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A strong influence of external magnetic fields on the relaxation time constant T1 of glass cells serving as reservoirs for polarised 3 He, observed for various alkali metal coated cells made of different glass types, was initially associated with the presence of a large number of ferromagnetic clusters on the glass surface. Later experiments showed the presence of the socalled "T1 hysteresis" phenomenon with a similar distinctiveness also in uncoated cells made of pure synthetic quartz glass. It suggests that the origin of such a relaxation is a macroscopic magnetisation in the bulk of the cell. We present the results of a multi SQUID system investigation on magnetised and non-magnetised quartz glass cells, Cs-coated as well as bare-wall, to be used as neutron spin filters at HMI Berlin. The presence of a macroscopic remanent magnetic moment in the cells after their exposition to external magnetic fields has been experimentally shown. More than 80% of the remanent magnetic moment of the magnetised cells was found to be concentrated in the region of the glass valves. SQUID measurements reveal the existence of some remanent magnetisation in all valve parts and also in the vacuum grease, but most magnetic are the plastic parts and the O-ring. Different valve and sealing types have been compared in order to find the less magnetisable one.© He relaxation in the magnetised cells to the presence of a large number of ferromagnetic relaxation centres, assumed to be created by a reaction of Rb with iron-containing impurities on the glass surface. These results stimulated us to start with investigations on the magnetic field influence on the relaxation behaviour in refillable (valved) cells made of quartz glass. The concentration of Fe impurities in quartz glass is much lower than in borosilicate or aluminosilicate glasses, (0.2 ppm in quartz glass compared to 210 ppm in GE 180). Thus one could not expect to see the effect as distinct as in Pyrex. Nevertheless a strong influence of external magnetic fields on the relaxation time constant T1 has been found also in quartz glass cells [2]. Moreover the phenomenon has been observed both in Cs-coated and in bare-wall cells. According to Ref.[3], the relaxation mechanism induced by an exposition of a quartz glass cell to an external magnetic field which exceeds only a few hundred Gauss is much stronger than the initial surface relaxation. It can only be removed by degaussing the * Corresponding author. Present address: TUM FRM II,

For further development and optimization of novel uncooled magnetoelectric (ME) sensors, a better understanding of spectral power distribution and signal strength of nerve signals is of high interest. For obtaining information on these signal properties, Superconducting Quantum Interference Device (SQUID) measurements were performed at the Physikalisch-Technische Bundesanstalt (PTB) in Berlin. Signal amplitudes were subject-dependent and ranged from 17 fT to 60 fT in a frequency range from 100 Hz to 1 kHz. The required SQUID averaging time was in the range of minutes, while for current ME sensors significantly longer averaging times are expected to be necessary.

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