LANSA - A LARGE NEUTRON SCINTILLATOR ARRAY FOR NEUTRON SPECTROSCOPY AT NOVA

A very sensitive neutron time-of-flight spectrometer is now in use at Nova. LaNSA consists of 960 channels of a neutron sensitive liquid scintillator (10 X 10 X 10 cm) coupled to a photomultiplier tube followed by a discriminator, TDC, and ADC to allow the measurement of neutron arrival time as well as pulse size. LaNSA is capable of measuring yields as low as 2.3 X 10(5) DT neutrons (100 detected hits) with resolution of 2.3 ns (170 keV for 14-MeV neutrons with 20-m flight path). Shielding and collimation provide background levels low enough to allow measurement of secondary and tertiary reaction neutrons. Details of design, testing, calibration, and experimental results will be presented.