Apparatus for Measuring the Energy Spectra of Mass-Selected Particles in Coincidence with Fission

An apparatus used to observe the energy spectrum of protons in coincidence with 14-Mev deuteron-induced fission is described. One feature is a mass identifier which operates over a range of 5 to 25 Mev and gives good separation of protons, deuterons, and tritons. Its operation depends on measuring the particle energy loss, ΔE, in a transmission counter and the residual energy, E, in a separate counter. The E and ΔE pulses are introduced into an electronic computer which in 1 μsec produces a pulse whose height is closely proportional to mass. The accuracy of mass separation is illustrated by a representative case in which less than 0.1% of the elastically scattered deuterons appear in the proton energy spectrum. In the presence of the complicating effects of cyclotron beam modulation, the chance coincidence correction to the proton-fission coincidence spectrum is made by simultaneously measuring the delayed and undelayed spectra.