JP5853847B2 - Measuring method and apparatus for particle beam distribution - Google Patents

Description

  The present invention relates to a particle beam distribution measuring method and apparatus, and more particularly to a particle beam distribution measuring method and apparatus suitable for measuring the distribution of an electron beam generated from an electron gun of an electron beam irradiation apparatus. About.

  In the electron beam irradiation apparatus, when the electron beam intensity fluctuates spatially in the electron beam irradiation region, the irradiation amount of the irradiated object varies locally. Therefore, it is desirable to measure the spatial distribution of the electron beam dose with high accuracy. Therefore, in Patent Document 1, a rod-like collector electrode (current measuring element) is provided outside the irradiation window of the electron beam irradiation apparatus along the short side of the irradiation window, and the collector electrode is translated in the long side direction of the irradiation window. The distribution of the electron beam is measured from the current flowing through the collector electrode.

  Further, in Patent Document 2, a plurality of current measuring elements are two-dimensionally arranged immediately below an electron beam irradiation window, and the current flowing through each current measuring element is measured. It is described to measure the distribution.

Japanese Patent Laid-Open No. 11-248893 JP 2001-221897 A

  However, in the scanning measurement described in Patent Document 1, it takes time to perform the measurement. In addition, the scanning measurement described in Patent Document 1 and the array measurement described in Patent Document 2 are the same in size of the current measuring element. Since only (size) resolution can be obtained, the resolution is poor. In the multi-array described in Patent Document 2, the resolution increases when a large number of small elements are arranged finely, but the measurement is complicated and a very expensive apparatus or system is obtained.

  On the other hand, as in the reference example shown in FIG. 1, electrons 12 emitted from a cathode electron gun (hereinafter referred to as a cathode electron gun) 10 are transferred to a transparent conductive glass (hereinafter referred to as anode glass) 16 as an anode. It is conceivable to measure the fluorescence distribution from the back side (the lower side in the figure) of the anode glass 16 by colliding with the phosphor 14 applied on the vacuum side of the surface having the property.

However, since the phosphor 14 is applied to the vacuum side, when gas is released from the phosphor 14 and the degree of vacuum decreases, discharge occurs and the cathode deteriorates rapidly. Further, under high voltage and high current, the anode glass 16 is damaged and the vacuum is broken, so that there are problems such as difficulty in measurement. Therefore, in this method, the maximum voltage is 20 to 30 kV, the average current density including pulses and scanning is about 10 μA / cm ² , and the maximum heat input to the anode glass 16 is 0.2 to 0.3 W / cm ^2. It can only be applied up to the level.

  The present invention has been made to solve the above-mentioned conventional problems, and it is an object to enable easy and highly accurate distribution measurement of a high-voltage, high-power particle beam without using a current measuring element. To do.

The present invention relates to a method for measuring the distribution of particle beams irradiated from a particle beam irradiation apparatus, wherein the particle beam is applied to a boundary between a vacuum and an atmosphere of a particle beam irradiation unit of the particle beam irradiation apparatus or an atmosphere side of a transmission window. sequentially arranged a metal plate and a scintillator and a camera for receiving all of the particle beam emitted to the atmosphere from the irradiation unit, all colliding a particle beam to said metal plate to generate X-rays, generated in the metal plate X line, was converted into light by the scintillator is the light generated from the scintillator as capture by the camera that has solved the above problems.

The present invention is also a device for measuring the distribution of particle beams irradiated from a particle beam irradiation device, wherein the particle beam irradiation unit of the particle beam irradiation device has a vacuum-atmosphere boundary or a transmission window on the atmosphere side . a metal plate subjected to any particle beam emitted to the atmosphere from the particle beam irradiation section, and the scintillators to convert the X-rays generated in the metal plate on the light by the collision of all of the particle beam, from said scintillator It is an object of the present invention to provide a particle beam distribution measuring apparatus comprising a camera that captures generated light in sequence .

  Here, a means for cooling the metal plate may be further provided.

  According to the present invention, the particle beam is not received by a small current measuring element, but is received by a single large metal plate. In addition, the current generated by the particle beam is not measured, but the generated X-ray is instantaneously measured by a camera using a scintillator arranged on the atmosphere side. As a result, the entire irradiation distribution can be measured instantaneously at high speed and with high resolution on the atmosphere side, and is inexpensive.

Sectional drawing which shows the structure of the reference example which measures an electron beam distribution with the fluorescent substance apply | coated to anode glass Sectional drawing which shows embodiment of particle beam distribution measurement which concerns on this invention Cross-sectional view showing a state where X-rays are also generated Sectional drawing and top view which show the structure of the Example of a particle beam distribution measuring apparatus. The figure which similarly shows the constitution of the electron gun Figure showing an example of measurement results

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the present embodiment, as shown in FIG. 2, the electrons 12 generated by the cathode electron gun 10 are received by a metal plate 20 disposed on the boundary between the vacuum and the atmosphere or on the atmosphere side of the transmission window 18. A scintillator 22 that generates fluorescence when X-rays enter is disposed on the opposite side of the metal plate 20 from the electron collision portion, and the light generated from the scintillator 22 is captured by a high-sensitivity camera or a normal CCD camera 24. In the figure, reference numeral 25 denotes a camera hood of the CCD camera 24.

  FIG. 3 shows a state in which braking or characteristic X-rays 21 are generated in the metal plate 20. As the material of the metal plate 20, for example, a SUS304 stainless steel plate, copper, a nickel-based alloy, or a material obtained by evaporating tungsten on the vacuum side in order to increase the X-ray dose can be used. The thickness of the metal plate 20 is optimized in consideration of the X-ray divergence and the cooling property of the metal plate depending on the acceleration energy and energy density of the electron beam, but is 0.1 in the range of acceleration energy of 20 to 200 keV. About -5.0 mm is preferable. X-rays are divergent, so that the thinner the plate thickness, the higher the resolution of fluorescence measurement possible, but the more difficult it is to heat and cool the electron beam. On the other hand, the thicker the plate, the better the cooling performance but the lower the resolution. It is necessary to select the optimum plate thickness according to the applied current density. Further, the higher the energy of the electron beam, the more the X-ray converges and the resolution becomes higher, but it is necessary to increase the plate thickness in consideration of heating and a high X-ray dose. From the viewpoint of leakage X-ray management and safety, it is better to increase the plate thickness and reduce the atmospheric X-ray dose.

  As the scintillator 22, for example, a general scintillator commercialized for medical use or industrial use, an X-ray phosphor, a medical X-ray intensifying screen, or the like can be used. If it is expensive but the energy density is high, it is better to use a ceramic type scintillator.

  As the CCD camera 24, for example, a general monochrome camera can be used, but a cooled high-sensitivity CCD camera used for astronomical observation or the like or a camera that can easily perform digital processing is preferable.

  The configuration of an embodiment of the electron beam distribution measuring apparatus according to the present invention is shown in FIGS. 4 (a) (sectional view) and (b) (plan view). In the figure, 26 is a mounting flange, 28 is a lead glass for preventing X-rays from leaking to the outside, 30 is a cooling pipe, and 31 is a camera dark box for photographing.

  In the present embodiment, the cathode electron gun has seven electron gun units 10a in which 37 cathode electron guns 10 made of, for example, CNT (carbon nanotube) are arranged in a honeycomb shape as illustrated in FIG. Accordingly, the metal plate 20 also has a portion corresponding to the set of cathode electron guns 10 for each electron gun unit 10a and a portion of the passage 20a through which cooling water flows between the electron gun units 10a. And have. In the figure, 10b is an electron gun holder.

  By providing the cooling water passage 20a in this way, the metal plate 20 can be cooled according to the load.

  The measurement result of an Example is shown to Fig.6 (a), (b). FIGS. 6A and 6B show electron beam measurement results with an acceleration voltage of 40 kV and an output current of 3.5 mA (output 140 W). As the metal plate 20 for generating X-rays, a 0.5 mm thick SUS304 stainless steel plate is used, and as the scintillator 22, X-ray phosphor DRZ-HIGH (phosphor for use in a digital X-ray imaging apparatus) : Gadolinium oxysulfide). FIG. 6A shows the result when the distance between the metal plate 20 and the scintillator 22 is 10 mm, and is a defocused image. This is because the electron beam energy is low at an acceleration voltage of 40 kV, and X-rays diverge at an angle of about 30 to 45 degrees. FIG. 6B shows the result when the distance between the metal plate 20 and the scintillator 22 is about 1 mm, and the electron beam distribution from each of the 37 × 7 = 259 electron gun units 10 can be accurately measured. The result of converting the measured image data of FIG. 6B into a two-dimensional intensity distribution by digital processing is FIG. 6C, and it can be seen that the output distributions can be clearly compared.

  In the above embodiment, the present invention is applied to the measurement of electron beam distribution. However, the application target of the present invention is not limited to this, and general particle beam measurement such as charged particle beams including ion beams can be performed. Is possible. The present invention can also be applied to a particle beam irradiation apparatus that does not have a transmission window.

DESCRIPTION OF SYMBOLS 10 ... Cathode electron gun 10a ... Electron gun unit 10b ... Electron gun holder 12 ... Electron 14 ... Phosphor 16 ... Transparent conductive glass (anode glass)
DESCRIPTION OF SYMBOLS 18 ... Transmission window 20 ... Metal plate 20a ... Cooling water passage 21 ... X-ray 22 ... Scintillator 24 ... CCD camera 25 ... Camera hood 26 ... Mounting flange 28 ... Lead glass 30 ... Cooling piping 31 ... Dark box for camera

Claims (3)

A method for measuring the distribution of particle beams irradiated from a particle beam irradiation apparatus,
A metal plate , a scintillator, and a camera that sequentially receive all the particle beams irradiated from the particle beam irradiation unit to the atmosphere on the boundary between the vacuum and the atmosphere of the particle beam irradiation unit of the particle beam irradiation apparatus or the atmosphere side of the transmission window. Place and
X-rays are generated by colliding all the particle beams with the metal plate ,
The X-rays generated in the metal plate, is converted into light by the scintillator,
Measurement method of particle beam distribution, characterized in that capture light generated from the scintillator by the camera. A device for measuring the distribution of particle beams irradiated from a particle beam irradiation device,
On the boundary between the vacuum and the atmosphere of the particle beam irradiation unit of the particle beam irradiation apparatus or the atmosphere side of the transmission window ,
A metal plate that receives all the particle beams irradiated into the atmosphere from the particle beam irradiation unit ;
And scintillators for converting the optical X-rays generated in the metal plate by the impact of all of the particle beam,
A camera that captures light generated from the scintillator;
Is a particle beam distribution measuring device.   3. The particle beam distribution measuring apparatus according to claim 2, further comprising means for cooling the metal plate.