JPH0619466B2 - Two-dimensional charge position detection electrode - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a position-sensitive detector for detecting a two-dimensional barycentric position of a charge distribution, and more particularly to a charge distribution generated by incidence of radiation. To a detector for measuring the two-dimensional barycentric position of the.

(Prior art) Electrical detection of radiation is generated by the charge generated inside the detector by the incidence of radiation, specifically, the charge generated by the ionization action when the radiation is incident, and the radiation entering the scintillator. By electrically extracting the electric charge generated by further irradiating the photoelectric conversion material with the generated optical pulse, the electric charge generated by multiplying this inside, or the electric charge induced on the electrode by these, To be achieved.

When a plurality of independent detectors such as a scintillation counter are arranged and used, the radiation incident position can be obtained by calculating the output of each detector so as to find its center position. Such a method has been put to practical use in the medical field and the like in order to determine the change with time of the position of the radioactive isotope. However, the arithmetic processing circuit used at this time has a problem that it is considerably complicated and expensive to obtain high resolution.

There has been proposed a position-sensitive radiation detector capable of detecting a radiation incident position without using such a plurality of independent radiation detectors and arithmetic circuits. As this position sensitive radiation detector, a resistance layer type and a split electrode type are known. The resistance layer type utilizes that the charges generated at the incident position are divided by the resistance value that changes depending on the incident position. Since this resistance layer type uses a resistance layer, the rise of the output pulse is delayed, and the low detection speed and low count rate pose a problem. The split-electrode type position-sensitive detector detects a charge generated by absorption of radiation or a center position (electrical center of gravity) of an opposite sign charge induced in a certain range on an electrode for signal readout by the charge-sensitive detection. It is a form of detecting with a container, and has the characteristics of high speed and high count rate as compared with the resistance layer type.

Here, a backgammon type, a wedge-and-strip type, and a load capacitive coupling type charge divider are known as examples of the divided electrode type position-sensitive detector.

The backgammon type is as follows. FIG. 5 is a conceptual diagram for explaining the principle, and assuming that the charge −Q is generated by the incidence, the electrode 50 placed below the electrode −Q has a sign different from that of the charge −Q due to electrostatic induction. Electrode 5
1 is induced. The electrode 50 is a serrated thin wire-shaped insulating portion 52.
Is divided into two regions 53 and 54 by the, and the induced charge 51 is divided into regions 5 at a ratio proportional to the coordinate in the x direction in FIG.
It is divided into 3, 54 as Q _A and Q _B. The barycenter x-coordinate of the induced charge is represented by Q _A / (Q _A + Q _B ).

The wedge-and-strip type is as follows. FIG. 4 is a concept for explaining the principle. The electrode 40 is divided into three regions, that is, a wedge region 43, an intermediate region 44, and a strip region 45, which are insulated from each other by a sawtooth-shaped thin wire insulating portion 41 and a rectangular wave-shaped thin wire insulating portion 42. The pitch of the sawtooth and the rectangular wave are constant, and they have a structure in which they interdigitate. The width of the strip-shaped portion (strip) that is inserted between the sawtooth (wedge) of the rectangular wave is gradually narrowed from the left to the right in the figure. Wedge area 43, the intermediate region 44, the charge amount _Q A induced in the strip region _45, Q B, _{Q C}
Then, the position of the center of gravity of the charge distribution in the x direction can be determined by Q _A / (Q _A + Q _B + Q _C ) similarly to the backgammon type principle. On the other hand, the position in the y-direction can be determined by _{Q C / (Q A + Q} B + Q C). That is, the wedge-and-strip type can two-dimensionally determine the barycentric position of the charge distribution.

The structure of the load-capacitive coupling type charge divider is shown in FIGS.
It is shown in FIG. The charge dividers 14 are arranged at regular intervals,
A plurality of strip electrodes 16 of equal width separated from each other by an insulator 15 and an area of the strip electrodes 16 facing each other via an insulator 17 and overlapping therewith linearly increase and decrease along the X direction. It is composed of two triangular electrodes 18 and 19. Therefore, in the charge divider 14, the capacitance between the n-th strip electrode 16 and the triangular electrode 18 is C _nA , 3
If the capacitance between the rectangular electrodes 19 is C _nB , C _nA linearly increases as n increases, and C _nB decreases as n increases. Charges are induced on the position detection electrode 10 which has the strip electrodes 13 which are insulated from each other by the insulator 12 at equal widths and at equal intervals and which are connected to the strip electrodes 16 of the charge divider 14 by the copper wire 21. And its charge is divided at a ratio according to the X coordinate of its center of gravity and taken out as Q _A and Q _B from the two triangular electrodes 18 and 19 of the charge divider 14, respectively, and the coordinates are Q _A / (Q is obtained as _a + _{Q B).} This load-capacitive coupling type charge divider is 1
The position of the center of gravity of the charge can be detected only dimensionally, but RADIOI
SOTOPES Mikio Yamamoto et al., Vol. 24, No. 6, June 1975, used in combination with the two-dimensional proportional counter disclosed on pages 3 to 9 to detect the radiation incident position two-dimensionally. It will be possible. The two-dimensional proportional counter is composed of a plurality of anode wires stretched in parallel and a cathode divided in a direction perpendicular to the wires.

(Problems to be Solved by the Invention) The present invention is intended to provide a two-dimensional position-sensitive detector, but in the above-mentioned split electrode type two-dimensional position-sensitive radiation detector (wedge and strip type). Has a shape in which a division pattern is included, and it is difficult to create it when aiming for high resolution or when it is applied to a small area detector. However, there is a problem in that the position resolution is limited.

In addition, the method used for the above-mentioned two-dimensional proportional counter is 2
Since it is necessary to detect the position of the electrode surface of one sheet and use it, there is a problem that it cannot be applied as an anode of a microchannel plate or a parallel plate avalanche counter tube.

(Means for Solving the Problem) The above-mentioned problem is electrically bisected by the sawtooth boundary portion, and at least one of the bisected portions is orthogonal to the repeating direction of the sawtooth boundary portion. This is achieved by using electrodes for two-dimensional position detection, which are further divided at equal intervals in the direction of rotation, and each of the divided portions is connected to a load coupling capacitance charge divider.

(Operation) The two-dimensional position detecting electrode of the present invention is used in combination with a charge-capacitive coupling type charge divider, and is extracted from the charge divider.
By obtaining the ratio of the two charge amounts, the two-dimensional barycentric position of the distribution of the charges induced or flowed into the two-dimensional position detecting electrode can be obtained. Therefore, the radiation or pulsed light incident position can be detected two-dimensionally.

(Effects of the Invention) Since the two-dimensional position detection electrode of the present invention does not undergo electrode division in a complicated shape such as the wedge-and-strip type, it is extremely easy to manufacture and the stray capacitance between electrodes is small.

The capacitance network formed by the charge divider is in series with the stray capacitance between the strip electrodes, and by appropriately setting the capacitance size, the input capacitance to the charge-sensitive preamplifier is rather reduced. it can. Therefore, the electrical noise is not increased and can be further reduced depending on the conditions.

Since no resistance or delay line is used, there is an advantage that a high-speed, high count rate position-sensitive radiation detector can be configured.

Further, as compared with a two-dimensional proportional counter, it can be constructed on a single plane, so that it is easy to make when aiming for high resolution or when it is applied to a small area detector. There is also an advantage that the size and weight can be easily achieved.

(Example) Below, the Example of this invention is described in detail.

FIG. 2 is a plan view of a two-dimensional radiation position detector using an example of the position detection electrode of the present invention. The position detecting electrode 18 shown here is largely divided into two regions by sawtooth-shaped insulating fine wires 24, and in each of the one region, each of the saw teeth is a small region 25 insulated from each other. Each of them is sequentially electrically connected to each strip-shaped region 16 on the surface of the charge divider 14 in a one-to-one manner from the end by a conductor 21. The other one of the regions 26 is directly connected to the charge-sensitive preamplifier, and also the two triangular electrodes 1 on the rear surface of the charge divider 14 are connected.
8 and 19 are each also connected to a charge sensitive preamplifier.

The electric charges induced in the position detection electrode 23 are first divided into two in the y direction by the sawtooth pattern on the position detection electrode 23, and at the same time, in one region, each sawtooth forms a small region insulated from each other. Therefore, it is further divided into a large number of partial charges corresponding to them. These partial charges are supplied via the triangular electrodes 18 and 19 on the back surface of the charge divider 14, and the ratio Q _A / (Q of the amount of electricity supplied from the triangular electrodes 18 and 19 is supplied. _{From A} + Q _B ), the position coordinate in the repeating direction (x direction) of the sawtooth pattern is determined by the principle of the charge coupling capacitance method. Further, the position coordinate in the y direction orthogonal to this is the ratio Q _C / (Q _A + Q _B between the two charges divided by the sawtooth pattern.
+ Q _C) by it can be determined by the same principle as backgammon method.

Another embodiment for two-dimensional position reading is shown in FIG. The conductor on the position detection electrode 30 is a sawtooth-shaped insulating thin wire 31.
The two areas are roughly divided in the y direction, and in each area, each of the saw teeth is made into triangular small areas 32 and 32 'which are insulated from each other. Each of which is 2 on each side
Strip electrodes 16, 1 on the surface of one charge divider 14, 14 '
6'and 1 to 1 are electrically connected from the end by conductors 19 and 19 '. Each triangular electrode 1 on the back of the charge divider
A total of four charge sensitive preamplifiers, 8, 19, 18 'and 19', are connected respectively. The electric charge induced in the position detection electrode 30 is greatly increased in the y direction by the sawtooth pattern on the position detection electrode 30.
At the same time, the sawtooths form small regions that are insulated from each other, so that a large number of partial charges corresponding to them are further divided in the x direction. These partial charges are generated by a total of four triangular electrodes 15, 16, 1 on the back surface of the charge divider.
It will be supplied from 5 ', 16' via a capacity network.

The position coordinate in the repeating direction (x direction) of the sawtooth pattern is the ratio of the sum of charges extracted from the triangular electrodes 18 and 18 ′ of the two charge dividers to the total induced charge amount, that is, (Q _A +
Q _C ) / (Q _A + Q _B + Q _C + Q _D ). Further, the position coordinate in the y direction orthogonal to this is the backgammon by the ratio (Q _C + Q _D ) / (Q _A + Q _B + Q _C + Q _D ) between the two charges divided by the sawtooth pattern. It can be determined by the same principle as the type. According to the method shown in FIG. 2, when the detected charge is shifted to the right side of the detection electrode, Q _A + Q _B becomes small and the position resolution in the x direction may be deteriorated. However, the method shown in FIG. 3 is used. Then, the denominator becomes the total induced charge in both directions, so such a problem does not occur.

Although the present invention has been described in detail above, the position detecting electrode of the present invention can be used as an anode of a microchannel plate or a parallel plate avalanche counter, or a cathode of a multi-wire proportional counter.

[Brief description of drawings]

1A and 1B are a plan view and a cross-sectional view of a one-dimensional radiation detector using a charge-coupling capacitance type charge divider, and FIG. 2 is a two-dimensional radiation position detector using the position detection electrode of the present invention. FIG. 3 is a plan view of another two-dimensional radiation position detector using the position detection electrode of the present invention, FIG. 4 is an explanatory view of a backgammon type position-sensitive radiation detector, and FIG. The figure is an explanatory view of a wedge-and-strip type position-sensitive radiation detector. (Explanation of Codes) Q ... Generated charge, 51 ... Induced charge region, 51, 41, 42, 15, 24, 31 ... Thin line insulating part, 10 ... One-dimensional position detection electrode, 14, 14 '... ... Charge divider, 16, 16 '... Charge divider band conductor, 17 ... Insulator layer, 18, 19 ... Triangular electrode, 21,21' ... Conductor, 23, 30 ... Two-dimensional position Detection electrodes, 25, 32, 32 '... Small area conductors.

Claims (1)

[Claims] 1. A sawtooth-shaped boundary portion is electrically bisected, and at least one of the bisected portions is further divided at equal intervals in a direction orthogonal to the extending direction of the sawtooth-shaped boundary portion. A two-dimensional charge position detection electrode, each of which is connected to a load-coupling capacitance charge divider.