SINGLE SPHERE MULTIPLE DETECTOR NEUTRON SPECTRONMETER

ACCURATE MEASUREMENT OF NEUTRONS IS DIFFICULT AND REQUIRES COMPLEX, EXPENSIVE EQUIPMENT. IT IS AN ESPECIALLY SERIOUS PROBLEM FOR DOSIMETRY WHERE SEVERAL TECHMICAL ISSUES MAKE THE ACCURATE DTERMINATION OF RADIATION DOSE EXTREMELY DIF- FICULT. FOR EXAMPLE, NEUTRONS OCCUR OVER A WIDE RANGE OF ENERGIES AND HAVE DIFFERENT PHYSICAL PROPERTIES AS A FUNC- TION OF ENERGY. THE MOST COMMON APPROACH TO MAKING FIELD MEASUREMENTS OF NEUTRON SPECTRA AND DOSE IS TO USE A BONNER SPHERE INSTRUMENT. THIS IS A SINGLE NEUTRON DETECTOR PLUS A SET OF MODERATING SPHERES OF DIAMETERS RANGING FROM 3 TO 12 INCHES. BY COMBINING THE DETECTOR COUNT RATE WHEN IT IS INSERTED INTO EACH SPHERE, AN UNFOLDING OF THE NEUTRON PROBLEM. INSTEAD OF USING A SINGLE DETECTOR WITH SEVERAL BONNER MODERATORS, A LARGE NUMBER OF SMALL, INEXPENSIVE AC- TIVE DETECTORS EMBEDDED IN A SINGLE MODERATOR WILL BE USED THE ADVANTAGE OF AN ACTIVE DEVICE ARE SIGNIFICANT: THE RADIATION MEASUREMENTS WILL BE IMMEDIATELY AVAILABLE FOR ANALYSISAND REPEATED EXPERIMENTS IN DIFFERENT POSITIONS WILL BE RELATIVELY EASY. THUS THE PROPOSED INSTRUMENT WILL BE A VALU- ABLE NEW TOOL FOR BOTH PHYSICS RESEARCH AND HEALTH PHYSICS. SPECTRUM GICES AN ESTIMATE OF THE QUALITY FACTOR FOR THE FIELD. THIS PROCESS IS TIME CONSUMIN AND HAS SOME FUNDAMEN TAL INTERPRETATION PROBLEMS. THE PROPOSED NEW INSTRUMENT WILL USE A NOVEL APPROACH TO ADDRESS THIS PROBLEM. INSTEAD OF USING A SINGLE DETECTOR WITH SEVERAL BONNER MODERATORS, A LARGE NUMBER OF SMALL, INEXPENSIVE ACTIVE DETECTORS EMBED-DED IN A SINGLE MODERATOR WILL BE USED. THE ADVANTAGES OF AN ACTIVE ARE SIGNIFICANT: THE RADIATION MEASUREMENTS WILL BE IMMEDIATELY AVAILABLE FOR ANALYSIS AND REPEATED EXPERI- MENTS IN DIFFERENT POSITIONS WILL BE RELATIVELY EASY. THUS, THE PROPOSED INSTRUMENT WILL BE A VALUABLE NEW TOOL FOR BOTH PHYSICS RESEARCH AND HEALTH PHYSICS.