-\validity of former assumptions so that more reliable calculations may be made in shielding design. The present work is concerned with the attenuation characteristics of. a shield when the rays from the source enter fhe shield obliquely. To a first approximation, the effective thickness of the shield _ has been assumed to be the length of path of the ray in the shiel id - that is, the more oblique the direction of incidence, the longer the bath and the greater the degree of shielding. In this study it has been Bhown that While oblique thickness of the barrier may be utilized in desig g equip- ment to shield against the primary rays, the contribution of sc tered radiation from within the shield may become appreciable. Scatt ed radia- tion increases significantly as the obliquity of the incident rdy increases, because of the shorter path length for a number of the scattered rays. Data obteined from these investigations will be applicable to the design of protective shielding for personnel operating cyclotro S, Van de Graaff generators, or handling Cobalt 60 and radium sources whi th are used in research and therzpy. Radiation Instruments Program (UNCLASST¥TED} Recent work under the cooperative contract with the vow. Bureau of otendards for stucies in the radiation instrument field includ 1. Study cf Film Dosimeters. A report has been completed tion of the several types of film dosimeters in use at the vari instailations. on the evalug: bus Corris S12 CTR The work consisted of two carts: E ARCHIVES