LTS SQUID gradiometer system for in vivo magnetorelaxometry

A system for spatially resolved magnetorelaxometry in spatially expanded ob jects (e.g. for in vivo investigations) in a disturbed environment is prese nted. The system is based on an LTS SQUID gradiometer with a field gradient sensitivity of 30 fT cm(-1) Hz(-1/2) and an intrinsic balance of some 10(- 5). A Helmholtz coil of 80 cm diameter allows the magnetization of the samp les with fields up to 7 mT. A nonmagnetic x-y stage (driven by step motors) covers a scanning area of 40 cm x 25 cm. We present spatially resolved mea surements of the Neel relaxation of samples (dried ferrofluid) and compare them with model calculations. The data acquisition and monitoring as well a s the filtering and fitting procedure are discussed.