INTENSE GAMA-RAY BEAMS

STANDARD MONTE CARLO AND FN METHODS FOR RADIATION TRANSPORT WILL BE USED TO STUDY A NEWLY PROPOSED SHIELD CONFIGURATION FOR PROTECTION AGAINST PARALLEL OR SLIGHTLY DIVERING GAMA RAY BEAMS IN A SPACE (NON-SCATTTERING) ENVIRONMENT. THE NEW CONFIGURATION EMPLOYS LAYERED SHIELDS, WITH CONSIDERABLE SEPARATION BETWEEN THE LAYERS, TO SHADOW THE TARGET, OF THE ASSUMPTION THAT THE DIRECTION OF INCIDENCE IS KNOWN. BY SUITABLE CHOICE OF LAYER SEPARATION AND DIMENSIONS MULTIPLE SCATTERING OF PHOTONS TOWARDS THE LINE OF SIGHT CAN BE MINIMIZED AND MAXIMUM ATTENUATION, THEORETICALLY ATTAINABLE ONLY WITH ZERO-AREA BEAMS SHOULD BE APPROCHABLE. THE ATTENUATION IS EXPECTED TO EXCEED THAT OF CONVENTIONAL SHIELDS BY A FACTOR OF 10 OR MORE, FOR A GIVEN TOTAL THICKNESS. OPTIMUM CONFIGURATIONS (SPACING, MATERIALS, ETC.) AND POSSIBLE APPLICATIONS TO OTHER RADIATIONS SUCH AS NEUTRONS WILL BE STUDIED. PHASE I STUDIES WILL IDENTIFY THE MOST IMPORTANT GEOMETRICAL AND MATERIAL FACTORS IN THE DESIGN OF OPTIMUM CONFIGURATIONS. EXPERIMENTAL WORK BOTH TO ESTABLISH NEEDED DATA (E.G., RAYLEIGH AND BOUND-ELECTRON COMPTON SCATTERING) AND TO VERIFY COMPUTATIONS MAY BE UNDERTAKEN IN PHASE II, WHOSE PERFORMANCE IS CONTINGENT ON OBTAINING INDICATIONS OF FEASABILITY DURING PHASE I.