arXiv subjects

S. Zatschler

Publications and source records attributed to S. Zatschler.

8 recordsLinked to original sources

arXiv2026

Radiopurity material assays and radiation exposure projections for superconducting qubit measurements at SNOLAB

Interactions of cosmic rays and other forms of ionizing radiation pose a significant challenge to the reliable operation of state-of-the-art quantum devices and error correction in quantum computing based on superconducting circuits which are typically fabricated on semiconductor substrates. Shielded by 2 km of rock overburden, the Cryogenic Underground TEst facility (CUTE) at SNOLAB provides a unique ultra-low radiation environment to probe the performance of quantum technologies with a particular interest in quantum coherence studies. In this article, we present the findings of an extensive material assaying program in preparation for the first underground operation of superconducting qubits at SNOLAB. The radioactivity levels identified by the material assays enter a thorough Monte Carlo study based on the Geant4 particle physics tracking code. From these simulations, we estimate the rates of energy deposits from radiogenic sources expected for a quantum-device assembly operated in the CUTE facility. We further characterize the spectral components of the projected background and identify the dominant particle interaction types. Finally, we outline how crystal dynamics simulations using the G4CMP solid-state physics extension for Geant4 can inform the community-wide efforts to identify effective strategies to mitigate the effects of high-energy particle impacts.

physics.ins-det↗

arXiv2025

Applying Geant4's Importance Biasing to improve the efficiency of SuperCDMS background simulations

Experiments searching for extremely rare events surround their sensitive detectors with several layers of different shielding materials to protect them from external radiation and to achieve their low-background requirements to be able to observe a potential signal. Standard Monte Carlo simulations that propagate particles through the thick shielding, usually do not penetrate the shield in sufficient numbers to properly model the external background, which is crucial for understanding the experiment's background composition. Geant4 is a widely used toolkit to simulate the passage of particles through matter and it offers various biasing techniques, among them being importance biasing, which has been intensively explored for application in background simulations for the SuperCDMS experiment. In this article, the basic working principle of importance biasing is explained. Furthermore, we provide guidance for developers for their own implementation of a biasing scheme. A new track property, the "biasing index", is introduced to allow different track topologies to be distinguished. Validation studies and optimal parameters for biasing gammas and neutrons are presented and caveats are discussed. In this work, simulations run with importance biasing achieved an efficiency boost of about $\mathcal{O}(10^4)$ for gammas and up to 500 for neutrons. By applying these techniques, we show that energy distributions simulated with and without importance biasing are consistent with each other within statistical uncertainty at a fraction of the consumed computing time.

hep-ex↗

arXiv2024

Improved Modelling of Detector Response Effects in Phonon-based Crystal Detectors used for Dark Matter Searches

Various dark matter search experiments employ phonon-based crystal detectors operated at cryogenic temperatures. Some of these detectors, including certain silicon detectors used by the SuperCDMS Collaboration, are able to achieve single-charge sensitivity when a voltage bias is applied across the detector. The total amount of phonon energy measured by such a detector is proportional to the number of electron-hole pairs created by the interaction. However, crystal impurities and surface effects can cause propagating charges to either become trapped inside the crystal or create additional unpaired charges, producing non-quantized measured energy as a result. A new analytical model for describing these detector response effects in phonon-based crystal detectors is presented. This model improves upon previous versions by demonstrating how the detector response, and thus the measured energy spectrum, is expected to differ depending on the source of events. We use this model to extract detector response parameters for SuperCDMS HVeV detectors, and illustrate how this robust modelling can help statistically discriminate between sources of events in order to improve the sensitivity of dark matter search experiments.

physics.ins-det↗

arXiv2023

G4CMP: Condensed Matter Physics Simulation Using the Geant4 Toolkit

G4CMP simulates phonon and charge transport in cryogenic semiconductor crystals using the Geant4 toolkit. The transport code is capable of simulating the propagation of acoustic phonons as well as electron and hole charge carriers. Processes for anisotropic phonon propagation, oblique charge-carrier propagation, and phonon emission by accelerated charge carriers are included. The simulation reproduces theoretical predictions and experimental observations such as phonon caustics, heat-pulse propagation times, and mean charge-carrier drift velocities. In addition to presenting the physics and features supported by G4CMP, this report outlines example applications from the dark matter and quantum information science communities. These communities are applying G4CMP to model and design devices for which the energy transported by phonons and charge carriers is germane to the performance of superconducting instruments and circuits placed on silicon and germanium substrates. The G4CMP package is available to download from GitHub: github.com/kelseymh/G4CMP.

hep-ex↗

arXiv2017

Suppression of alpha-induced lateral surface events in the COBRA experiment using CdZnTe detectors with an instrumented guard-ring electrode

The COBRA collaboration searches for neutrinoless double beta-decay ($0νββ$-decay) using CdZnTe semiconductor detectors with a coplanar-grid readout and a surrounding guard-ring structure. The operation of the COBRA demonstrator at the Gran Sasso underground laboratory (LNGS) indicates that alpha-induced lateral surface events are the dominant source of background events. By instrumenting the guard-ring electrode it is possible to suppress this type of background. In laboratory measurements this method achieved a suppression factor of alpha-induced lateral surface events of $5300^{+2660}_{-1380}$, while retaining $85.3\pm0.1\%$ of gamma events occurring in the entire detector volume. This suppression is superior to the pulse-shape analysis methods used so far in COBRA by three orders of magnitude.

physics.ins-det↗

arXiv2016

Characterization of a large CdZnTe coplanar quad-grid semiconductor detector

The COBRA collaboration aims to search for neutrinoless double beta-decay of $^{116}$Cd. A demonstrator setup with 64 CdZnTe semiconductor detectors, each with a volume of 1cm$^3$, is currently being operated at the LNGS underground laboratory in Italy. This paper reports on the characterization of a large (2 $\times$ 2 $\times$ 1.5)cm$^3$ CdZnTe detector with a new coplanar-grid design for applications in $γ$-ray spectroscopy and low-background operation. Several studies of electric properties as well as of the spectrometric performance, like energy response and resolution, are conducted. Furthermore, measurements including investigating the operational stability and a possibility to identify multiple-scattered photons are presented.

physics.ins-det↗

arXiv2015

The COBRA demonstrator at the LNGS underground laboratory

The COBRA demonstrator, a prototype for a large-scale experiment searching for neutrinoless double beta-decay, was built at the underground laboratory Laboratori Nazionali del Gran Sasso (LNGS) in Italy. It consists of an array of 64 monolithic, calorimetric CdZnTe semiconductor detectors with a coplanar-grid design and a total mass of 380g. It is used to investigate the experimental challenges faced when operating CdZnTe detectors in low-background mode, to identify potential background sources and to show the long-term stability of the detectors. The first data-taking period started in 2011 with a subset of the detectors, while the demonstrator was completed in November 2013. To date, more than 250kg d of data have been collected. This paper describes technical details of the experimental setup and the hardware components.

physics.ins-det↗

arXiv2015

Long-Term Stability of Underground Operated CZT Detectors Based on the Analysis of Intrinsic $^{113}$Cd β$^{-}$-Decay

The COBRA collaboration operates a demonstrator setup at the underground facility LNGS (Laboratori Nazionali del Gran Sasso, located in Italy) to prove the technological capabilities of this concept for the search for neutrinoless double beta-decay. The setup consists of 64 $(1\times\!1\times\!1)$ cm$^{3}$ CZT detectors in CPG configuration. One purpose of this demonstrator is to test if reliable long-term operation of CZT-CPG detectors in such a setup is possible. The demonstrator has been operated under ultra low-background conditions since more than three years and collected data corresponding to an exposure of 218 kg$\cdot$days. The presented study focuses on the long-term stability of CZT detectors by analyzing the intrinsic, fourfold forbidden non-unique $^{113}$Cd single beta-decay. It can be shown that CZT detectors can be operated stably for long periods of time and that the $^{113}$Cd single beta-decay can be used as an internal monitor of the detector performance during the runtime of the experiment.

physics.ins-det↗