Search

Transition Edge Sensors (TES) are superconducting microcalorimeters that can be used for single-photon detection with extremely low backgrounds. When they are within their superconducting transition region, small temperature fluctuations - like the energy deposited by single photons - lead to large resistance variations. These variations can be measured using Superconducting Quantum Interference Devices (SQUIDs). This technology is planned to be used as a single-photon detector for later runs of the ALPS II experiment, a light-shining-through-walls experiment at DESY Hamburg, searching for Axion-Like Particles (ALPs), which are possible Dark Matter (DM) candidates. Due to the very low dark count rates in our setup, our TES system might be viable for direct DM searches at sub-MeV masses through electron-scattering of DM in the superconducting chip, as well. Simulations concerning background rejection and calibration methods demonstrate the needed sub-eV sensitivity already.

Axions and axion-like particles are hypothetical particles predicted in extensions of the standard model and are promising cold dark matter candidates. The Any Light Particle Search (ALPS II) experiment is a light-shining-through-the-wall experiment that aims to produce these particles from a strong light source and magnetic field and subsequently detect them through a reconversion into photons. With an expected rate $\sim$ 1 photon per day, a sensitive detection scheme needs to be employed and characterized. One foreseen detector is based on a transition edge sensor (TES). Here, we investigate machine and deep learning algorithms for the rejection of background events recorded with the TES. We also present a first application of convolutional neural networks to classify time series data measured with the TES., Comment: 11 pages, 5 figures, accepted for publication in Annals of Physics. Contribution to the Patras 2022 Workshop on Axions, WIMPs, and WISPs

The application of cryogenic single photon detectors has found great use in high precision particle physics experiments such as ALPS (Any Light Particle Search) II, which implements it for fundamental studies to search for new particles. ALPS II is a light-shining-through-a-wall experiment searching for axion-like-particles, which couple to photons. The extremely low rate of photons generated by the conversion of such axion-like-particles necessitates a detector setup capable of low energy (~ 1 eV; as dictated by cavity optics) single photon detection with high efficiency and an ultra-low background level, with long-term stability. This can be realised by a Transition Edge Sensor (TES) setup with low-temperature SQUID readout., Comment: Proceedings contribution to EPS-HEP 2021, submitted to Proceedings of Science

The European X-ray Free Electron Laser (XFEL.EU) is currently being commissioned in Schenefeld, Germany. From 2017 onwards it will provide spatially coherent X-rays of energies between 0.25\,keV and 25\,keV with a unique timing structure. One of the detectors foreseen at XFEL.EU for the soft X-ray regime (energies below 6\,keV) is a quasi column-parallel readout FastCCD developed by Lawrence Berkeley National Lab (LBNL) specifically for the XFEL.EU requirements. Its sensor has 1920$\times$960 pixels of 30\,$\mu$m $\times$30\,$\mu$m size with a beam hole in the middle of the sensor. The camera can be operated in full frame and frame store mode. With the FastCCD a frame rate of up to 120~fps can be achieved, but at XFEL.EU the camera settings are optimized for the 10\,Hz XFEL bunch-mode. The detector has been delivered to XFEL.EU. Results of the performance tests and calibration done using the XFEL.EU detector calibration infrastructure are presented quantifying noise level, gain and energy resolution., Comment: 3 pages, 5 figures, 2016 IEEE Nuclear Science Symposium, Medical Imaging Conference and Room-Temperature Semiconductor Detector Workshop (NSS/MIC/RTSD, to be published in the conference record

The high efficiency, low-background, and single-photon detection with transition-edge sensors (TES) is making this type of detector attractive in widely different types of application. In this paper, we present first characterizations of a TES to be used in the Any Light Particle Search (ALPS) experiment searching for new fundamental ultra-light particles. Firstly, we describe the setup and the main components of the ALPS TES detector (TES, millikelvin-cryostat and SQUID read-out) and their performances. Secondly, we explain a dedicated analysis method for single-photon spectroscopy and rejection of non-photon background. Finally, we report on results from extensive background measurements. Considering an event-selection, optimized for a wavelength of $1064~{\rm nm}$, we achieved a background suppression of $\sim 10^{-3}$ with a $\sim 50~\%$ efficiency for photons passing the selection. The resulting overall efficiency was $23~\%$ with a dark count rate of $8.6 \cdot 10^{-3}~{\rm s}^{-1}$. We observed that pile-up events of thermal photons are the main background component., Comment: 17 pages, 9 figures. Accepted by Journal of Modern Optics

Light-shining-through-walls experiments are the search experiments for weakly interacting slim particles (WISPs) with the smallest model dependence. They have the advantage that not only the detection, but also the production of the WISPs takes place in the laboratory and can thus be controlled. Using lasers is the preferred option for most of the mass region and has led to the world's most stringent laboratory limits (ALPS I) there. At CERN, OSQAR promises to surpass these and at DESY ALPS II is currently set up, which is planning to probe the axion-like particle to photon coupling down to $|g_{a\gamma}|\gtrsim 2\cdot10^{-11}$ GeV$^{-1}$, which is in a region favored by many astrophysical hints., Comment: 6 pages, 5 figures, 2 tables; Contributed to the 10th Patras Workshop on Axions, WIMPs and WISPs, CERN, June 29 to July 4, 2014

An essential design requirement of the ALPS-II experiment is the efficient detection of single photons with a very low instrumental background of 10 {\mu}Hz. In 2011 the ALPS collaboration started to set up a TES detector (Transition-Edge Sensor) for ALPS-II, the second phase of the experiment. Since mid of 2013 the setup is ready for characterization in the ALPS laboratory: an ADR cryostat (Adiabatic Demagnetization Refrigerator) as millikelvin environment, a low noise SQUID (Superconducting Quantum Interference Device) with electronics for read-out and a fiber-coupled high-efficient TES for near-infrared photons as sensor. First measurements have shown a good discrimination between noise and 1064 nm signals., Comment: 4 pages, 3 figures; proceedings of 9th Patras Workshop on Axions, WIMPs, and WISPs, Mainz, 24-28 June 2013

This document constitutes an excerpt of the Technical Design Report for the second stage of the "Any Light Particle Search" (ALPS-II) at DESY as submitted to the DESY PRC in August 2012 and reviewed in November 2012. ALPS-II is a "Light Shining through a Wall" experiment which searches for photon oscillations into weakly interacting sub-eV particles. These are often predicted by extensions of the Standard Model and motivated by astrophysical phenomena. The first phases of the ALPS-II project were approved by the DESY management on February 21st, 2013., Comment: 78 pages, v2: Updated Figs. with recent data, some clarifications and references added. Matches version accepted by JINST