Research on 3He spin filter cells made of quartz glass

We report the first experimental observation of a T1 dependence on the magnetic history in uncoated as well as in cesiated cells made out of quartz glass. A huge decrease (about one order of magnitude) of the relaxation time constant T1 occurred solely due to short exposure of the cells to an external magnetic field of 0.7 T. Partial or total restoring of the initial relaxation time constant T1 could be achieved by a careful degaussing of the magnetised cells. The magnetisation turned out to be very stable in time, keeping T1 unmodified during a few months or even years. The relaxation time T1 was measured directly in the neutron beam from the decay of the polarised neutron flipping ratio. The cell preparation procedures are also presented.