|author(s)||V Zakosarenko, R Stolz, L Fritzsch, H-G Meyer, A Fleischmann, C Enss|
|title||SQUID gradiometer for ultra-low temperature magnetic micro-calorimeter|
|source||Supercond. Sci. Technol. 16 (2003) 1404–1407|
First-order integrated planar SQUID gradiometers with pick-up loops of 40 µm in diameter and a baseline of 200 µm were designed specially for the readout of signals from magnetic micro-calorimeters. The SQUID has to operate in magnetic fields up to 5 mT and at temperatures down to 7 mK. The design is a first step to develop a multi-pixel x-ray detector, which can be used in high-resolution x-ray fluorescence analysis. Chip coils with a heater switch produce a magnetic field up to a few millitesla in persistent current mode. A SQUID-array amplifier was used to readout the signal of the SQUID gradiometer. The intrinsic noise of the gradiometer at 4.2 K is lower than 1 µ0 Hz−1/2. The SQUID can withstand external magnetic fields up to 7 mT without losing its performance. The results of a test with the SQUID gradiometer at ultra low temperatures are reported.