Organosilicon luminencent compositions for scintillation detectors

Abstract

Application of organosilicon materials in the detection devices is one of the promising directions in the improvement of their characteristics. Especially efficient are these materials when used as a polymer base of the converting elements.

Described in this paper are compositions and results of the use of polymer luminescent compositions for the increase of chemical resistance and improvement of CsI and CsI (Tl) crystals' characteristics; the latter being in the form of the truncated pyramids with the cross-section as a polygonal and up to 320 mm long. They are intended for furnishing complex modular systems of calorimeters.

The authors studied the effect of the polymer structure (of the stair and branched structure), chemical nature of the luminescent admixtures and their concentration in the composition on the variation of scintillation and performance characteristics of the detectors.

It was shown that application of thin film (15±5 μm) siloxane spectrum shifting coatings to all the facets of the pyramid except for the base which serves as the output window allows not only to reliably protect the scintillator from the effect of the atmosphere moisture but also to correct efficiently its characteristics. The advantage of such coatings is a high stability of their optical and luminescent properties in time, good adhesion and chemical inertness to the scintillator material.

Application of siloxane compositions as coating for CsI gives a possibility to shift the intrinsic luminescence of the crystal towards the region of a higher transparency of the material and better sensitivity of PMT, this allowing to increase the light yield of the fast component by the factor of 1.5. In case of CsI the nonuniformity of the light yield along the pyramid can be lowered while not worsening but even increasing the mean light yield. Such coating is easily removed by a solvent and applied again to the surface not changing the size of the scintillator and the grade of surface treatment.