Performance of the prototype LANL solid deuterium ultra-cold neutron source

A prototype of a solid deuterium (SD2) source of Ultra-Cold Neutrons (UCN) is currently being tested at LANSCE. The source is contained within an asse mbly consisting of a 4 K polyethylene moderator surrounded by a 77 K beryll ium flux trap in which is embedded a spallation target. Time-of-flight meas urements have been made of the cold neutron spectrum emerging directly from the flux trap assembly. A comparison is presented of these measurements wi th results of Monte Carlo (LAHET/MCNP) calculations of the cold neutron flu xes produced in the prototype assembly by a beam of 800 MeV protons inciden t on the tungsten target. A UCN detector was coupled to the assembly throug h a guide system with a critical velocity of 8 m/s (Ni-58). The rates and t ime-of-flight data from this detector art: compared with calculated values. Measurements of UCN production as a function of SD. volume (thickness) are compared with predicted values. The dependence of UCN production on SD, te mperature and proton beam intensity are also presented. (C) 2000 Elsevier S cience B.V. All rights reserved.