Dresden 2011 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 11: Poster Session: Matter at Low Temperature

TT 11.2: Poster

Montag, 14. März 2011, 14:00–18:00, P4

Noise Contributions in Metallic Magnetic Calorimeters — •S. Heuser, S. Kempf, A. Fleischmann, L. Gastaldo, A. Kampkötter, C. Pies, J.-P. Porst, P. Ranitzsch, S. Schäfer, S. Vick, T. Wolf, and C. Enss — Uni Heidelberg, Heidelberg

Metallic magnetic calorimeters (MMCs) are particle detectors operated at a temperature below 100 mK. The energy deposited by an absorbed particle produces an increase of the detector temperature which induces a change of magnetization of the paramagnetic Au:Er temperature sensor sitting in a small magnetic field. Low-noise high-bandwidth dc-SQUIDs are used to detect the change of flux in a pick-up coil. In the last years MMCs showed a rapid progress both in the achieved energy resolution and in the reproducibility of the performance. Presently the energy resolution for x-rays is 2.8 eV (FWHM) at 6 keV. Detector modeling predicts sub-eV sensitivity for the next generation of devices. To achieve this goal, each noise source needs to be under control. The thermal fluctuation noise (TFN), dependent on the thermodynamical properties of the detector, is only finite intrinsic resolution limit. The read-out noise mainly depends on the properties of the SQUID and its coupling to the sensor. Magnetic Johnson noise is due to fluctuating current in normal metal in the vicinity of the pick-up coil. Finally we have observed a 1/f noise contribution caused by the sensor material, which can presently only be described empirically. In order to achieve optimal performance of MMCs, the last three noise contribution should be negligible in respect to the TFN. We discuss all these noise sources in detail and how they affect the detector performance.