1. LTD12, Paris Microstructured magnetic calorimeter with meander shaped pickup coil A. Burck S. Kempf, S. Schäfer, H. Rotzinger, M. Rodrigues, T. Wolf, A. Fleischmann, L. Gastaldo, C. Enss Kirchhoff-Institute for physics University Heidelberg

2. LTD12, Paris weak thermal link Metallic magnetic calorimeter sensor: Au:Er (~100-1000 ppm) x-ray dc-SQUID magnetometer Wärmebad paramagnetic sensor absorber B thermal bath

3. LTD12, Paris cylindrical sensor circular SQUID-loop external magnetic field planar sensor meander shaped pickup loop with transformer coupling Sensor readout schemes

4. LTD12, Paris Why meander shaped pickup coils ? natural 2d geometry with high filling factor no external field coil needed bias field is multipole field of high order: magnetic detektor response has multipole character reduced magn. cross talk between pixel reduced pickup of magnetic Johnson noise field decays exponentially with distance  allows for superconducting absorbers

5. LTD12, Paris Characterisation: Prototype-detector setup: large area detector, A sensor = 1mm1mm sputter deposited sensor, Au:Er 750 ppm, natural isotope mixture ( 22.9 % 167 Er) C sens  0.4 nJ/K expected ΔE FWHM ~ 25eV no absorber 3.5 mm

6. LTD12, Paris Magnetization  magnetization of the sputter deposited Au:Er shows bulk-properties for temperatures in the range between 2 K-300 K  promising result

7. LTD12, Paris Magnetization theory  Au:Er-sensor can reliably be microstructured  magnetization of the sputter deposited Au:Er shows bulk-properties for temperatures down to 45 mK  deviation below 45 mK is most likely caused by a general thermal decoupling of the detector from the heat bath bath Au:Er, 750 ppm

8. LTD12, Paris Fluorescence spectrum of 55 Mn Baseline 17700 events (50 minutes) rate: ~ 15 events/s T = 30 mK, I F = 55 mA Averaged K α -pulse I F = 40 mA T = 39 mK time K α -line  E FWHM =162 eV  E FWHM =106 eV

9. LTD12, Paris Signal size and Heat capacity  measured signalsize is 30% - 50% smaller than the expected behaviour  measured heat capacity is a factor of 1.3 – 2 larger than the expected behaviour  additional heat capacity and/or loss of phonons

10. LTD12, Paris Summary & Outlook meander: promising geometry reduced cross talk reduced magn. Johnson noise no external field coil needed better SNR results: magnetisation of the sputter deposited Au:Er shows bulk properties down to 45 mK sensor can reliably be microstructured microstructured detektor shows promising results future:continue with microstructering... arrays + multiplexing theory Au:Er, 750 ppm