Design and Calibration of a Broad Range Magnetic Neutron Spectrometer

A broad range, low deflection magnetic neutron spectrometer has been constructed to measure the neutron spectrum from pulsed and steady state sources. The instrument will cover an energy range of from 1 to 15 MEV and is designed for an energy resolution of approximately 10 percent. A collimated beam of neutrons is allowed to impinge on a thin polyethylene radiator producing recoil protons. A small forward cone of these protons, corresponding to the full energies of the incident neutrons, is allowed to enter the magnetic field. The protons are analyzed and focus at some point outside the magnetic field. The focal line is straight and makes about a 10° angle with the pole piece edge With 6 MEV incident neutrons, a 0.001 inch radiator, and a 0.5 inch slit width, the energy resolution ig 9.3% and the efficiency is 5.1 x 10-8counts per neutron incident on the radiator.