A method of improving the fractional standard deviation in the count rate for an NM-65 neutron supermonitor
Date
1968
Authors
Coughlan, Padraig Austin
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Abstract
Neutron monitors are commonly used to investigate small fluctuations in the nucleonic component of cosmic rays at sea level. The monitors achieve a high counting rate by using a lead target to produce multiple evaporation neutrons. However, the large variations in the number of neutrons per evaporation result in a non-Poissonian distribution of the count rate. An experimental method of detecting only the randomly distributed nuclear disintegrations has been devised.
The evaporation neutrons are produced in bursts well separated in time so that the detector can be made sensitive only to bursts by the use of an appropriate dead time. For the NM-64 monitor the use of a 1200 microsecond dead time improves the fractional standard deviation by 18 percent.