Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 5: Superconductivity - Cryodetectors

TT 5.2: Vortrag

Montag, 25. Februar 2008, 12:00–12:15, H 3010

Numerical Optimization of the Energy Resolution of Magnetic Calorimeters — •J.-P. Porst, A. Burck, C. Domesle, C. Höhn, S. Kempf, S. Lausberg, A. Pabinger, C. Pies, S. Schäfer, R. Weldle, A. Fleischmann, L. Fleischmann, and C. Enss — Kirchhoff-Institut für Physik, INF 227, 69120 Heidelberg

We present numerical optimizations of the energy resolution of metallic magnetic calorimeters (MMC) with paramagnetic Au:Er temperature sensors. Energy deposited in such a detector leads to a change of magnetization of the paramagnetic sensor located in a weak magnetic field. SQUIDs are used to detect this change. The response of a MMC upon the deposition of energy depends on several parameters including the absorber heat capacity, the thermodynamic properties of the sensor material, and the geometry of the temperature sensor and the pickup loop. The specific heat and the magnetization of Au:Er can be calculated numerically with confidence. Furthermore, the following noise contributions are considered in these calculations: the thermodynamic fluctuations of energy, the magnetic Johnson noise, the flux noise of the SQUIDs and the 1/f-noise, so far observed in Au:Er-based MMCs. All mentioned noise contributions are parameterized. We performed a numerical optimization of the signal to noise ratio and thus the energy resolution of MMCs for different applications with absorber heat capacities ranging from 1 pJ/K to 1 nJ/K. The optimal parameters found, like shape and size of sensor and pickup coil, concentration of magnetic ions and the optimal magnetic field are presented. The contribution of each noise source to the detector performance is discussed.