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.