Studies of neutron emission during the start-up phase of the Alcator C tokamak

Alcator C operations commenced with discharge cleaning and tokamak operation using hydrogen filling gas. Before and during these experiments no deuterium gas was allowed into the device. The earliest operation resulted in dosimeter readings of a few roentgen per shot in the vicinity of the limiter and a localized source of neutron emission of up to 109 neutrons per shot which were subsequently identified as having photonuclear origin. After seven months of operation, conditions were achieved that resulted in substantially lower photonuclear activity. Subsequently, deuterium fill gas was allowed into the device and measurement of neutron flux and energy spectra indicated that the majority of neutron emissions in Alcator C high-density deuterium discharges were consistent with having thermonuclear origins. (author)