Light yield improvement in lead tungstate

A new approach to the possibilities of increase in the light yield (LY) of scintillations in lead tungstate (PWO) is discussed. The abrupt LY decrease above 200 K is connected with the start of rotations of WO4 tetrahedra which disturbs electrostatic separation between non-equilibrium electrons and holes, thus accelerating their non-radiative recombination. The logarithmic decrease of LY with elongation of the crystals is attributed to the capture of the emitted light by a new type of the surface light waves, created during the internal total reflection at the surfaces. Two ways of PWO LY increase are proposed: to retard WO4 tetrahedra rotations and to eliminate the creation of the surface light waves. Two experimental results are attracted to demonstrate the validity of these ways: the relative increase of the light emission at PWO surfaces and LY increase after deposition of transparent quartz coating onto PWO surface, which reduces the internal total reflection.