Non-magnetic flexible heaters for spin-exchange optical pumping of 3 He and other applications.

Spin polarized ³ He gas is currently widely used in various scientific fields and in medical diagnosis applications. The spin polarization of ³ He nuclei can be achieved by spin-exchange optical pumping (SEOP). In SEOP, the ³ He gas is enclosed in a glass cell together with alkali metals and is then heated to maintain the alkali metal vapor pressures at the appropriate levels. However, polarized ³ He gas is highly sensitive to any inhomogeneity in its magnetic field, and any small field gradients caused by the heaters may cause degradation of the ³ He polarization. To overcome this conflict between the heating process and the magnetic field, we have developed electrical heaters that essentially cause no magnetic fields. These heaters are thin and are flexible enough to be bent to within a radius of a few centimeters. These carefully designed heater elements and a double layer structure effectively eliminate magnetic field generation. The heaters were originally developed for SEOP applications, but can also be applied to other processes that need to avoid unwanted magnetic fields.