RU1471546C - Method of obtaining cesium iodinite-base scintillator - Google Patents

Abstract

The invention relates to a technology for producing scintillators and can be used in the manufacture of x-ray and gamma radiation detectors in medical and industrial tomography. The aim of the invention is to reduce the afterglow in the millisecond range. The invention describes a method for the study of scintillator based on cesium iodide, including drying cesium iodide and drying an absorber — boron oxide or boric acid when heated at a speed of 5-15 deg / s to 100-250 0 and constant evacuation, mixing dried components, introducing graphite into the mixture in an amount of 1-10% by weight of cesium iodide, drying the resulting mixture with continuous evacuation, melting the dried mixture, introducing the activator — sodium or thallium into the obtained melt, holding the melt with subsequent directed crystallization crystallization and annealing of the obtained crystal. The invention allows to obtain crystals based on cesium iodide, the afterglow of which in the millisecond range is 2-9 times lower and the radioluminescence intensity is 2-2.5 times higher than the similar characteristics of crystals obtained in a known manner. In this case, the crystals have no foreign inclusions. 1 tab.

Description

vj

The invention relates to a technology for producing torr scintillas and can be used in the manufacture of an X-ray and gamma-ray detector in medical and industrial tomography.

The aim of the invention is to reduce the afterglow of the scintillator in the millisecond range.

Example 1. In the ampoule, 5P g of boron oxide or boric acid of qualification is placed especially pure or spectrally pure. The ampoule is connected to a vacuum system and placed in an oven. With continuous evacuation, the furnace is heated at a speed of up to 250 ° C. During the heat treatment, the contents of the ampoule are shaken to prevent sintering manually or by means of a vibrator. Pre-dried with cesium iodide in the amount of ZOO g is mixed with 100 mg of dried boron oxide. The conical part of the ampoule with a diameter of 50 mm was filled with the resulting mixture. For the remainder of the charge to avlput

Joint venture

OS

25 g of qualifying graphite is spectrally pure and the rest of the ampoule is filled. The ampoule with the charge is placed in the furnace and the mixture is dried under continuous vacuum for 10 hours. The vacuum ampoule with the charge is placed in the upper chamber of the growth furnace at, then the charge It is melted under vacuum, after which 2 g of the activator, thallium iodide, are introduced into the melt. Without breaking the vacuum in the ampoule, disconnect it from the vacuum system and maintain the melt for 10 hours. Then, directed crystallization is carried out in a vertical furnace at a speed of 2 mm / h. The resulting crystal was removed from the ampoule by flash melting, annealed at 550 ° C and cooled to room temperature at a rate. -.

The table shows the properties of the crystals obtained according to the invention and the data of comparative examples.

From the data presented in the table it follows that the afterglow value of the crystals obtained according to the invention is 2–9 times lower, and the radioluminescence intensity is 2–2.5 times higher than the similar characteristics of crystals obtained in a known manner. D) In this case, the crystals have no foreign inclusions.

An increase in the heating rate during the heat treatment of the absorber above 15 deg / h leads to its sintering, and therefore, its further use leads to the formation of oxygen-containing impurities in the crystal and an increase in the afterglow intensity. Lower heating rate lower

5 ° / h is not practical due to the large increase in the heat treatment time. Modes of heat treatment of the absorber are selected from the conditions of removal of adsorbed and crystallization water. Adsorbed in the lag is removed at a temperature above

0

5, Oh

0

g

at, a minimum afterglow is achieved. A further increase in temperature is impractical.

An adsorbent is used to clean the melt from flakes. The choice of adsorbent is due to the fact that it should easily float to the surface of the melt, entrainment of impurities. Its mass fraction should significantly exceed the mass fraction of suspended particles, but the crystal should not be contaminated with adsorbent particles.

Graphite was chosen as the adsorbent, which is used to purify the melt of the products of the interaction of boron oxide with impurities.

The advantages of manufacturing include an increase in the transparency of the crystal to its own radiation, as well as an increase in the yield of products from these crystals.

Claims (1)

Claims A method for producing a cesium iodide scintillator, including drying cesium iodide and an absorber — boron or boric acid, mixing the dried components and drying the resulting mixture with continuous vacuum, melting the dried mixture, introducing sodium or thallium activator into the obtained melt holding the melt followed by directed crystallization and annealing the obtained crystal, characterized in that, in order to reduce the afterglow of the scintillator in the millisecond range, absorb the drying of the original is carried out by heating at a rate of 5-15 ° C / h to 100 - 250 C and a constant Rovani evacuated, and the charge before drying administered graphite in an amount of 1-10% by weight of cesium iodide.