arXiv subjects

M. Wegner

Publications and source records attributed to M. Wegner.

13 recordsLinked to original sources

arXiv2025

Microwave SQUID Multiplexer Readout Performance Using a Direct-RF RFSoC-Based Software-Defined Radio

In this work, we report the experimental readout results of a {\mu}MUX device using a Direct-RF SDR prototype based on the ZCU216 Radio-Frequency System-on-Chip (RFSoC) evaluation board. First, the analog performance of the SDR system was evaluated both in loopback and coupled to the cryogenic multiplexing system. Then, the SDR system performance was optimized for {\mu}MUX readout, focusing on bolometric applications. Finally, the minimum demodulated flux noise was obtained through the optimally conditioned readout of a {\mu}MUX channel. The results presented are comparable to those obtained with traditional SDR architectures and demonstrate that the Direct-RF SDR prototype is suitable for the readout of {\mu}MUX devices. We anticipate that Direct-RF SDR technology will play a key role in enabling the next generation of SDR readout systems for frequency-multiplexed low-temperature detector arrays.

physics.ins-det↗

arXiv2025

Development of a microwave SQUID multiplexer for magnetic microbolometers

The search for primordial B-modes in the cosmic microwave background (CMB) requires highly sensitive and scalable detector systems. The magnetic microbolometer (MMB) is an emerging detector concept that exploits the magnetic properties of paramagnetic materials at sub-kelvin temperatures, offering bolometers with a high dynamic range and low intrinsic noise. In recent years, the microwave SQUID multiplexer ($\mu$MUX) has become a key technology to efficiently read large low temperature detector arrays, enabling the readout of hundreds to thousands of detectors over a single transmission line with low noise and minimal power dissipation while reducing the cryogenic setup complexity. In this work, we report the design, fabrication and characterization of a $\mu$MUX optimized for MMB detectors and share our latest experimental results from a bolometer prototype. These findings provide valuable insight of the $\mu$MUX in advancing next-generation CMB instrumentation and also demonstrate its suitability for novel detector technologies such as the MMB.

physics.ins-det↗

arXiv2025

Full-scale Microwave SQUID Multiplexer Readout System for Magnetic Microcalorimeters

The deployment of large cryogenic detector arrays, comprising hundreds to thousands of individual detectors, is highly beneficial for various cutting-edge applications, requiring large statistics, angular resolution or imaging capabilities. The readout of such arrays, however, presents a major challenge in terms of system complexity, parasitic heat load, and cost, which can be overcome only through multiplexing. Among the various multiplexing approaches, microwave SQUID multiplexing currently represents the state of the art, in particular for magnetic microcalorimeter (MMC) readout. In this work, we demonstrate the successful operation of the latest generation of our microwave SQUID multiplexer-based readout system, based on a SQUID multiplexer tailored for MMC readout and a custom full-scale software-defined radio (SDR) electronics, capable of handling up to 400 channels. The system operates reliably across the entire 4-8 GHz frequency band and achieves sufficiently low flux noise levels in flux-ramp-demodulated readout. Our results confirm that our system is fully functional and provides a scalable path towards future large-scale, high-resolution MMC experiments.

physics.ins-det↗

arXiv2024

Optimal Demodulation Domain for Microwave SQUID Multiplexers in Presence of Readout System Noise

The Microwave SQUID Multiplexer ({\mu}MUX) is the device of choice for the readout of a large number of Low-Temperature Detectors in a wide variety of experiments within the fields of astronomy and particle physics. While it offers large multiplexing factors, the system noise performance is highly dependent on the cold and warm-readout electronic systems used to read it out, as well as the demodulation domain and parameters chosen. In order to understand the impact of the readout systems in the overall detection system noise performance, first we extended the available {\mu}MUX simulation frameworks including additive and multiplicative noise sources in the probing tones (i.e. phase and amplitude noise), along with the capability of demodulating the scientific data, either in resonator's phase or scattering amplitude. Then, considering the additive noise as a dominant noise source, the optimum readout parameters to achieve minimum system noise were found for both open-loop and flux-ramp demodulation schemes in the aforementioned domains. Later, we evaluated the system noise sensitivity to multiplicative noise sources under the optimum readout parameters. Finally, as a case study, we evaluated the optimal demodulation domain and expected system noise level for a typical Software-Defined Radio (SDR) readout system. This work leads to an improved system performance prediction and noise engineering based on the available readout electronics and selected demodulation domain.

physics.ins-det↗

arXiv2024

Transport of Intensity Phase Retrieval in the Presence of Intensity Variations and Unknown Boundary Conditions

The so-called Transport of Intensity Equation (TIE) phase retrieval technique is widely applied in light, x-ray and electron optics to reconstruct, e.g., refractive indices, electric and magnetic fields in solids. Here, we present a largely improved TIE reconstruction algorithm, which properly considers intensity variations as well as unknown boundary conditions in a finite difference implementation of the Transport of Intensity partial differential equation. That largely removes reconstruction artifacts encountered in state-of-the-art Poisson solvers of the TIE, and hence significantly increases the applicability of the technique.

cond-mat.mtrl-sci↗

arXiv2021

Metallic magnetic calorimeter arrays for the first phase of the ECHo experiment

The ECHo experiment has been designed for the determination of the effective electron neutrino mass by means of the analysis of the end-point region of the Ho-163 electron capture spectrum. Metallic magnetic calorimeters enclosing Ho-163 are used for the high energy resolution calorimetric measurement of the Ho-163 spectrum. For the first phase of the experiment, ECHo-1k, a 72-pixel MMC array has been developed. The single-pixel design has been optimised to reach 100% stopping power for the radiation emitted in the Ho-163 electron capture process (besides the electron neutrino) and an energy resolution < 10 eV FWHM. We describe the design of the ECHo-1k detector chip, the fabrication steps and the characterisation at room temperature, at 4 K and at the final operation temperatures. In particular, a detailed analysis of the results from these tests allowed to define a quality check protocol based on parameters measurable at room temperature. We discuss the performance achieved with the two ECHo-1k detector chips - the first one with Ho-163 implanted in gold and the second one with Ho-163 implanted in silver - which have been used for the high statistics measurement of the ECHo-1k experiment. An average activity per pixel of 0.81 Bq and 0.71 Bq and an average energy resolution of 6.07 eV FWHM and 5.55 eV FWHM have been achieved with these two detectors, fulfilling the requirements for the first phase of the ECHo experiment.

physics.ins-det↗

arXiv2021

Multichannel read-out for arrays of metallic magnetic calorimeters

Metallic magnetic micro-calorimeters (MMCs) operated at millikelvin temperature offer the possibility to achieve eV-scale energy resolution with high stopping power for X-rays and massive particles in an energy range up to several tens of keV. This motivates their use in a wide range of applications in fields as particle physics, atomic and molecular physics. Present detector systems consist of MMC arrays read out by 32 two-stage SQUID read-out channels. In contrast to the design of the detector array and consequently the design of the front-end SQUIDs, which need to be optimised for the physics case and the particles to be detected in a given experiment, the read-out chain can be standardised. We present our new standardised 32-channel parallel read-out for the operation of MMC arrays to be operated in a dilution refrigerator. The read-out system consists of a detector module, whose design depends on the particular application, an amplifier module, ribbon cables from room temperature to the millikelvin platform and a data acquisition system. In particular, we describe the realisation of the read-out system prepared for the ECHo-1k experiment for the operation of two 64-pixel arrays. The same read-out concept is also used for the maXs detector systems, developed for the study of the de-excitation of highly charged heavy ions by X-rays, as well as for the MOCCA system, developed for the energy and position sensitive detection of neutral molecular fragments for the study of fragmentation when molecular ions recombine with electrons. The choice of standard modular components for the operation of 32-channel MMC arrays offer the flexibility to upgrade detector modules without the need of any changes in the read-out system and the possibility to individually exchange parts in case of damages or failures.

physics.ins-det↗

arXiv2016

MICADO: first light imager for the E-ELT

MICADO will equip the E-ELT with a first light capability for diffraction limited imaging at near-infrared wavelengths. The instrument's observing modes focus on various flavours of imaging, including astrometric, high contrast, and time resolved. There is also a single object spectroscopic mode optimised for wavelength coverage at moderately high resolution. This contribution provides an overview of the key functionality of the instrument, outlining the scientific rationale for its observing modes. The interface between MICADO and the adaptive optics system MAORY that feeds it is summarised. The design of the instrument is discussed, focussing on the optics and mechanisms inside the cryostat, together with a brief overview of the other key sub-systems.

astro-ph.IM↗

arXiv2014

First Calorimetric Measurement of OI-line in the Electron Capture Spectrum of $^{163}$Ho

The isotope $^{163}$Ho undergoes an electron capture process with a recommended value for the energy available to the decay, $Q_{\rm EC}$, of about 2.5 keV. According to the present knowledge, this is the lowest $Q_{\rm EC}$ value for electron capture processes. Because of that, $^{163}$Ho is the best candidate to perform experiments to investigate the value of the electron neutrino mass based on the analysis of the calorimetrically measured spectrum. We present for the first time the calorimetric measurement of the atomic de-excitation of the $^{163}$Dy daughter atom upon the capture of an electron from the 5s shell in $^{163}$Ho, OI-line. The measured peak energy is 48 eV. This measurement was performed using low temperature metallic magnetic calorimeters with the $^{163}$Ho ion implanted in the absorber. We demonstrate that the calorimetric spectrum of $^{163}$Ho can be measured with high precision and that the parameters describing the spectrum can be learned from the analysis of the data. Finally, we discuss the implications of this result for the Electron Capture $^{163}$Ho experiment, ECHo, aiming to reach sub-eV sensitivity on the electron neutrino mass by a high precision and high statistics calorimetric measurement of the $^{163}$Ho spectrum.

physics.ins-det↗

arXiv2013

The Electron Capture $^{163}$Ho Experiment ECHo: an overview

The determination of the absolute scale of the neutrino masses is one of the most challenging present questions in particle physics. The most stringent limit, $m(\barν_{\mathrm{e}})<2$eV, was achieved for the electron anti-neutrino mass \cite{numass}. Different approaches are followed to achieve a sensitivity on neutrino masses in the sub-eV range. Among them, experiments exploring the beta decay or electron capture of suitable nuclides can provide information on the electron neutrino mass value. We present the Electron Capture $^{163}$Ho experiment ECHo, which aims to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured energy spectrum following electron capture of $^{163}$Ho. A high precision and high statistics spectrum will be measured with arrays of metallic magnetic calorimeters. We discuss some of the essential aspects of ECHo to reach the proposed sensitivity: detector optimization and performance, multiplexed readout, $^{163}$Ho source production and purification, as well as a precise theoretical and experimental parameterization of the calorimetric EC spectrum including in particular the value of $Q_{\mathrm{EC}}$. We present preliminary results obtained with a first prototype of single channel detectors as well as a first 64-pixel chip with integrated micro-wave SQUID multiplexer, which will already allow to investigate $m(ν_{\mathrm{e}})$ in the eV range.

physics.ins-det↗

arXiv2013

Multiplexed readout of MMC detector arrays using non-hysteretic rf-SQUIDs

Metallic magnetic calorimeters (MMCs) are widely used for various experiments in fields ranging from atomic and nuclear physics to x-ray spectroscopy, laboratory astrophysics or material science. Whereas in previous experiments single pixel detectors or small arrays have been used, for future applications large arrays are needed. Therefore, suitable multiplexing techniques for MMC arrays are currently under development. A promising approach for the readout of large arrays is the microwave SQUID multiplexer that operates in the frequency domain and that employs non-hysteretic rf-SQUIDs to transduce the detector signals into a frequency shift of high $Q$ resonators which can be monitored by using standard microwave measurement techniques. In this paper we discuss the design and the expected performance of a recently developed and fabricated 64 pixel detector array with integrated microwave SQUID multiplexer. First experimental data were obtained characterizing dc-SQUIDs with virtually identical washer design.

physics.ins-det↗

arXiv2013

The Electron Capture $^{163}$Ho Experiment ECHo

The determination of the absolute scale of the neutrino masses is one of the most challenging questions in particle physics. Different approaches are followed to achieve a sensitivity on neutrino masses in the sub-eV range. Among them, experiments exploring the beta decay and electron capture processes of suitable nuclides can provide necessary information on the electron neutrino mass value. In this talk we present the Electron Capture 163-Ho experiment ECHo, which aims to investigate the electron neutrino mass in the sub-eV range by means of the analysis of the calorimetrically measured energy spectrum following the electron capture process of 163-Ho. A high precision and high statistics spectrum will be measured by means of low temperature magnetic calorimeter arrays. We present preliminary results obtained with a first prototype of single channel detectors as well as the participating groups and their on-going developments.

physics.ins-det↗

arXiv2012

MOONS: a Multi-Object Optical and Near-infrared Spectrograph for the VLT

MOONS is a new conceptual design for a Multi-Object Optical and Near-infrared Spectrograph for the Very Large Telescope (VLT), selected by ESO for a Phase A study. The baseline design consists of 1000 fibers deployable over a field of view of 500 square arcmin, the largest patrol field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8um-1.8um and two resolution modes: medium resolution and high resolution. In the medium resolution mode (R=4,000-6,000) the entire wavelength range 0.8um-1.8um is observed simultaneously, while the high resolution mode covers simultaneously three selected spectral regions: one around the CaII triplet (at R=8,000) to measure radial velocities, and two regions at R=20,000 one in the J-band and one in the H-band, for detailed measurements of chemical abundances. The grasp of the 8.2m Very Large Telescope (VLT) combined with the large multiplex and wavelength coverage of MOONS - extending into the near-IR - will provide the observational power necessary to study galaxy formation and evolution over the entire history of the Universe, from our Milky Way, through the redshift desert and up to the epoch of re-ionization at z>8-9. At the same time, the high spectral resolution mode will allow astronomers to study chemical abundances of stars in our Galaxy, in particular in the highly obscured regions of the Bulge, and provide the necessary follow-up of the Gaia mission. Such characteristics and versatility make MOONS the long-awaited workhorse near-IR MOS for the VLT, which will perfectly complement optical spectroscopy performed by FLAMES and VIMOS.

astro-ph.IM↗