THE DETERMINATION OF MAGNETIC-MOMENTS OF EXTENDED SAMPLES IN A SQUID MAGNETOMETER

A method is developed for the extraction, from SQUID magnetometer data , of a value for the total magnetic moment of an extended sample. Back ground drift associated with the superconducting magnet is usually a s erious problem in these experiments and we show, using computer simula tions, that our method deals successfully with this. Reasonably good e stimates are required of the length of the sample and of the number of readings over which the background drift is correlated. The method us es a matched filter to carry out deconvolution in the presence of corr elated noise. The approach is illustrated for a wire sample of Ni-Cr a lloy in extended and compressed forms. Results are analysed for pure w ater and oxidized human blood, giving volume susceptibility values of (- 9.060 +/- 0.003) x 10(-6) and (- 7.390 +/- 0.003) x 10(-6) respecti vely.