A PROMPT GAMMA NEUTRON-ACTIVATION ANALYSIS FACILITY USING A DIFFRACTED BEAM

A prompt gamma neutron activation analysis facility has been construct ed at the MIT Research Reactor using a diffracted beam from a multilay ered graphite monochromator. A beam of 0.0143 eV neutrons of intensity 6 X 10(6) n/cm2s is available at the sample position. Backgrounds are low due to the use of the diffracted beam and are further improved by a sapphire crystal in the beam line. This design allowed the Ge detec ting crystal to be placed close to the sample position, approximately 4 cm, with a resultant high detection efficiency. The sensitivity of t he facility is reported for several representative pure elements. The major impetus for the construction of this facility was the need for a ccurate analyses of B-10 in biological samples for neutron capture the rapy research. Detailed results for this type of analysis are provided . The sensitivity of this diffracted beam facility currently exceeds t hat of two representative direct beam facilities using reactors of twi ce the power of the MITR-II. Possible major improvements in sensitivit y, more than an order of magnitude, and in background levels are outli ned for future development.