Influence of crystalline surface quality on TlBr radiation detector performance
In this study, TlBr detectors were fabricated from crystals purified by the multipass zone refining and grown by the Bridgman method. Detectors were prepared using TlBr 0.3-mm-thick wafers, with surface submitted to different mechanical and chemical treatments. Optical microscopy and scanning electron microscopy evaluated the TlBr wafers surface quality. To analyze the surface quality influence in the detector response, systematic measurements of the pulse height spectra and energy resolution were carried out for each prepared radiation detector. The radiation response for these detectors was performed under /sup 241/Am gamma radiation excitation at room temperature. The influence of the surface quality of the TlBr wafer on its performance as a radiation detector was observed.
Development of the technology for growing TlBr detector crystals
Abstract The results of the development of the TlBr crystals growth technology are presented. For the purification of the TlBr salts, the combination of the vacuum distillation (VD) methods and directed crystallization (DC) was applied. The processes of the vacuum distillation were made in the vertical one-zone pipe furnace with the resistance heater. The equipment for the processes of directed crystallization is the vertical two-zone pipe furnace with the resistance heater. The processes of growth were made at the same device as DC, but with slightly modified modes. Technology modes for all technological processes are presented. All investigated crystals were grown from the melt by Bridgman–Stockbarger method. The values of the specific resistance of the grown crystals, the ratio of the transport characteristics of the electrons and holes are presented. The possible technological reasons affecting the electrophysical parameters of the crystal are analysed. The results of the development of the single and pixel detectors on the basis of the developed crystals are presented.
Characterization of ceramic composite membrane filters for hot gas cleaning
Abstract Novel composite ceramic membrane filters suitable for hot gas cleaning operations have been prepared from fly ash and titania particles on stainless steel woven mesh substrates. Both membranes had a structure like a solid packed bed with a thickness of less than 100 μm. In the domain of laminar flow, significant differences in the pressure drop between experimental results and those predicted from the Kozeny-Carman relationship were found, particularly for flow through the titania membrane. Membrane filters with extremely small pores such as the titania membrane are greatly affected by slip up to 80% in permeability at elevated temperatures. Efficiencies of filtration of typical coal fired power station exhaust fly ashes were found to be greater than 909% for both titania and ash membranes, whilst there was greater variation in the pressure drops in the ash membrane than in the titania at typical gas flows.