UA34650A - Method to make scintillation detector - Google Patents

Abstract

Method is proposed for making scintillation detector. It includes obtaining diffuse reflector on the surface of scintillator through dissolving surface layer of crystal with water with following drying in dewatered box and crystal packing to sealed container. Drying of crystal is performed in atmosphere of carbon dioxide. After that, at scintillator packing to sealed container, one forms in its volume atmosphere of carbon dioxide.

Description

The invention relates to technical physics, in particular, to detecting devices for recording ionizing radiation and can be used in the manufacture of scintillation detectors.

The main problems in the production of detectors are: first, the creation of a reflective shell on the side and back surface of the scintillator. The layer of reflective material must be minimal, otherwise the efficiency of radiation registration will be low: secondly, careful removal of residual moisture from the surface of scintillators and from the structural materials of the detector and reliable sealing of the container. Long-term storage and, especially, the use of detectors at elevated temperatures leads to the condensation of adsorbed water on the surface of the scintillator. Scintillation materials are, of course, hygroscopic, and even a small amount of water on the surface leads to irreversible deterioration of their characteristics (Grynev B.V. Seminozhenko V.P.

Scintillating detectors of ionizing radiation for harsh conditions of operation. Kharkiv:

Basis, 19931.

There is a known method of manufacturing a scintillation detector (French Patent Mo 2607262, cl. (301 T 1/202). which includes cleaning the container from gases reactive to the scintillator element; installing an alkaline-halide scintillator (for example, a very hygroscopic MaKTI) ) into this container, creating an atmosphere in it that does not react with the scintillator element at 150-2007С, assembling and sealing the detector. At the same time, the inert atmosphere is represented by one or more gases selected from the group of He, Agg2, CO" and M". When using these gases, of which helium and argon are truly inert (and therefore relatively expensive), the likelihood of residual moisture entering the container is reduced. This method involves anhydrous treatment of scintillator surfaces, or additional operations aimed at its thorough dehydration, which greatly complicates the technological process. In terms of content (dehydration, inert atmosphere), this method blocks the reaction that effectively occurs at the specified temperatures:

Mai!-3/202-Mai!Oz, which is the only possible one under the specified conditions (Smirnov N.N., Kraynyukov KI. Thermodynamics of the processes of thermal decomposition of sodium iodide by acid-containing components of air.

Single crystal. scintillators and organic luminophores. Kharkov. VNYY single crystals. -1969. -

Me1 .-0.59-683), if the sealing of the container is not carried out in an inert atmosphere, but in dry air, which is usually used. On the other hand, the method does not solve the problem of residual moisture and it cannot be applied to detectors for radiations with weak penetrating ability. because the MoO reflector layer, which is used as a standard, absorbs most of these radiations, as a result of which their intensity is weakened and the scintillation characteristics deteriorate.

As a prototype, the method of manufacturing scintillation detectors (AS Me 1457605, class (30171/202)) was chosen, when the prepared surfaces of scintillators are covered with a water film. The essence of the method is that in the manufacture of scintillation detectors Ma(TI) a diffuse reflector is applied to the surface of the crystal by transfer of the surface layer of the scintillator from a monocrystalline state to a polycrystalline state by dissolving this layer with water and subsequent drying. This leads to the destruction of the thin surface reflective layer of the scintillator and the formation of a finely dispersed polycrystalline reflective layer. which is firmly connected to the surface. This layer has a white color. not bad reflectivity, its thickness is determined by the degree of hydration of the scintillator surface.

The disadvantage of the prototype is that water not only dissolves the main substance, but also interacts with it, as a result of which hydroxides are formed, which sharply reduce the characteristics of the reflective coating.

It is known that sodium hydroxide Maon is opaque in the near-ultraviolet part of the spectrum, and the hydroxide of the activator - THION - in the visible region of the spectrum, as a result of which the optical and scintillation characteristics of the detectors deteriorate.

The basis of the invention is the task of improving scintillation and operational characteristics of detectors. The solution to this problem is provided by the fact that in the method of manufacturing a scintillation detector, which includes obtaining a diffuse reflector on the surface of the scintillator by dissolving the surface layer of the crystal with water followed by drying in a dehydrated box and packing the crystal in a sealed container, according to the invention, drying of the single crystal is carried out in the atmosphere carbon dioxide and then, when packing the scintillator in an airtight container, and its volume creates a reactive atmosphere of carbon dioxide.

The use of carbon dioxide in the process of drying a single crystal after applying a diffuse reflector on its surface leads to the fact that carbon dioxide effectively interacts with hydroxides even at room temperature and normal pressure. turning them into carbonates. It is necessary to determine that carbon dioxide remains chemically inert in relation to the main substance of the scintillator. The carbonates of the main substance and the activator - MagСО3 and ТИ2СО3С, which are formed in the surface film, have a reflection coefficient even better than that of the main substance. As a result, this reflector increases the light output from the detector and improves its scintillation characteristics.

The use of carbon dioxide gas (in the claimed method, the gas is not inert, but chemically active) to fill the volume of the container improves the operational characteristics of the detector, because during its storage CO2 continues to carbonize the remaining hydroxides in the reflective coating. Moreover. recondensation of residual moisture from structural materials onto the surface of single crystals does not lead to damage to the detector, because the same carbonates are formed as a result. The scintillation characteristics of detectors made in this way do not deteriorate over time, that is, their service life is extended.

The claimed method includes the following operations: 1. Applying a diffuse reflector to the surface of the scintillator by dissolving its surface layer with water. 2. Drying of crystals in a carbon dioxide atmosphere. 3. Filling the volume of the detector with carbon dioxide in the process of containerization of the scintillator.

Examples of the implementation of the method.

Example 1.

Eight experimental detectors measuring 30x5 mm were made from one part of the Ma(TI) crystal, homogeneous in terms of the activator content. For 4 detectors, a diffuse reflector on the surface of the scintillator was created by dissolving its surface layer with water for 1 minute, after which the crystals were dried in a dehydrated box (in an atmosphere of dry air, see the prototype), installed in a cup made of fluoroplastic with a wall thickness of 2 mm, such a mandrel with the crystal was placed in a standard container without optical contact between the crystal and the glass and the container was sealed. For the other 4 detectors, the reflector was created in the same way, but further drying of the crystal and sealing of the detector was carried out in a carbon dioxide atmosphere.

The graph shows radioluminescence (RL) spectra, where 1 corresponds to detectors made in

СО", 2 - corresponds to detectors manufactured according to the prototype. The RL intensity for all detectors manufactured according to the proposed method is higher by 1095 on average. It can be seen that even for normalized RL spectra, the area under curve 1 is larger than under curve 2. The shape of spectrum 1 corresponds to the activator glow of Mat).

When a thin Mylar film (a standard reflector for X-ray detectors) was used as an additional reflector between the crystal and the container, the RL intensity was lower, but the shape of the spectra and the ratio of light output for the samples were the same.

These results indicate an increase in light output by improving the reflectivity of the coating for detectors manufactured in a CO atmosphere."

Example 2.

From the same part of the crystal (see example 1), 4 standard scintillation detectors Ma((TI) were made

30x5 mm (optical contact between crystal and glass, ModO reflector between crystal and container). On the first two, a diffuse reflector is applied according to the prototype, on the others according to the method. that is claimed To speed up the process, the last two crystals were dried in a stream of carbon dioxide heated to 40-6O0"C for 2 hours. After drying, the detectors were packed and sealed in the standard way.

The results of measurements of light output and energy separation are given in table. 1. It can be seen that the site penetration and energy separation of the last two detectors are noticeably better.

Table mit Atmosphere t, I, UESV Y nshishish Air 35

Air and 59 shnnnshkzh TVOOOLOOVO OVO 7

Example 3.

Maa (TI) scintillation detectors with a size of 30x3 mm (optical contact, polished surfaces, Maa reflector) would be manufactured. The diffuse reflector was not applied to the side and rear surfaces of the scintillator. Half of the detectors were processed and packed in containers in an atmosphere of dry air (0.0395 СО"), and the other half - in an atmosphere of carbon dioxide (9095 СО"). The relative humidity in each case was deliberately increased to 1295. When stored for a year, the light output and energy resolution of the first three crystals deteriorated, while the other three (made in the atmosphere

CO"), these parameters have practically not changed. The results of measurements of light output and energy separation are given in table. 2. Next, the detectors were unpacked. Measurements of their absorption in the IR region of the spectrum showed that in the first series of samples, an admixture of OH ions was detected on the surfaces, and in the second - an admixture of COz7.

Tabnytsia 2 p y Sho at the beginning in a year at the beginning in a year storage, storage 727 Air 3 | Repeat | 90 | in 2.8 41 so | 1vv17va 35 | 3.5 51777 со5 |. in sog (| you

Thus, the claimed method allows: 1) to increase the reflective capacity of the diffuse reflector applied to the surface of the crystal and to significantly improve its scintillation characteristics regardless of the detector design, 2) to increase the degree of protection of the crystal from remaining moisture, which allows to extend the term scintillation detector services. count 08 - / in / and "7 /

The same; ; / A 2 o more and "a 300 z5o 400450 BYU 0000 y

Fig.

Claims (1)

The method of manufacturing a scintillation detector, which includes obtaining a diffuse reflector on the surface of the scintillator by dissolving the surface layer of the crystal with water, followed by drying in a dehydrated box and packing the crystal in a hermetic container, which is characterized by the fact that the drying of the crystal is carried out in an atmosphere of carbon dioxide, and then, when packing scintillator into a hermetic container, creating an atmosphere of carbon dioxide in its volume.