The variation with space and time of the neutron energy distribution in pulsed BeO assemblie

Time dependent spatial distributions have been measured in -2 -2 BeC assemblies covering the buckling range 0.0083 cm to 0.0399 cm , referred to a density of 2.96 gm cm . This buckling range covers assemblies with decay curves that can be described by a discrete decay constant ( X ^ X*)^ a pseudodiscrete decay constant C\*< X X^) and a decay constant that changes with time (X > /V ). It was found K that the extrapolated length derived from these spatial distributions \ v^ -2 did not change with time if A < A . At a buckling of 0,0292 cm , (X-^X^), the extrapolated length changed by (0. 5 ^ 0. 25)per cent./1,000 us in the time range 1.4 ms to 2.9 ms and by (2„0-0.5)per cent.71,000 ps over a similar time range Tlie decay consta nta t oft het hel arngexets t hbiughcekrl insgpa, ti0a.l0 39m9o dec m"( th,e ( A2 1>1 A K ). 2 mode) did not lie on the X(B ) curve of the fundamental. In the region X < A < X„ the decay constants were in general higher than those for