H. Rotzinger

Bio: H. Rotzinger is an academic researcher from Heidelberg University. The author has contributed to research in topics: Magnetization & Paramagnetism. The author has an hindex of 6, co-authored 10 publications receiving 109 citations.

Beta Spectrometry with Magnetic Calorimeters

Abstract: Absolute activity measurements of alpha, beta and gamma emitting radioactive sources are important in numerous fields such as therapeutic radiology and the characterization of nuclear waste. Conventional ionization and liquid scintillation detectors, which are commonly used for these applications, have an energy dependent quantum efficiency and severe limitations in energy resolution. As a novel alternative we have developed a detector based on a metallic magnetic calorimeter (MMC) with a gold absorber that covers the full solid angle of 4π around the radioactive source. Deposition of energy in the absorber causes a temperature rise and results in a change of magnetization of a parametric Au:Er sensor, which can be measured by a low-noise high-bandwidth dc-SQUID. The detector has equal sensitivity for beta and gamma radiation. In this paper we describe a detector which has a deviation from linear behavior for energies up to 700 keV of smaller than 0.5% and an overall quantum efficiency for beta particles in this energy range close to unity. We show the data of our experiments measuring the decay of 36Cl and compare the results to the theoretically expected spectrum for this second order forbidden non-unique β-decay. We discuss the observed contributions to noise, the quantum efficiency and the achieved energy resolution.

Metallic magnetic calorimeters (MMC): detectors for high-resolution X-ray spectroscopy

Abstract: X-ray detectors based on the concept of magnetic calorimetry are well suited for high-resolution spectroscopy. Metallic magnetic calorimeters (MMC) make use of a metallic paramagnetic temperature sensor, which is in tight thermal contact with a metallic X-ray absorber. The paramagnetic sensor is placed in a small magnetic field. Its magnetization is used to monitor the temperature, which in turn is related to the internal energy of the calorimeter. High-energy resolution can be obtained by using a low-noise, high-bandwidth DC SQUID to measure the small change in magnetization upon the absorption of an X-ray. With recent prototype detectors an energy resolution of Δ E FWHM =3.4 eV for X-ray energies up to 6.5 keV has been achieved. We discuss general design considerations, the thermodynamic properties of such calorimeters, the energy resolution, and the various sources of noise, which are observed in MMCs.

Metallic Magnetic Calorimeters for X-Ray Spectroscopy

Abstract: An increasing number of experiments employ low-temperature radiation/particle detectors which are based on a calorimetric detection scheme and operate at temperatures below 100 mK. Metallic magnetic calorimeters use a metallic paramagnetic temperature sensor in tight thermal contact with the X-ray absorber. The magnetization of the sensor is used to monitor the temperature change of the detector upon the absorption of single photons, which is proportional to the absorbed energy. Low-noise high-bandwidth dc superconducting quantum interference devices read out the small changes in magnetization. An energy resolution of DeltaE FWHM = 2.7 eV was obtained for X-ray energies up to 6 keV.

Feasibility study of absolute activity measurement with metallic magnetic microcalorimeters

Abstract: We report on a feasibility study on precise determination of mass-specific activity of low-energy emitting radioisotopes. Conventional methods of activity measurement suffer from source self-absorption and a strong decrease in detection efficiency for low-energy electrons and photons. We propose a new method based on metallic magnetic microcalorimeters with the source embedded in the detector target in a 4 π geometry. First results with a 55 Fe source show that electrons and photons are detected with a detection efficiency close to unity and with little loss of energy for electrons. The aim of this study is to provide standards of activity with very low uncertainties in the framework of radiation metrology.

Neutrino mass limit from tritium β decay

Abstract: This paper reviews recent experiments on tritium β-spectroscopy searching for the absolute value of the electron neutrino mass m(νe). By the use of dedicated electrostatic filters with high acceptance and resolution, the uncertainty on the observable m2(νe) has been pushed down to about 3 eV2. The new upper limit of the mass is m(νe) < 2 eV at 95% C.L. In view of erroneous and unphysical mass results obtained by some earlier experiments in β decay, particular attention is paid to systematic effects. The mass limit is discussed in the context of current neutrino research in particle- and astrophysics. A preview is given of the next generation of β-spectroscopy experiments currently under development and construction; they aim at lowering the m2(νe) uncertainty by another factor of 100, reaching a sensitivity limit m(νe) < 0.2 eV.

Reference-free X-ray spectrometry based on metrology using synchrotron radiation

Abstract: X-ray spectrometry is a wide spread technique for revealing reliable information concerning the elemental composition and binding state in various materials. Reference-free quantitation in X-ray spectrometry is based on the knowledge of both the instrumental and fundamental atomic parameters. Instrumental or experimental parameters involve the radiant power and spectral purity of the excitation radiation, the beam geometry, the solid angle of detection, and the response behavior and efficiency of the detector. The reliability of the quantitation equally depends on the relative uncertainty of the atomic fundamental parameters involved. Both the values and estimated uncertainty of atomic fundamental parameters given in the literature can be improved by dedicated experiments: By means of transmission and fluorescence experiments with tunable synchrotron radiation, the mass absorption coefficient and fluorescence yield of Al was determined. Furthermore, the transition probabilities of the fluorescence lines belonging to the Cu-Liii and Lii subshells were determined using a superconducting tunnel junction detector offering an energy resolution of about 10 eV in the soft X-ray range. Selected techniques and applications of reference-free X-ray spectrometry are presented. A particular advantage of reference-free quantitation modes is their capability to directly probe new materials without the need to wait for appropriate standard reference materials.

Penning traps as a versatile tool for precise experiments in fundamental physics

Abstract: This review article describes the trapping of charged particles. The main principles of electromagnetic confinement of various species from elementary particles to heavy atoms are briefly described. The preparation and manipulation with trapped single particles, as well as methods of frequency measurements, providing unprecedented precision, are discussed. Unique applications of Penning traps in fundamental physics are presented. Ultra-precise trap-measurements of masses and magnetic moments of elementary particles (electrons, positrons, protons and antiprotons) confirm CPT-conservation, and allow accurate determination of the fine-structure constant α and other fundamental constants. This together with the information on the unitarity of the quark-mixing matrix, derived from the trap-measurements of atomic masses, serves for assessment of the Standard Model of the physics world. Direct mass measurements of nuclides targeted to some advanced problems of astrophysics and nuclear physics are also presented.

The electron capture in 163Ho experiment – ECHo

Abstract: Neutrinos, and in particular their tiny but non-vanishing masses, can be considered one of the doors towards physics beyond the Standard Model. Precision measurements of the kinematics of weak interactions, in particular of the$^{3}$H β-decay and the$^{163}$Ho electron capture (EC), represent the only model independent approach to determine the absolute scale of neutrino masses. The electron capture in$^{163}$Ho experiment, ECHo, is designed to reach sub-eV sensitivity on the electron neutrino mass by means of the analysis of the calorimetrically measured electron capture spectrum of the nuclide$^{163}$Ho. The maximum energy available for this decay, about 2.8 keV, constrains the type of detectors that can be used. Arrays of low temperature metallic magnetic calorimeters (MMCs) are being developed to measure the$^{163}$Ho EC spectrum with energy resolution below 3 eV FWHM and with a time resolution below 1 μs. To achieve the sub-eV sensitivity on the electron neutrino mass, together with the detector optimization, the availability of large ultra-pure$^{163}$Ho samples, the identification and suppression of background sources as well as the precise parametrization of the$^{163}$Ho EC spectrum are of utmost importance. The high-energy resolution$^{163}$Ho spectra measured with the first MMC prototypes with ion-implanted$^{163}$Ho set the basis for the ECHo experiment. We describe the conceptual design of ECHo and motivate the strategies we have adopted to carry on the present medium scale experiment, ECHo-1K. In this experiment, the use of 1 kBq$^{163}$Ho will allow to reach a neutrino mass sensitivity below 10 eV/c$^{2}$. We then discuss how the results being achieved in ECHo-1k will guide the design of the next stage of the ECHo experiment, ECHo-1M, where a source of the order of 1 MBq$^{163}$Ho embedded in large MMCs arrays will allow to reach sub-eV sensitivity on the electron neutrino mass.