Wide Angle Polarization Analysis With Neutron Spin Filters

We report substantial improvements in a compact wide angle neutron spin filter system that was recently employed on the Multi-Axis Crystal Spectrometer at the Center for Neutron Research at the U. S. National Institute of Standards and Technology. The apparatus consists of a cylindrical He-3 polarizer cell and wide-angle He-3 analyzer cells, a vertical solenoid to provide a uniform magnetic field, and a shielded radio-frequency solenoid for the polarizer cell. Nuclear magnetic resonance is employed to reverse the polarization in the polarizer cell and monitor the He-3 polarization in all cells. The first experiment using this apparatus was carried out with cylindrical analyzer cells with limited angular coverage due to low polarizations in fused quartz cells. We present results for aluminosilicate glass analyzer cells that cover 110. and have long relaxation times (100 h to 400 h). Using two 100 W diode bars spectrally narrowed with chirped volume Bragg gratings, we have obtained 65 % -80 % 3He polarization in these cells. The He-3 polarization has been measured by neutron transmission and electron paramagnetic resonance. Additional progress includes an improved holding field solenoid and decreased spin-flip losses.(C) 2012 Published by Elsevier B.V.