High resolution neutron time-of-flight experiments using the harwell 15 MeV linear electron accelerator

Abstract

A technique is described for producing neutron pulses of 0.25 μsec duration at 400 p.p.s. The electron gun of the Harwell 15 MeV linear accelerator is pulsed from an external modulator during the period of the normal radio frequency pulse of 2 μsec duration. Using timing channels of 0.2 μsec duration and a flight path of 31.8 m a nominal resolution of 8 mμsec m⁻¹ is obtained. The neutron output during the 0.25 μsec pulse is approximately 60% of the output obtained when using the normal 2 μsec electron pulse. Total cross section measurements using a bismuth sample demonstrate the improved resolution in the energy region of 10 to 20 keV.