Richard Weldle

Bio: Richard Weldle is an academic researcher from Heidelberg University. The author has contributed to research in topics: Particle detector & Magnetization. The author has an hindex of 2, co-authored 2 publications receiving 21 citations.

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.

Physics and applications of metallic magnetic calorimeters for particle detection

Abstract: An increasing number of experiments and applications employ low temperature particle detectors. Following the calorimetric detection principles, the energy released in the detector leads to a temperature increase which is measured by a very sensitive sensor. Metallic magnetic calorimeters are composed by an energy absorber, optimized for the particles to be detected, in good thermal contact with a metallic paramagnetic sensor positioned in a weak magnetic field. A change in the sensor magnetisation follows the change of the detector temperature. High energy resolution can be obtained by using a low-noise, high-bandwidth DC-SQUID to measure the corresponding change of flux. We discuss the thermodynamic properties, the energy resolution, the microfabrication and general design considerations of magnetic calorimeters as well as their application in high resolution x-ray spectroscopy, beta spectroscopy and absolute activity measurements.

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.

Large-format platinum silicide microwave kinetic inductance detectors for optical to near-IR astronomy

Abstract: We have fabricated and characterized 10,000 and 20,440 pixel Microwave Kinetic Inductance Detector (MKID) arrays for the Dark-speckle Near-IR Energy-resolved Superconducting Spectrophotometer (DARKNESS) and the MKID Exoplanet Camera (MEC). These instruments are designed to sit behind adaptive optics systems with the goal of directly imaging exoplanets in a 800-1400 nm band. Previous large optical and near-IR MKID arrays were fabricated using substoichiometric titanium nitride (TiN) on a silicon substrate. These arrays, however, suffered from severe non-uniformities in the TiN critical temperature, causing resonances to shift away from their designed values and lowering usable detector yield. We have begun fabricating DARKNESS and MEC arrays using platinum silicide (PtSi) on sapphire instead of TiN. Not only do these arrays have much higher uniformity than the TiN arrays, resulting in higher pixel yields, they have demonstrated better spectral resolution than TiN MKIDs of similar design. PtSi MKIDs also do not display the hot pixel effects seen when illuminating TiN on silicon MKIDs with photons with wavelengths shorter than 1 µm.

The $$^{229}$$ 229 Th isomer: prospects for a nuclear optical clock

Abstract: The proposal for the development of a nuclear optical clock has triggered a multitude of experimental and theoretical studies. In particular the prediction of an unprecedented systematic frequency uncertainty of about $$10^{-19}$$ has rendered a nuclear clock an interesting tool for many applications, potentially even for a re-definition of the second. The focus of the corresponding research is a nuclear transition of the $$^{229}$$ Th nucleus, which possesses a uniquely low nuclear excitation energy of only $$8.12\pm 0.11$$ eV ( $$152.7\pm 2.1$$ nm). This energy is sufficiently low to allow for nuclear laser spectroscopy, an inherent requirement for a nuclear clock. Recently, some significant progress toward the development of a nuclear frequency standard has been made and by today there is no doubt that a nuclear clock will become reality, most likely not even in the too far future. Here we present a comprehensive review of the current status of nuclear clock development with the objective of providing a rather complete list of literature related to the topic, which could serve as a reference for future investigations.

Cryogenic measurement of alpha decay in a 4π absorber

Abstract: We established Q spectroscopy, a novel method for the study of alpha decay, by combining 4π detection scheme with a low-temperature microcalorimeter. A 4π metal absorber guarantees absolute measurement of radioactivity without energy loss in the source and absorber. As a clear demonstration of Q spectroscopy, the 241Am alpha source enclosed by a thin gold foil was measured below 100 mK. Its resulting energy spectrum has two dominant peaks with 10 keV FWHM. The more dominant one corresponds to the complete absorption of the Q value, the total decay energy, and the less dominant one to γ-ray escapes. Consequential one-to-one correspondence with high-energy resolution appears between mixed radioisotopes and peaks in Q spectroscopy, which will simplify procedures of nuclear material analysis.