JP2002286847A - Semiconductor radiation detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector having a small size and high energy resolution. SOLUTION: The peak sensitivity wavelength of this radiation detector can be adjusted to <=500 nm which is close to the light emitting peak wavelength of an oxide scintillator by not using a silicon photodiode as a photodiode, but a semiconductor light receiving element having light receiving peak sensitivity of <=500 nm which is close to the light emitting peak wavelength of the oxide scintillator as the photodiode. To be concrete, this detector uses a semiconductor light receiving element formed by using a compound semiconductor having a forbidden band width of >=2.5 eV as a base material as the photodiode. To be more concrete, this detector uses a semiconductor light receiving element composed of a thallium bromide(TlBr) as the photodiode. Consequently, the sensitivity of this semiconductor radiation detector can be increased and the size of this detector can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gamma camera, X
Semiconductor radiation detector suitable for use in X-ray CT (X-ray CT), positron emission nuclide tomography (PET), γ-ray nondestructive inspection equipment, etc. The present invention relates to a radiation detecting device having an element.

[0002]

2. Description of the Related Art Conventionally, as a radiation detecting device, a scintillation counter for detecting light emission from a scintillator mainly by a photodetector such as a photomultiplier tube or a silicon photodiode has been used in fields such as medicine, engineering, and physics. It's being used.

As scintillators, for example, oxide scintillators such as GSO, LSO, LuAP, and YAP for use in PET have attracted attention because of their high fluorescence output and short fluorescence decay time.

[0004] Silicon photodiodes have advantages such as higher quantum efficiency, smaller size and greater resistance to mechanical shock than photomultiplier tubes. Therefore, if they can be combined with the above-mentioned oxide scintillator, they will be smaller. A scintillation counter with high energy resolution can be configured.

[0005]

However, a photodiode made of silicon has a high quantum efficiency wavelength of 500 nm due to its physical properties (bandwidth of about 1.1 eV).
It exists in a long wavelength region of １０００1000 nm. Therefore, the silicon photodiode has a drawback that the quantum efficiency is reduced in a short wavelength region (less than 500 nm), and the silicon photodiode has a drawback of about 350 nm to 450 nm in combination with each of the oxide scintillators having a peak wavelength in the short wavelength region. Is not suitable.

Therefore, the emission wavelength of the scintillator is set to the high quantum efficiency wavelength range (about 500 n) of the silicon photodiode.
m or more), the addition of additives to the scintillator has been devised, but it has not reached the practical range.

[0007] The present invention has been devised to solve the above-mentioned problems of the prior art, and has as its object to provide a radiation detection apparatus which is small and has high energy resolution.

The present inventor has noticed that other semiconductor light-receiving elements have the same advantages that the quantum efficiency is higher than that of a silicon photodiode photomultiplier tube, that they are small, and that they are resistant to mechanical shock.

[0009]

In order to achieve the above object, according to the present invention, there is provided a semiconductor light receiving device having a light receiving peak sensitivity of 500 nm or less which is close to the light emitting peak wavelength of an oxide scintillator, instead of a silicon photodiode as a light detector. An element was used. This is specifically the band gap 2.5e
Semiconductor light-receiving element using a compound semiconductor of V or higher, more specifically, a light-receiving peak sensitivity of 430 nm and 500 n
thallium bromide (TIB
r).

As shown in FIG. 3, a silicon photodiode has a light-receiving peak sensitivity between 900 nm and 1000 nm, whereas a photodiode made of thallium bromide (TlBr) has a sensitivity near 430 nm,
It can be seen that light of nm or less can be detected efficiently.

[0011]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a structure of a semiconductor radiation detecting apparatus to which the present invention is applied. A photodiode 3 made of thallium bromide (TlBr) is provided on a substrate 1 via an electrode 2. Its thickness is about 450 μm. A scintillator crystal 5 made of, for example, LSO is provided on the upper surface of the photodiode 3 via a transparent electrode 4.
Are laminated. Its thickness is about 4 mm. The upper end face of the scintillator crystal 5 in the figure receives radiation. The photodiode 3, the transparent electrode 4, and the scintillator crystal 5 are covered with a light shielding material 6. Reference numerals 7 and 8 are signal extraction lines.

FIG. 2 shows a cesium 137 (scintillation counter) using the above-mentioned semiconductor radiation detecting device (scintillation counter).
^{137 Cs)} is a graph showing the spectral analysis result at the time of irradiation with the. It can be seen that it is detected with high energy resolution.

[0014]

As is apparent from the above description, according to the semiconductor radiation detecting apparatus according to the present invention, the photodetector has a light receiving peak sensitivity of 500 nm or less, which is close to the light emitting peak wavelength of the oxide scintillator, instead of a silicon photodiode as a photodetector. By using a semiconductor light-receiving element having the following, specifically, a semiconductor light-receiving element made of a compound semiconductor having a band gap of 2.5 eV or more, more specifically, a semiconductor light-receiving element made of thallium bromide (TlBr) is used. The peak sensitivity wavelength of the detector can be reduced to 500 nm or less, which is close to the emission peak wavelength of the oxide scintillator, and a highly sensitive and small semiconductor radiation detector can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a semiconductor radiation detecting apparatus to which the present invention is applied.

FIG. 2 shows cesium 1 detected by the semiconductor radiation detector of FIG.
Graph showing the spectral analysis results when irradiated with 37 ⁽¹³⁷ Cs).

FIG. 3 shows a silicon photodiode and thallium bromide (T
1B is a graph comparing spectral sensitivity characteristics with a photodiode composed of 1Br).

[Explanation of symbols]

Reference Signs List 1 substrate 2 electrode 3 photodiode made of thallium bromide (TlBr) 4 transparent electrode 5 scintillator crystal 6 light shielding material 7, 8 signal extraction line

[Procedure amendment]

[Submission date] May 24, 2001 (2001.5.2)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

Further, a silicon photodiode has high quantum efficiency compared with the photomultiplier tube, because it has advantages such as strong mechanical impact small, if be combined with the oxide scintillator, small Thus, a scintillation counter having high energy resolution can be configured.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008] The present inventor has high quantum efficiency compared with the photomultiplier tube of silicon photodiodes, advantages such as strong mechanical shock compact was focused on the point also applies to other semiconductor photodetector.

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Onabe 5-6-27 Yoto, Utsunomiya, Tochigi Pref. CA19 CB01 CB11 5F088 AA01 AB07 BA01 BB07 HA10 HA15 LA03 LA07 LA08

Claims (3)

[Claims] 1. A radiation detecting apparatus comprising: a scintillator that receives radiation and emits light; and a semiconductor light receiving element, wherein a peak wavelength of light emitted from the scintillator and a light receiving peak sensitivity of the semiconductor light receiving element are both 500 nm or less. A semiconductor radiation detection device. 2. The method according to claim 1, wherein the semiconductor light receiving element has a band gap of 2.
The semiconductor radiation detecting device according to claim 1, wherein the semiconductor radiation detecting device is made of a compound semiconductor of 5 eV or more. 3. The semiconductor detector according to claim 2, wherein said compound semiconductor is thallium bromide (TlBr).