Very long nuclear relaxation times of spin polarized helium 3 in metal coated cells

Functional lung imaging using hyperpolarized gas MRI

“…This direct process excites the He nucleus with circularly polarized laser light at a wavelength of 1083 nm and allows more rapid production of polarized gas, 0.4 liter/hour of up to 60% polarized He-3 at atmospheric pressure (36,37). Production capacity with either technique is sufficient to provide He-3 by either local or central production (36,38) with transport in specialized containers (39) and is comparable in preparation time to clinical radiochemistry processes.…”

Fundamental mechanisms of 3He relaxation on glass

“…(22) predicts that bare Pyrex is of marginal utility for polarized 3 He storage, a fact that has been verified by several investigators [5,14,15]. As discussed in Section 4.1, this situation changes drastically for cells containing alkali metals.…”

Long-Lifetime Low-Scatter Neutron Polarization Target

“…It would be inconvenient if they could not operate for at least several hours before recharging. The material that has been exploited by most groups is aluminosilicate glass (e.g., Corning 1720 and GE-180), from which manifolds with up to 100 h 3 He polarization lifetimes have been made [23,24]. For reasons that are only recently becoming clear, certain glass manifolds have a very low depolarizating effect on 3 He.…”

“…It is not known why the lifetimes are not even longer, however it may be that aluminum acquires ferromagnetic impurities on the surface while being formed. We suggest that much longer lifetimes are achievable by using appropriate coatings such as have been used to greatly decrease the depolarization effects of borosilicate glass [24]. In the case of borosilicate glass, the 3 He polarization lifetime was increased from 1 hour for uncoated cells to as much as 100 hours for cells that were internally coated with cesium.…”