Silicon Drift Detectors Research Articles

Charge Sharing Assessment and Active Collimation in Monolithic Arrays of Silicon Drift Detectors

Charge Sharing Assessment and Active Collimation in Monolithic Arrays of Silicon Drift Detectors

Development of silicon drift detectors for synchrotron radiation sources

Synchrotron radiation facilities are essential interdisciplinary research platforms, with performance and efficiency closely tied to detector technology. To meet future requirements, especially the High Energy Photon Source (HEPS), we have conducted key technological research and development on single-element and array Silicon Drift Detectors (SDDs). The research and testing were conducted at the Platform of Advanced Photon Source Technology (PAPS). The test results indicate that the single-element SDD has achieved an energy resolution of 143 eV@5.9 keV (−35 °C), and the 20-unit array-SDD has reached an energy resolution of better than 300 eV@13.96 keV (−40 °C).

Insight into the Impact of Electron Drift Trajectory on Charge Collection in Silicon Drift Detector

The internal electric field distribution is one key design consideration, which affects the charge collection efficiency in silicon drift detectors (SDDs). The internal electrostatic potential distributions along SDD front and back surfaces, which are determined by the applied voltages at cathode electrodes, define the final internal field distribution. Front-back bias coupling leads to the complexity of electrode structure design and voltage tuning. Device simulation is performed to investigate the performance of SDDs with varied bias voltages. When the cathode bias is −40 V with the first ring bias of −15 V and the outermost ring bias of −80 V, the detector is biased with a uniform electric field distribution, favorable electron drift trajectories. The simulation results provide new insight into the influence of internal electric field and electron drift trajectories on the charge collection efficiency. According to the analysis of simulation results, a 2000 × 2000 μm area concentric silicon drift detector was designed and fabricated. The electrical characteristics of the designed detectors were studied to show the validity of the proposed device design methodology. The internal electric field distribution and electron drift trajectories can be tuned to improve the charge collection efficiency.

Testing the Pauli Exclusion Principle across the Periodic Table with the VIP-3 Experiment.

The Pauli exclusion principle (PEP), a cornerstone of quantum mechanics and whole science, states that in a system, two fermions can not simultaneously occupy the same quantum state. Several experimental tests have been performed to place increasingly stringent bounds on the validity of PEP. Among these, the series of VIP experiments, performed at the Gran Sasso Underground National Laboratory of INFN, is searching for PEP-violating atomic X-ray transitions in copper. In this paper, the upgraded VIP-3 setup is described, designed to extend these investigations to higher-Z elements such as zirconium, silver, palladium, and tin. We detail the enhanced design of this setup, including the implementation of cutting-edge, 1 mm thick, silicon drift detectors, which significantly improve the measurement sensitivity at higher energies. Additionally, we present calculations of expected PEP-violating energy shifts in the characteristic lines of these elements, performed using the multi-configurational Dirac-Fock method from first principles. The VIP-3 realization will contribute to ongoing research into PEP violation for different elements, offering new insights and directions for future studies.

Light Element (C, N, O) Quantification by EDXS: Application to Meteorite Water Content and Organic Composition.

Quantifying light elements such as carbon, nitrogen, and oxygen in a transmission electron microscope (TEM) is a challenging however essential task in biology, materials, or earth and planetary sciences. We have developed an approach that allows precise quantification by energy-dispersive X-ray spectroscopy (EDXS), using sensitive windowless silicon drift detectors and homemade Python routines for hyperspectral data processing. K-factors were determined using wedge-shaped focused ion beam sections. To correct for X-ray absorption within the sample, the sample mass thickness is determined by the-revisited-two-lines method (Morris, 1980). No beam current measurement is required. Applying this method to the K and L lines of iron, we found that the tabulated mass absorption coefficient at the energy of the iron L lines was too low. This is due to X-ray self-absorption at the iron edge. Using reference material, we experimentally determined an absorption coefficient that gave the expected results. We then analyzed the complex phyllosilicate mixture of the Orgueil meteorite. We show that the N/C ratio of organics can be obtained with an accuracy better than 5 at.% and that oxygen can be quantified accurately enough to infer the hydroxyl content of phyllosilicates.

Development of high-efficiency X-ray detectors based on 1 mm thick monolithic SDD arrays

We present the novel 2× 4 monolithic Silicon Drift Detectors (SDD) array of 1 mm thickness developed within the context of the SIDDHARTA-2 experiment for high-energy X-ray spectroscopy measurements of light kaonic atom transitions. It represents a state-of-the-art advancement in terms of detection efficiency with respect to the previous generation of detectors, having a thickness of 450 μm. The sensor features eight square SDD units with an active area of 8 × 8 mm2 each, arranged in a 2 × 4 matrix. Therefore, the total active area of the array is 32 × 16 mm2 while the total chip area is 36 × 20 mm2, including a 2-mm dead region on each side of the array. This new version of SDD arrays, manufactured by Fondazione Bruno Kessler (FBK), includes an additional electrode on its entrance window, designed to reduce charge sharing between adjacent channels and improve energy resolution. This article describes two different detection modules based on these arrays: the first module includes a single array, whereas the second one is composed of two 1 mm thick SDD arrays in a stacked configuration, in order to reach 2 mm of effective thickness and further increase the module detection efficiency. The first spectroscopic measurements obtained with the two modules will be also reported in the paper, showing the spectroscopic improvements that can be obtained with the additional electrode on the window and the efficiency improvements that can be obtained with the stacked module.

Development of a silicon drift detector array to search for keV-scale sterile neutrinos with the KATRIN experiment

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.

A thermionic electron gun to characterize silicon drift detectors with electrons

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 β-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 105 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.

Extracting the electronic structure of light elements in bulk materials through a Compton scattering method in the readily accessible hard x-ray regime

Our Compton profile measurements of Ti and TiH2 using readily available hard X-ray radiation at 27.5 keV, detected by both a Hitachi Vortex silicon-drift detector and a high-resolution superconducting transition-edge sensor array, are found to be in excellent accord with state-of-the-art density functional theory based calculations. The spherically averaged difference between the Compton profiles of TiH2 and Ti is well described by an inverted parabola, supporting an itinerant behavior of the electron gas screening the protons in the Ti matrix. Our experimental approach, validated by two different detectors, extends the applicability of Compton scattering technique to the readily accessible hard x-ray regime (below 30 keV). Our study suggests possibilities for experiments at low-flux bending magnet synchrotron beamlines and paves the way for the development of tabletop Compton experiments with x-ray tubes.

Development of an x-ray polarimeter at the SOLEIL synchrotron.

Synchrotron radiation facilities provide highly polarized x-ray beams across a wide energy range. However, the exact type and degree of polarization vary according to the beamline and experimental setup. To accurately determine the angle and degree of linear polarization, a portable x-ray polarimeter has been developed. This setup consists of a silicon drift detector that rotates around a target made of high-density polyethylene. The imprint generated in the angular distribution of scattered photons from the target at a 90-degree angle between the incident x-rays and detector has been exploited to determine the beam polarization. Measurements were conducted at the GALAXIES beamline of the SOLEIL synchrotron. The expected angular distribution of the scattered photons for a given beam polarization was obtained through simulations using the Geant4 simulation toolkit. An excellent agreement between simulations and the collected data has been obtained, validating the setup and enabling a precise determination of the beam polarization.

A Novel Position-Sensitive Linear Winding Silicon Drift Detector.

A novel position-sensitive linear winding silicon drift detector (LWSDD) was designed and simulated. On the frontside (anode side), the collecting anodes were set on both sides of the detector, and an S-shaped linear winding cathode strip was arranged in the middle, which can realize independent voltage division and reduce the complexity of external bias resistor chain compared with the traditional linear silicon drift detector. The detectors were arranged in a butterfly shape, which increased the effective area of the detectors and improved the collection efficiency. The linear winding silicon drift detector can obtain one-dimensional position information by measuring the drift time of electrons. The 2D position information of the incident particle is obtained from the anodes coordinates of the readout signal. One-dimensional analytically exact solutions of electric potential and field were obtained for the first time for the linear winding silicon drift detector. The simulation results show that the electric potential distribution inside the detector is uniform, and the "drift channel" inside the detector points to the collecting anodes on both sides, which proves the reasonable and feasible design of the linear winding silicon drift detector.

Scattered high-energy synchrotron radiation at theKARA visible-light diagnostic beamline.

To characterize an electron beam, visible synchrotron light is often used and dedicated beamlines at synchrotron sources are becoming a more common feature as instruments and methods for the diagnostics are, along with the accelerators, further developed. At KARA (Karlsruhe Research Accelerator), such a beamline exists and is based on a typical infrared/visible-light configuration. From experience at such beamlines no significant radiation was expected (dose rates larger than 0.5 µSv h-1). This was found not to be the case and a higher dose was measured which fortunately could be shielded to an acceptable level with 0.3 mm of aluminium foil or 2.0 mm of Pyrex glass. The presence of this radiation led to further investigation by both experiment and calculation. A custom setup using a silicon drift detector for energy-dispersive spectroscopy (Ketek GmbH) and attenuation experiments showed the radiation to be predominantly copper K-shell fluorescence and is confirmed by calculation. The measurement of secondary radiation from scattering of synchrotron and other radiation, and its calculation, is important for radiation protection, and, although a lot of experience exists and methods for radiation protection are well established, changes in machine, beamlines and experiments mean a constant appraisal is needed.

Enhancing Performances of the VOXES Bragg Spectrometer for XES Investigations

Utilizing a dispersive crystal for X-ray Emission Spectroscopy (XES) significantly enhances the energy resolution when compared with spectroscopy performed with just silicon drift detectors. This high resolution is particularly valuable for studying metals, as it offers essential insights into their electronic structures and chemical environments. Conducting such experiments in the laboratory, as opposed to synchrotron light sources, presents challenges due to the reduced intensities of X-ray tubes and, consequently, low signal rates, with the effect of increasing the acquisition time. In this study, we demonstrate that XES spectra can be acquired within a few hours for a CuNiZn metallic sample alloy while still maintaining a good energy resolution and a large dynamic range. This is achieved with the VOXES spectrometer, developed at INFN National Laboratories of Frascati (LNF), along with a background reduction procedure that enhances the signal from emission lines under study. This study is a showcase for improving the efficiency of XES in tabletop setup experiments.

Assessment of performance rates on the elemental comparison of small and irregular glass fragments using µ-XRF and LIBS

This study describes a systematic assessment of the performance rates when analyzing small and irregular glass fragments using micro-X-ray Fluorescence Spectrometry (µ-XRF) and Laser Induced Breakdown Spectroscopy (LIBS). One hundred glass fragments were collected from the inner and outer panes of a vehicle windshield to assess the false exclusion rates. Additionally, 100 glass fragments originating from different vehicle windshields were used to evaluate the discrimination capabilities. To compare the effects of fragment size on the performance rates, half of the collected fragments were small (longest length between 0.4 mm and < 1 mm, and thickness greater than 0.4 mm for LIBS and 0.1 mm for μ-XRF), and the other half were full-thickness fragments (2 mm and greater). The study shows that precision deteriorates for small/irregular fragments and comparison items must have a similar size, shape, and thickness to minimize error rates. Thus, comparisons between full-thickness and small/irregular fragments should be avoided, regardless of the analytical method. Although this general concept is well known for µ-XRF, this effect was not previously reported as a concern for LIBS. Moreover, this study provides new sampling and comparison recommendations when using modern silicon drift detectors (SDD) and reduced fragment size. Using a 3 s (3 %RSD) comparison interval reduces the false exclusion rates to < 12 % for µ-XRF, and to < 4 % for LIBS when using either a 3 s or 4 s (3 % RSD) criterion. At least 4 known fragments are recommended for full thickness fragments and 6 to 9 known fragments for the small/irregular comparisons.

Comparing the output of measured and GEANT4 simulated X-ray tubes

Monte Carlo simulation codes that model particle interactions with matter, including GEANT4, can be used to support the development of novel X-ray tubes and instruments for applications in industry and research. Based on our knowledge, simulations of the output of transmission-geometry X-ray tubes have not yet been conducted in GEANT4. Simulations of reflection-geometry tubes are scarce, with a limited number of studies investigating the capability and accuracy of GEANT4 in this domain. Therefore, the aim of this work is to benchmark GEANT4 for the characterisation of X-ray tubes with industry applications, using for the first time a range of X-ray tubes geometries and high voltages. In this work, GEANT4 is benchmarked against experimental measurements performed at the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia, with both transmission and reflection X-ray tubes. High voltages between 17 kV and 42.5 kV for tungsten, molybdenum, gold, and silver targets are investigated. The measurements have been performed with a MXR packaged X-ray tube (reflection) and Magnum X-ray tubes (transmission) and a fast silicon drift detector (SDD). Our study shows that GEANT4 predicts the bremsstrahlung continuum output of transmission and reflection X-ray tubes, in agreement with the experimental measurements. The Penelope physics models, distributed with GEANT4, and the GEANT4 X-ray fluorescence data libraries ANSTO HF, based on the Hartree-Fock approach, exhibit the best agreement against experimental measurements. Depending on the high voltage, target and X-ray line agreement was found to vary between 10% and 300%. Differences between GEANT4 and experimental data are more significant for lower voltage X-ray tube measurements and are most likely due to limitations in the ionisation electron cross-section and/or atomic relaxation data libraries used. As next steps, it is recommended to validate GEANT4 against other, independent experimental measurements to corroborate the results of this work. In addition, it would be useful to repeat the same study with other general purpose Monte Carlo codes for radiation physics to compare their capability against GEANT4 in this application domain.

Anode capacitance measurement of silicon drift detectors in operating conditions

We describe a technique for measuring with high accuracy and precision the capacitance of the anode of a semiconductor drift detector (SDD) fully biased in operating conditions and connected to the front-end electronics. The proposed method does not require the use of a probe station, making it suitable for low-cost and easy-to-setup application environments. We have performed measurements on four SDDs with different geometries and production processes, observing a total capacitance ranging from 20 fF to 75 fF, depending on the bias conditions. Different components of the anode capacitance with respect to the front cathode and the adjacent drift cathodes have been measured and commented as well. Precision in the capacitance measurements better than 0.1 fF has been obtained. These results can be effectively used for the optimization of the front-end electronics for SDDs to achieve minimum electronic noise.

Design and 3D Electrical Simulations for a Controllable Equal-Gap Large-Area Silicon Drift Detector.

In this study, a controllable equal-gap large-area silicon drift detector (L-SDD) is designed. The surface leakage current is reduced by reducing the SiO2-Si interface through the new controllable equal-gap design. The design of the equal gap also solves the problem whereby the gap widens due to the larger detector size in the previous SDD design, which leads to a large invalid area of the detector. In this paper, a spiral hexagonal equal-gap L-SDD of 1 cm radius is selected for design calculation, and we implement 3D modeling and simulation of the device. The simulation results show that the internal potential gradient distribution of the L-SDD is uniform and forms a drift electric field, with the direction of electron drift pointing towards the collecting anode. The L-SDD has an excellent electron drift channel inside, and this article also analyzes the electrical performance of the drift channel to verify the correctness of the design method of the L-SDD.

On the forensic relevance of tattoos: distinguishing black inks with energy dispersive spectroscopy and backscattered scanning electron microscopy.

This study aimed to analyze black tattoo inks by means of energy dispersive spectroscopy and backscattered scanning electron microscopy. The sample consisted of five types of commercial tattoo pigments of the black colour (Easy Glow™, Electric Ink™, Iron Works™, Master Ink™, and Viper™). An Energy Dispersive Spectroscopy (EDS) detector (Silicon Drift Detector - SDD - type) attached to a Scanning Electron Microscope (SEM) device (Tescan Vega3 LMU, Libusina, Czech Republic) was used. X-ray characteristic signs were detected for each tattoo ink in an interval between 0 and 2.5keV. The electron acceleration potential in the microscope was 15keV. Two regions were analyzed for each sample (n = 10). On each region, a micrography of backscattered electrons (BSE) was obtained. Means and standard deviations (SD) of the weight percentages (Wt%) were calculated. C and O were predominant, with a mean O/C ratio between 2.69 and 2.74 Wt%. Electric Ink and Master Ink were the most similar pigments, while Easy Glow was the most distinctive - with agglomerates of Al that had a concentration 25 × higher than other specimens. Other compounds detected in the sample were Cl and Cu. EDS and SEM were efficient to distinguish black tattoo inks. These are our preliminary outcomes on the use of EDS and SEM to analyze black tattoo inks. Thus, careful interpretation is necessary to avoid rash applications in human identification practice.

The XGIS instrument on-board THESEUS: detector principle and read-out electronics

The functionality and experimental performance characterization of the latest four channel version of ORION ASIC, a very low noise multichip read out and processing electronics customized for the X and Gamma Imaging Spectrometer (XGIS) instrument onboard the Transient High-Energy Sky and Early Universe Surveyor (THESEUS) mission, is presented. XGIS is a set of two coded-masked wide field deep sky cameras using monolithic SDDs (Silicon Drift Detectors) and CsI:Tl (Thallium doped-Cesium Iodide) scintillator-based X-γ ray detectors. This paper highlights the design, working principle and the expected performances of the XGIS, on a small scale 2×2 prototype. Furthermore, the evolution timeline of different versions of ORION with detailed performance observations and analysis for spectroscopic resolution, electronic noise and the operational linear energy ranges of both X and the γ processors of the four-pixel ASIC version bonded to a 2×2 SDD array are emphasized. Each 2×2 SDD array element is electrically and dimensionally equivalent to single elements of the THESEUS 8×8 SDD array.

A versatile beamline for soft x-ray reflectivity, absorption, and fluorescence measurements at Indus-2 synchrotron source.

A versatile beamline for performing reflectivity, fluorescence, and absorption experiments in the soft x-ray region of 100-1500eV is commissioned on a bending magnet port of the Indus-2 synchrotron source. A high vacuum 2-axis reflectometer with x, y, and z sample scanning stages is installed. This reflectometer is used to measure the reflectivity of large samples up to 300mm in length and 5kg in weight. This feature is useful for characterizing x-ray optical elements, such as mirrors, gratings, and multilayers. A flange mounted silicon drift detector is installed in the downstream of the reflectometer for soft x-ray fluorescence measurements. The soft x-ray absorption measurements are carried out in the total electron yield and partial fluorescence yield modes. Integration of three different experimental techniques in the experimental station makes the beamline versatile for materials science applications as it provides structural, chemical, and electronic state information by performing the required experiments in an identical environment. The beamline uses a varied line spacing plane grating monochromator and gives a high flux (∼109 to 1011 photon/s) with a moderate resolution (λ/Δλ ~1000-5000). A three-mirror-based higher harmonic setup is incorporated to get rid of harmonics and to get a high spectral purity monochromatic beam with less than 0.1% harmonic content. In the present article, the beamline optical scheme, mechanical configuration, and details of the experimental setups are presented, along with a few representative results of each experimental mode.