JPH03257745A - X-ray generating device - Google Patents

Abstract

PURPOSE:To equalize the current distribution of linear electron beams in the longer direction when short pulse voltage is applied by branching each feeder line symmetrically from a point where pulse voltage is applied up to a cathode at all times, and thereby making each individual inductance and capacitance of the feeder lines identical. CONSTITUTION:A feeder line 11 is branched at a point 6 where voltage is applied, that is, a first step symmetrically into two directions. At a second step, the tip ends of branches at the first step are furthermore branched symmetrically into two directions respectively so as to be formed into four feeder lines. And so on, the feeder lines of 2n ends which are symmetrically branched respectively, are made up at a n-th step. This thereby allows each individual inductance and capacitance of the feeder lines which are determined by their own geometric location to be identical, and applied voltage of each cathode 2 at tip end sections of the feeder lines is in an identical wave form so that each current value of electron beams emitted from the respective cathodes is thereby identical. By this constitution, the space distribution of linear electron beams is much more equalized, and the dosage of X-rays in a linear irradiation area is thereby much more equalized.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an electron gun for an X-ray generator, and in particular to an electrode for improving the uniformity of the spatial distribution of a pulsed electron beam emitted from the electron gun. and related to power supply lines.

[Conventional technology]

FIG. 2 shows an X-ray generator for irradiating a long and narrow region with short pulses of X-rays. This device consists of a Naifetsu cathode 2 and an anode (target) for generating a linear electron beam.
3 constitutes a cold cathode electron gun.

Bremsstrahlung X-rays generated at the anode (target) 3 are extracted from the vacuum vessel 4 through the X-ray transmission window 7. In order to generate an electron beam, a negative pulse voltage is applied from a pulse power source 8 to a plate-shaped power supply line 1 via an introduction terminal 6 in an insulator 5. At this time, differences occur in the current paths formed on the plate-shaped power supply line from the point where the pulse voltage is applied to each point in the longitudinal direction of the knife cathode. That is, as shown in FIG. 3, there is a difference between the inductance and capacitance in the current path near the center of the feed line 1 and the inductance and capacitance in the current path near the ends. For this reason,
When a pulse voltage is applied, as shown in FIG. 4, the current distribution becomes uneven at the center and end portions of the feed line, and there is a problem in that a uniform electron beam cannot be obtained from the cathode portion in the longitudinal direction.

Traditionally, methods for solving this problem have been described in Soviet Journal Quantum Electron 14 (
3), 1984, pp. 356-359 (Sov
, J. Quantum Electron, 14 (
3).

1984, pp. 356-359). In the above paper, in order to apply a pulse voltage uniformly to a long and narrow discharge region in a laser device, a peaking capacitor is arranged in a laser chamber along the longitudinal direction of an electrode. This peaking capacitor has the role of accumulating charge during the time from application of a pulse voltage until the start of discharge between the electrodes, and supplying charge to the discharge section in a short time after the start of discharge. A large number of secondary power sources (peaking capacitors) can be installed along the longitudinal direction of the electrode.

Note that related devices of this type include, for example,
Applied Physics Letters 48(19), 19
1986, pp. 1237 to 1239 (^pp1.
Phys, Lett, VoQ, NdI3.1986
There is an X-ray generating device described in ゜pp1237-pp1239).

[Problem to be solved by the invention]

Since the above conventional technology is used for high-pressure gas laser equipment, it does not take into consideration the use in high vacuum areas, and in equipment that requires high vacuum such as cold cathode electron guns, the peaking capacitor is used to release gas. There was a problem that the required degree of vacuum could not be obtained. In addition, since the area near the electrodes of the X-ray generator is irradiated with xg at a high dose rate, the peaking capacitor is exposed to radiation, so processing such as X-ray shielding must be done internally, making the equipment larger and more complex. There was a problem.

An object of the present invention is to make the current distribution in the longitudinal direction of the linear electron beam uniform when a short pulse voltage is applied when a cold cathode electron gun generates the linear electron beam.

Another object of the present invention is to provide an apparatus that achieves the above object without incorporating circuit elements in the vacuum vessel that are a source of outgassing or require X-ray shielding.

[Means to solve the problem]

In order to achieve the above object, the present invention branches the power supply line from the point where the pulse voltage is applied to the knife-etched cathode symmetrically in two directions from one point so that the whole forms a tournament tree. A power supply line is constructed by combining busbars.

In addition, in order to achieve the above object, the present invention makes a cut (slit) in the feeder line of the board to separate the current path in the feeder line, and the current path from the point where the pulse voltage is applied to the knife etched cathode is cut. The current path may be constructed by symmetrically branching the current path in two directions from one point and making cuts (slits) in a single plate-shaped power supply line so as to form a tournament tree as a whole.

In order to achieve the above-mentioned other objects, the present invention does not incorporate circuit elements that become a gas emission source or require X-ray shielding in the vacuum container, and only the shape of the power supply line is incorporated in the two types of means. This has been changed from the conventional plate-shaped feeder cable and has been improved.

[Effect]

FIG. 5 shows a power supply line 11, a divided knife-etched cathode 2, and an anode (target) 3 according to the present invention. Power line 1
1 is bifurcated symmetrically at a voltage application point 6 (first stage). In the second stage, the branch destinations in the first stage are further branched in a two-way symmetrical manner to form four power supply lines. Similarly, in the n-th stage, 2n feeder lines are each branched symmetrically.

For this reason, the inherent inductance and capacitance of each feeder line determined by the geometrical arrangement become equal, and the voltage applied to each cathode 2 at the tip of the feeder line is applied with the same waveform, resulting in emission from each cathode 2. The current values of the electron beams also become equal.

The emitted electron beam is discrete, but as shown in Figure 4, the current value of the electron beam does not differ between the longitudinal center and the ends.The electron beam collides with the anode (target). X-rays are generated, but in the energy range of the X-rays used in this device, they are emitted in all directions from the source, so the discrete X-ray sources are dispersed somewhat densely in the longitudinal direction. If so, xi overlaps and becomes uniform in the irradiation area.

FIG. 6 shows a power supply line 13 and a divided knife-etched cathode 2 according to the present invention. Anode (target) 3 is shown. Power line 1
3, a cut (slit) is made in the conductive plate to divide the current path. As in the case shown in Figure 5, the inductance and capacitance of each current path are equal, and each cathode 2
The applied voltages are applied with the same waveform, and as a result, the current values of the electron beams emitted from each cathode 2 are also equal.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a plan view (
a) and a cross-sectional view (b). In the apparatus, a cathode 2 and a pJh electrode (target) 3 are installed in a vacuum container 4, and constitute a cold cathode electron gun.

An X-ray transmission window 7 is provided below the anode (target) 3 for irradiating X-rays to the outside. The anode (target) and the vacuum vessel are grounded, and when a negative high voltage pulse is applied from the pulse power source 8 to the feeder line 1 inside the vacuum vessel 4 through the introduction terminal 6 into the insulator 5, Electrons are emitted from the tip of the connected cathode 2. Electrons accelerated by the electric field between the cathode and the anode collide with the anode (target) 3 and generate bremsstrahlung X-rays. At this time, in the eight feeder lines 1 branched symmetrically from the introduction terminal 6, the inductance and capacitance of each feeder line are equal, and the electron beam current values emitted from each cathode portion 2 are also equal. The electron beams emitted from each cathode section 2 are discrete in the longitudinal direction, but the current value of the electron beams is the same for both the central cathode and the end cathodes. The X-rays generated when the electron beam collides with the anode (target) 3 overlap in the irradiation area and are made uniform, resulting in a substantially uniform X-ray dose both at the center and at the ends in the longitudinal direction.

Another embodiment of the invention is shown in FIG. Power supply [9
uses a single conductive plate and creates eight divided current paths by making slits. Since the current path between the point 6 where a negative high voltage pulse is applied and the cathode 2 branches symmetrically like the feeder line 1 shown in FIG. 1, the specific inductance and capacitance of each current path are equal. The electron beam current values emitted from each cathode section 2 also become equal.

Another embodiment of the invention is shown in FIG. divided cathode 2
is fixed on an insulator 9, and a cable 1o is connected from the introduction terminal 6 to each cathode. All cables have the same inherent impedance. As a result, the inductance and capacitance up to each cathode are balanced, and a uniform electron beam can be obtained as a whole.

Another embodiment of the invention is shown in FIG. In this case, the cathode power supply line 14 is shaped like a sector, the distance from the introduction terminal 6 to the cathode 2 is equal, and the impedance is the same at both the center and the ends.

As shown in FIG. 9, it is necessary to form the anode in an arc shape in accordance with the arc of the cathode, and to equalize the distance between the cathode and the anode.

Another embodiment of the invention is shown in FIG. This is done by providing a recess in the center of the flat feeder line 12 up to the cathode 2 and reducing the cross-sectional area of the conductor at the center, so that the impedance at the center is about the same as the impedance at the ends. . FIG. 11 is an example of a cross-sectional view of this power supply line. This balances the impedance,
A uniform electron beam can be obtained.

FIG. 12 shows a laser pre-ionization system using an X-ray generator using the present invention. X-rays generated at the anode 3 of the X-ray generator pass through the X-transparent window 7 and are irradiated into the laser chamber. In the laser chamber, the laser gas between the electrodes is pre-ionized by X-rays incident from the back side of one of the electrodes.

〔Effect of the invention〕

According to the present invention, since the spatial distribution of the linear electron beam is made uniform, the uniformity of the X-ray dose in the linear irradiation area is improved.

Furthermore, since no circuit element that would become a gas generation source is built into the vacuum container, it can be used in the high vacuum region required by cold cathode electron guns.

Furthermore, since no circuit elements whose performance would be degraded by X-ray irradiation are built into the vacuum container, no internal X-ray shielding is required.

Furthermore, in the method of making cuts (slits) in two conductive plates, manufacturing is easy because bus bars are combined.

[Brief explanation of drawings]

Figure 1 is a plan view (, ) and a cross-sectional view ( ) of an embodiment of the present invention.
b), Figure 2 is a plan view (,) and cross-sectional view (b) of the conventional example.
, FIG. 3 is a plan view showing the current path of the conventional example, FIG. 4 is an explanatory diagram of the current distribution of the conventional example, FIGS. 5 and 6 are plan views of the power supply line of the present invention, and FIG. Figure 8, Figure 9, Figure 10,
FIG. 11 is a plan view, a sectional view, and a perspective view of the present invention.
FIG. 2 is a sectional view of a system for laser pre-ionization using an X-ray generator using the present invention. 10... Cable, 11... Power supply line (busbar),
12... Feeding line (flat plate), 13... Feeding line (slit), 14... Feeding line (fan-shaped), 2... Cathode, 3...
...Anode, 4...Vacuum container, Death...Insulator, 6...
・Introduction terminal, 7...Figure 1 (α) (b) Figure 2 (α) (b) Funeral diagram Figure 5 Figure 7 voltage marks m, Figure 7 (α) (b,) Figure 8: Figure '-10 Atsushi Figure 11 AJ side arrows a, z

Claims (1)

[Claims] 1. In a cold cathode electron gun that generates a linear electron beam, the feeder lines from the point where a pulse voltage is applied to the cathode are always branched symmetrically, and each feeder line has its own characteristic characteristics. X characterized by equal inductance and capacitance
Line generator. 2. The X-ray generator according to claim 1, wherein the power supply line is divided and each of the power supply lines forms a tournament tree. 3. In claim 1, a cut is made in the plate-shaped feeder line from the point where the pulse voltage is applied to the cathode to divide the current path in the feeder line, and each current path is separated from the point where the pulse voltage is applied. An X-ray generator that always branches symmetrically and has equal inherent inductance and capacitance for each current path. 4. In a cold cathode electron gun that generates discrete linear electron beams, the cathode is divided and each cathode is connected from the feeding point to each cathode with a cable having the same specific impedance.
Line generator. 5. An X-ray generator characterized in that, in a cold cathode electron gun that generates a linear electron beam, the feed line from the point where a pulse voltage is applied to the cathode is made into a fan-shaped flat plate. 6. In a cold cathode electron gun that generates a linear electron beam, the feeder line from the point where the pulse voltage is applied to the cathode is constructed from a conductor flat plate, and by changing the thickness of this conductor flat plate, the central part An X-ray generator characterized by balancing the impedance of the end portion and the end portion. 7. A laser preionization system using the X generator according to claim 1, 2, 3, 4, 5 or 6.