Progress of 3He spin-exchange for neutron polarization in Julich

Nuclear spin-polarized (3)He efficiently polarizes neutrons over a wide energy range including cold, thermal and hot neutron spectra by means of its strongly spin-dependent absorption of neutrons. At Forschungszentrum Julich we are studying the optical polarization of (3)He by two methods, metastable exchange and spin-exchange, in order to optimize the neutron polarization at various spectrometers of the FRJ-2 reactor. For the spin-exchange method we designed an open, refillable cell system. In contrast to the conventional sealed cells adopted at many other laboratories, we will be able to vary many crucial parameters in the (3)He cell, such as gas ratios of (3)He and N(2), total gas pressure, and temperature while always working in the same experimental environment of a single cell. Laser polarized Rb vapor is used to polarize (3)He through the spin-exchange interaction, and NMR is employed to determine the polarization of the (3)He after calibration with a proton (water) NMR signal. In this paper we will report the (3)He polarization and relaxation rate, T(1), observed for various gas conditions. (C) 2004 Elsevier B.V. All rights reserved.