A NOVEL DETECTOR FOR NEUTRON SPECTROSCOPY

NEUTRON SPECTROMETERS ARE WIDELY USED IN NUCLEAR PHYSICS RESEARCH. UNFORTUNATELY, THE PERFORMANCE OF EXISTING SPECTROMETERS IS LIMITED BY THE TECHNOLOGY OF THE NEUTRON DETECTORS USED IN THEM. THIS RESEARCH AIMS TO PRODUCE A NEW TYPE OF NEUTRON DETECTOR THAT IS IDEALLY SUITED FOR USE IN NEUTRON SPECTROMETERS OPERATING IN THE ENERGY RANGE OF 1 TO 100 KEV. THE DETECTOR SHOULD HAVE GAMMA-RAY AND THERMAL/EPITHERMAL NEUTRON REJECTION IMPROVED BY AN ORDER OF MAGNITUDE. IMPROVED GAMMA-RAY REJECTION RESULTS FROM A FACTOR OF THREE INCREASED PULSE HEIGHT FOR NEUTRON DETECTION RELATIVE TO GAMMA DETECTION AND SUPERIOR PULSE HEIGHT RESOLUTION. IMPROVED THERMAL/EPITHERMAL NEUTRON REJECTION RESULTS FROM THE GEOMETRY OF THE DETECTOR ALLOWING IT TO BE READILY SHIELDED AGAINST THE THERMAL/EPITHERMAL NEUTRON BACKGROUND WITHOUT SIGNIFICANT LOSS OF DETECTION EFFICIENCY FOR NEUTRONS WITH ENERGIES HIGHER THAN 1 KEV. THE NEW DETECTOR IS BASED ON THE SEMICONDUCTING SYSTEM LITHIUM-THALLIUM-BROMINE AND OWES ITS NEUTRON SENSITIVITY TO THE PRESENCE OF LITHIUM-6 AS A MAJOR CONSTITUENT. PRELIMINARY WORK HAS SHOWN THAT CRYSTALS OF THIS MATERIAL CAN BE GROWN IN THE LABORATORY; NEUTRON DETECTORS HAVE BEEN FABRICATED FROM THESE CRYSTALS. PHASE I OF THE RESEARCH PROGRAM FABRICATES NEUTRON DETECTORS FROM THIS MATERIAL AND DEMONSTRATES THEIR UTILITY FOR USE IN NEUTRON SPECTROMETERS.