JPH0688747A - Cooling type photodetector - Google Patents

Abstract

PURPOSE:To provide a cooling type photodetector which realizes a simple and small configuration, easy operation and maintenance, as well as, a low cost. CONSTITUTION:A vacuum cell type light entrance window 12 is provided in front of a photoelectric surface 10a of a photomultiplier 10, and a cooling block 16 provided with a Peltier element 18 for cooling the photoelectric surface 10a is assigned. A box 20 housing these components is attached with a radiating plate 30 which radiates the heat of the Peltier element 18, and a side wall surface 12b of the light entrance window 12 acts as an optical reflection surface. The heat of the Peltier element 18 is transferred to the light entrance window 12 through bath the radiating plate 30 and the box 20, and at the same time, a diffused light L1 from a sample 70 directly enters into the photoelectric surface 11a, and a diffused light L2 enters there through reflection on the side wall surface 12b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to a cooling type photodetector having a photoelectric conversion element for detecting weak light and converting it into an electric signal and having a cooling function for cooling the photoelectric conversion element. Regarding the device.

[0002]

2. Description of the Related Art A cooled photodetector is generally used to detect faint diffused light emission such as chemiluminescence and biological photons. This detection device includes a light incident window on which light from a sample is incident, a photoelectric conversion element (photomultiplier tube) for detecting light transmitted through the light incident window, and a cooling element (for cooling a photoelectric surface of the photoelectric conversion element ( Peltier element) and a heat dissipation means for dissipating the heat generated in the cooling element.

A specific example of this detecting device is shown in FIG. In this detection device, a head-on type photomultiplier tube 50 is used, and a thin vacuum cell type light incident window 52 is installed in front of the photocathode 50a of the multiplier tube 50 as an adiabatic light incident window. In order to cool the photocathode 50a of the photomultiplier tube 50, an annular cooling block 56 provided with a Peltier element 54 is arranged around the multiplier tube 50. The Peltier element 54 itself is cooled by a suitable heat radiating means (not shown). Further, the photomultiplier tube 50, the light incident window 52, and the cooling block 56 are housed in a box 58 having a shape as shown in the figure, and a ring-shaped heater 60 is provided in a portion of the box 58 adjacent to the light incident window 52. It is attached, and the heater 60 heats the light incident window 52.

In such a detection device, the diffused light L emitted from the sample 70 passes through the light entrance window 52, enters the photocathode 50a of the photomultiplier tube 50, and is an electric signal in the multiplier tube 50. Is converted to. By the way, in this detector, the photomultiplier tube 50 is normally cooled to 0 ° C. or lower in order to reduce the noise level, while the sample 70 is usually kept at about room temperature. Therefore, a temperature difference of 40 ° C. or more occurs between the photocathode 50 a of the multiplier 50 and the sample 70. Therefore, the surface of the light incident window 52 facing the photocathode 50a and the sample 7
A temperature difference also occurs between the light incident window surface 52a on the 0 side and dew condensation occurs on the light incident window surface 52a.
It is prevented by heating the light incident window 52 (especially the light incident window surface 52a) at 0. In addition, in order to prevent dew condensation on the light incident window surface 52a, in addition to the heating by the heater, dry air, dry nitrogen gas, or the like is forcibly blown onto the light incident window surface 52a.

Further, as another measure for preventing dew condensation on the light incident window surface 52a, the thickness of the light incident window 52 is specifically increased to about 25 to 50 mm. In this case, dew condensation is reduced, but the photocathode 50a
And the sample 70 become longer, and the photocathode 5 of the multiplier tube 50 increases.
There is another problem that the solid angle of 0a with respect to the sample 70 becomes small and the detection sensitivity of weak light decreases.

[0006]

As described above, when the thickness of the vacuum cell type light incident window 52 is increased, the dew condensation on the light incident window surface 52a is reduced, but the photocathode 50a of the photomultiplier tube 50 is reduced. Since the solid angle formed with respect to the sample 70 is small, the sensitivity of detecting weak light such as chemiluminescence and biological photons is reduced.

On the contrary, if the thickness of the light incident window 52 is reduced in order to increase the solid angle formed with respect to the sample 70, dew condensation easily occurs on the light incident window surface 52a, so that the heater 60 as shown in FIG. Therefore, it is necessary to heat the light incident window 52 and blow dry air or the like on the light incident window surface 52a.
Therefore, there is a problem that the structure of the detection device becomes complicated and large, the operation and maintenance thereof become complicated, and the device becomes expensive.

Therefore, the present invention has been made by paying attention to the above problems, and in a detector having a cooling function for a photomultiplier tube, a simple and compact structure, easy operation and maintenance,
It is also an object of the present invention to provide a cooled photodetector that realizes low cost.

[0009]

In order to achieve the above-mentioned object, a cooling type photodetector of the present invention is provided with a photoelectric entrance for detecting a light incident window on which light from a sample is incident and a light transmitted through the light incident window. In a cooling type photodetector comprising a conversion element, a cooling element for cooling the photoelectric surface of the photoelectric conversion element, and a heat dissipation means for dissipating the heat generated in the cooling element, the heat of the cooling element is incident on the light incident window. It is characterized in that a heat transfer means for transferring to the window surface is provided.

Since this detection device is provided with the heat transfer means, the heat generated in the cooling element (Peltier element) is transmitted to the light incident window surface and the light incident window surface is heated to prevent dew condensation. It For this reason, a heater and a blowing mechanism of dry air, which have been conventionally used to prevent dew condensation on the light incident window surface, are unnecessary. Therefore, the dew condensation prevention mechanism has a simple and compact structure, its operability is improved, and it is easy to maintain.
In addition, the cost is low.

In addition to the above characteristic structure, by making the side wall surface of the light incident window a light reflecting surface, the diffused light emitted from the sample is reflected by the side wall surface and becomes a photo surface of the photomultiplier tube. Since the light is incident, the incident efficiency of the diffused light on the photocathode is increased.
Therefore, even if a thick vacuum cell type light incident window is used as the light incident window, the detection sensitivity for weak light such as chemiluminescence and biological photons does not decrease.

[0012]

The cooling type photodetector of the present invention will be described below with reference to examples. A device according to one embodiment is shown in FIG. In this detector, a cylindrical vacuum cell type light incident window 12 made of a light transmissive material (eg, quartz) is used as an adiabatic light incident window in front of the photoelectric surface 10a of the photomultiplier tube 10 which is a photoelectric conversion element. Is installed and the side wall surface 1 of the light entrance window 12 is installed.
2b is coated with a light reflecting substance such as aluminum, and the side wall surface 12b is a light reflecting surface (mirror surface).

A portion of the photomultiplier tube 10 and the light incident window 12 around the photocathode 10a of the photomultiplier tube 10 is surrounded by a magnetic shield tube 14, and an annular cooling block 16 is provided on the tube 14. A low temperature side of a Peltier element 18 as a cooling element is attached to the cooling block 16. Therefore, the photocathode 10a is the cooling block 16
And is cooled down to room temperature or lower by the Peltier device 18 via.

The photomultiplier tube 10, the light incident window 12, the cooling block 16, the Peltier element 18, etc. are housed in a box 20 having the shape shown in the figure, and the light incident window 12 is fixed to the box 20. Further, the space inside the box 20 (hatched area in the figure) is filled with urethane foam 22 as a heat insulating material. A heat radiating plate 30 having a heat radiating fin 32 as a heat radiating means for radiating the heat generated in the Peltier element 18 is attached integrally to the box 20 in contact with the high temperature side of the Peltier element 18, and the heat radiating fin 32 is further forced. A fan 34 for electrically cooling the air is provided.
Most of the heat generated in the Peltier element 18 by this heat dissipation means is the heat dissipation plate 30, the heat dissipation fins 32, and the fan 34.
Is dissipated outside the device. Along with the heat dissipation, a part of the heat of the Peltier element 18 is transferred to the light incident window 12 by the heat transfer means composed of the heat dissipation plate 30 and the box 20, and the light entrance window 12 of the light entrance window 12 is transferred. The surface 12a is warmed.

A socket 40 is attached to the rear portion of the photomultiplier tube 10, an electric wire 42 such as a signal line or a high-voltage supply line is connected to the socket 40, and a water gap exists between the electric wire 42 and the box 20. An airtight seal 44 is provided to prevent entry. In the detection device configured as described above, the sample 7
The diffused light emitted from 0 enters the light incident window 12 through the light incident window surface 12 a of the vacuum cell type light incident window 12. Of the diffused light, the light ray L1 having a small angle with the optical axis passes through the light entrance window 12 and directly enters the photocathode 10a of the photomultiplier tube 10. Further, the light ray L2 having a large angle with the optical axis is
The light is reflected by the light-reflective side wall surface 12b of the light incident window 12 and then enters the photocathode 10a. In any case ray L
1, L2 are detected by the photomultiplier tube 10 and converted into electric signals.

While the detector is operating, the photocathode 10a of the photomultiplier tube 10 is cooled by the Peltier element 18, so that the noise level can be kept low. On the other hand, since the light incident window surface 12a of the light incident window 12 is heated by the heat from the Peltier element 18 transmitted through the heat dissipation plate 30 and the box 20, there is a temperature difference between the photocathode 10a and the sample 70. Even if there is, dew condensation does not occur on the light incident window surface 12a. Further, since the side wall surface 12b of the light incident window 12 is a light reflecting surface, the diffused light from the sample 70 is efficiently guided to the photocathode 10a. That is, by increasing the thickness of the light incident window 12,
Even if the solid angle formed by the photocathode 10a of the photomultiplier tube 10 with respect to the sample 70 becomes small, the detection sensitivity does not decrease, and even weak light can be detected with high sensitivity.

Although the vacuum cell type light incident window is adopted as the heat insulating type light incident window in the above-mentioned embodiment, for example, the heat insulating type light incident window having the side wall surface of the transparent plastic block having a small thermal conductivity as the light reflecting surface is used. It is also possible to use
Further, in the above embodiment, the adiabatic light incident window has a cylindrical shape, but it may have a spheroidal shape in order to improve the light condensing property of the diffused light. Further, in addition to the forced air cooling using the fan, natural air cooling or water cooling may be used.

[0018]

As described above, the cooling type photodetector of the present invention has the heat transfer means for transferring the heat of the cooling element to the light entrance window surface of the light entrance window, and therefore has the following effects. . (1) Since the light incident window surface of the light incident window is heated by the heat from the cooling element, dew condensation on the light incident window surface can be prevented. (2) In order to prevent dew condensation on the light incident window surface of the light incident window, there is no need to install a heater or a mechanism for blowing dry air, etc. Is simple and small, the device is easy to operate and maintain, and the device is low-priced. (3) By using the side wall surface of the light incident window as a light reflecting surface, the diffused light from the sample is efficiently incident on the photoelectric conversion element, and the light detection sensitivity is improved. (4) It is possible to provide a chemiluminescence detection device that can be used by anyone.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts of a detection device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a detection device according to a conventional example.

[Explanation of symbols]

 10 Photomultiplier tube (photoelectric conversion element) 10a Photoelectric surface 12 Vacuum cell type light incident window 12a Light incident window surface 12b Light-reflecting side wall surface 18 Peltier element (cooling element) 20 Box 30 Heat sink 70 Sample L1, L2 Diffusion light

Claims (2)

[Claims] 1. A light incident window on which light from a sample is incident, a photoelectric conversion element for detecting light transmitted through the light incident window, a cooling element for cooling a photoelectric surface of the photoelectric conversion element, and a cooling element generated. A cooling-type photodetector comprising: a heat-dissipating means for dissipating heat, wherein a heat-transfer means for transferring the heat of the cooling element to a light-incident window surface of the light-incident window is provided. apparatus. 2. The cooling type photodetector according to claim 1, wherein the side wall surface of the light incident window is a light reflecting surface.