JPH0310189A - Measurement of shape of charged particle beam - Google Patents

Abstract

PURPOSE:To always achieve an accurate measurement eliminating a drop in permeability of light with a higher radiation resistance by using a pure water Cerenkov light for a charged particle beam shape monitor. CONSTITUTION:A pure water Cerenkov light emitting body 8 is arranged in a course of a charged particle beam 2 and an analog signal adder 9 is connected to photomultipliers 3 at both ends thereof. The pairs of photomultipliers 3 is placed tight on a Cerenkox light takeoff window and a Cerenkov light is incident into a corresponding photomultiplier 3 through upper and lower takeoff windows to be converted an electrical signal and then, outputted after amplified. The electrical signals outputted are added up with an adder 9 and the signals are measured with a measuring resistance 5 and an oscilloscope 4 to obtain an output proportional to the number of charged particles incident into a certain position and width of a section of the beam 2. Moreover, an arm 7 for scanning is driven to repeat measurements shifting the position of the light emitting body 8 thereby enabling measurement of a relative intensity distribution in the section of the beam 2, namely, a shape of the beam 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is based on I! The present invention relates to a charged particle beam shape measurement method for measuring the shape of a high-energy charged particle beam generated by an electric particle accelerator or the like.

[Prior Art] Conventionally, there is a method for measuring the shape of a charged particle beam of this type, which is related to the applicant's previous IN (Japanese Patent Application No. 135548/1983), which is shown in FIGS. 4 and 5. Explain with reference to. In FIG. 4, a sensor section (1a) at one end of an optical fiber (1) is placed in the path of a charged particle beam (2). The other end of the optical fiber (1) is connected to a photomultiplier tube (3). The output of the photomultiplier tube (3) is connected to an oscilloscope (4), and a measuring resistor (5) is connected halfway there. The photomultiplier tube (3) is a high voltage power supply (6)
It is operated by.

In FIG. 5, a scanning arm (7) supports an optical fiber sensor section (1a), and the sensor section (1a) is installed at an angle of α with respect to the traveling direction of the charged particle beam (2). .

'tr Charge particle beam shape determination is such that a charged particle beam (2) colliding with an optical fiber sensor part (la) emits directional Cerenkov light in the sensor part (1a) tilted by α, and then This Cerenkov light is transmitted through an optical fiber (1
), the photoelectrons reach the photomultiplier tube (3) through repeated complete reflections, and are ejected by Cherenkov light at the photocathode of the photomultiplier tube (3). ) The high voltage applied from the photomultiplier tube (
3) If the charges amplified and outputted in the beam are measured using a measuring resistor (5) and an oscilloscope (4), the relative number of charged particles in the cross section of the charged particle beam (2) can be determined. By repeating the above measurement while further driving the scanning arm (7) and shifting the position of the optical fiber sensor (1a), it is possible to determine the intensity distribution in the cross section of the charged particle beam (2), that is, the shape of the charged particle beam. can be measured.

Here, the tilt angle α of the optical fiber sensor (1a) is determined by the refractive index of the core and cladding of the optical fiber (1) and the speed of the charged particle beam (2).6 [Problems to be Solved by the Invention] Traditional charged particle beam shape measurement methods such as
The sensor part undergoes radiation deterioration due to the contrast of the charged particle beam, resulting in a decrease in light transmittance and a corresponding decrease in the output signal, leading to inaccuracies in the measurement of the charged particle beam shape, and in severe cases. There was a problem that it became impossible to measure.

This invention was made to solve the above problems, and has good radiation resistance, no decrease in light transmittance,
The purpose of this invention is to obtain a method for measuring the shape of a charged particle beam that can always accurately measure the shape of a charged particle beam.

[Means for Solving the Problems] In the present invention, the light transmittance does not decrease due to radiation deterioration even after long-term high-intensity charged particle beam control.

[Example] The following is a sample of this invention! , an example will be explained with reference to FIGS. 1 to 3. 6 In FIG.
are arranged, and analog signal adders (9) are connected to photomultiplier tubes (3) at both ends thereof. FIG. 2 shows the section A in FIG. 1 in detail, and FIG. 3 shows the pure water Cerenkov light emitter (8) in detail.

In FIG. 3, Cerenkov light extraction windows (8b) are attached to the top and bottom of a hollow housing (8a). In addition, a Cerenkov light condensing mirror (8c) is mounted on the inner wall of the housing (8a).
is provided. Cherenkov light (2a) is emitted by charged electron particles (2) that have entered pure water (8d) of a pure water Cherenkov light emitter (8). Cherenkov light (2)
Light a) has sharp directivity, propagates through pure water (8d), is reflected by the Cherenkov light condenser mirror (8c), and is extracted from the upper and lower Cherenkov light extraction windows (8b).

In Figure 2, a pair of photomultiplier tubes (3) are placed in close contact with the Cherenkov light extraction window (8b), and the Cherenkov light (2a) is transmitted through the upper and lower Cherenkov light extraction windows (8b).
), the light enters the corresponding photomultiplier tube (3), where it is converted into an electrical signal, amplified, and output. The electrical signals output from each photomultiplier tube (3) are added by the analog signal adder (9) shown in Figure 1, and then added to the measuring resistor (
5) and an oscilloscope (4), an output proportional to the number of charged particles incident on a certain position and width of the cross section of the charged particle beam (2) is obtained.

Furthermore, by repeating the above measurements while driving the scanning arm (7) and shifting the position of the pure water Cherenkov light emitter (8), it is possible to obtain the relative intensity distribution of the cross section of the charged particle beam (2), that is, the charged The shape of particle beams can be measured.

In the above example, pure water Cerenkov photoluminescent material (8
) were provided with two Cerenkov light extraction windows (8b) at the top and bottom, and two photomultiplier tubes (3) were installed correspondingly, but the Cerenkov light extraction window (8b) was set as one obstacle, and the photomultiplier tube (
3) may also be combined into one.

In addition, the casing (8a) of the pure water Cerenkov light emitter (8)
The inner wall surface of the mirror may be obscured by a Cerenkov light focusing mirror (8c), or a material with a frosted glass-like surface may be used as long as it has a good reflectance.

[Effects of the Invention 1 As described above, 5 According to the present invention, since a pure water Cerenkov luminescent material is used in the charged particle vinyl-shaped monitor, there is no attenuation of the light transmission of the luminous material due to radiation damage, and accurate charging can be achieved. This has the effect of being able to measure the cross-sectional shape of a particle beam.

[Brief explanation of drawings]

1 to 3 are for explaining one embodiment of the present invention, in which FIG. 1 is a circuit diagram, FIG. 2 is a perspective view of the sensor section,
FIGS. 3(a) and 3(b) are a side view and a front view of the light emitter section. Figures 4 and 5 are for explaining the conventional charged particle beam shape measurement method. Figure 4 is a circuit diagram, and Figure 5 (a)
(b) is a front view and a side view of the senna portion. (2)...Charged particle beam, (3)...Photomultiplier tube,
(4)...Oscilloscope, (8) Pure water Cherenkov light emitter, (9)...Analog signal adder. In each figure, the same reference numerals indicate the same or corresponding parts. Representative Person

Claims (1)

[Claims] A method for measuring the shape of a charged particle beam, in which a sensor unit having a pure water Thielenkov light emitter is inserted in the path of a charged particle beam, and the intensity distribution in a cross section of the charged particle beam is measured using Thierenkov light emitted in pure water.