Mechanical Doppler compensation for electron excitation of NRF photons

Identification of Special Nuclear Material (SNM) by Nuclear Resonance Fluorescence is developing as a promising method but is currently limited by available photon sources. A very limited source spectrum (≪ 1 eV width at MeV energies) is ideal. One method of providing this source is by electron excitation of a target containing the nucleus of interest. In this method, however, the photon energy mismatch caused by the nuclear recoil must be accounted for. We propose to provide this Doppler compensation by directing an MeV-range electron beam at a rotating target loaded with the nucleus of interest. Rotation rates are in excess of 200,000 RPM for the NRF lines of interest in SNM detection. Some design scenarios will be discussed, along with issues pertaining to nuclear physics and materials science.