasma is used as an X-ray source (1)
: High brightness X-rays can be obtained. (2): The radiation source is a point light source Ki.
There are It can be used for X-ray lithography and chromatographic measurements. Conventionally, this type of experiment was mainly conducted by irradiating a solid planar target with laser light (for example, S
ov.

Phys, Tech, Phys, 28(7), P86
3 (1983)).

However, this method has the following drawbacks for practical use. That is, it takes time and effort to replenish the target material, and in particular, it is necessary to break the vacuum after all the targets set in the vacuum container have been exhausted, resulting in a considerable loss of time. In addition, the plasma-converted material adheres to the laser entrance window and the X-ray extraction window, leading to loss of laser irradiation power, destruction of the window, and attenuation of the X-rays. The following proposal has been made as a method for preventing plasma substances from adhering to windows (for example, Japanese Patent Publication No. 158842/1984). That is, this is a method of using as a target a substance whose product is gasified after plasma formation (for example, ice, solid ammonia, solid argon, krypton, xenon, solid carbon dioxide, etc.). However, this method requires that the target be cooled to a low temperature, which requires complicated equipment. Furthermore, the equipment for supplying the target becomes complex (eg, Journal of the Atomic Energy Society of Japan).

26(7), P594 (1984)).

[Purpose of the invention]

This invention improves the drawbacks of the prior art described above, and uses a laser or charged particle beam to produce a high-intensity The purpose is to provide a radiation source.

[Summary of the invention]

In order to achieve such an object, the present invention uses a liquid metal (for example, mercury) as a target material, and supplies this liquid metal into a vacuum container through a capillary or an oriswiss in synchronization with a laser pulse (or charged particle beam pulse). I have to.

This supply is specifically in the form of droplets, each droplet being irradiated with a laser to form a plasma and to obtain X-rays. In addition,
During flight, the plasma material collides with a window, etc., depressurizes it, recombines, and becomes neutral. However, by using a material that does not react with liquid metal to form an alloy in the window or vacuum container, the target material can be absorbed by the window. It flows downward without adhesion, preventing window deterioration.

Additionally, in order to synchronize droplet generation and laser pulse, K
For example, mechanical vibration may be applied to a capillary or orifice or the liquid metal flowing therein, or pressure may be applied in pulses to a liquid metal reservoir. In particular, the liquid metal flowing downward is collected in a thin tube provided at the bottom of the vacuum container, and flows into the liquid metal reservoir while keeping the height of the liquid metal column constant so that it matches the external pressure. Therefore, it can be easily collected. Furthermore, the vacuum container is kept airtight by the liquid metal within the capillary.

〔Effect of the invention〕

According to the present invention, there is little deterioration and it can be used repeatedly.
Moreover, the target material can be easily supplied and recovered, and a high-brightness X-ray source with a simple configuration can be obtained.

[Embodiments of the invention]

Examples of the present invention will be described in detail. In FIG. 1, a thin tube 2 is arranged at the upper part of a vacuum container 1, and mercury as a liquid metal is supplied from a supply mercury reservoir 3 which is a reservoir for mercury for a target. The side surface of the container 1 is provided with a laser entrance window 4 and a laser transmission window 5 constituting a beam da/par. A laser 81 as a beam for generating Gutsuma is passed through the laser entrance window 4 through a condensing lens 6.
The mercury droplet 9 is irradiated through the mercury droplet 9. The mercury droplet 9 is guided (by surface tension) to the tip of the capillary tube 2, and is caused to drop by the excitation of the piezo element 10, which is concentrated at the tip of the capillary tube 2. The amount of mercury supplied at this time, q, is the height difference between the mercury surface of the mercury reservoir and the tip of the capillary, hl is the inner diameter of the capillary, and the length is l, where η is the viscosity of mercury, and ρ is the mass of the mercury. The density P represents the pressure of the mercury reservoir (generally atmospheric pressure).

When mechanical vibration (frequency f) is applied to the capillary using a piezoelectric vibrator 1O, the mercury breaks into droplets 9 at intervals of period 1/f after ejecting from the capillary. This interval is set so as to be synchronized with the laser pulse. Further, the size d of the droplet at this time is as follows.

Since d can be selected to match the condensing diameter of the laser beam, the capillary size and hl can be selected within a range that allows stable droplets.

The above method cannot be used when the laser's return frequency is small (10Hz or less). If the surface tension of mercury is σ, select l t D t ht etc. so that the above formula is satisfied, and prevent mercury from jumping out of the capillary due to the surface tension. When a single pulse of intense vibration is applied, a droplet is ejected from the tubule. This diameter varies depending on the vibration intensity, but it is close to the inner diameter of the capillary. As described above, mercury droplets are supplied into the vacuum container in synchronization with laser pulses, and the mercury is turned into plasma by irradiating the droplets with focused laser light.
Generates X-rays.

The piezo element 10 has a ceramic part 1 as shown in FIG.
6 and electrodes 17 and 18 with pressure on both sides so as to vibrate in the thickness direction. The electrode 17 is insulated and fixed to the collar part 191'l provided at the end of the thin tube 2, and the electrode 181C is insulated and fixed to the support part 20 on the container side.

This piezo element IO is connected to a drive power source 2 that generates an alternating current voltage.
It vibrates when 1 is applied. That is, the tip of the capillary tube 2 vibrates due to the AC voltage applied by the drive power source 21, and the mercury in the capillary tube 2 becomes droplets 9 and drips.

In order to synchronously irradiate the mercury droplets 9 with laser light, the AC signal 22 of the drive power source 21 is converted into a rectangular wave signal 24 by the waveform shaper 23, and this rectangular wave signal 24 is input to the mono-multivibrator 25. pulse signal 26. A synchronized pulse signal 28 is obtained via a delay circuit 27 which delays the pulse generation time of this pulse signal 26 in order to match the position of the droplet 9 with the emission time of the laser beam. The laser device 29 is driven by this synchronized pulse signal 28) and irradiates the laser beam 81 onto the small mantle 9 to turn it into plasma and generate X-rays. The generated X-rays are extracted and utilized through polyethylene thin films 15 attached to X-ray extraction windows 13 provided at several locations around the vacuum container, as shown in FIG. For example, in the X-ray extraction window 13, for example, a semiconductor chip 30, which is used to manufacture a semiconductor device by irradiating X-rays, is arranged. This plasma mercury returns to neutral mercury atoms by recombination, but does not adhere to the glass or the window of the polyethylene 15, and instead flows into the thin tube 71 provided at the bottom 7 of the vacuum container. The height of mercury that accumulates in this thin tube is the height corresponding to 1 atm, approximately 76
cm, the length of the capillary should be 76 on or more.

Furthermore, the container is kept airtight by the mercury in the capillary. Then, while keeping the temperature constant, the mercury is collected at the mercury reservoir 8.
It accumulates in

As described above, mercury flows from the supply mercury reservoir to the recovery mercury reservoir, and one supply and one recovery can be easily performed.

[Other embodiments of the invention]

Next, other embodiments of the present invention will be described. Figure 4 shows
This is an example in which instead of using a piezo element to create the mercury droplet 9, pressure is applied to the mercury reservoir. Note that the same components as those in the above-mentioned embodiment will be described with the same reference numerals. In this embodiment, the mercury reservoir 3 is made up of a pipe 31 that communicates with the inside at the top, a high-speed electromagnetic pulp 32 that interrupts the gas flow flowing through the pipe 31, and a gas cylinder 33 that applies gas to flow into the pipe 31. There is.

This high-speed electromagnetic pulp 32 is driven by a drive control device (not shown) so that the dropping position of the mercury droplet 9 coincides with the laser irradiation time at a predetermined timing. A high-speed electromagnetic pulp 32 and a gas cylinder 33 are used to apply pressure to the mercury reservoir 3 in a pulsed manner. If the magnitude of the change in pressure applied to the mercury reservoir 3, JP, is sufficiently smaller than the basic pressure P0 of the mercury reservoir 30, then the frequency of pressure fluctuation can be reduced to f
Then, the relationship in equation (2) is the same! ! That applies. In addition, when the repetition rate is small, the conditions of the thin tube etc. are selected so as to satisfy the relationship of equation (3), and the pulse pressure ΔP is applied to the mercury reservoir in synchronization with the laser pulse, and ΔP is adjusted so as to satisfy the equation (4). Once selected, the mercury is ejected from the exit of the tubule in synchronization with the laser pulse. At this time, the diameter of the droplet is determined by the pressure application time Δt, ΔP, etc., but the diameter of the thin tube is the largest factor. The recovery of mercury, etc. is the same as in I/'i Figure 1.

Further, as a configuration for applying pressure to the mercury reservoir, an acoustic element such as a piezo element may be arranged on a part of the inner wall of the mercury reservoir.

In the above embodiments, a laser was used as the beam for plasma generation, but an electron beam was used instead.

Charged particle beams such as light ion beams and heavy ion beams may also be used.

As described above, by using the present invention, it is possible to obtain a high-brightness X-ray source with a simple configuration, with little deterioration caused by using a laser or charged particle beam, with high reversibility, with easy supply and recovery of the target material. can.

An orifice may be used instead of the mercury supply capillary. Also, the supply of mercury does not have to come from the top as shown in the figure.
It may also be supplied from the side. In addition to mercury, metals such as gallium, cesium, indicum, and potassium may be used as the liquid metal. At this time, it is necessary to select the material paying attention to the reaction between the liquid metal and the container, window, etc. The liquid metal supply/recovery system may have any shape as long as it recovers the liquid metal while maintaining pressure balance.

In addition, in order to quickly remove the liquid metal from the window, a method may be used that heats the window or the like to lower the viscosity of the liquid metal or evaporate it.

The inside of the vacuum container in which X-rays are generated does not necessarily have to be vacuum, and if necessary, a gas such as He may be sealed at low pressure. Furthermore, when using a continuous beam (laser), it is sufficient to irradiate the liquid metal at a position before it breaks up into small droplets, without using mechanical vibrations, pressure pulses, etc.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention, FIG. 2 is a circuit diagram, FIG. 3 is a partial sectional view, and FIG. 4 is a sectional view showing the structure of another embodiment of the invention. . 1... Vacuum vessel for plasma generation, 2... Thin tube for supply. 3... Liquid metal reservoir for supply, 4... Laser entrance window,
5... Laser transmission window or beam damper, 6...
・Lens for condensing light, 8...Liquid metal reservoir for recovery, 9...
Liquid metal droplet, 10... Piezo element, 32... High-speed electromagnetic pulp, 33... Gas cylinder, 71... i'1.81... V-Boo light for recovery.

Claims (3)

[Claims] (1) In a device that generates X-rays by irradiating a target with a plasma generation beam and turning it into plasma, a liquid metal is used as the target, and this liquid metal is placed in a plasma generation container in synchronization with the plasma generation beam. A thin tube is suspended from the bottom of the plasma generating container, a liquid metal reservoir is provided at the lower end of the thin tube, and the liquid metal is supplied through the thin tube to reduce the pressure inside the plasma generating container and the liquid metal reservoir. A plasma X-ray generator characterized in that the plasma X-ray generator is configured to move the liquid metal to the liquid metal reservoir and recover the liquid metal so that the pressures are balanced. (2) The plasma X-ray generator according to claim 1, characterized in that the liquid metal is mercury. (3) The plasma X-ray generation device according to claim 1, wherein the plasma generation container is a vacuum container.