The Spectroscopy Focusing Array (SFA) is one of the three instruments on the eXTP satellite. It consists of six telescopes plus focal plane cameras, where five are equipped with a Silicon Drift Detector (SDD) array. These five SFA-T (T stands for timing) instruments are used for observations with high time resolution (better than 10 microseconds), high throughput (dead time less than 5

NewAthena's Wide Field Imager (WFI) uses detectors made up from Depleted P-Channel Field Effect Transistor (DEPFET) pixels operated in rolling shutter mode. The Large Detector Array (LDA) contains a 2 × 2 array of 512 × 512 pixels Large Detectors (LDs) allowing for a field of view of 40' × 40' with a frame time of 2 ms while the 64 × 64 pixels Fast Detector (FD) can observe very bright X-ray sources due to a faster frame time of 0.08 ms. Prototype sensors (64 × 64 pixels) were used to analyse the sensor's operational range and to optimise the ASIC and DEPFET parameters i.e. current and voltage settings, as well as the DEPFET read-out timing parameters, resulting in an improved energy resolution, reduced noise and otherwise improved sensor characteristics.

For X-ray imaging and photon detection, silicon drift detectors (SDDs) with several cells on a single chip and associated application-specific integrated circuits (ASICs) with multi-channel readout are widely used. This work presents a reset management circuit for a parallelized readout system for multi-cell SDDs. The readout system under investigation consists of a 19-cell SDD chip and three ASICs with reset capabilities. Yet, another reset management circuit is required, which handles the seamless reset operation between all ASICs and the SDD chip. With regard to its versatility and real-time capability, a field programmable gate array (FPGA) is used to implement the reset management circuit. For the design and implementation of this circuit, the time delays of all involved signal paths are investigated in detail. Measurements prove the functionality of the presented reset management. Furthermore, it is also shown how the reset management influences the dead time of the entire system. Although this work covers a system with three ASICs, the reset management is applicable for other SDD systems using two or more parallelized readout circuits.

Sterile neutrinos are hypothetical particles in the minimal extension of the Standard Model of Particle Physics. They could be viable dark matter candidates if they have a mass in the keV range. The Karlsruhe tritium neutrino (KATRIN) experiment, extended with a silicon drift detector focal plane array (TRISTAN), has the potential to search for keV-scale sterile neutrinos by measuring the kinematics of the tritium beta-decay. The collaboration targets a sensitivity of 10-6 on the mixing amplitude sine Theta. For this challenging target, a precise understanding of the detector response is necessary. In this work, we report on the characterization of electron backscattering from the detector surface, which is one of the main effects that influence the shape of the observed energy spectrum. Measurements were performed with a tandem silicon drift detector system and a custom-designed electron source. The measured detector response and backscattering probability are in good agreement with dedicated backscattering simulations using the GEANT4 simulation toolkit.

The ASPECT-BET (An sdd-SPECTrometer for BETa decay studies) project aims to develop a novel technique for the precise measurement of forbidden β spectra in the 10 keV - 1 MeV range. This technique uses a Silicon Drift Detector (SDD) as the main spectrometer, surrounded, if necessary, by a veto system to reject events with only partial energy deposition in the SDD. Accurate knowledge of the spectrometer's response to electrons is essential to reconstruct the theoretical shape of the β spectrum. To compute this response, GEANT4 simulations optimized for low-energy electron interactions are used. In this article, we present the performance of these simulations in reconstructing the electron spectra, measured with SDDs, of a ^109Cd monochromatic source, both in vacuum and in air. The allowed β spectrum of a ^14C source is also measured and analyzed, and it is shown that the experimental shape factor commonly used in the literature to reconstruct the measured spectrum is not necessary to explain the spectrum.

The depleted p-channel field effect transistor is the chosen sensor type for the Wide Field Imager of the Athena mission. It will be used in two types of cameras. One will enable observations of a field of view of 40' x 40' by using an array of four 512 x 512 pixel sensors in a 2 x 2 configuration. A second, small one is designed to investigate bright, point-like sources with a time resolution of up to 40 microseconds. Sensors of final size, layout, and technology were fabricated, assembled and characterised. Also, first results from the flight production are available and confirm the excellent performance. In order to be able to estimate the future performance of degraded detectors, a simulation was developed that takes into account the non-analytical threshold effects on the basis of measurement results. We present the measurement analysis and the comparison of simulated and measured values as well as first attempts to use the Monte Carlo simulation to predict performance results based on noise measurements.

A silicon drift detector (SDD) module has been developed to be used in high-time resolution X-ray spectroscopy. The module consists of a 19-cell SDD chip and three readout application-specific integrated circuits (ASICs). With respect to timing and energy resolution, the readout ASIC with its programmable setting parameters is characterized. Based on the results of this characterization, analytical rules for these setting parameters are established to obtain the optimum performance of the module. The performance of the module is verified by means of measurements. With the ascertained parameter values and selecting the available shaping time of 1.02 mu s, a minimum time interval of 1.87 mu s between pulses and an energy resolution of 176 eV at 5.9 keV and at a temperature of-30(degrees)C are achieved.

The ASPECT-BET project, or An sdd-SPECTrometer for BETa decay studies, aims to develop a novel technique for the precise measurement of forbidden beta spectra in the 10 keV–1 MeV range. This technique employs a Silicon Drift Detector (SDD) as the main spectrometer with the option of a veto system to reject events exhibiting only partial energy deposition in the SDD. A precise understanding of the spectrometer’s response to electrons is crucial for accurately reconstructing the theoretical shape of the beta spectrum. To compute this response, GEANT4 simulations optimized for low-energy electron interactions are used and validated with a custom-made electron gun. In this article we present the performance of these simulations in reconstructing the electron spectra measured with SDDs of a 109Cd monochromatic source, both in vacuum and in air. The allowed beta spectrum of a 14C source was also measured and analyzed, proving that this system is suitable for the application in ASPECT-BET.

Sensors with repetitive non-destructive readout, which achieve a deep sub-electron noise have been established for high precision applications. The Depleted P-channel Field-Effect Transistor with Repetitive Non-Destructive Readout - so-called RNDR-DEPFET - provides an active pixel sensor on a fully depleted silicon bulk with the capability to collect, store and read out charge carriers within each pixel. The readout process takes place by shifting the collected electrons between two readout nodes within one pixel in order to enable statistically independent measurements. In a conventional mode like the rolling shutter operation, the collected electrons are removed after the desired number of readings has been reached. However, the active pixel concept enables a continuous or incremental sampling of the signal during charge collection in combination with a high level of parallelization, as well. In this mode, the charge collection and readout takes places simultaneously and electrons are just removed before the storing capacity of the readout node has been exceeded. After the working principle of RNDR-DEPFET detectors has been demonstrated on a 64x64 pixel sensor, a incremental readout mode with a high time resolution of single electron events is studied. A time resolution in the order of 300 mu s for single electron detection is demonstrated, which significantly improves the capabilities for background rejection and detection of rare signals. The paper concludes with an evaluation of applications for light dark matter searches and astrophysical applications.

The TRISTAN detector is a new detector for electron spectroscopy at the Karlsruhe Tritium Neutrino (KATRIN) experiment. The semiconductor detector utilizes the silicon drift detector technology and will enable the precise measurement of the entire tritium beta decay electron spectrum. Thus, a significant fraction of the parameter space of potential neutrino mass eigenstates in the keV-mass regime can be probed. We developed a custom electron gun based on the effect of thermionic emission to characterize the TRISTAN detector modules with mono-energetic electrons before installation into the KATRIN beamline. The electron gun provides an electron beam with up to 25 keV kinetic energy and an electron rate in the order of 1E5 electrons per second. This manuscript gives an overview of the design and commissioning of the electron gun. In addition, we will shortly discuss a first measurement with the electron gun to characterize the electron response of the TRISTAN detector.

Sterile neutrinos in the keV mass range present a viable candidate for dark matter. They can be detected through single β -decay, where they cause small spectral distortions. The Karlsruhe Tritium Neutrino (KATRIN) experiment aims to search for keV-scale sterile neutrinos with high sensitivity. To achieve this, the KATRIN beamline will be equipped with a novel multi-pixel silicon drift detector focal plane array named TRISTAN. In this study, we present the performance of a TRISTAN detector module, a component of the eventual 9-module system. Our investigation encompasses spectroscopic aspects such as noise performance, energy resolution, linearity, and stability.

We present a silicon drift detector (SDD) system for the spectroscopy focusing array (SFA) of the enhanced X-ray timing and polarimetry (eXTP) mission. The SFA focuses on fast timing (time resolution below 10 mu s) and good spectroscopy capabilities (energy resolution better than 180 eV @ 6 keV). The sensor, consisting of 19 hexagonally shaped pixels with a total sensitive area of 5.05 cm(2), is connected to three high time resolution spectroscopy (HTRS) ASICs, allowing a fast readout of the detector signals. The detector works in a Charge-Sensitive Amplifier configuration. We assembled a prototype detector module and present here its mechanical design, describe the used sensor, and report about its performance.

ComPol is a proposed CubeSat mission dedicated to long-term study of gamma-ray polarisation of astrophysical objects. Besides spectral and timing measurements, polarisation analysis can be a powerful tool in constraining current models of the geometry, magnetic field structure and acceleration mechanisms of different astrophysical sources. The ComPol payload is a Compton telescope optimised for polarimetry and consists of a 2 layer stacked detector configuration. The top layer, the scatterer , is a Silicon Drift Detector matrix developed by the Max Planck Institute for Physics and Politecnico di Milano. The second layer is a calorimeter consisting of a CeBr 3 scintillator read-out by silicon photo-multipliers developed at CEA Saclay. This paper presents the results of the prototype calorimeter calibration campaign, executed in March 2022 at IJCLab Orsay and simulations of the expected performance of the polarimeter using updated performance figures of the detectors.

65Zn is a common calibration source, moreover used as a radioactive tracer in medical and biological studies. In many cases, γ-spectroscopy is a preferred method of 65Zn standardization, which relies directly on the branching ratio of Jπ(65Zn) = 5/2− → Jπ(65Cu) = 5/2− via electron capture (EC*). We measure the relative intensity of this branch to that proceeding directly to the ground state (EC0) using a novel coincidence technique, finding IEC0/IEC* = 0.9684 ± 0.0018. Re-evaluating the decay scheme of 65Zn by adopting the commonly evaluated branching ratio of Iβ+ = 1.4271(7)% we obtain IEC* = (50.08 ± 0.06)%, and IEC0 = (48.50 ± 0.06)%. The associated 1115 keV gamma intensity agrees with the previously reported NNDC value, and is now accessible with a factor of ∼2 increase in precision. Our re-evaluation removes reliance on the deduction of this gamma intensity from numerous measurements, some of which disagree and depend directly on total activity determination. The KDK experimental technique provides a new avenue for verification or updates to the decay scheme of 65Zn, and is applicable to other isotopes.

In the search for dark matter particle candidates, the mass region below 1 GeV/c^22 is relatively unprobed. Utilizing a low-noise silicon sensor as a sensitive target material, we aim to study the event signature of recoils between dark matter candidates and bound electrons. As the deposited energy is only a few eV, a sensor capable of detecting these low signals is required. We present first measurements on a prototype pixel matrix. It is based on the RNDR DePFET principle and provides a deep sub-electron readout noise of 0.2e^-− and below.

Potassium-40 is a widespread, naturally occurring isotope whose radioactivity impacts subatomic rare-event searches, nuclear structure theory, and estimated geological ages. A predicted electron-capture decay directly to the ground state of argon-40 has never been observed. The KDK (potassium decay) collaboration reports strong evidence of this rare decay mode. A blinded analysis reveals a nonzero ratio of intensities of ground-state electron-captures (I_{EC^{0}}) over excited-state ones (I_{EC^{*}}) of I_{EC^{0}}/I_{EC^{*}}=0.0095±[over stat]0.0022±[over sys]0.0010 (68% C.L.), with the null hypothesis rejected at 4σ. In terms of branching ratio, this signal yields I_{EC^{0}}=0.098%±[over stat]0.023%±[over sys]0.010%, roughly half of the commonly used prediction, with consequences for various fields [27L. Hariasz et al., companion paper, Phys. Rev. C 108, 014327 (2023)PRVCAN2469-998510.1103/PhysRevC.108.014327].

We present the first experimental results achieved with a monolithic array of 166 Silicon Drift Detectors (SDD). This detector was developed for the TRISTAN experiment, targeting the search for a sterile neutrino in the keV mass range by means of accurate Beta spectroscopy of the Tritium decay. We briefly report on the design and characterization with X-rays of the full signal chain: from the SDD array, operated in a planar configuration with all the components of the final system, to the acquisition platform simultaneously acquiring all 166 channels. The average energy resolution is better than 250 eV FWHM at 5.9 keV at a temperature of 0 degrees C, a 6 mu s shaping time, and an average count rate of 1 kcps per channel, 100 times smaller than the final experiment one.

We report on the characterization of a monolithic array of 166 Silicon Drift Detectors (SDD) with integrated JFET. This high-density detection module (4 cm by 4 cm) was designed and assembled within the TRISTAN development of the KATRIN experiment for search of sterile neutrinos in the keV mass range by means of beta spectroscopy. The detector was commissioned in the KATRIN monitor spectrometer and was exposed both to X-ray photons (at 5.9 keV of Fe55) and electrons (at 32.2 keV energy of Kr83m) reaching state-of-the-art homogeneity and energy resolution: 157 eV and 352.8 eV FWHM respectively (with 2 us shaping time and -33°C cooling).