JPS61140042A - Reflecting type x-ray generating tube - Google Patents

Abstract

PURPOSE:To strengthen a reflecting target and prevent temperature of the target from being raised, and to thereby form a high power ultra-short X-ray pulse generator tube by supporting the target with an anode exposed in part externally of a vessel. CONSTITUTION:A spherical X-ray entrance window 2 is fixedly mounted frontally of a cylindrical vacuum glass vessel 3, and a photoelectric surface 1 is formed interiorly of said window. A converging electrode 4 is arranged interiority of the vacuum glass vessel 3, said converging electrode forming an electron lens serving to project photoelectrons produced from the photoelectric surface 1 in a prescribed direction. A target 5, sufficiently thick, fixedly mounted on an anode electrode 7 is disposed at a focal position where spreading of the electron beams 11 is made minimum with use of the converging electrode 4. The anode 7 is fixed on the vessel with part thereof exposed externally of the vessel, whereby temperature of the target 5 can be prevented from being raised by forcedly cooling that portion.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a reflection type X-ray generating tube capable of generating ultra-short X-ray pulses with large power.

(Prior art) A normal X-ray generator is configured to heat a cathode with a heater to generate thermoelectrons, form a narrow electron beam using an electrostatic focusing system, and irradiate a target with it to generate X-rays. ing.

Although there is a strong desire to perform various measurements using sharp pulsed X-rays, X-ray generators using hot cathode-type electrodes are not suitable for high frequency response.

In order to meet the above requirements, the inventor of the present invention has already proposed an X-ray generating tube using a photocathode (photocathode) as an electron source.

FIG. 4 is a sectional view showing the gist of the X-ray generating tube according to the proposal.

That is, an electron beam excited by an ultrashort light pulse 8 of a laser light source (not shown) and generated from a photocathode 1 is focused by a focusing electric field wA4, becomes a minute spot, and irradiates the X-ray target 5'.

The X-rays generated by the electron beam 11 first pass through the X-ray target 5 itself, and then pass through the beryllium metal window 6 and are taken out of the container.

This X-ray is an X-ray pulse 1 corresponding to the ultrashort optical pulse 8.
It becomes 0.

The X-rays generated in this manner have a sharp pulse shape and can be used in various applications.

However, in the apparatus with the above configuration, the thickness of the target 5 cannot be made very thick in order to reduce the attenuation of the generated X-rays when they pass through the target 5 itself.

Therefore, the electron beam power (voltage×current) cannot be increased very much, so there is a problem that the output power of X-rays is limited and a large output cannot be obtained.

A titanium film of about 10 μm is used as the target 5 of the above-mentioned device, but in this case, the electron beam acceleration is
KV, the upper limit of the current amount is approximately 10 μA.

If a beam current higher than this is supplied, the target 5 will become red hot and a hole will be formed.

(Object of the Invention) An object of the present invention is to provide a reflection type X-ray generator tube capable of generating ultra-short X-ray pulses with large output.

(Structure of the Invention) In order to solve the above object, a reflective X-ray generating tube according to the present invention includes a vacuum container, a photocathode formed in the vacuum container, and a method for directing photoelectrons generated by the photocathode in a fixed direction. project,
and an electron lens for focusing the electron beam as a minute spot on the target, a reflective target that generates X-rays when irradiated with the spot-shaped electron beam formed by the electron lens, and an anode that supports the target in the container. and a thin metal plate that allows the X-rays to easily pass through to the outside of the container.

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1 will be explained in detail.

FIG. 1 is a sectional view showing an embodiment of a reflection type X-ray generating tube according to the present invention.

A spherical X-ray entrance window 2 is placed in the front of a cylindrical vacuum glass container 3.
is fixed, and a photocathode 1 is formed on its inner surface.

A focusing electrode 4 forming an electron lens for projecting photoelectrons generated by the photocathode 1 in a fixed direction is arranged inside the vacuum glass container 3.

A sufficiently thick target 5 fixed to the anode electrode 7 is placed at a focal position where the electron beam 11 spreads minimally by the focusing electrode 4.

The anode 7 is fixed to the container, and a portion is exposed outside the container.

The surface of the target 5 is inclined about 1° with respect to the incident line of the electron beam 11.

A window 6 made of a thin metal plate (Be) with a thickness of 500 μm or less is provided so that the X-rays 9 generated on the surface of the target 5 are transmitted to the outside of the container, and the X-rays 9 pass through the window 6. and removed from the container.

The surface of this window is the X-ray 9 generated on the surface of the target 5.
It is installed at right angles to.

The material of the target 5 is determined depending on the required X-ray energy.

Next, the target material and the characteristic X-ray energy of that material are shown.

Titanium (Ti) 4.5KeV Vanadium (
V) 4.96KeV Chromium (Cr)
5.42KeV iron (Fe) 6.
42KeV cobalt (Co) 6.92
KeV Nickel (Ni) 7.47KeV Calcium (Ca) 8.04KeV As mentioned above, in the present invention, a part of the anode 7 is exposed outside the container, so this part is forcibly cooled to lower the temperature of the target 5. rise can be limited.

FIG. 2 is a sectional view showing an embodiment of an anode cooling structure.

In this embodiment, cooling fins 12 are provided on the anode 7, and the cooling fins 12 are forcibly cooled by an air cooling fan 13.

FIG. 3 is a sectional view showing another embodiment of the cooling structure for the anode section.

In this embodiment, a Peltier element 15 is provided on the end face of the anode 7. Power for generating the Peltier effect is connected to this Peltier element 15 via a terminal 16.

A water cooling pipe 17 having a cooling water inlet/outlet 19 is brought into contact with this Peltier element 15 to further increase the cooling effect.

(Effects of the Invention) As explained in detail above, the X-ray generating tube according to the present invention has
Since the reflective target is supported in the container by the anode, the target itself can be made stronger compared to the case where the above-mentioned pass-through target is used.

Further, although the anode supporting the target in the container has a heat dissipation effect, it can limit the temperature rise of the target 7).

Furthermore, since the anode can be exposed outside the container and forcibly cooled, the electron beam power can be significantly increased compared to the conventional transmission target method.

The resulting output limit is determined by the electron flow emission capability of the photocathode.

In conventional devices, the upper limit of photocurrent was about 10 pA, but in the above-mentioned forced cooling example, by increasing the area of the photocathode and increasing the electric field strength in front of it,
It can be increased from 1 mA to 10 mA.

Furthermore, since the generated X-rays do not need to pass through the target itself, the efficiency of extracting them to the outside can be significantly increased.

Since the X-ray generating tube according to the present invention uses a photocathode as an electron source like the previous application by the present inventor, it can similarly obtain high-speed pulsed X-rays.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a reflection type X-ray generating tube according to the present invention. '$2 rl! J, t7/f'gRO)
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It is a □ side view. FIG. 3 is a sectional view showing another embodiment of the cooling structure for the anode section. FIG. 4 is a sectional view showing an example of the configuration of the X-ray generator according to the previous invention. 1... Photocathode 2... Light incidence window 3... Vacuum glass container 4... Focus electrode 5... Target 6... Be window 7... Anode electrode 8
...Light pulse 9...X-ray 10...X
Line pulse 11...Electron beam 12...Air cooling fin 13...Air cooling fan 14...Air flow 15...
・Peltier element 16...Peltier element current terminal 17...Water cooling pipe 18...Water inlet 19...
water outlet

Claims (3)

[Claims] (1) a vacuum container, a photocathode formed in the vacuum container, and projecting photoelectrons generated by the photocathode in a certain direction;
and an electron lens for focusing the electron beam as a minute spot on the target, a reflective target that generates X-rays when irradiated with the spot-shaped electron beam formed by the electron lens, and an anode that supports the target in the container. and a thin metal plate that easily transmits the X-rays to the outside of the container. (2) A reflection type X-ray generating tube according to claim 1, wherein a part of the anode supporting the target is exposed to the outside of the vacuum container so that it can be cooled. (3) The reflective X-ray generating tube according to claim 1, wherein the thin metal plate is a beryllium plate.