Large-size bismuth silicate (Bi4Si3O12) scintillating crystals of good quality

We have achieved a considerable improvement in the growth of large Bi4Si3O12 crystals, offering the possible application in γ-ray detectors at high energies. Clear blocks with transverse/longitudinal dimensions as large as 25 mm200 mm were produced with good reproducibility. The pulse height uniformity along the longitudinal axis is within ±2%. The internal attenuation is less than 0.1%/cm at wavelengths above 400 nm. The radiation-induced optical absorption, which is about 2.5 m−1 at 104 rad (102 Gy) for the absorption coefficient at 480 nm, does not increase greatly even if the accumulated dose increases up to 108 rad. Spontaneous recovery continues for at least several tens of days, although the recovery is never complete. UV annealing occurs to some extent, in contrast to the case of BGO which darkens upon exposure to UV light. The scintillation characteristics are similar to those of small crystals reported previously. The light output is 25% of BGO and typical decay constants are 2.1 ns (for 6% of intensity), 40 ns (13%) and 112 ns (81%).