JPS584992B2 - Radiation incident position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A conventional position-sensitive counter has an anode formed of a high-resistance wire, usually a quartz wire coated with carbon.

However, the coating is easily damaged by the electron avalanche caused by the incidence of radiation, resulting in a short lifespan.

Further, for example, when observing the diffraction angle of X-rays, an arc-shaped position-sensitive counter tube is required, so the anode must be stretched in an arc shape.

For this reason, if the anode is formed from an extremely thin metal wire, a large number of support wires will be required, which will cause disturbances in the electric field and reduce the resolution of position detection.

In order to eliminate the above-mentioned drawbacks, there are some that are held in an arc shape by anode electrostatic force or electromagnetic force.
Since the holding force is not sufficient, the angle measurement range is limited to about 60 degrees or less.

Furthermore, by stretching the anode in a straight line, arranging multiple grids concentrically in front of it, and applying an appropriate potential to each grid, the incident angle of the radiation and the position where the avalanche electrons enter the anode can be determined. Although there are some devices that provide a one-to-one correspondence between the angles, they have drawbacks such as not being able to increase the angle measurement range beyond about 60 degrees and requiring a large counter.

The present invention provides a radiation incident position detection device that does not have the above-mentioned drawbacks.

The drawings are diagrams showing a longitudinal section of a radiation counter and the configuration of its external circuit in an embodiment of the present invention.

That is, the counter tube 1 is a tubular airtight container bent into a semicircle with a radius of 50 mm, and a suitable ionized gas is sealed inside.

A linear anode 2 made of piano wire or tungsten wire having a diameter of 0.2 to 0.3 mm, for example, is stretched along the axis of the container, and both ends are held by insulating rings 3.

In addition, there are many cathodes 4, 4 on the inner surface of the outer tube wall.
. . . are arranged in a line, each facing each position of the anode.

The anode 2 in such a proportional counter is connected to a high voltage source 5
Connect each cathode 4, 4...
are connected to the induced charge amplifiers 6, 6, . . ., respectively, and the output of each amplifier is connected to the first group of resistors R1.
, R2...Rn and the second group of resistors R'1. R'2......In addition to one of R/n, the other ends of the resistors of each group are connected in parallel to the first terminal 7 and the second terminal 8, respectively. .

Further, the input terminals of amplifier circuits 9 and 10 having feedback resistors Ro or sides are connected to the terminals 7 and 8, respectively, and the input ends of the amplifier circuits 9 and 10 are connected to the terminals 7 and 8, respectively, and the input ends of the amplifier circuits 9 and 10 are
The output of 0 is added to the arithmetic unit 13.

The output of this arithmetic unit is applied to a multiple wave height analyzer 14, and the output thereof is applied to a storage device 15, a cathode ray tube, or other display device.

In the above device, the resistors R1, R2...
. . . parallel circuit and amplifier circuit 9 and its feedback resistor R
6, and resistance R/,, R'2...
・ parallel circuit and amplifier circuit 10 and its feedback resistance R′o
each constitute an operational amplifier.

Therefore, both the first terminal 7 and the second terminal 8 maintain substantially the ground potential.

Furthermore, when radiation enters any position within the counter tube 1 and causes ionization of the gas in that part, the generated electron avalanche immediately flows into the anode, and a negative charge is induced in the cathode near the ionization position.

For example, change the position of each cathode sequentially from the top of the drawing x
1. x2・・・・・・・・・Xn, position Xi
Let qi be the charge induced on the cathode of
The voltages produced at the outputs of are kqiRo/R1 and kqiR'o/R'i, respectively.

For this reason, assuming that a, b, and c are constants, and that R6 and Rlo are equal, the resistors R1 and R2 are・－・・・・・・・・・
...and R/1. R/2・・・・・・・・・・・・
The output voltages Va and vb appearing at the output terminal of the amplifier circuit due to the induced charges of all the cathodes are given by:

Therefore, Va/(Va+Va)−aΣqixi/cR0Σ
qi is obtained.

This formula shows that the center of the induced charge generated on each cathode by the electron avalanche, that is, the position of the cathode that generated the maximum charge, is proportional to Va/(Va + Vb).
The arithmetic unit 13 calculates this value and applies it to the multiwave analyzer 14, so that the analyzer applies a signal to the element at the position corresponding to the cathode in the storage device 15 and stores it.

In other words, if the same charge is sequentially applied to each cathode at position x1jX2..., the output of amplifier circuit A will increase linearly and sequentially, and the output of amplifier circuit B will conversely decrease. and the resistance R so that their sum is kept constant.
1JR2...and R'1. R'
2. As mentioned above, one of Va or vb and their sum (Va+
By determining the ratio to Vb), the incident position of the radiation can be detected regardless of the total amount of induced charges.

Furthermore, in the device of the present invention, the anode of the proportional counter can be formed of a sufficiently thick metal wire.

Therefore, by simply holding both ends of the anode, the anode can be bent into an arc shape without providing a support wire in between, which eliminates the disadvantage that position detection resolution is degraded due to disturbance of the electric field caused by the support wire. , and a wide-angle arc-shaped proportional counter tube can be easily formed.

That is, if an X-ray diffraction sample is placed, for example, at the center point of the circular arc, and the X-rays diffracted by the sample are made incident on the above-mentioned counter tube,
Since the diffracted X-rays are always incident at right angles to the anode, highly accurate position detection can be performed.

Moreover, since the incident position calculated by simple addition and division as described above immediately corresponds to the diffraction angle of the X-ray, processing of the measured values is also easy.

[Brief explanation of the drawing]

The drawings show a longitudinal section of a radiation counter and the configuration of an external circuit in an embodiment of the present invention. In the figure, 1 is a proportional counter, 2 is an anode, 3 is an insulator ring, 4 is a cathode, 5 is a high voltage source, 6 is an amplifier,
R,, R2...... are the resistances of the first group,
R'1. R12...... is a second group of resistors, 7 is a first terminal, 8 is a second terminal, 9 and 10 are amplifier circuits, 11 and 12 are waveform shaping amplifiers, and 13 is a Arithmetic unit, 14
1 is a multiple wave height analyzer, and 15 is a storage device.

Claims (1)

[Scope of Claims] 1. A linear anode is stretched in a container filled with ionized gas, and a plurality of cathodes are arranged so as to face each position of the anode, and the An output pulse sent out from each cathode by gas ionization is applied to one end of the two resistors belonging to the first group and the second group, respectively, and the other end of the resistor of the first group and the second group is substantially It is connected in parallel to a first terminal and a second terminal held at ground potential, respectively, and the ratio of the output of the first or second terminal to the sum of the outputs sent from the first terminal and the second terminal is the ionization. A radiation incident position detection device characterized in that the values of the resistances in each group are selected to correspond to the positions where the radiation occurs. 2. The radiation incident position detection device according to claim 1, in which the anode is stretched in an arc shape.