JPH0412447A - Position sensing radioactive ray detector - Google Patents

Abstract

PURPOSE:To realize a detector which has a simple and strong structure and can use a simple electric signal processing circuit by stretching a linear anode and position reading electrodes in an airtight container with a radioactive ray incidence window in the preset mode. CONSTITUTION:An anode wire 2 is stretched along an incidence window 4 in an airtight container 1 having the radioactive ray incidence window 4 made of beryllium and concurrently serving as a cathode, and position reading electrodes 3a, 3b are stretched. The electrodes 3a, 3b are stretched in the directions so that their distances from the anode wire 2 are increased or decreased. The electrode 3a is gradually separated from the anode wire 2 from one end of the anode wire 2 toward the other end, and the electrode 3b gradually approaches the anode wire 2. The position coordinates X of the electron avalanche generated at the point A on the anode wire 2 by the incident radioactive rays are calculated based on the charges induced on the electrodes 3a, 3b respectively and the distances between the electrodes 3a, 3b and the anode wire 2 respectively.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is a position-sensitive device that operates in a proportional counting state for detecting the incident position of radiation and observing the intensity distribution of radiation incident at each position. It relates to radiation detectors.

[Prior art 1] Conventionally, various position-sensitive radiation detectors have been used, but those that operate in a proportional counting state include a multi-wire proportional counter, a resistive anode wire proportional counter, and the "Pack-Gasen method".
There are proportional counter tubes with special shaped position reading electrodes, such as the ``wedge and strip method.''

These counters are usually used to detect the position of charged particles such as α-rays and β-rays, neutron beams, If a liquid (for example, liquid xenon) is used as the medium, it is also possible to detect the position of γ-rays with considerably high energy. Further, the detection medium is filled in an airtight container (inside the detector) in a gas flow state or in a sealed state.

[Problems to be Solved by the Invention] Among the conventional techniques, does the multi-wire proportional counter accurately measure a large number of thin wires? 1A2J! In addition, the circuit system for position detection becomes complicated. The resistance anode wire proportional counter is
Although the structure is simple, it is difficult to obtain an anode wire with an appropriate resistance value (
The comb is extremely easy to break.

In the ``Pack Gasen method'', a sawtooth conductor pattern is formed on a printed circuit board, and this is used as a position reading electrode.The circuit system is relatively simple, but the production of fine patterns requires high machining accuracy and requires high-temperature operation. When manufacturing a sealed proportional counter tube that requires gas venting, it is difficult to select an insulating substrate, making it impossible to use normal printed circuit board manufacturing techniques.

Furthermore, if the proportional counter tube is made into a cylindrical shape, it becomes difficult to manufacture an electrode pattern for position reading.

The present invention has a position reading electrode with a simple and durable structure that uses less insulation, and a relatively simple electric signal processing circuit so that it can be used for manufacturing a position-sensitive radiation detector of a detection medium sealed type. The aim is to create a position-sensitive radiation detector that can be used.

[Means for Solving the Problems] In order to achieve the above object, the present invention has a radiation entrance window made of beryllium, mylar, etc., and is provided in an airtight container of an ionization detection medium that also serves as a cathode. An anode wire was stretched along the anode wire, and one pair (or two or more pairs as described later) of position reading electrodes a and b were provided along this anode wire.

The distance between the position reading electrodes and the anode line varies along the anode line in an inverse relationship to each other. That is, one of the pair of position reading electrodes, e.g. a, gradually moves away from the anode line from one end of the anode line to the other (when the other position reading electrode, conversely, moves away from the anode line). The state changes from a close state to a state where the position reading electrode a and the distance from one point on the anode line to position reading electrode b are the same at any point on the anode line.

There may be one pair of position reading electrodes having the above relationship, or two or more pairs may be provided with the anode line as the axis of symmetry, and one of the pair of position reading electrodes may be omitted. Further, the airtight container of the ionization detection medium does not necessarily have to serve as a cathode, and a separate cathode may be provided within the airtight container of the ionization detection medium.

[Operation] In the most basic case where l pairs of position reading electrodes are installed along the anode line, and the anode line and the position reading electrode are on the same plane (this plane is designated as a), the position reading electrode's Explain the action. (FIG. 2) In this case, the one-position reading electrodes face each other in parallel with the anode line in between, and the radiation passes through the radiation incidence window and enters the vicinity of the anode line almost perpendicularly to the plane α. If the incident radiation generates a charge Q due to an electron avalanche on the person on the anode wire, the charge corresponding to this charge, that is, the charge whose total amount is equal to Q and has a different sign from Q, will be applied to the cathode and the position reading electrode. is induced by Of these, charges Q a, Q induced on position reading electrodes a, b
b is the position reading electrode a from the person on the anode line, respectively.
, b is a function of the distance 1iLa,Lb, and as the distance from point A increases, the induced charge becomes smaller. If the distance from one end of the anode wire to the person is X, then La and Lb are each a function of X, and finally the charges Qa and Qb induced on the position reading electrodes a and b are functions of X. , Qa / (Qa + Qb) or Qb / (Qa + Qb).

Furthermore, by using the charge Q generated on the anode wire by the electron avalanche, it is possible to obtain a value corresponding to X as Q a / Q or Q b /Q, and It is also possible to omit one of them.

Incidentally, the disturbance of the electric field caused by attaching the position reading electrode can be ignored in practical terms, considering that charge multiplication due to electron avalanche occurs very close to the anode line (several tens of microns). Furthermore, even if errors due to disturbances in the electric field become a problem in strict measurements, since these errors occur with a certain regularity, they can be corrected.

[Example] An example will be described with reference to the drawings. Figure 1 shows an example in which the anode wire and the position reading electrode are on the same plane. Radiation Ijij flo) is incident near the anode wire through the radiation entrance window (4) provided on the cathode, indicated by a dotted line. However, a detection medium such as PR gas is filled in a sealed container that also serves as a cathode in a gas flow state or in a sealed state.

FIG. 2 shows the positional relationship of the anode wire 1 position reading electrode when viewed from directly above FIG. 1, and serves as an aid to the explanation of the function of the position reading electrode.

FIG. 3 shows an example of the positional relationship of the anode wire, the position reading electrode, and the cathode (or the airtight container for the detection medium) when the positive TFI wire and the position reading electrode are not on the same plane. As the position reading electrode (3b) moves away from the anode line and moves along the anode line from left to right in the figure, the position reading electrode (3a) moves closer to the anode line (3a).

FIG. 4 shows an embodiment in which the cathode has a cylindrical shape and the anode wire and the position reading electrode are on the same plane. In this case as well, the radiation passes through the entrance window (4) and enters the vicinity of the anode ray.

In each of the above embodiments, there is one pair of position reading electrodes, but it is also possible to provide two or more pairs of position reading electrodes with the anode line as the axis of symmetry. FIG. 5 shows an example of the mutual positional relationship of the electrodes when three pairs of position reading electrodes are provided in a cylindrical detector. In this case, (3a) f3b
) as a pair of position reading electrodes, (3al
(13b,) may be considered as a pair of position reading electrodes. Whichever way you think about it, (3al (13al
f23al is connected to send the charge signals from these three position reading electrodes together to one charge-sensitive preamplifier. f3bl (13b) f23bl is also connected in the same way and sends a charge signal to the other charge-sensitive preamplifier.

In FIG. 5, a hermetic seal for inter-electrode insulation is omitted (not shown), but an auxiliary line is shown on the side of the detector by a chain line to clarify the positional relationship between the electrodes.

Furthermore, although Fig. 5 shows an example in which the outer shape of the detector (or the shape of the cathode) is cylindrical, the anode wire and position reading electrode system of the type shown in Fig. It is also possible to install the detector in the detector, and the embodiment does not define the outer shape of the detector.

[Effects of the Invention] Since the present invention is configured as described above, it produces the following effects.

Because the structure is extremely simple, position-sensitive radiation detectors of any shape and size can be easily manufactured (as long as the performance as a detector is not impaired), and in particular, it is possible to manufacture a detector with a sealed detection medium. This is significantly easier than existing methods.

As an example is shown in FIG. 6, by changing the positional relationship between the anode wire and the position reading electrode, the position resolution of the detector can be easily changed (improved). In the example of FIG. 6, the positional resolution of FIG. 6(bl) is better than that of FIG. 6(al).

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of the present invention, in which a cathode which also serves as an airtight container for a detection medium is indicated by a dotted line. FIG. 2 is an explanatory diagram of the action of the position reading electrode. FIG. 3 is a perspective view showing the electrode arrangement of the embodiment of the present invention, and FIG. 4(a) is a longitudinal cross-sectional view of the embodiment of the present invention. Fig. 5 is a perspective view showing the electrode arrangement when there are three pairs of position reading electrodes, and Fig. 6 is an explanatory diagram showing the relationship between the electrode arrangement and position resolution.・Cathode 2...Anode rays 3a, 3b, 13a, 13b, 23a, 23b -=
-...Position reading electrode 4...Radiation entrance window 5...Insulator such as hermetic seal lO
...... Radiation Q a, Q b ...... Charge induced on the position reading electrode

Claims (3)

[Claims] (1) A linear anode is stretched in an airtight container with a radiation entrance window, and along this anode line, two electrodes whose distance from the anode line changes in an inverse relationship to each other, i.e., two When one of the electrodes gradually moves away from the anode wire from one end of the anode wire to the other, the other electrode changes from being away from the anode wire to approaching it. A position-sensitive radiation detector that is equipped with two electrodes, which serve as a pair of position reading electrodes, and operates in a proportional counting state. (2) A position-sensitive radiation detector according to claim (1), in which two or more pairs of position-reading electrodes are provided with the anode line as an axis of symmetry. (3) A position-sensitive radiation detector according to claim (1) or (2), in which one of the pair of position reading electrodes is omitted.