Polarized 3He gas circulating technologies for neutron analyzers

The United States and other countries are investing in neutron scattering facilities due to their promise for research that can catalyze advances in energy, telecommunications, manufacturing, plastics, transportation, biotechnology, and health. One new type of instrument, the wide-angle polarized neutron spectrometer, is severely constrained by the volume of high-quality polarized 3He gas that can reliably be produced. In a prior project, our team developed a prototype large-scale 3He polarizer with potential for addressing this need. By illuminating a large multi-liter glass polarizer cell inside a pressure vessel with a 1.2 kW wavelength-locked laser, we had demonstrated spin-up rates of 20% per hour for 50 STP liters, a world record. During Phase 1 of this project, we designed and had built an industrial-scale titanium vacuum pump. During Phase 2 we assembled a test rig with uniform field, transfer lines, and diagnostics. We demonstrated that this compressor could evacuate polarized 3He from an analyzer into a reservoir while retaining 3He polarization within a few percent. A second goal, the development of commercial-ready software and hardware infrastructure that could operate the system stably over time periods of several days was also achieved. Finally, the third Phase 2 goal, and much of the effort, was directed towards fabricating, filling, and testing 8.5 liter aluminosilicate glass cells for the polarizer. We were successful in flawlessly fabricating and filling three GE180 cells, achieving lifetime over 12 hours and delivering our ultimate polarization of 60%. Calculations show that additional tuning of the laser could have provided as much as 70%. We propose a sequential Phase IIB continuation of this project for new research and development tasks that extend beyond the scope of the original Phase II grant. Firstly, we will investigate new cell preparation techniques, including applying sol-gel coatings on these 8.5 liter cells fabricated from both borosilicate and aluminosilicate glasses to achieve long 40+ hour lifetime and high polarizations of 75% or more. Secondly, we will pursue 85% polarization by implementing a novel architecture external cavity pump laser we recently invented that can produce multi-kilowatt output at line-widths much narrower than any commercially available pump laser, as low as 30pm. Thirdly, we propose to demonstrate our 3He gas circulation and polarizer technology at a US neutron scattering facility as an essential first step of our commercialization strategy. Opportunities for commercializing this technology are outstanding. New large-angle neutron scattering spectrometer installations at laboratories throughout the world are actively seeking turnkey commercial polarized 3He solutions, while spin-off applications include neonatal lung imaging and optical pumping of alkali vapor lasers for missile defense.