MagniLium™ production on the HeliBox-Z100 hyperpolarizer

Xemed also announced in May 2007 that our model HeliBox-Z100 platform would become commercially available beginning in spring 2009 (orders in summer 2008). The core of this system is an 8.3 liter cylindrical aluminosilicate vessel. New technology under development allows safe operation at six amagat, six atmospheres at STP and almost nine atmospheres pressure at its operating temperature of 250°C. Total capacity of the vessel is fifty liters of ³He.

Hybrid spin-exchange optical pumping is provided by a 10:1 dual alkali mixture of potassium and rubidium allowing four hour spin-up times. Illumination is provided by a laser system consisting of three diode bar stacks, each with twelve 100W bars. Laser output delivered to the cell is approximately 3 kW at 795nm with a spectral width of 2nm in a 10cm diameter beam with a divergence under 2 mr.

Helium asymptotic polarization dependence on the X-factor as defined by Babcock et al. [Babcock06]. The different curves on a graph correspond to different T1 relaxation values for a 4h spin-exchange time (~250°C oven temperature and D=3.9 alkali vapor ratio).

Recent research has shown that asymptotic polarization achieved with spin-exchange optical pumping is dominated by the so-called X-factor of the cell. This X-factor is observed to be stable and reproducible for individual cells, but varies from cell to cell. Extrapolating existing data, we estimate that the X-factor of an aluminosilicate cell with our surface-to-volume ratio of 0.4 cm-1 can be expected to fall in the range around 0.2 and cell depolarization lifetime between 20 and 50 hours, leading to expectations for an asymptotic polarization between 71% and 78%.

A diagnostic recirculation system allows frequent checks of gas polarization and gas purity. Gas is extracted from the vessel through a gravity actuated ball-check-valve. A manifold allows either diagnosis or use. For diagnosis, the gas can be delivered to an NMR for polarization monitoring. Alternatively, the gas can be delivered to a gas sampling system with turbo-pump and residual gas analyzer to examine trace impurities. Gas can then be recirculated through getter pumps and back to the pumping cell. Finally, the manifold also allows delivery of the MagniLium™ to a Tedlar bag for diagnostic applications.

Performance

With a spin-up time of four hours and an asymptotic polarization as high as 78%, we project that polarization of 65%-70% can be achieved within twelve hours with 50 liters. Consequently we rate this polarizer at 65% polarization at an output usage of 100 liters/day. Lower usage will allow the polarization to continue rising to its asymptotic polarization.