Polarizer/analyzer filter for nuclear resonant scattering of synchrotron radiation

Abstract

A silicon (840) channel-cut crystal with a large asymmetry is used to linearly polarize synchrotron radiation generated by an undulator source at the 14.413 keV nuclear resonance of 57Fe. The resulting σ̂-polarized radiation is then scattered from an 57Fe foil placed in a magnetic field that effects σ̂→π̂ polarization conversion within the resonant bandwidth. A second crystal of the same type is placed in a crossed position to suppress the nonresonant radiation while transmitting the π̂-polarized resonant radiation. A polarization suppression factor of 6×10−7 has been obtained. The suppression of the nonresonant radiation allowed monitoring the decay of the nuclear levels after 1 ns of their excitation.