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AbslmcL A 19-channel DZSQUID based neummagnerometer is under mnstructian at the Univenity of 'kente PT). Except for the myasrat all elements of the system are developed at the UT It comprises 19 wire-wound fint-order gradiometen in a hexagonal mnfiguration. ?he gradiometen are connected to planar ocsoulos fabricated with a NbIAI, AIO,/Nb technology. For this mnnection we developed a method to bond a Nb wire to a Nb thin-film. The SQUIB are placed in mmpanmenlalised Nb modules.Further, aternal feedback is incorporated in order to eliminate crou mlk ktween the gradiometen. The electronics basically mnsist of a phase-locked Imp operating with a modulation frequenq of LOO kHz. Between SQUID and preamplifier a small Iransformer is used to limit the noise mntribulion of the preamplifier. In the paper the werall system is desmibed, and special attention is paid to the SQUID module @ending, mmpanments, alernal-feedback setup, output Iransformer). IntmductionDuring the last few years biomagnetic instrumentation has changed from singlechannel SQUID systems to multichannel magnetometer units. In this way the magnetic field distribution around a subjects's body can be measured much faster and more reliably. Furthermore, spontaneous activity in the body can now be studied. Multichannel systems of about 7.0 to 30 channels aredeveloped by or Are under construction in university groups, for instance in Helsinki and Rome, at the PTB in Berlin and in industries like BTi, Siemens and Philips.At the University of Wente a 19-channel DC SQUID magnetometer for brain research is under construction. In this paper several aspects of the system are described. First, the sensing-coil unit will be considered, that has been optimised with respect to the signal-to-noise ratio of the overall system. Then, attention is paid to the SQUID module in which other topics such as cross talk elimination by means of external feedback and bonding of a niobium wire to a niobium thin-film pad are involved. Finally, the electronics are shortly described. L. Sensing-coil unitFirst-order gradiometers are used as the sensing coils. Second-order gradiometers are not required, bccause our biomagnetim laboratory is on a low-noise location and t On leave from:

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Nearly quantum-limited Superconducting QUantum Interference Devices (SQUIDs) have to be used in resonant mass gravitational wave antennas to reach a displacement sensitivity of the order of 10,21 mJ-iHz in a bandwidth of 100 Hz around the resonance frequency of about 900 Hz. The design of these SQUIDs will be described. We show that a good coupling between the inductive readout circuit and the SQUID can be obtained by choosing a relatively large hole size of the washer-type SQUID configuration.