Double-sided Strip Detectors Research Articles

E-ΔE detection module of DGFRS-2 setup

Thе paper describes a new E-ΔE detection module which includes a position-sensitive double-sided strip detector (DSSD) and a low-pressure pentane-filled ΔE chamber for detection of Evaporation Residues (ERs) in complete fusion reactions. The goal is to synthesize superheavy isotopes at the new DC-280 (Dubna Cyclotron) cyclotron of the Joint Institute for Nuclear Research (JINR). With the 48Ca ion beam intensity of about 5–7 pμA (particle micro ampere) and the ΔE counter count rate of approximately 104 sec−1, we observe a decrease in the overall registration efficiency of the gas ΔE counter. The paper proposes a solution to this problem: introduction of an additional negatively biased electrode, which results in the stabilization of the ΔE detector operation.

Energy Resolution from a Silicon Detector's Interstrip Regions.

In this work, we present a novel approach for improving the energy resolution from particles impinging on the interstrip regions of silicon strip detectors. We employed three double-sided strip detectors from the GRIT array and a triple α-source under laboratory conditions. The results showed that the interstrip resolution depends not only on the impinging side but also on whether it is a P- or an N-interstrip. We obtained the interstrip energy resolution down to 0.4%, and, depending on the scenario, the resolution was enhanced by a factor of 2. We believe that this new rotation method allows for the possibility of applying particle identification methods on interstrip events, which in most cases are dismissed during data recording.

Silicon vertex detector of the Belle II experiment

The silicon vertex detector (SVD) is installed at the heart of the Belle II experiment, taking data at the high-luminosity B-Factory SuperKEKB since 2019. The SVD is a four-layer double-sided strip detector with tracking and particle-identification capabilities. In this paper, we report on the performance of the reconstruction of SVD hits. The detector has shown a stable and above-99% hit efficiency, with a large signal-to-noise in all sensors since the beginning of data taking. Cluster position and time resolution have been measured with 2020 and 2022 data and show excellent performance and stability. In particular, the cluster-position resolution is between 7 and 12 μm for the small-pitch sensors, in reasonable agreement with the expectations, while the cluster time resolution is measured to be below 3 ns. The effect of radiation damage is visible, but not affecting the performance. As the luminosity increases, higher machine backgrounds are expected and the excellent hit-time information in SVD can be exploited for background rejection. In particular, we have recently developed a novel procedure to select hits by grouping them event-by-event based on their time. This new procedure allows a significant reduction of the fake rate, while preserving the tracking efficiency, and it has therefore replaced the previous cut-based procedure. We have developed a method that uses the SVD hits to estimate the track time (previously unavailable) and the collision time. It has a similar precision to the estimate based on the drift chamber readout but its execution time is three orders of magnitude smaller, allowing a faster online reconstruction that is crucial in a high luminosity regime. The track time is a powerful information that allows, together with the aforementioned grouping selection, to raise the occupancy limit above that expected at nominal luminosity, leaving room for a safety factor. Finally, in June 2022 the data taking of the Belle II experiment was stopped to install a new two-layer DEPFET detector (PXD) and upgrade components of the accelerator. The whole silicon tracker (PXD+SVD) has been extracted from Belle II, the new PXD installed, the detector closed and commissioned. We briefly describe the SVD results of this upgrade.

2-mm-thick large-area CdTe double-sided strip detectors for high-resolution spectroscopic imaging of X-ray and gamma-ray with depth-of-interaction sensing

We developed a 2-mm-thick CdTe double-sided strip detector (CdTe-DSD) with a 250μm strip pitch, which has high spatial resolution with a uniform large imaging area of 10 cm2 and high energy resolution with high detection efficiency in tens to hundreds keV. The detector can be employed in a wide variety of fields for quantitative observations of hard X-ray and soft gamma-ray with spectroscopic imaging, for example, space observation, nuclear medicine, and non-destructive elemental analysis. This detector is thicker than the 0.75-mm-thick one previously developed by a factor of ∼2.7, thus providing better detection efficiency for hard X-rays and soft gamma rays. The increased thickness could potentially enhance bias-induced polarization if we do not apply sufficient bias and if we do not operate at a low temperature, but the polarization is not evident in our detector when a high voltage of 500 V is applied to the CdTe diode and the temperature is maintained at −20 °C during one-day experiments. The “Depth Of Interaction” (DOI) dependence due to the CdTe diode’s poor carrier-transport property is also more significant, resulting in much DOI information while complicated detector responses such as charge sharings or low-energy tails that exacerbate the loss in the energy resolution.In this paper, we developed 2-mm-thick CdTe-DSDs, studied their response, and evaluated their energy resolution, spatial resolution, and uniformity. We also constructed a theoretical model to understand the detector response theoretically, resulting in reconstructing the DOI with an accuracy of 100 μm while estimating the carrier-transport property. First, we evaluated the energy resolution using 22Na, 133Ba, and 57Co reconstructing the DOI effect from the energy correlation on both the anode and cathode sides. We obtained an energy resolution of 4.3 keV (FWHM) at 356 keV. Second, we formulated a theoretical detector-response model that reproduced the experimental data. Using the model, we determined the mobility-lifetime products of carriers μτe,h=(4±1)×10−3,(1.15±0.05)×10−4 [cm2/V] with the space charge density of nsp=−6.0×1010 [1/cm−3] and then reconstructed the DOI with an accuracy of 100 μm. Finally, we evaluated the spatial resolution and demonstrated to resolve patterns of 250-μm-width slits with an X-ray test chart. We found no positional variation in the detector response. We realized the detector that has high energy resolution and high 3D spatial resolution with a uniform large imaging area.

A diamond double-sided strip detector for alpha-tagging in associated particle imaging

- In associated particle imaging, neutrons from deuterium-tritium fusion are used to interrogate objects of interest. The associated particle imaging technique utilizes an alpha-tagging sensor in the neutron generator to detect the alpha particle that is emitted antiparallel to the neutron, providing neutron birth time and direction. This technique of neutron imaging and induced fission imaging can provide higher contrast image reconstructions and better estimations of fissile material mass than passive measurement techniques. The performance goals of an alpha-tagging sensor in associated particle imaging are a 700-ps timing resolution, a 0.5 mm spatial resolution, high level of radiation hardness, low sensitivity to X-rays, high signal-to-noise ratio, and survivability in the high temperature bake out of the neutron generator. Currently employed YAP scintillators are overwhelmed by the intense X-ray field in the neutron generator, requiring a new alpha tagging sensor design to be developed. We have developed and tested a diamond double-sided strip detector as a proposed sensor for associated particle imaging. Diamond is radiation hard, has a low sensitivity to X-rays, fast timing capabilities, high signal-to-noise ratio, and can withstand the temperatures of bake-out. The spatial resolution can be accomplished with a charge division readout and double-sided strip design. We measured the timing resolution of a single crystal chemical vapor deposition (CVD) diamond with a Cividec C6 charge amplifier readout by measuring the time-of-flight of 241Am alpha particles between a thin plastic scintillator and the diamond. We also fabricated a polycrystalline CVD diamond double-sided strip detector with charge division readout to test the spatial resolution of the design. We found that the detector met both the 700-ps timing resolution and the 0.5 mm spatial resolution goals (both reported as FWHM resolution).

Gamma-ray computed tomography system with a double-sided strip detector

We have developed a γ-ray computed tomography system using a CdTe double-sided strip detector. Owing to a 250 μm fine strip pitch and high energy resolution with photon-counting capability, the system provides highly accurate images, with which the materials and their distributions inside the target can be determined according to the photon transmittances. We evaluated the key performance of the system, conducting transmission measurements for Al, Cu, and Pb plates and also for Al, Fe, Cu, and Pb rod-phantoms, both using X-rays (∼30 keV) and γ-rays (∼80 keV) from a 133Ba source. The measured transmittances agreed well with the calculated values from simulations. We successfully reconstructed the three-dimensional structure of the rod-phantom and distinguished the elements inside the phantom. Compared with the simulated photon transmittances, we found that material identification based on tomographic images obtained with the system is efficient as long as the target object does not contain thick high-Z elements.

Non-destructive 3D imaging method using muonic X-rays and a CdTe double-sided strip detector

Elemental analysis based on muonic X-rays resulting from muon irradiation provides information about bulk material composition without causing damage, which is essential in the case of precious or otherwise unreachable samples, such as in archeology and planetary science. We developed a three-dimensional (3D) elemental analysis technique by combining the elemental analysis method based on negative muons with an imaging cadmium telluride double-sided strip detector (CdTe-DSD) designed for the hard X-ray and soft gamma-ray observation. A muon irradiation experiment using spherical plastic samples was conducted at the Japan Proton Accelerator Research Complex (J-PARC); a set of projection images was taken by the CdTe-DSD, equipped with a pinhole collimator, for different sample rotation angles. The projection images measured by the CdTe-DSD were utilized to obtain a 3D volumetric phantom by using the maximum likelihood expectation maximization algorithm. The reconstructed phantom successfully revealed the 3D distribution of carbon in the bulk samples and the stopping depth of the muons. This result demonstrated the feasibility of the proposed non-destructive 3D elemental analysis method for bulk material analysis based on muonic X-rays.

Study of the Proton Irradiation Effects in n-FZ DSSD for the Si Tracker at R3B Experiment

The R3B collaboration aims to assemble an experimental setup with high resolution and efficiency to perform kinematically complete measurements of reactions with high-energy RIBs (radioactive ion beams). In the R3B experimental setup, the silicon tracker is positioned closest to the target region and can provide high-resolution position measurements of light-charged particles like protons. The three layers of the silicon tracker are constructed with a total of 30 Si double-sidedstrip detectors (DSSD). In this paper, as an option of 23 MeV proton irradiated n-type Float-Zone(Fz)Si double-sidedstrip detector (DSSD) havebeen considered, and by taking the two-trapproton irradiation damage model, the bulk damage effect and the macroscopic performance of the Sidouble-sidedstrip detector (DSSD) have been discussed. The detector is irradiated with three values of proton fluences (equivalent to 1Mev neutron fluence): 2×1014,5×1014 and 8×1014 cm-2. By using the Shockley-Read-Hall recombination (SRH) formulation, the full depletion voltage and leakage current have been measured as a function of the irradiation dose, finally the device and process parameters and specifications for the Si double-sidedstrip detector (DSSD) used in the R3B silicon tracker experimenthavebeen proposed.

Correcting for spatially dependent intrinsic efficiency on a germanium double-sided strip detector to improve nuclear forensics response

Correcting for spatially dependent intrinsic efficiency on a germanium double-sided strip detector to improve nuclear forensics response

Gamma-ray imaging performance of the GRI+ Compton camera

GRI+ (Gamma-Ray Imager) is a cart-based Compton camera developed at the University of Liverpool. The system comprises three electrically-cooled semiconductor detectors; two planar double-sided strip detectors (Si(Li) and HPGe) and an HPGe coaxial detector. The mobile cart houses the necessary components for data acquisition and analysis, providing complete functionality for imaging gamma-ray sources in an industrial setting. This paper reports on the operation of the system and the methods used to improve intrinsic system performance. The processing chain for extracting information pertaining to gamma-ray interactions has been developed and the imaging performance is characterised using an analytical reconstruction code. The obtainable Angular Resolution Measure (ARM) from a Cs-137 point source placed 10.5 cm from the front of the Si(Li) cryostat was determined to be 4.12∘ after the application of data processing techniques. The system energy resolution, which is key to isotope identification and image quality, was calculated to be less than 0.5% at 1332.5 keV.

Evaluation of a Digital Shaping Amplifier for Double-Sided Silicon Strip Detectors (DSSD)

This paper reports the digital implementation of analog shaping amplifiers by digital pulse processing in gamma-ray spectroscopy. For digital implementation, a numerical algorithm was developed by referring to the semi-Gaussian filter of the analog shaping amplifier. In order to verify the developed algorithm, we evaluated the obtained energy spectrum and compared the energy resolution with the existing analog processing results. The gamma-ray detector used a double-sided strip detector, and the preamplifier signal of the detector was digitized directly by using a commercial digitizer. Using the standard gamma-ray sources Am-241 (59 keV), Ba-133 (81 keV), and Co-57 (122 keV), we were able to detect gamma rays in a relatively low energy region. The energy resolution was improved at energies below 100 keV compared to the result of treatment with an analog shaping amplifier.

Development of a low-noise front-end ASIC for CdTe detectors

We present our latest ASIC, which is used for the readout of Cadmium Telluride double-sided strip detectors (CdTe DSDs) and high spectroscopic imaging. It is implemented in a 0.35 μm CMOS technology (X-Fab XH035), consists of 64 readout channels and has a function that performs simultaneous AD conversion for each channel. The equivalent noise charge of 54.9e−± 11.3e− (rms) is measured without connecting the ASIC to any detectors. From the spectroscopy measurements using a CdTe single-sided strip detector, the energy resolution of 1.12 keV (FWHM) is obtained at 13.9 keV, and photons within the energy from 6.4 keV to 122.1 keV are detected. Based on the experimental results, we propose a new low-noise readout architecture making use of a slew-rate limited mode at the shaper followed by a peak detector circuit.

Imaging and spectral performance of a [formula omitted] pitch CdTe Double-Sided Strip Detector

We have evaluated the performance of a fine pitch CdTe Double-sided Strip Detector (CdTe-DSD), which was originally developed for the focal plane detector of a hard X-ray telescope to observe the Sun. The detector has a thickness of 750 μm and has 128 strip electrodes with a 60 μm strip pitch orthogonally placed on both sides of the detector and covers an energy range 4 keV to 80 keV. The study of the depth of photon interaction and charge sharing effects are of importance in order to provide good spectroscopic and imaging performance. We study the tail structure observed in the spectra caused by charge trapping and develop a new method to reconstruct the spectra based on induced charge information from both anode and cathode strips. By applying this method, energy resolutions (FWHM) of 0.76 keV and 1.0 keV can be obtained at photon energies of 14 keV and 60 keV, respectively, if the energy difference between the anode and cathode is within 1 keV. Furthermore, the tail component at 60 keV is reduced, and the energy resolution of the 60 keV peak is improved from 2.4 keV to 1.5 keV (FWHM) if the energy difference is greater than 1 keV. In order to study the imaging performance, we constructed a simple imaging system using a 5 mm thick tungsten plate that has a pinhole with a diameter of 100 μm. We utilize a 133Ba radioisotope of 1 mm in diameter as a target source in combination with a 100 μm slit made from 0.5 mm thickness tungsten. We imaged the 133Ba source behind the 100 μm slit using a 30 keV peak, with a 100 μm pinhole placed at the center of the source-detector distance. By applying a charge sharing correction between strips, we have succeeded in obtaining a position resolution better than the strip pitch of 60 μm.

Benchmarking simulations of the Compton Spectrometer and Imager with calibrations

The Compton Spectrometer and Imager (COSI) is a balloon-borne gamma-ray (0.2-5 MeV) telescope designed to study astrophysical sources. COSI employs a compact Compton telescope design utilizing 12 high-purity germanium double-sided strip detectors and is inherently sensitive to polarization. In 2016, COSI was launched from Wanaka, New Zealand and completed a successful 46-day flight on NASA's new Super Pressure Balloon. In order to perform imaging, spectral, and polarization analysis of the sources observed during the 2016 flight, we compute the detector response from well-benchmarked simulations. As required for accurate simulations of the instrument, we have built a comprehensive mass model of the instrument and developed a detailed detector effects engine which applies the intrinsic detector performance to Monte Carlo simulations. The simulated detector effects include energy, position, and timing resolution, thresholds, dead strips, charge sharing, charge loss, crosstalk, dead time, and detector trigger conditions. After including these effects, the simulations closely resemble the measurements, the standard analysis pipeline used for measurements can also be applied to the simulations, and the responses computed from the simulations are accurate. We have computed the systematic error that we must apply to measured fluxes at certain energies, which is 6.3% on average. Here we describe the detector effects engine and the benchmarking tests performed with calibrations.

Development of 60 [formula omitted] pitch CdTe double-sided strip detectors for the FOXSI-3 sounding rocket experiment

FOXSI-3 (Focusing Optics X-ray Solar Imager) is an international sounding rocket experiment to observe hard X-rays from the Sun. The previous two flights successfully demonstrated the efficacy of the concept of direct solar imaging in hard X-ray band. For the third launch scheduled in the summer of 2018, we have fabricated a prototype of the CdTe Double-sided Strip Detector.To evaluate the basic performance, laboratory tests were conducted. Energy resolution (FWHM) of 0.8 keV at 13.9 keV and 1.3 keV at 59.5 keV are confirmed. Since the optic angular resolution is finer than the strip pitch of the detector at the focal plane, sub-strip position determination is important to make full use of the high precision of the optic. To test the possibility of sub-strip resolution, we developed a new method of investigating the detector strips with a fine multi-pinhole collimator. The results of the analysis were highly favorable and we confirmed the sub-strip resolution by making sub-strip images of multi-pinholes and flat-irradiation. The spectral uniformity over the detector is also confirmed using the sub-strip image of flat-irradiation.

Long-term test of a stacked CdTe mini-HXI setup

This work presents a long-term operation of two stacked CdTe double sided strip detectors that are comparable with the CdTe detectors onboard Hitomi’s HXI. The goal of this test is to study the evolution of the spectroscopic performance of the detectors during a one year operation cycle which resembles the in-orbit operation cycle of Hitomi HXI. Crystal defects inside CdTe cause a degradation of the spectroscopic performance (polarization effect) of the crystal which is becoming worse during detector operation. In order to prevent crystal polarization, the detectors are reset (switch-off of the depletion voltage) once a day. Our main investigation was to study if a long-term degradation can occur as a result of incomplete depolarization during the reset. We present the hardware setup and the analytical steps that were used to investigate the detector stability during each day and over the whole testing period. For the anode signals our results show at 60 keV: a daily line drift of (−2.8±0.7) eV/ks while the long-term drift is (−1.5±1.2) eV/day. The degradation of the energy resolution is measured to be (+2.4±0.3) eV/ks FWHM and the loss of efficiency is (−0.29±0.02) %/ks.

A compact imaging system with a CdTe double-sided strip detector for non-destructive analysis using negative muonic X-rays

A CdTe double-sided strip detector (CdTe-DSD) is an ideal device for imaging and spectroscopic measurements in the hard X-ray range above 10 keV. Recent development enables us to realize an imager with a detection area of ∼10 cm2. An energy resolution of 1–2 keV (FWHM) and a position resolution of a few hundred μm are available from the detector. This type of imager has been long awaited for non-destructive elemental analysis, especially by using negative muons, because energies of characteristic X-rays from muonic atoms are about 200 time higher than those from normal atoms. With the method that uses negative muons, hard X-ray information gives the spatial distribution of elements in samples at a certain depth defined by the initial momentum of the muon beam. In order to study three-dimensional imaging capability of the method, we have developed a compact imaging system based on CdTe-DSD and a ϕ 3 mm pinhole collimator as the first prototype. We conducted experiments with samples which consist of layers of Al, BN and LiF irradiated by negative muon beams in MUSE/J-PARC and successfully reconstruct hard X-ray images of muonic X-rays from B, N and F at various depths.

A high-resolution CdTe imaging detector with multi-pinhole optics for in-vivo molecular imaging

High-resolution CdTe semiconductor detectors with both fine position resolution and high energy resolution hold great promise to improve measurement in various hard X-ray and gamma-ray imaging experiments. In the field of in-vivo molecular imaging, where the molecules labeled with radioisotopes are injected into a small animal and their distribution in a body is detected by gamma-ray imaging detectors externally, a large detection area is also required to obtain a number of projections from multiple pinholes. We have developed a prototype imaging system consisting of a 32 mm-wide CdTe double-sided strip detector equipped with multi-pinhole optics. We describe its imaging capability, as studied through experiments with radioisotopes for medical use (125I and 111In) and a 3D phantom.

Astronomical imaging with the X-ray observatory Hitomi

We report an imaging capability of the Japan-led X-ray observatory Hitomi, formerly known as ASTRO-H. It carries four scientific instruments of Soft X-ray Imager (SXI: CCD camera), Hard X-ray Imager (HXI), Soft X-ray Spectrometer, and Soft Gamma-ray Detector, allowing us to perform a wide-band high-sensitive imaging spectroscopy. We highlight the specification and the performance we obtained with primarily regard to X-ray and soft gamma-ray imaging. Primary imaging instrument SXI utilizes four large-area X-ray CCDs positioned at the focal plane of Soft X-ray Telescope (SXT-I). Imaging area with a size of 62mm square makes a largest field of view (FoV) of 38′ square among the focal plane X-ray detectors, which enables us to observe extended objects such as clusters of galaxies and galactic supernova remnants with a single pointing in the soft X-ray band from 0.4 to 12keV. HXI employs the hybrid sensors consisting of four layers of double-sided silicon strip detectors and a single layer of cadmium telluride double-sided strip detector covering the energy band from 5 to 80keV. After the successful launch of Hitomi on February 17th, 2016 and the subsequent start up of all the instruments, imaging performance of both imagers are verified as expected from the ground calibration tests. The position of the active galactic nucleus of the central galaxy NGC1275 in the Perseus cluster is precisely seen by SXI, while the positional difference of line-of-sight velocity dispersion of the hot intracluster medium is measured inside by SXS. From the observation of Crab nebula, we obtain the on-pulse hard X-ray image with HXI as well as the time-averaged image in which the torus of the pulsar wind nebula can be seen.

Thick silicon microstrip detectors simulation for PACT: Pair and Compton Telescope

PACT is a space borne Pair and Compton Telescope that aims to make a sensitive survey of the gamma-ray sky between 100keV and 100MeV. It is based upon two main components: a silicon-based gamma-ray tracker and a crystal-based calorimeter. In this paper we will explain the imaging technique of PACT as a Multi-layered Compton telescope (0.1–10MeV) and its major improvements over its predecessor COMPTEL. Then we will present a simulation study to optimize the silicon tracker of PACT. This tracker is formed of thousands of identical silicon double sided strip detectors (DSSDs). We have developed a simulation model (using SILVACO) to simulate the DSSD performance while varying its thickness, impurity concentration of the bulk material, electrode pitch, and electrode width. We will present a comprehensive overview of the impact of each varied parameter on the DSSD performance, in view of the application to PACT. The considered DSSD parameters are its depletion voltage, capacitance, and leakage current. After the selection of the PACT DSSD, we will present a simulation of the performance of the PACT telescope in the 0.1–10MeV range.