CN201212910Y - A Cherenkov detector - Google Patents

Abstract

The utility model discloses a Cerenkov detector, which comprises: a Cerenkov radiator for emitting Cerenkov light; a photodiode coupled to one end of the Cerenkov radiator; A reflective film, coated on the remaining surfaces of the Cerenkov radiator except the end face coupled with the photodiode; a light-shielding layer, arranged on the outside of the Cerenkov radiator, the photodiode, and the reflective film, The leads of the photodiodes are drawn out from the light-shielding layer. The utility model adopts a photodiode as a readout device to make it more stable and reliable in the field of radiation imaging; the light collection efficiency is improved through the design of the reflective film; because the Cerenkov radiator has good light transmission performance, it can be used along the The incident direction of the ray is made very long, thereby improving the detection efficiency of X-rays and increasing the final Cerenkov signal output value. These measures enhance the usability of the Cherenkov detector in the field of radiation imaging.

Description

A Cherenkov detector

technical field

The utility model relates to the field of radiation imaging, in particular to a Cerenkov detector.

Background technique

A Cherenkov detector is a radiation detector that measures charged particles traveling faster than the speed of light in a medium. It consists of a radiation body that can produce the Cerenkov effect coupled with a photosensitive device. Radiator is transparent solid, liquid (distilled water is often used) or gas. It is applied to the measurement of high-energy charged particles, such as cosmic rays, high-energy accelerator particles, etc. In the application, according to different experimental purposes, different types of detectors are made to measure the speed, intensity or energy of charged particles. control signal etc. The Cherenkov detector has the advantages of simple structure and easy manufacturing process; its disadvantage is that the radiation intensity is too weak, and it is necessary to use a photomultiplier tube with high sensitivity and low noise, a good light collection system, and an anti-coincidence device to eliminate the background and other measures.

Cerenkov detectors are often used in high-energy physics because of the low light yield, that is, low sensitivity, and the distribution of the number of photons is inversely proportional to the wavelength of light, and rays with a velocity below a certain threshold do not produce Cerenkov Traditionally, photomultiplier tubes are generally used as the photoelectric conversion devices of Cerenkov detectors. The photomultiplier tubes are required to shield external electromagnetic interference, and compared with photodiodes used in radiation imaging, the quantum efficiency is low. , and the cost is high; these characteristics limit its application in the field of radiation imaging. However, because the generation mechanism of the Cherenkov signal is different from the scintillation detectors and gas detectors commonly used in the field of radiation imaging, it has special application value.

Utility model content

The purpose of this utility model is to provide a photodiode as an optical readout device, which can work in a common radiation imaging environment, and by selecting a suitable Cerenkov radiator and reflective layer design to improve the final signal output range , to improve the performance of Cherenkov detectors when they are used in the field of radiation imaging.

In order to achieve the above object, the technical solution of the utility model provides a Cerenkov detector, comprising: a Cerenkov radiator; a photodiode coupled to one end of the Cerenkov radiator; a reflective film, plated on the remaining surfaces of the Cerenkov radiator except the end face coupled with the photodiode; the light-shielding layer is arranged on the outside of the Cerenkov radiator, photodiode, and reflective film, and the photoelectric The leads of the diodes are drawn out from the light-shielding layer.

Wherein, the Cerenkov radiator is circular.

Wherein, the Cerenkov radiator is rectangular.

Wherein, the Cerenkov radiator is made of a material that is transparent and has an attenuation length of more than 1 m for light.

Wherein, the Cerenkov radiator is quartz glass.

Wherein, the Cerenkov radiator is organic glass.

Wherein, the reflective film is a reflective film that produces specular reflection.

Wherein, the reflective film adopts a specular reflective film ESR.

Wherein, the reflective film is aluminum foil.

Wherein, the light-shielding layer is black plastic tape.

The above-mentioned technical solution is only a preferred technical solution of the utility model, which has the following advantages: a photodiode is used as a readout device to make its work more stable and reliable in the field of radiation imaging; the light collection efficiency is improved through the design of the reflective film ; The angle between the direction of most Cerenkov light and the direction of X-ray incidence is not more than 90 degrees. Cherenkov light generates a signal on the photodiode; because the Cerenkov radiator has good light transmission performance, it can be made very long along the incident direction of the ray, thereby improving the detection efficiency of X-rays and improving the final Cerenkov signal output value , these measures enhance the usability of Cherenkov detectors in the field of radiation imaging.

Description of drawings

Fig. 1 is the structural representation of a kind of Cherenkov detector of the utility model embodiment;

Fig. 2 is A-A sectional view among Fig. 1;

Fig. 3 is a schematic structural diagram of the Cherenkov detector in use according to the embodiment of the present invention.

Among them, 1: Cerenkov radiator; 2: photodiode; 3: reflective film; 4: light-shielding layer; 5: Cherenkov detector array; 6: inspected object; 7: accelerator.

Detailed ways

Below in conjunction with accompanying drawing and embodiment, the specific embodiment of the utility model is described in further detail. The following examples are used to illustrate the utility model, but not to limit the scope of the utility model.

Referring to FIG. 1 and FIG. 2 , the Cherenkov detector in this embodiment is composed of a Cherenkov radiator 1 , a photodiode 2 , a reflective film 3 and a light-shielding layer 4 . The change in light causes the current in the photodiode to change, which converts the light signal into an electrical signal. The Cerenkov radiator 1 is rectangular or cylindrical; the Cherenkov radiator 1 is made of a material that is transparent and has good transmittance to ultraviolet light, such as made of plexiglass or quartz glass, and the transmittance Good means that the light attenuation length is more than 1m; the length of the Cerenkov radiator 1 can be determined by the size of the X-ray energy and the properties of the material of the Cerenkov radiator. The photodiode 2 is coupled to one end of the Cherenkov radiator 1 , and the sensitive area of the photodiode 2 faces the Cherenkov radiator 1 . Except for the end face coupled with the photodiode 2, the Cherenkov radiator 1 is coated with a reflective film 3 on the other surfaces, and the reflective film 3 is a reflective film for specular reflection. When coating the reflective film 3, the reflective side of the reflective film 3 should face the Cerenkov radiator 1, and the non-reflective side should face the light-shielding layer 4. The reflective film 3 can use the specular reflective film ESR of 3M Company in the United States. (Enhanced Specular Reflector) or aluminum foil, preferably the specular reflection film ESR of 3M Company in the United States, which does not contain metal components and has a reflectivity of more than 98.5%. The reflective film 3 and the photodiode 2 are separated from the outside world by a light-shielding layer 4 except for the lead wires. The light-shielding layer 4 can protect visible light from light, but X-rays can pass through effectively, meeting the above requirements. The light layer 4 is fine, for example, choose cheap and easy-to-use black plastic tape.

When the Cherenkov detector in this embodiment is used, X-rays are incident from the opposite side of the photodiode 2 , that is, incident into the Cherenkov detector from the side facing the sensitive area of the photodiode. The recoil electrons produced by the Compton scattering of X-ray photons in the Cherenkov radiator 2 also move forward, and most of the direction of the Cherenkov light produced by the recoil electrons also propagates forward, so The specular reflection through the reflective film 3 reaches the photodiode to generate a signal. In this embodiment, the design of the mirror surface utilizes the directional characteristics of Cerenkov light to improve the light collection efficiency.

In this embodiment, the Cerenkov radiator used is made of materials with good transmittance to visible light and near-ultraviolet light, so the self-absorption in the light transmission process is small, and it can do a good job in the X-ray incident direction. Long, the length can be determined according to the energy of X-rays.

Referring to Fig. 3, when the utility model is applied, a plurality of Cerenkov detectors 1 of the utility model are arranged into a Cerenkov detector array 5 with a sector or an L-shaped angle, so that the Cerenkov detectors The central axis points to the target point of the accelerator 7 . When the inspected object 6 passes through the X-ray beam, the X-rays passing through the inspected object 6 are incident on the Cherenkov detector array 5, and the X-rays are incident on the Cerenkov detector array 5 from the surface facing the sensitive area of the photodiode. In the Cherenkov detector, it firstly interacts with the Cherenkov body to generate secondary electrons, and the part of the secondary electrons in which the energy is high enough will emit Cherenkov light. If the X-ray energy is low, So that if the energy of the secondary electrons it produces is lower than the threshold, it will not produce Cherenkov light; that is, the detector has requirements for the energy of X-ray photons; under the determination of the X-ray energy spectrum structure, Cherenkov detection The size of the output signal of the detector is proportional to the X-ray intensity, and the Cerenkov detector outputs the output signal of the thickness, density, material and other characteristics of the object in the reaction box according to the change of the X-ray intensity, and through the corresponding readout The circuit converts the output signal into a grayscale image, so that the perspective image of the object 6 to be inspected can be obtained. The readout circuit can be an ordinary electrical circuit, and its design only needs to be able to convert the output signal into a grayscale image. The readout circuit belongs to common knowledge for those skilled in the field of electrical circuits, so it will not be discussed here. detail.

It can be seen from the above embodiments that the embodiment of the utility model uses a photodiode as a readout device to make its work more stable and reliable in the field of radiation imaging; the design of the reflective film improves the light collection efficiency; most The angle between the direction of Cerenkov light and the direction of X-ray incidence does not exceed 90 degrees. Specular reflection can make Cherenkov light directional transmission, reduce the number of reflections, and help make more Cerenkov light in optoelectronics The signal is generated on the diode; because the Cerenkov radiator has good light transmission performance, it can be made very long along the incident direction of the ray, thereby improving the detection efficiency of X-rays and increasing the final Cherenkov signal output value. These measures enhance The availability of Cherenkov detectors in the field of radiation imaging.

The utility model above is also applicable to the situation where a radioactive isotope source is used as the radiation source.

The above is only the preferred embodiment of the utility model, and it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the utility model, some improvements and modifications can also be made. And retouching should also be regarded as the protection scope of the present utility model.

Claims (10)

1. A Cerenkov detector, characterized in that it comprises: Cherenkov radiators, used to emit Cherenkov light; a photodiode coupled to one end of the Cerenkov radiator; A reflective film, coated on the remaining surfaces of the Cerenkov radiator except the end surface coupled with the photodiode; The light-shielding layer is arranged outside the Cerenkov radiator, the photodiode, and the light-reflecting film, and the leads of the photodiode are drawn out of the light-shielding layer. 2. The Cerenkov detector according to claim 1, wherein the Cerenkov radiator is circular. 3. The Cerenkov detector according to claim 1, wherein the Cerenkov radiator is rectangular. 4. The Cerenkov detector according to claim 2 or 3, characterized in that the Cerenkov radiator is made of a transparent material with an attenuation length of more than 1 m for light. 5. The Cerenkov detector according to claim 4, wherein the Cerenkov radiator is quartz glass. 6. The Cerenkov detector according to claim 4, wherein the Cerenkov radiator is organic glass. 7. The Cerenkov detector according to claim 1, characterized in that the reflective film is a reflective film that produces specular reflection. 8. The Cerenkov detector according to claim 7, wherein the reflective film is a specular reflective film ESR. 9. The Cerenkov detector according to claim 7, wherein the reflective film is aluminum foil. 10. The Cerenkov detector according to claim 1, wherein the light-shielding layer is black plastic tape.

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