Array Of Silicon Drift Detectors Research Articles

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.

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.

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

The TRISTAN 166-pixel detector: Preliminary results with a planar setup

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 250eV FWHM at 5.9keV at a temperature of 0 °C, a 6 μs shaping time, and an average count rate of 1kcps per channel, 100 times smaller than the final experiment one.

Development of a large array of Silicon Drift Detectors for high-rate synchrotron fluorescence spectroscopy

An array of small-area Silicon Drift Detectors (SDD), named Hera, has been developed at Brookhaven National Laboratory (BNL) in the past few years. Its primary application is high-rate spectroscopy at synchrotrons. Each SDD pixel is a 1 mm × 1 mm square to match the footprint of the original diode-based pixel detector called Maia, which was developed for the same application. The replacement of the diode with an SDD allows for better energy resolution at short shaping times and an increased stability of the detector. 32, 96, and 384-channel arrays were designed and fabricated and achieved a Full Width Half Maximum (FWHM) as low as 176 eV at 5.9 keV with peaking time of 1 μs at -13°C. The sensor design, simulation, fabrication, its readout system, and its spectroscopic performance are reported.

Development of multi-element monolithic germanium detectors for X-ray detection at synchrotron facilities

In past years efforts have concentrated on the development of arrays of Silicon Drift Detectors for X-ray spectroscopy. This is in stark contrast to the little effort that has been devoted to the improvement of germanium detectors, in particular for synchrotron applications. Germanium detectors have better energy resolution and are more efficient in detecting high energy photons than silicon detectors. In this context, the detector consortium of the European project LEAPS-INNOV has set an ambitious R&D program devoted to the development of a new generation of multi-element monolithic germanium detectors for X-ray detection. In order to improve the performance of the detector under development, simulations of the different detector design options have been performed. In this contribution, the efforts in terms of R&D are outlined with a focus on the modelization of the detector geometry and first performance results. These performance results show that a signal-to-background ratio larger than 1000 can be achieved in the energy range of interest from 5 keV to 100 keV.

The Effects of Different Anode Positions on the Electrical Properties of Square-Silicon Drift Detector.

The Silicon Drift Detector (SDD) with square structure is often used in pixel-type SDD arrays to reduce the dead region considerably and to improve the detector performance significantly. Usually, the anode is located in the center of the active region of the SDD with square structure (square-SDD), but the different anode positions in the square-SDD active area are also allowed. In order to explore the effect on device performance when the anode is located at different positions in the square-SDD active region, we designed two different types of square-SDD in this work, where the anode is located either in the center (SDD-1) or at the edge (SDD-2) of its active region. The simulation results of current density and potential distribution show that SDD-1 and SDD-2 have both formed a good electron drift path to make the anode collect electrons. The experimental results of device performance at the temperature range from −60 °C to 60 °C show that the anode current of the two fabricated SDDs both decreased with the decrease of temperature, but their voltage divider characteristics exhibited high stability resistance value and low temperature coefficient, thereby indicating that they could both provide corresponding continuous and uniform electric field at different temperatures. Finally, SDD-1 and SDD-2 have energy resolutions of 248 and 257 eV corresponding to the 5.9 keV photon peak of the Fe-55 radioactive source, respectively. Our experimental results demonstrate that there is no significant impact on the device performance irrespective of the anode positions in the square-SDD devices.

Towards the TRISTAN detector: Characterization of a 47-pixel monolithic SDD array

Multi-pixel Silicon Drift Detectors (SDD), widely employed in X-ray applications, can also be applied to electron spectroscopy experiments. The objective of the TRISTAN project is to equip the KATRIN beam line with a multi-pixel SDD focal plane array. This would allow to extend the physics program of KATRIN, whose main goal is the determination of the neutrino mass via a precise measurement of the tritium beta decay spectrum close to the endpoint. An extension of the measurement interval would enable a sensitive search for physics beyond the standard model, in particular keV-scale sterile neutrinos, a prime dark matter candidate. The SDD technology guarantees excellent energy resolution and high throughput capabilities. A custom 47-pixel prototype, based on a monolithic SDD tile, has been developed and tested for the TRISTAN project. The full functionality of the system has been verified for all 47 channels. Good spectroscopic performance has been observed with a 55Fe X-ray source. This is a crucial step towards the realization of the final 21-fold 166-pixel TRISTAN focal plane detector.

Development of a Detector for Gamma-Ray Spectroscopy Based on Silicon Drift Detector Arrays and 2<formula formulatype="inline"><tex Notation="TeX">${^\prime}{^\prime}$</tex> </formula> Lanthanum Bromide Scintillator

This work describes the development of a gamma detector based on silicon drift detectors (SDDs) to read out large ${\hbox{LaBr}}_3$ : ${\hbox{Ce}}$ scintillators for gamma-ray astronomy applications, within an activity supported by the European Space Agency (ESA). SDDs, characterized by high quantum efficiency and low electronic noise, when coupled with a scintillator are good candidates for gamma-ray spectroscopy applications in a wide energy range, e.g., from 150 keV to 15 MeV. The gamma-ray detector prototype presented here is composed of a 2 ${^\prime}{^\prime}$ $\times$ 2 ${^\prime}{^\prime}$ ${\hbox{LaBr}}_3$ : ${\hbox{Ce}}$ scintillator coupled with four SDD arrays arranged in a $2 \times 2$ format (a total of 36 SDDs). This detection system is operated with custom readout application specific integrated circuits (ASICs) and a data acquisition (DAQ) system. With this prototype gamma-camera, an energy resolution of 3.4% FWHM at 662 keV has been measured. Spectroscopy measurements have been carried out between 300 keV and 1800 keV and the achieved results are consistent with the electronic noise of the SDD technology. In this work, we report on the SDD based detection head’s design, its X-ray characterization, readout electronics, experimental setups and gamma-ray spectroscopy results. Finally, perspectives with the possible use of an improved SDD technology are discussed.

Development of arrays of Silicon Drift Detectors and readout ASIC for the SIDDHARTA experiment

This work deals with the development of new Silicon Drift Detectors (SDDs) and readout electronics for the upgrade of the SIDDHARTA experiment. The detector is based on a SDDs array organized in a 4×2 format with each SDD square shaped with 64mm2 (8×8) active area. The total active area of the array is therefore 32×16mm2 while the total area of the detector (including 1mm border dead area) is 34×18mm2. The SIDDHARTA apparatus requires 48 of these modules that are designed and manufactured by Fondazione Bruno Kessler (FBK). The readout electronics is composed by CMOS preamplifiers (CUBEs) and by the new SFERA (SDDs Front-End Readout ASIC) circuit. SFERA is a 16-channels readout ASIC designed in a 0.35μm CMOS technology, which features in each single readout channel a high order shaping amplifier (9th order Semi-Gaussian complex-conjugate poles) and a high efficiency pile-up rejection logic. The outputs of the channels are connected to an analog multiplexer for the external analog to digital conversion. An on-chip 12-bit SAR ADC is also included. Preliminary measurements of the detectors in the single SDD format are reported. Also measurements of low X-ray energies are reported in order to prove the possible extension to the soft X-ray range.

First results of a novel Silicon Drift Detector array designed for low energy X-ray fluorescence spectroscopy

We developed a trapezoidal shaped matrix with 8 cells of Silicon Drift Detectors (SDD) featuring a very low leakage current (below 180pA/cm2 at 20°C) and a shallow uniformly implanted p+ entrance window that enables sensitivity down to few hundreds of eV. The matrix consists of a completely depleted volume of silicon wafer subdivided into 4 square cells and 4 half-size triangular cells. The energy resolution of a single square cell, readout by the ultra-low noise SIRIO charge sensitive preamplifier, is 158eV FWHM at 5.9keV and 0°C. The total sensitive area of the matrix is 231mm2 and the wafer thickness is 450μm. The detector was developed in the frame of the INFN R&D project ReDSoX in collaboration with FBK, Trento. Its trapezoidal shape was chosen in order to optimize the detection geometry for the experimental requirements of low energy X-ray fluorescence (LEXRF) spectroscopy, aiming at achieving a large detection angle. We plan to exploit the complete detector at the TwinMic spectromicroscopy beamline at the Elettra Synchrotron (Trieste, Italy). The complete system, composed of 4 matrices, increases the solid angle coverage of the isotropic photoemission hemisphere about 4 times over the present detector configuration. We report on the layout of the SDD matrix and of the experimental set-up, as well as the spectroscopic performance measured both in the laboratory and at the experimental beamline.

Monolithic arrays of SDDs and low noise CMOS readout for X-ray spectroscopy measurements in nuclear physics experiments

This work deals with the development of Silicon Drift Detectors (SDDs) of different sizes and low noise CMOS read-out preamplifiers in view of their use in nuclear physics experiments, like the SIDDHARTA upgrade supported by Italian INFN. In this work we report about the recent SDDs and CMOS preamplifiers development, with particular emphasis on X-ray measurements at cryogenic temperatures. The SDDs presented are designed as single square shaped units of different areas 64 mm2 (8mm × 8mm) or 144 mm2 (12mm × 12mm) and also as monolithic arrays of 9 elements (8mm × 8mm each, total area 26mm × 26mm) in a3 × 3 format. The detectors have been designed and manufactured by the Fondazione Bruno Kessler (FBK). The read-out of the SDDs is based on the CMOS preamplifier (CUBE) for both the single unit and the 3 × 3 array. The CMOS technology is intrinsically more robust at lower temperatures with respect to the more conventional JFET transistor used in SDDs readout. A measured resolution of 123 eV on the Mn-Kα line with the optimum shaping time and a resolution of 126.4 eV with 250 ns shaping time have been obtained with round shaped 10 mm2 SDDs detectors. This last result leads to excellent spectroscopy performances even with very high input count rates making the SDD+CUBE combination very attractive also for synchrotron applications. The nine detectors array in addition to the preamplifiers the use of a multichannel ASIC for signal shaping and peak detection of all the units and of a custom Data Acquisition System. Also preliminary measurements of low energies lines are reported in order to prove the possibility of soft X-ray detection.

Silicon Drift Detectors and CUBE Preamplifiers for High-Resolution X-ray Spectroscopy

In this work we present the results of the experimental characterization of Silicon Drift Detectors (SDDs) readout by CUBE preamplifiers for X-ray spectroscopy measurements. One specific goal of the work was to characterize SDDs of different sizes cooled at low temperature in view of their use in the upgrade of the SIDDHARTA nuclear physics experiment. Beside the target application, the results of this work are also of interest for a more extended use of the SDDs in other X-ray spectroscopy applications. The SDDs have been designed as single units with square shape of different areas, $64$ mm $^{2}$ ( $8~\hbox{mm} \times 8~\hbox{mm}$ ) and $144 $ mm $^{2}$ ( $12~\hbox{mm} \times 12~\hbox{mm}$ ), and also as monolithic array of $3 \times 3$ elements of the $8~\hbox{mm} \times 8~\hbox{mm}$ unit (total area $26~\hbox{mm} \times 26~\hbox{mm}$ ). The read-out of the SDDs is based on a CMOS (Complementary Metal Oxide Semiconductor) preamplifier (CUBE) both for the single unit and for the $3 \times 3$ array. For the readout of the array, an Application Specific Integrated Circuit (ASIC) has been used. An energy resolution better than 124 eV at the ${\rm Mn} - {\rm K}\alpha $ line has been measured with a $64 $ mm $^{2}$ SDD cooled at the temperature of 50 K. The energy resolution remains good ( $ eV) also at short shaping time (250 ns) thanks to the noise feature of the CUBE preamplifier. Results of measurements on SDDs of different format and also on arrays of SDDs are presented in this work.

Development of a detector based on Silicon Drift Detectors for gamma-ray spectroscopy and imaging applications

This work deals with the development of a new gammadetector based on Silicon Drift Detectors (SDDs) to readout largeLaBr3:Ce scintillators for gamma-ray spectroscopy and imagingapplications. The research is supported by the European Space Agency throughthe Technology Research Programme (TRP) and by Istituto Nazionale di FisicaNucleare (INFN) within the Gamma project. The SDDs, produced at FondazioneBruno Kessler (FBK) semiconductor laboratories, are designed as monolithicarrays of 3 × 3 units, each one of an active area of 8 mm × 8 mm (overall area of 26 mm × 26 mm). The readout electronics and thearchitecture of the camera are briefly described and then first experimentalresults coupling the SDD array with a 1'' × 1'' LaBr3:Cescintillator are reported. An energy resolution of 3% FWHM at 662 keV hasbeen measured at -20°C, better than coupling the same scintillator witha photomultiplier tube. The same scintillator is also used to evaluateposition sensitivity with a 1 mm collimated Cs-137 source. The maindifficulty in determining the position of the gamma-ray interaction in thecrystal is associated to the high thickness/diameter ratio of the crystal(1:1) and the use of reflectors on all lateral and top sides the crystal.This last choice enhances energy resolution but makes imaging capabilitymore challenging because light is spread over all photodetectors.Preliminary results show that the camera is able to detect shifts in themeasured signals, when the source is moved with steps of 5 mm. A modifiedversion of the centroid method is finally implemented to evaluate theimaging capability of the system.

Silicon Drift Detectors for Readout of Scintillators in Gamma-Ray Spectroscopy

In this work, we report on a new development of Silicon Drift Detectors (SDDs) for gamma-ray spectroscopy with space science applications. The research is supported by the European Space Agency through the Technology Research Programme (TRP). The final goal of the development is the realization of monolithic arrays of SDDs which will be assembled to readout large (2” and 3”) LaBr3(Ce) scintillators. We present here the results of the development of a single SDD prototype, with 8 × 8 mm2 active area, produced at Fondazione Bruno Kessler (FBK) semiconductor laboratories. We discuss the design issues related to the specific use of this device as a photo-detector for scintillators. Then, we focus on the read-out electronics. Since this SDD does not include a front-end transistor on the silicon chip, we have adopted a CMOS charge preamplifier (CUBE) recently developed at Politecnico di Milano. This preamplifier has allowed the achievement of state-of-the-art noise performance using a SDD technology process without the integration of the FET (Field Effect Transistor) on the detector chip. A quantum efficiency of about 80% has been measured for the SDD at the emission wavelength band of LaBr3 (360-380 nm). First experimental measurements consisting of direct 55 Fe irradiation of the SDD without scintillator, have demonstrated energy resolution of 140 eV and 129 eV at -20°C and -43°C respectively. By coupling the SDD with a LaBr3(Ce) scintillator (9 mm diameter), we have measured energy resolution of 5.6% FWHM and 2.6% FWHM at 122 keV and 662 keV respectively.

Arrays of silicon drift detectors for an extraterrestrial X-ray spectrometer

Arrays of Silicon Drift Detectors (SDD) were designed, produced and tested. These arrays are the central part of an X-Ray Spectrometer (XRS) for measuring the abundances of light surface elements (C–Fe) fluoresced by ambient radiation on the investigated celestial object. The basic building element (or cell) of the arrays consists of a single hexagonal SDD. Signal electrons drift toward the center of the hexagon where a very low capacitance anode is located. The hexagonal shape of an individual SDD allows for a continuous covering of large detection areas of various shapes. To match the number of SDD cells with the external Application Specific Integrated Circuit (ASIC), two arrays, one with 16 and another with 64 cells were developed. One side of SDDs, called the window side, is a continuous thin rectifying junction through which the X-ray radiation enters the detector. The opposite side, called the device side contains electron collecting anodes as well as all other electrodes needed to generate the drift field and to sink leakage current produced on Si–SiO 2 interface. On both sides of the detector array there is a system of guard rings, which smoothly adjusts the voltage of the boundary cells to the ground potential of the silicon outside the sensitive volume. The drift voltage inside the detector is generated by an implanted rectifying contact, which forms a hexagonal spiral. This spiral produces the main valley where signal electrons drift as well as the voltage divider to produce the drift field. System performance is shown by a spectrum of Mn X-rays produced by the decay of 55Fe.

Performance Characterization of a Silicon Drift Detector for Gamma Ray Imaging

This study examined the intrinsic performance of silicon drift detector (SDD)-based gamma detectors under a variety of conditions. The prototype detector consisted of an array of seven hexagon-shaped SDDs optically coupled to a single slab of a scintillator. The active area of the SDD sensor was 15.2 mm in diameter, as measured from one vertex to another. The detector unit (SDD array, scintillator and preamplifier circuits) was operated in a cooling chamber with a typical operating temperature of -20°C. Nitrogen gas was supplied to the detector unit to prevent condensation. The drift time was measured using a LED pulse generation device and the longest drift time was measured to be 4.6 μsec from the edge of the sensor. The intrinsic energy resolution with a BBFe source for direct X-ray conversion was 3% at the 5.9 keV peak. For indirect conversion, i.e. photon detection, the energy resolution for CsI(Tl) and Nal(Tl) was 7.9% and 8.2% with a 13 μsec and 2.71 μsec shaping time, respectively. For this indirect conversion measurement, the temperature was set to -20°C and a 1 × 1 × 1 cm3 cube scintillator was coupled directly to the sensor. For the intrinsic spatial resolution measurement with a hole-phantom (3 × 2 mm diameter holes), the x and y directional profiles at a center hole were 2.2 and 2.1 mm in FWHM, respectively. Overall, the intrinsic performance of the SDD prototype is quite promising and advantages of this technology makes it highly feasible for use as a gamma ray detector.

Silicon drift photodetector arrays for the HICAM gamma camera

Silicon drift detectors (SDDs) have shown to be a competitive device for the readout of scintillators with respect to conventional photodetectors, thanks to their high quantum efficiency and low electronics noise. Recently, they have been successfully employed in first small prototypes of Anger cameras to achieve sub-millimeter spatial resolution in gamma-ray imaging. To cover larger formats of Anger cameras, in particular in the framework of the HICAM project, specially focused on human imaging, we have developed new SDD arrays of larger active areas. To assemble photodetector planes of several cm 2, we have designed a basic unit composed by a linear array of 5 SDDs of 1 cm 2 active area each. In this work, we present the results of the experimental characterization of these photodetector arrays in direct X-ray detection to evaluate the electronics noise, as well as gamma-ray detection with a scintillator.

The DRAGO gamma camera

In this work, we present the results of the experimental characterization of the DRAGO (DRift detector Array-based Gamma camera for Oncology), a detection system developed for high-spatial resolution gamma-ray imaging. This camera is based on a monolithic array of 77 silicon drift detectors (SDDs), with a total active area of 6.7 cm(2), coupled to a single 5-mm-thick CsI(Tl) scintillator crystal. The use of an array of SDDs provides a high quantum efficiency for the detection of the scintillation light together with a very low electronics noise. A very compact detection module based on the use of integrated readout circuits was developed. The performances achieved in gamma-ray imaging using this camera are reported here. When imaging a 0.2 mm collimated (57)Co source (122 keV) over different points of the active area, a spatial resolution ranging from 0.25 to 0.5 mm was measured. The depth-of-interaction capability of the detector, thanks to the use of a Maximum Likelihood reconstruction algorithm, was also investigated by imaging a collimated beam tilted to an angle of 45 degrees with respect to the scintillator surface. Finally, the imager was characterized with in vivo measurements on mice, in a real preclinical environment.

Imaging performances of the DRAGO gamma camera

In this work, we present the results of the experimental characterization of the DRAGO gamma camera. This camera is based on a monolithic array of 77 Silicon Drift Detectors (SDDs), with a total active area of 6.7 cm 2, coupled to a single CsI(Tl) scintillator crystal, 5 mm thick. The use of an array of SDDs provides high quantum efficiency for the detection of the scintillation light together with a very low electronics noise. A very compact detection module based on the use of integrated readout circuits has been developed. Performances achieved in gamma-ray imaging using this camera are here reported. When imaging a 0.2 mm collimated 57Co source (122 keV) over different points of the active area, a spatial resolution ranging between 0.25 and 0.5 mm has been measured. The depth of interaction capability of the detector, thanks to a maximum likelihood reconstruction algorithm here adopted, has been also investigated by imaging a collimated beam tilted to an angle of 45° with respect to the scintillator surface.