JP3490770B2 - Target device and X-ray laser device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a target device for generating X-rays and an X-ray laser device for generating X-rays by causing a plasma phenomenon due to discharge and laser ablation.

[0002]

2. Description of the Related Art Conventionally, as this type of X-ray generator,
There is an X-ray generator using the vacuum spark method shown in FIG. In this device, the capacitor 2 is charged by the power supply 1, and the high voltage generated by this charging is applied between the discharge electrodes in the vacuum container 3. The discharge electrode is composed of a Cu—W cathode 4 and an anode 5, and the inside of the vacuum container 3 is 10 ⁻⁵ To by a pump.
It is evacuated to about rr. Laser light for trigger is applied to the tip of the anode 5 through a hole formed in the cathode 4. This trigger laser light is a YAG laser (100 mJ, 10 MW, 1.06 μm), is focused by the focus lens 6, and is taken into the vacuum chamber 3 through the glass window 7. When a high voltage is applied between the electrodes, a laser beam is focused on the anode 5 to generate surface plasma, which induces electron avalanche between the electrodes. As a result, the cathode 4
And a discharge occurs between the anode 5. Then, the accelerated electron concentrated on the anode 5 evaporates the anode electrode metal material, and this electrode metal material becomes the constituent atoms of the main plasma. The discharge plasma is self-focused by the Z-pinch effect,
Emit characteristic X-rays of the anode metal. This X-ray is
It is taken out from the vacuum container 3 to the outside through the beryllium window 8 having a thickness of 100 μm and is used for a predetermined purpose.

Most conventional X-ray laser devices are based on pumping by a high-power laser shown in FIG. This equipment is being researched at Lawrence Livermore National Laboratory using both NOVA two beams used for inertial fusion experiments by both electron collision excitation and recombination plasma schemes. is there. NO
The second harmonic (λ = 0.53 μm) of the two VA beams (reference numerals 21 and 22) is condensed in a line shape having a width of 300 μm and a length of several mm to several cm. The pulse width of the beam is 100 picoseconds to several nanoseconds in FWHM, and the peak intensity reaches 5TW. A thin metal film is used as the target 23, and a plastic film sandwiched between them is used to increase the plasma density. This makes X-rays
Emitted in the axial direction of the linear plasma. In one axial direction,
A multilayer mirror 24 is placed as a laser cavity to increase the gain. Then, the X-ray laser light is extracted in the other axial direction. For the experiment using neon plasma as the target 23, Se, Sr,
Y, Mo, etc., and Eu, Yb, etc. are used for nickel, and gains have been observed for these targets.

[0004]

However, in the above-described X-ray generator using the vacuum spark method, the anode itself generates X-rays by vaporization by the laser light, and therefore the life of the anode electrode 5 is reduced. Was short. Therefore, it is necessary to frequently replace the anode electrode 5 when the device is repeatedly operated, and this replacement work is very troublesome. Further, since the shape of the anode was deformed by evaporation of the anode itself, the electric field distribution between the cathode and the anode was changed, and the generation position of the gaseous plasma was changed. The fluctuation of the position of this X-ray point source is
The application of the X-ray generator to the X-ray microscope and the like has been greatly restricted.

Further, in the vacuum spark method, there is an advantage that a spark gap switch for causing a discharge between the electrodes is not required, but on the other hand, it is possible to control the timing of distributing the metal atoms between the electrodes and the timing of starting the main discharge. It was difficult. Therefore, power supply 1
The efficiency of converting the electric energy supplied from the X-rays into X-rays was low, and the reproducibility of the X-ray light intensity was poor.

Further, the amount of metal vapor generated in the vacuum spark method is determined mainly by the capacitance value of the capacitor 2 which is the main discharge power source, and the intensity of X-ray generation also depends on this capacitance value. Therefore, it is difficult to individually control the amount of metal vapor generated and the intensity of X-ray generation. Furthermore, since the spatial distribution of the metal vapor between the electrodes is determined by the discharge plasma, it is difficult to control the spatial distribution of the metal vapor generated between the electrodes.

Further, in the conventional X-ray laser device,
Since pumping by a high-power laser is basically used, it is unavoidable that equipment such as the laser for inertial fusion will be diverted. This large-scale installation has brought great limitations to practical applications.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a target device which extends the life of the discharge electrode and reduces the time and effort required for electrode replacement work.

Another object of the present invention is to provide an X-ray laser device capable of controlling the amount of metal vapor generated from a target and improving the efficiency of converting supplied electric energy into X-rays.

[0010]

Therefore, a target device according to the present invention comprises an insulating target substrate having a target for receiving a laser beam to generate a gaseous plasma and having an irradiation surface irradiated with the laser beam. , The target is fixed to the target substrate so as to be opposed to each other, and when a predetermined voltage is applied between the targets, discharge is performed under the interposition of gaseous plasma, and a pair of discharge plasmas are generated. And an electrode body. Further, on the back surface side of the irradiation surface of the target substrate, a control conductor that extends along the arrangement direction of the pair of electrode bodies and is provided with a predetermined potential is arranged. The one electrode body is provided with a first through hole for guiding the X-ray generated between the pair of electrode bodies to the outside.

On the other hand, the X-ray laser device according to the present invention is
A laser light source, a vacuum container having an entrance window for guiding the laser light emitted from the laser light source to the inside, a target arranged in the vacuum container and receiving the laser light to generate gaseous plasma, the laser light The insulating target substrate provided on the irradiation surface to be irradiated and the target are fixed to the target substrate so as to face each other with the target placed therebetween, and when a predetermined discharge voltage is applied between them, the interposition of gaseous plasma It is provided with a pair of electrode bodies which originally discharge and generate discharge plasma, and a power supply means which applies a discharge voltage between the pair of electrode bodies. Further, on the back side of the irradiation surface of the target substrate, a control conductor that extends along the arrangement direction of the pair of electrode bodies and is provided with a predetermined potential is arranged. Of the first electrode body has a first through hole for guiding the X-rays generated between the pair of electrode bodies to the outside, and the other second electrode body of the first electrode body of X is generated between the pair of electrode bodies. It has a second through hole that allows the wire to pass therethrough. An X-ray reflector that reflects the X-rays that have passed through the second through hole to the first electrode body side is arranged near the end of the second through hole.

[0012]

In the target device according to the present invention, the irradiation surface of the target substrate receives the laser light emitted from the outside, and when the laser light is irradiated to the target arranged at this portion, the metal element forming the target is formed. However, it is in the form of gas between both electrode bodies and is uniformly distributed. In this state, when a predetermined voltage is applied between the pair of electrode bodies, discharge plasma can be generated during this period, and the generated plasma causes Z pinch. On the other hand, by applying, for example, a ground potential to the control conductor arranged on the back surface of the target substrate, the generated plasma is stably formed along the control conductor.

Further, in the X-ray laser device according to the present invention, such a target substrate, each electrode body, etc. are arranged in a vacuum container, and plasma generated in the same manner is
Due to the Z-pinch effect, atoms or ions become more ionized thin plasma, and X-rays are generated. The X-ray emitted along the arrangement direction of the two electrode bodies passes through the second through hole of the second electrode body, is reflected by the X-ray reflector, and returns to the first electrode body side. Therefore, the gain of X-rays emitted to the outside through the first through hole of the first electrode body is increased, and laser oscillation occurs.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 schematically shows an X-ray laser device. The X-ray laser device includes a target device T arranged in the vacuum container 31, an excimer laser light source 43 for irradiating the target device T with laser light, a capacitor bank 49 for supplying a discharge voltage described later, and the like. Constitute.

The target device T has a target base 38 formed of an insulator having a size of 5 × 15 mm, and one stripe-shaped germanium is vapor-deposited as a target 39 on this surface. An anode 34 and a cathode 35 are arranged on both sides of the target 39, and the distance between the anode 34 and the cathode 35 is set to 10 mm and fixed to the target base 38.

Further, as enlargedly shown in FIGS. 2 and 3, tunnels 36 for transmitting the generated X-rays are provided inside the anode 34 and the cathode 35, respectively. The tunnel 36 and the target 39 are located on substantially the same straight line. An X-ray reflection mirror 37 for increasing the X-ray gain is provided near the end of the tunnel 36 in the cathode 35.

At the center of the back surface of the target base 38,
A control conductor 40 electrically connected to the anode 34 is provided. The control conductor 40 is used for the target base 3
8 This is for controlling the position of the discharge generated on the front surface to be stable, and the target base 38 is processed into a shape in which the outer edge of the back surface is projected in a frame shape so that the discharge does not go around to the back surface. There is.

On the other hand, the vacuum container 31 for accommodating the target device T therein is provided with an emission window 41 on its upper wall for taking out X-rays generated between the anode 34 and the cathode 35 to the outside of the vacuum container. An entrance window 42 is provided for allowing the laser light emitted from the excimer laser light source 43 to enter the vacuum container 31. The internal pressure of the vacuum container 31 is maintained at a high degree of vacuum of 10 ⁻⁷ Torr by the rotary pump 32 and the turbo molecular pump 33.

A laser pulse is generated from the excimer laser light source 43, and the laser pulse is generated by the mirrors 44 and 45.
The optical path is converted by the lens 46, focused by the lens 46, and then incident on the entrance window 42. The incident laser pulse irradiates the target 39 on the target base 38 in the vacuum container 31 in a predetermined pattern. The laser pulse is output from the laser light source 43 according to the timing at which the trigger signal is output from the trigger signal generator 47.

A current introducing terminal 48 electrically connected to the cathode 35 through a conductive support shaft 55 is provided at the bottom of the vacuum container 31, and this current introducing terminal 48 is provided.
Is electrically connected to one end of a 22 μF capacitor provided inside the capacitor bank 49. Further, the anode 34 is set to the same ground potential as the vacuum container 31, and the vacuum container 31 is connected to one end of the spark gap switch 50. The other end of the spark gap switch 50 is connected to the other end of the capacitors provided in the capacitor bank 49. This capacitor is charged to a predetermined voltage by the charging device 51. The spark gap switch 50 is switched by the high pressure trigger generator 52. This switching is controlled by the trigger signal input from the trigger signal generator 47 via the delay device 53. The delay device 53 delays the trigger signal output from the trigger signal generator 47 by a fixed timing to activate the high voltage trigger generator 52. The trigger signal generator 47 and the delay device 5
3, the high voltage trigger generator 52 and the spark gap switch 50 constitute a discharge controller.

In the X-ray laser device constructed as described above, X-rays are generated as follows.

First, the trigger signal generator 47 causes the laser light source 43 and the delay device 53 to simultaneously operate as shown in FIG.
The trigger signal shown in the graph of (a) is output. The horizontal axis of this graph represents time t, and the vertical axis represents signal voltage. The laser light source 43 emits a laser pulse as shown in the graph of FIG. 4B by this trigger signal input. The horizontal axis of this graph represents time t, and the vertical axis represents laser light intensity. The laser output is about 1 J and the pulse width is 10 ns. The laser pulse emitted from the laser light source 43 is reflected by the mirrors 44 and 45, focused by the lens 46, and the target 3
9 is irradiated in the form of a 1 × 10 mm stripe pattern parallel to the electrode direction. When the target 39 is irradiated, the laser light intensity is about 1 GW / cm.
^{Is 2} . By this laser light irradiation, the germanium element having a density of about 10 ¹⁸ atoms / cm ³ constituting the target 39 is gas-like and uniformly distributed on the surface of the target 39 between the discharge electrodes.

On the other hand, the trigger signal output from the trigger signal generator 47 to the delay device 53 is input to the high voltage trigger generator 52 after being delayed for a certain time. The high voltage trigger generator 52 generates a high voltage pulse at the timing when the delayed trigger signal is input, and outputs the high voltage pulse to the spark gap switch 50. Spark gap switch 50
Closes its switch with the input of this high voltage pulse. The capacitors in the capacitor bank 49 are charging devices 5.
1 has been charged in advance to a high voltage of 30 kv, and the charging energy is 10 kJ. By closing the spark gap switch 50, the electric charge accumulated in the capacitor bank 49 is discharged, and the discharge current shown in the graph of FIG. 4C is generated. The horizontal axis of the graph shows time t, and the vertical axis shows the discharge current value. This discharge current causes a discharge between the anode 34 and the cathode 35 in the vacuum container 31. The start of discharge is delayed by the delay device 53 from the trigger signal output from the trigger signal generator 47 by the time T shown in the figure.

On the surface of the target 39 between the anode 34 and the cathode 35, the gaseous plasma separated from the target 39 is laser ablated and uniformly distributed. Therefore, when the spark gap switch 50 is closed and electric discharge occurs during this period, electric discharge plasma is generated on the surface of the target 39, and the electric discharge plasma causes Z pinch. Then, the control conductor 4 on the back surface of the target base 38
By the action of 0, the position of the Z-pinch discharge plasma is stabilized at a position along the control conductor 40. As a result, characteristic X-rays (wavelength 230 angstrom) of Ge ions for neon, which is a constituent element of the target 39, are generated. This X-ray is shown in the graph of FIG. 4D, where the horizontal axis represents time t and the vertical axis represents X-ray intensity. Each tunnel 3
The X-rays emitted in the axial direction connecting the 6 and the target 39 pass through the tunnel 36 of the cathode 35, reach the X-ray reflection mirror 37, and are reflected here. The reflected X-rays return to the anode 34 side, and as a result, the gain of the emitted X-rays is improved and laser oscillation occurs. Oscillated X
The wire is taken out of the vacuum container 31 through the emission window 41.

In the present embodiment, the metal vapor for generating X-rays uses a laser ablation target 39 provided separately from the anode and the cathode which are discharge electrodes. Therefore, unlike the conventional X-ray generator using the vacuum spark method in which the anode itself is used as the source of metal vapor, the discharge electrode is not consumed and the life of the electrode is extended. Therefore, even if X-rays are repeatedly generated, the interval at which the electrodes need to be replaced becomes long, and the labor for the electrode replacement work can be greatly saved. In addition, the anode is deformed and X
The position of the line source does not fluctuate, and the control conductor 4
By the action of 0, the position where plasma is generated becomes more stable, so that stable X-rays can be obtained.

Further, after the gaseous plasma is generated between the discharge electrodes composed of the anode and the cathode by the discharge control device, a high voltage is applied between the discharge electrodes with a predetermined delay and a plasma pinch phenomenon is caused. Is generated and X-rays are generated. That is, after the constituent elements of the target 39 are distributed between the discharge electrodes, a discharge is generated, and the discharge timing is set by the delay device 53 to an arbitrary timing optimum for the discharge. Therefore, the generation timing of the metal vapor generated by the laser pulse irradiation from the laser light source 43 and the main discharge timing generated by discharging the charge accumulated in the capacitor bank 49 are appropriately controlled individually. Therefore, it is possible to convert the electric energy into X-rays more efficiently.

The amount of metal vapor generated from the target 39 is controlled by the energy and wavelength of the laser light output from the laser light source 43, the irradiation area of the laser light on the target 39, etc., and serves as a main discharge power source. It does not depend on the capacity value of the bank 49. Further, the spatial distribution of the metal vapor between the discharge electrodes is controlled to some extent by changing the irradiation pattern of the laser light on the target 39. As a result, the amount of metal vapor generated and the intensity of X-ray generation can be individually controlled, and the reproducibility of the light intensity of X-rays generated is improved. Here, the optimum initial distribution of the target element between the discharge electrodes is the optimum laser light wavelength, laser pulse width, laser energy, laser irradiation distribution corresponding to each target element to be adopted, and the composition of the target 39 itself ( This can be achieved by appropriately selecting a thin film, liquid, etc.

[0029]

As described above, in the target device according to the present invention, the target provided on the target substrate is used as the source of the gaseous plasma.
The electrode body itself for discharging is not consumed, and the life of the electrode body is extended. Therefore, even if X-rays are repeatedly generated, the interval at which the electrodes need to be replaced becomes long, and the labor of the electrode replacement work can be greatly reduced.

Further, in the X-ray laser device according to the present invention, the position where the discharge finally occurs and the Z-pinch plasma is stabilized is determined by the position of the control conductor provided on the back surface of the target base. Therefore, it is possible to improve the efficiency of converting the electric energy into X-rays, and the fluctuation of the light emitting source is reduced.

In addition, the X-rays emitted along the arrangement direction of the pair of electrode bodies pass through the second through holes of the second electrode body and pass through the X-rays.
Since it is reflected to the side of the first electrode body by the line reflector, the gain of X-rays emitted to the outside via the first electrode body can be increased and laser oscillation can be generated. As a result, it is possible to provide an X-ray laser device that can obtain an extremely stable plasma position and a strong X-ray intensity.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a configuration of an X-ray laser device according to an embodiment.

FIG. 2 is a vertical sectional view showing a target device according to the present embodiment.

FIG. 3 is a perspective view of the target device shown in FIG. 2 as viewed from the back side.

FIGS. 4A and 4B are graphs showing signal waveforms of various parts of the X-ray laser device.

FIG. 5 is a sectional view showing an X-ray generator using a conventional vacuum spark method.

FIG. 6 is a diagram showing an outline of an X-ray laser device using a conventional plasma phenomenon.

[Explanation of symbols]

31 ... Vacuum pump, 32 ... Rotary pump, 33 ... Turbo molecular pump, 34 ... Anode (first electrode body), 35
... cathode (second electrode body), 36 ... tunnel (through hole), 37 ... X-ray reflection mirror, 38 ... target base, 39 ... target, 40 ... conductor (control conductor), 41
... window, 42 ... laser window, 43 ... YAG laser light source, 4
4 ... Mirror, 45 ... Half mirror, 46 ... Lens, 47
... trigger signal generator, 48 ... current introducing terminal, 49 ... capacitor bank, 50 ... spark gap switch, 5
1 ... Charging device, 52 ... High voltage trigger generating device, 53 ... Delay device

─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-63-304597 (JP, A) JP-A-63-304596 (JP, A) JP-B-53-29078 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) H05H 1/24 H05G 1/02 H01J 35/08 H05G 2/00

Claims (6)

(57) [Claims] 1. A target for generating a gaseous plasma in response to a laser beam and an insulating target substrate provided on an irradiation surface on which the laser beam is irradiated, and the target is disposed so as to face each other. The target substrate is fixed, and when a predetermined voltage is applied between them, discharge is performed under the interposition of the gaseous plasma, and a pair of electrode bodies that generate discharge plasma are provided, and the irradiation on the target substrate is performed. On the back side of the surface,
A control conductor that extends along the arrangement direction of the pair of electrode bodies and is provided with a predetermined potential is arranged. One of the pair of electrode bodies is one of the pair of electrode bodies. A target device having a first through hole for guiding X-rays generated therebetween to the outside. 2. The other second electrode body of the pair of electrode bodies has a second through hole for passing X-rays generated between the pair of electrode bodies. The target device according to claim 1, wherein an X-ray reflector that reflects the X-rays that have passed through the second through-holes to the first electrode body side is disposed near the end of the target device. 3. The target device according to claim 1, wherein the control conductor is electrically connected to one of the first and second electrode bodies that serves as an anode. 4. A laser light source, a vacuum container having an entrance window for guiding the laser light emitted from the laser light source to the inside, and a vacuum container disposed in the vacuum container and receiving the laser light to generate a gaseous plasma. The target is fixed to the insulating target substrate provided on the irradiation surface irradiated with the laser light and the target substrate so as to face the insulating target substrate, and a predetermined discharge voltage is applied between them. When the discharge is performed, a discharge is performed under the interposition of the gaseous plasma, and a pair of electrode bodies for generating discharge plasma, and a power supply means for applying the discharge voltage between the pair of electrode bodies are provided, the target On the back side of the irradiation surface of the substrate,
A control conductor that extends along the arrangement direction of the pair of electrode bodies and is provided with a predetermined potential is arranged. One of the pair of electrode bodies is one of the pair of electrode bodies. It has a first through hole for guiding the X-ray generated between the two, and the other second electrode body has a second through hole for passing the X-ray generated between the pair of electrode bodies. An X-ray laser device having an X-ray reflector that reflects the X-rays that have passed through the second through hole toward the first electrode body near the end of the second through hole. 5. The X-ray laser device according to claim 4, wherein the control conductor is electrically connected to one of the first and second electrode bodies that serves as an anode. 6. A discharge control means for controlling both an application timing of the discharge voltage applied from the power supply means to the pair of electrode bodies and an irradiation timing of laser light emitted from the laser light source to the target. The X-ray laser device according to claim 4, further comprising: