P.C.-O. Ranitzsch

Metallic magnetic calorimeters

Metallic magnetic calorimeters (MMC) are calorimetric particle detectors, typically operated at temperatures below 100 mK, that make use of a paramagnetic temperature sensor to transform the temperature rise upon the absorption of a particle in the detector into a measurable magnetic flux change in a dc‐SQUID. During the last years a growing number of groups has started to develop MMC for a wide variety of applications, ranging from alpha‐, beta‐ and gamma‐spectrometry over the spatially resolved detection of accelerated molecule fragments to arrays of high resolution x‐ray detectors. For x‐rays with energies up to 6 keV an energy resolution of 2.7 eV (FWHM) has been demonstrated and we expect that this can be pushed below 1 eV with the next generation of devices. We give an introduction to the physics of MMCs and summarize the presently used readout schemes as well as the typically observed noise contributions and their impact on the energy resolution. We discuss general design considerations, the micro‐fabrication of MMCs and the performance of micro‐fabricated devices. In this field large progress has been achieved in the last years and the thermodynamic properties of most materials approach bulk values allowing for optimal and predictable performance.

Characterization of low temperature metallic magnetic calorimeters having gold absorbers with implanted 163Ho ions

For the first time we have investigated the behavior of fully micro-fabricated low temperature metallic magnetic calorimeters (MMCs) after undergoing an ion-implantation process. This experiment had the aim to show the possibility to perform a high precision calorimetric measurement of the energy spectrum following the electron capture of 163 Ho using MMCs having the radioactive 163 Ho ions implanted in the absorber. The implantation of 163 Ho ions was performed at ISOLDE-CERN. The performance of a detector that underwent an ion-implantation process is compared to the one of a detector without implanted ions. The results show that the implantation dose of ions used in this experiment does not compromise the properties of the detector. In addition an optimized detector design for future 163 Ho

Low Temperature Magnetic Calorimeters For Neutrino Mass Direct Measurement

In the last years the mixing of the three neutrino flavor eigenstates through a unitary matrix has been experimentally proved. Presently one of the greatest challenges in neutrino physics is to establish the absolute value of the masses of the three neutrino mass eigenstates. The kinematic determination of electron neutrino and antineutrino mass by means of the analysis of calorimetric spectra of isotopes which undergo a beta or electron‐capture decay, with especially low energy available for the decay itself, represents an interesting method. In fact this method is less affected by theoretical models defining branching ratio among different decay modes. For the beta decay the isotope with the lowest Q‐value present in nature is the 187Re (Q about 2.5 keV) while for the electron capture decay the best candidate known is the 163Ho (Q about 2.5 keV). Since those experiments need to be extremely precise, they might suffer from unexpected systematic errors. It is therefore important to investigate in detail t...