Magnetization of 3He spin filter cells

A number of valved quartz glass 3He spin filter cells has been repeatedly exposed to various external magnetic fields in order to determine the influence of the induced wall magnetisation on the relaxation time in the cells. The procedures of magnetising and degaussing of the cells are described. A comparison of T1 measurements performed in the same cell by different methods attest the good reliability of the measurements as well as the time stability of T1 in the Cs coated quartz glass cells. No orientation dependence of the relaxation in fields of 8 G was observed. A strong dependence of T1 on the strengths of external magnetic fields, applied perpendicular to the direction of the otherwise for the cell used guide field, was observed at low and moderate fields. T1 decreases rapidly by increasing the field strength up to values of about 1 kG both in Cs coated and bare wall cells. Further increasing of the field to 7 kG has no significant influence on the relaxation value, suggesting the saturation of the cell magnetisation. Macroscopic magnetisation produced in the bulk of the glass as well as Cs caused magnetisation on the surface are proposed to be two different relaxation mechanisms present in the cells. The magnetisation induced in the cells has been determined independently of the 3He relaxation by SQUID measurements. The influence of Cs coating and of heating on T1 in magnetised cells is discusse