Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 21: Superconductivity: Poster Session

TT 21.52: Poster

Monday, March 16, 2015, 15:00–18:00, Poster B

Thermodynamical properties of Au:Ho dilute alloys for the ECHo collaboration — •Sebastian Haehnle — for the ECHo collaboration (http://www.kip.uni-heidelberg.de/echo/members), KIP Heidelberg University.

The absolute scale of the neutrino mass eigenstates is one of the puzzles in modern particle physics. One method to investigate the value of the electron neutrino mass is to analyse the high energy region of the ¹⁶³Ho electron capture spectrum. In the ECHo experiment low temperature metallic magnetic calorimeters are used for the calorimetric measurement of the EC spectrum of ¹⁶³Ho. To ensure 100% quantum efficiency the ¹⁶³Ho ions are implanted into the gold absorber. A detailed study of the thermodynamical properties of highly diluted Au:Ho is necessary to determine the detector response and to define the highest concentration possible for which the performance of the detectors is not reduced.

We determined Crystal-Field parameters for holmium in gold based on magnetization measurements from 2 K to 300 K, that would result in a non-Kramers doublet as groundstate with the first excited triplet state at 140 mK. We used numerical calculations for the combined Hamiltonian of the Crystal-Field and the Hyperfine interaction to predict a theoretical heat capacity at millikelvin temperatures. The results of the numerical calculation are compared to experimental results.