An unsuppressed array for gamma-ray coincidence measurements following neutron-induced reactions

Journal Article · Thu Jul 01 04:00:00 EDT 1999 · Transactions of the American Nuclear Society

OSTI ID:20005761

Yates, S W; Warr, N V; Brown, T B; Strano, M; Garrett, P E

A four-detector array was developed for measuring gamma-gamma coincidences following inelastic neutron scattering--i.e., the (n,n{prime}{gamma}) reaction--with accelerator-produced neutrons. Following the initial success in these measurements, this array was moved to the Weapons Neutron Research (WNR) area at the Los Alamos Neutron Science Center (LANSCE) for coincidence measurements with higher-energy neutrons from the LANSCE/WNR unmoderated neutron spallation source. Additional measurements with monoenergetic accelerator-produced neutrons with energies up to 24 MeV are in progress at the University of Kentucky. The Kentucky gamma-ray spectrometer (KEGS) consists of four unsuppressed high-purity germanium (HPGe) spectrometers at backward angles, {approximately}125 deg, to the direction of the incident neutrons. The GEANIE array at LANSCE pioneered the use of multidetector arrays at an unmoderated neutron spallation source and has produced some interesting results. However, the coincidence efficiency of this array, which is a modification of the Berkeley HERA array designed originally for use in heavy-ion reactions, is not optimal for the lower gamma-ray multiplicity of neutron-induced reactions. Therefore, KEGS was moved to LANSCE for measurements during a 2-month period in the fall of 1998. The configuration of the array was the same as that used in measurements at the University of Kentucky, but the massive lead shield, which gave rise to large backgrounds from reactions induced by the very energetic neutrons, was removed. Standard LANSCE/WNR methods were used to produce a collimated neutron beam. Coincidence measurements of the reaction products from high-energy (E{sub n}{lt} 500 MeV) neutrons on targets of {sup 59}Co, {sup 181}Ta, {sup 186}W, and {sup 196}Pt were performed. In these measurements, the neutron flight time is used to determine the neutron energy; therefore, TOF background suppression, one of the advantages of measurements with pulsed monoenergetic neutrons, is lost.

• Research Organization: Univ. of Kentucky, Lexington, KY (US)
• OSTI ID: 20005761
• Journal Information: Transactions of the American Nuclear Society, Journal Name: Transactions of the American Nuclear Society Vol. 81; ISSN 0003-018X; ISSN TANSAO
• Country of Publication: United States
• Language: English

Related Subjects

44 INSTRUMENTATION
66 PHYSICS
ACCELERATOR FACILITIES
COINCIDENCE SPECTROMETRY
GAMMA SPECTROMETERS
INELASTIC SCATTERING
NEUTRON REACTIONS
NEUTRON SOURCES