Accelerator energy calibration using nonresonant nuclear reactions

Abstract

A new technique is presented for determining directly the beam energy of an accelerator to within 2 keV. This technique uses the conventional backscattering spectrometry (BS) setup, i.e. Si surface barrier detector and electronics along with a multichannel analyzer. Two measurements are required. The first is a BS measurement of a standard calibration sample, e.g. 5 Å of FeW alloy deposited on SiO 2. This data defines two linear equations that relate the energy per channel m and the energy intercept b of the system to the beam energy E 1. The second measurement is of some positive- Q nuclear reaction, e.g. 15N( p, α) 12C,Q = 4.965 MeV. By writing the energy of the outgoing particle as a Taylor series about some initial energy guess and keeping terms to first order, we obtain a third linear equation relating m, b and E 1. A positive Q nuclear reaction is required to prevent these three equations from being homogeneous. These equations can be solved iteratively for E 1 along with m and b. This technique has the advantage that it can be readily applied at essentially any energy between 0.5 and 3 MeV. By contrast, only a small number of suitable resonances exist in this energy range.