A new thermal triple-axis spectrometer at the research reactor FRJ-2

Abstract

A high intensity triple-axis spectrometer is described, which has been commissioned only a year before the final shut-down of the FRJ-2 reactor in May 2006. It was designed both as an instrument for quasi-elastic scattering with polarisation analysis on an area detector, and as a triple-axis spectrometer with polarization analysis for measurements of magnetic and nuclear inelastic scattering. The instrument features two exchangeable monochromators (Cu [200] and PG [002]), which enable both horizontal and vertical focusing. High monochromatic neutron current densities at the sample position of up to 4 × 107cm− 2 s− 1 (for pyrolytic graphite at 34 meV) and energies of up to 117 meV (with copper) have been achieved at the FRJ-2 (thermal flux density: 3 × 1014cm− 2 s− 1). The utilization of 3He filters both as polarizer and analyzer will enable polarization analysis for high-energy neutrons. The spectrometer is presently being prepared for installation at the new Chinese research reactor CARR at the China Ins...