Recent advances in polarised 3He spin filters at the ILL

High level of 3He polarization maintained in an on-beam 3He spin filter using SEOP

“…• C. And optionally a transverse RF field for performing adiabatic fast passage spin reversal of the 3 He can be installed so that the system can be used also be used as a neutron flipper. Several such SEOP based polarizer have been constructed for NSF [1,8,9,10]A block diagram of our device is shown in Figure 1.…”

“…Much work has been done to optimize the use of polarized 3 He for use as neutron spin filters (NSF). Routinely experiments using 3 He NSF are conducted at many neutron sources worldwide.…”

“…At the JCNS we have chosen to work on in-situ polarization of the 3 He gas using the spin exchange optical pumping method (SEOP) [6]. 3 He polarizations of up to 80% in 3 He NSF cells have been verified with neutron measurements [2,4,7]. In these experiments the 3 He was polarized off-line, and thus undergoes T 1 nuclear magnetic decay of the 3 He polarization which typically has a time constant of 100-300 hours.…”

“…Long measurement times are often required in such experiments and the data quality is a function of the 3 He polarization. This is the case for neutron scattering where the 3 He can be used to analyze the spin of a scattered neutron beam and relatively small fluxes of polarized neutrons leads to experiment times longer than several days. Consequently the Jülich Centre for Neutron Science (JCNS) is developing spin-exchange optical pumping (SEOP) systems capable of polarizing the 3 He gas in place on a typical neutron instrument.…”

Magnetic Resonance Imaging: From Spin Physics to Medical Diagnosis

“…Mechanical compression attempts resumed only after the first multi-watt lasers for MEOP have been developed in the late 1980s [63], this time succeeding in reaching sufficient polarization and pressure for use in various experiments [64,65], in particular to prepare polarized 3 He targets for the measurement of the neutron electric form factor in scattering experiments of polarized electron beams [66]. Since then, various non-relaxing mechanical compression techniques have been applied to polarized 3 He, using a diaphragm pump [67], a peristaltic pump [68], or a piston compressor [69,70] for applications in lung MRI, in more accurate electron scattering experiments, and in neutron spin filters [71,72].…”