On the Radiation Thickness Gauge Utilizing γ Ray Back-Scattering (Part I)

Abstract

Basic data of radiation thickness gauge are given. The effect of distance between Co⁶⁰ and iron plate and their geometrical arrangements are experimentally determined to obtain optimum conditions. Effective scattering area is also determined and measurable maximum thickness, which is limited by the saturation of back-scattering, is achieved to be extended to 25_??_30mm by properly shielding the scattered rays from thin portions of the plate. Theoretical considerations on the design of the chamber most sensitive to scattered γ rays are given, 4mm for the wall thickness and 4 atm. pressure for the inner gas are found optimum for 70×70×200mm chamber size used in the experiment. The practical thickness gauge “Reflectron” is now being manufactured and in service in S Chemical Co's plant. Description of the apparatus in detail and data on various materials and backings will be reported shortly.