JPH09257946A - Radiation detection element and radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the energy resolution of radiation detector by use of series superconduction tunnel junction and also give a measurement function of radiation at the two-dimensional incident position in a surface of substrate. SOLUTION: A central junction 5 formed by connecting in series one or more superconduction tunnel junctions on a substrate 1 is disposed, and therearound a nonsensitive region 2 is arranged at which no superconduction tunnel junction is formed and which has an area ten times as large as the area of the central junction 5. Around the region 2 one or a plurality of independently operating series junction 3 are positioned so as to surround the region 2. In the case of arranging around the region 2 three or more series junctions independently operating, the incident position of radiation in two dimensions in the surface of substrate can be measured according to the time difference between signals generating from the junctions or the magnitudes of the signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation detecting element. More specifically, the present invention relates to X-ray, γ
The present invention relates to a detection element for detecting radiation such as rays and charged particles and light such as infrared rays.

[0002]

2. Description of the Related Art A large number of superconducting tunnel junctions are connected in series on a substrate so that phonons generated in the substrate due to the incidence of radiation on the substrate are absorbed by the superconducting tunnel junction, whereby a series of superconducting tunnel junctions are obtained. In a radiation detection element using a series superconducting tunnel junction (Fig. 1) (Japanese Patent Application No. 2-73430), in which a signal charge is extracted from the junction and the magnitude of the radiation energy is measured from the magnitude of the charge, If the conduction tunnel junction is evenly arranged on a certain part of the substrate, the signal strength greatly depends on the incident position of the radiation, and the energy resolution is greatly impaired. .

One of the reasons for this is that the proportion of phonons contributing to the signal varies depending on the incident position of the radiation. For example, the phonon due to the radiation incident on the end of that portion is not absorbed by the junction and is emitted from that portion. This is because the rate of dissipation is high. Another reason is that the phonons are mainly absorbed in different junctions depending on the incident position of the radiation, but the uniformity of the junction sensitivity is not sufficient.

A radiation detecting element in which a dead region without a superconducting tunnel junction is provided on a substrate, and one series superconducting tunnel junction is provided further around the dead region so as to surround the dead region (FIG. 2) (special feature). In Japanese Patent Application No. 4-150981), it is considered that the phonons generated near the center of the dead region diffuse in the dead region and are absorbed by almost all the junctions at the same time. Therefore, the dependency of the signal intensity on the radiation incident position is significantly reduced as compared with the element having no dead region. However, it was not enough to realize high energy resolution.

Further, as shown in FIG. 3, it has been known that when two series superconducting tunnel junctions are provided, one-dimensional position detecting ability in the lateral direction can be obtained. Since there is no resolution and the signal size and waveform differ depending on the incident position in the vertical direction, the horizontal position resolution was also limited, and it is difficult to improve the energy resolution by using that position resolution. It was

The series superconducting tunnel junction mentioned here is not limited to a junction in which one series is connected in series as in Japanese Patent Application No. 2-73430, but a series connection in which a plurality of series are connected in parallel. Contains.

[0007]

The problem to be solved by the present invention is to improve the energy resolution of a radiation detector using a series superconducting tunnel junction, and at the same time, to improve the two-dimensional incidence position of radiation in the plane of the substrate. It is also to give a measuring ability.

[0008]

The above-mentioned problems can be solved by the following means. A large number of superconducting tunnel junctions are connected in series on the substrate, and the phonons generated in the substrate due to the incidence of radiation on the substrate are absorbed by the superconducting tunnel junctions, so that the signal charges from the series superconducting tunnel junctions are absorbed. In a radiation detecting element using a series superconducting tunnel junction in which the magnitude of the radiation energy is extracted from the magnitude of the electric charge, a dead region having no superconducting tunnel junction is provided on the substrate as shown in FIG. A radiation detecting element, further comprising three or more series superconducting tunnel junctions that operate independently so as to surround the dead region, further around the dead region.

It is provided with means for independently amplifying the signals from the above-mentioned elements and respective series superconducting tunnel junctions, and means for measuring the time difference between these signals or means for measuring the ratio of the signal magnitudes. A radiation detector characterized by the above. A large number of superconducting tunnel junctions are connected in series on the substrate, and the phonons generated in the substrate due to the incidence of radiation on the substrate are absorbed by the superconducting tunnel junctions, so that the signal charges from the series superconducting tunnel junctions are absorbed. take out,
In a radiation detecting element using a series superconducting tunnel junction that measures the magnitude of the radiation energy from the magnitude of the charge, a dead region without a superconducting tunnel junction is provided on the substrate as shown in FIG. A radiation detecting element, wherein three or more independently operating series superconducting tunnel junctions are provided around the dead region so as to surround the dead region. And, as shown in FIG. 5, FIG. 6 or FIG. 7, a central junction constituted by connecting one or more superconducting tunnel junctions in series is provided on the substrate, and there is no superconducting tunnel junction around it. A radiation detecting element, wherein a dead region is provided, and one series superconducting tunnel junction or a plurality of independently operating series superconducting tunnel junctions are provided further around the dead region so as to surround the dead region.

An element in which a plurality of series superconducting tunnel junctions are provided around the dead zone, a means for independently amplifying signals from the central junction and each series superconducting tunnel junction, and a time difference between the signals are shown. A radiation detector comprising: a means for measuring or a means for measuring the magnitude of each signal.

[0011]

[Function] A series of three or more series superconducting tunnel junctions (series junctions), which operate independently so as to surround the dead zone, are provided around the dead zone, and the time difference of signals from each series junction or the magnitude of the signal is measured. Thereby, the incident position of the radiation incident on each dead region can be measured two-dimensionally. Deviation of the incident position from the center of the element when measuring the time difference between the signal from the whole or a part of the series junction around the dead zone and the signal from the center junction or the ratio of the magnitudes of these signals Can be measured.

Further, since the incident position can be measured, the incident position dependency of the signal magnitude can be corrected according to the incident position, and the energy resolution is improved. More specifically, for example, in the element of FIG. 4, comparing the generation time of the signal from the upper series junction and the signal from the lower series junction, when radiation enters the center of the element, the phonons generated by the radiation are The signals are generated almost at the same time because they reach both series junctions almost at the same time, and when incident above the center, the signal from the upper series junction is generated earlier. Taking advantage of this, the radiation Y in the device of FIG.
The axial incident position can be measured, and if the same time difference measurement is simultaneously performed on the left and right series junctions, the incident position in the X-axis direction can be measured and the two-dimensional incident position can be measured. The incident position can be measured in two dimensions by measuring the difference in the magnitude of the signal from each series junction instead of the time difference. The energy resolution can be improved by utilizing this two-dimensional position resolution. Using radiation of constant energy, the sum of the signal magnitudes from all junctions due to the radiation incident on position (X, Y) is A (X, Y) when it is incident on the center.
The radiation incident position dependency of the sum of the signal magnitudes, which is twice, is measured in advance, and in actual measurement, the sum of the signal magnitudes is A (X, Y) according to the incident position (X, Y). By dividing, the energy can be measured with high accuracy even though the magnitude of the signal depends on the incident position.

For example, in the element of FIG. 5, the time difference between the signal from the series junction and the signal from the central junction around the dead zone and the ratio of the magnitudes of these signals also depend on the deviation of the incident position from the element center. By providing a center junction at the center of the dead zone and measuring the time difference or magnitude ratio of the signals from the center junction and the series junction around the dead zone, the element center of the radiation incident position in the element with high symmetry can be measured. Can be accurately measured, and as a result, the incident position dependency of the signal magnitude can be corrected with higher accuracy according to the incident position.

[0014]

The present invention will be described in more detail below by showing examples of the present invention. In each of the examples, the joint has a thickness of about 400 μm and an area of 7 mm × 7 mm.
On the sapphire substrate as a lower electrode on the Nb film as Al
A film was provided, the surface of the Al film was oxidized to form a tunnel barrier, and the Nb film was used as an upper electrode on the tunnel barrier. As the radiation, α-particles of 5.3 MeV from ²¹⁰ Po were used, and the central portion of the device on the back surface of the substrate was irradiated. Moreover, the magnetic field was applied parallel to the substrate to suppress the direct current Josephson current.

(Embodiment 1) FIG. 4 shows a first embodiment.
Operates independently around a 3mm x 3mm dead zone 1
Four mm × 4 mm series junctions were produced. The α particles were irradiated from the back to a 1 mm × 1 mm area at the center of the dead area.
The energy of the radiation was measured by amplifying the signals from the four series junctions and adding up the magnitudes of the amplified signals. In that case, the energy resolution was equivalent to that of the conventional device of FIG. 2, and was about 70 keV.

By measuring the time difference between the signals from the top and bottom, and the left and right series junctions seen in FIG.
It was possible to measure the two-dimensional incident position with an accuracy of 2 mm. Regarding the time difference between the signals from the upper and lower series junctions, one signal is delayed after amplifying the signals from the respective series junctions so that the time difference does not become negative. The signal without delay is used as a start signal, and the delayed signal is used as a stop signal.
By inputting into C), the time difference is converted into the magnitude of the output from the converter. The signals from the left and right series junctions are similarly processed by another amplifier, delay device and TAC. The incident position in the plane is measured by these, and at the same time, the sum of the magnitudes of the signals from the amplifiers is also measured for each radiation. When the signal magnitude of each radiation is corrected using the incident position dependence data of the signal magnitude measured in advance by the same method, the energy resolution is about 55 ke.
Improved to V.

(Embodiment 2) One series junction is provided in a region having a width of 1 mm around a dead region having the same size as that of the device of Embodiment 1, and a 50 μm × 50 μm junction is formed at the center of the dead region.
A central junction was provided, which was connected in series. The ground terminal of the central junction is common with that of the series junction. FIG. 5 shows the structure. The irradiated area and the like are the same as in Example 1.

By measuring the time difference between the signals from the central junction and the series junction, the deviation of the radiation incident position from the element center could be measured with an accuracy of about 0.2 mm. In this case, since only the signals from the two amplifiers are processed, only one time-to-peak converter is required, and the only data required for each radiation is one time difference and the magnitude of the signal from the series junction. However, there is an advantage that the measurement is simpler than that of the first embodiment. However, in this case, there is no two-dimensional position resolution.

Further, when the ratio of the signal magnitudes from the central junction and the series junction was measured, the deviation of the radiation incident position from the element center could be measured with an accuracy of about 0.1 mm. In this case, the energy resolution was about 50 keV when the signal magnitude and the incident position data were simultaneously measured to correct the incident position dependency. In this case,
The data required for each radiation is only the signal from the series junction and the signal from the central junction, and there is also an advantage that the time-to-peak converter is not required. However, even in this case, there is no two-dimensional position resolution.

(Embodiment 3) As an element of the third embodiment,
As shown in FIG. 6, 50 μm × 50 μ at the center of the dead area
An element similar to the element of Example 1 was prepared except that the central junction of m was provided. With this element, almost the same energy resolution as in Example 2 and almost the same two-dimensional incident position resolution as in Example 1 were obtained.

(Embodiment 4) Embodiment 4 is shown in FIG. The dead area is close to a circle with a diameter of about 3 mm, and the central joint has a diameter of 1
It is a circular joint of 00 μm, and each series joint is 0.6 mm ×
In an element consisting of two series of 1.25 mm, by the same means as in Example 2, the ratio of the signal magnitude from the central junction to the sum of the signal magnitudes from the four series junctions is When the magnitude of the signal was corrected, the energy resolution of this device was 45 eV.

When the two-dimensional resolution is measured by using the time difference between the signals from the four series junctions, the position resolution is about 0.
1 mm. (Example 5) Example 5 is shown in FIG. Four 1 mm × 4 mm series junctions were produced around the 3 mm × 3 mm dead zone. However, these series junctions are connected in series with each other, and all four of them operate as one series junction. Immediately inside this series junction, four 0.06 mm × 2.5 mm series junctions that operate independently of each other were arranged for position detection. The α particle is 1mm at the center of the dead zone
A 1 mm area was illuminated from the back.

The energy of the radiation was measured by the magnitude of the signal from the outer one series junction. In that case, the energy resolution was about 75 keV. By measuring the difference in signal magnitudes from the top and bottom, and the left and right series junctions for position detection, it was possible to measure the two-dimensional incident position with an accuracy of about 0.1 mm. In this case, the energy resolution was about 60 keV when the signal magnitude and the incident position data were measured at the same time to correct the incident position dependency.

(Embodiment 6) Embodiment 6 is shown in FIG. As shown in the drawing, the structure is the same as that of the device of the fifth embodiment except that the number of serial junctions for position detection is two instead of four. For this device, the energy resolution was approximately 80 keV when the radiation energy was measured at the outer one series junction. Also, the two-dimensional incident position could be measured with an accuracy of about 0.15 mm from the magnitude of the signal from the two series junctions.
When the incident position dependency is corrected, the energy resolution is about 65.
It was keV. The element of this embodiment is characterized in that the incident position can be corrected simply by simultaneously measuring the magnitudes of the signals from the three series junctions.

[0025]

According to the present invention, the time difference or magnitude ratio between the signal generated from the series junction around the dead zone and the signal from the central junction due to the phonons generated by the radiation absorbed in the substrate is measured. The deviation of the incident position of the radiation from the central junction position can be measured, whereby the incident position dependency of the signal magnitude from the series junction around the insensitive layer can be corrected to improve the energy resolution.

In addition, it operates independently around the dead zone 4
When two or more series junctions are provided, it is possible to measure the radiation incident position in the two-dimensional plane of the substrate from the time difference between the signals generated from them and the difference in the magnitude of the signals.
Note that if the area of the central junction is made too large, the proportion of phonons absorbed in the central junction increases, so that the magnitude of the signal from the series junction around the dead zone shifts from the element center at the radiation incident position. Therefore, it becomes difficult to correct the energy of the radiation especially in the vicinity of the central junction. Therefore, it is preferable that the area of the central junction is 1/10 or less of that of the dead area, or less than the square of the thickness of the substrate.

The phonons generated by the radiation are 0.1
Since it is difficult to measure the time difference between about mm mm because it hardly spreads and spreads very rapidly, the area of the dead region should be 0.01 mm ² or more, more preferably 0.2 mm ² or more. Is good. Further, in order to obtain high positional resolution, it is preferable that the area of the dead region is four times or more the square of the thickness of the substrate.

As a substrate to be used, a single crystal substrate of an insulator such as sapphire, a single crystal substrate of a semiconductor such as Si or GaAs, or a metal such as Nb or gold is used so that phonons are not easily attenuated in energy during diffusion. Single crystal substrates are preferred.

[Brief description of drawings]

FIG. 1 is an example of a structure of a conventional element.

FIG. 2 is an example of a structure of a conventional element.

FIG. 3 is an example of a structure of a conventional element.

FIG. 4 is a plan structure diagram of a first embodiment of the present invention.

FIG. 5 is a plan structural view of a second embodiment of the present invention.

FIG. 6 is a plan structure diagram of a third embodiment of the present invention.

FIG. 7 is a plan structural view of a fourth embodiment of the present invention.

FIG. 8 is a plan structure diagram of a fifth embodiment of the present invention.

FIG. 9 is a plan structure diagram of a sixth embodiment of the present invention.

[Explanation of symbols]

 1 substrate 2 dead region 3 series superconducting tunnel junction 4 bonding pad 5 center junction 6 position detection series junction

Claims (4)

[Claims] 1. A large number of superconducting tunnel junctions are connected in series on a substrate, and phonons generated in the substrate due to incidence of radiation on the substrate are absorbed in the superconducting tunnel junction, whereby a series of superconducting tunnels. In a radiation detection element using a series superconducting tunnel junction that extracts the signal charge from the junction and measures the amount of radiation energy from the magnitude of the charge, a dead area without a superconducting tunnel junction is provided on the substrate A radiation detecting element, characterized in that three or more series superconducting tunnel junctions independently operating so as to surround a dead region are provided around the region. 2. A plurality of superconducting tunnel junctions are connected in series on a substrate, and the phonons generated in the substrate due to the incidence of radiation on the substrate are absorbed by the superconducting tunnel junction, whereby the series superconducting tunnels. In a radiation detection element using a series superconducting tunnel junction that extracts the signal charge from the junction and measures the magnitude of the energy of the radiation from the magnitude of the charge, it is necessary to surround a dead region without a superconducting tunnel junction on the substrate. Provide one or more series junctions,
A radiation detector characterized in that two or more series junctions for measuring the incident position of radiation two-dimensionally are provided inside or outside thereof. 3. A plurality of superconducting tunnel junctions are connected in series on a substrate, and the phonons generated in the substrate due to the incidence of radiation on the substrate are absorbed by the superconducting tunnel junction, whereby the series superconducting tunnels. In a radiation detection element using a series superconducting tunnel junction that takes out a signal charge from the junction and measures the magnitude of the radiation energy from the magnitude of the charge, one or more superconducting tunnel junctions are connected in series on the substrate. The central junction is configured by connecting to, the dead zone without the superconducting tunnel junction is provided around it, and one series superconducting tunnel junction or independently so as to surround the dead zone further around the dead zone. A radiation detecting element comprising a plurality of series superconducting tunnel junctions that operate. 4. An element provided with a plurality of series superconducting tunnel junctions around the dead region according to claim 1, claim 2, or claim 3, and signals from the central junction and each series superconducting tunnel junction. A radiation detector, characterized by comprising: a means for independently amplifying a signal and a means for measuring a time difference between signals or a means for measuring the magnitude of each signal.