Integrated Readout Research Articles

Spectral Performance of the Follow-up X-Ray Telescope on Board the EP Satellite

The Follow-up X-ray Telescope (FXT) is one of the two main scientific instruments on board the Einstein Probe astronomical satellite, which was launched in 2024 January. FXT focuses on the energy range of 0.3–10 keV and mainly conducts follow-up observations of transients and burst sources. It consists of two units of completely independent optical system and detector system (FXT-A and FXT-B). The focal plane detector adopts PNCCD provided by Max Planck Institute for Extraterrestrial Physics. FXT was designed to have three operating modes with different integration times and readout schemes, namely full-frame mode, partial-window mode and timing mode. We conducted a detailed calibration for PNCCD at the Institute of High Energy Physics before launch. Our results demonstrate that both FXT-A and FXT-B exhibit excellent spectral performance. The energy resolution (Full Width at Half Maximum) of FXT-A and FXT-B are both better than 85 eV at 1.487 keV. We determined a mean equivalent noise charge around 2.8 e− for FXT-A and FXT-B in three operating modes at −90°C ± 0.5°C, except for a few noisy pixels in full-frame mode. In addition, we measured the relation of charge transfer inefficiency as function of photon energy and confirmed the ability to detect photons in the energy range of 0.3–10 keV. These calibration results have been ingested into the initial version of calibration database and applied to the analysis of scientific data acquired by FXT.

An Ultrasensitive Molecularly Imprinted Point-Of-Care Electrochemical Sensor for Detection of Glial Fibrillary Acidic Protein.

Accurate assessment of neurological disease through monitoring of biomarkers has been made possible using the antibody-based assays. But these assays suffer from expensive development of antibody probes, reliance on complicated equipments, and high maintenance costs. Here, using the novel reduced graphene oxide/polydopamine-molecularly imprinted polymer (rGO/PDA-MIP) as the probe layer, a robust electrochemical sensing platform is demonstrated for the ultrasensitive detection of glial fibrillary acidic protein (GFAP), a biomarker for a range of neurological diseases. A miniaturized integrated circuit readout system is developed to interface with the electrochemical sensor, which empowers it with the potential to be used as a point-of-care (POC) diagnostic tool in primary clinical settings. This innovative platform demonstrated good sensitivity, selectivity, and stability, with imprinting factor evaluated as 2.8. A record low limit-of-detection (LoD) is down to 754.5 agmL-1, with a wide dynamic range from 1 to 106 fgmL-1. The sensing platform is validated through the analysis of GFAP in clinical plasma samples, yielding a recovery rate range of 81.6-108.8% compared to Single Molecule Array (Simoa). This cost-effective and user-friendly sensing platform holds the potential to be deployed in primary and resource-limited clinical settings for the assessment of neurological diseases.

A compact and highly integrated 128-channel FPGA-based readout electronics for nuclear imaging application

As silicon photomultiplier (SiPM) technology develops, its possible applications are being growingly expanded. However, the current technical obstacle is the signal readout from large-scale, multi-pixel SiPMs, especially in a large nuclear imaging device. Although the application-specific integrated circuits (ASICs) provide ways to reach that goal, it needs a long period with iterative electronic process and a very high cost. We developed a high-integrated positron emission tomography (PET) electronics system with field programmable gate array based charge-to-digital converter (FPGA-QDC) technology instead of the ASICs. Unlike traditional FPGA-based charge readout method in which low-voltage differential signaling (LVDS) receivers serve as analog voltage comparators, in the proposed electronics system voltage-referenced receivers work as analog comparators.Theoretically, nearly all of input/output (I/O) ports in the FPGA can achieve the function of analog comparators using voltage-referenced I/O standard. The electronics system is constructed using off-the-shelf low-cost commercial components. Therefore, it is feasible to fast build a distributed readout system with multiple such electronics system. The flexibility and reconfigurability of the FPGA provide multi-channel grouping and diverse triggering for different kinds of detector configurations, such as row/column summation and resistor-based readout. These features are greatly sought after in readout electronics for the SiPM-based radiation detectors. Experimental results show that the proposed highly-integrated electronics system overcomes the bottleneck that has limited the development of advanced PET detectors and scanners.

Carbon-silicon based hybrid quantum dot short wave infrared photodetector

Recently infrared photodetectors based on low-dimensional semiconductors have developed rapidly. However, due to its poor light absorption and incompatibility with traditional silicon-based readout circuit processes, the sensitivity and integration of such photodetectors are limited. In this work, we proposes a 64 × 64 quantum dot short-wavelength infrared (SWIR) photodetector composed of carbon nanotube thin film transistor (CNT TFT) and silicon-based ROIC. CNT TFT's gate is constructed by PbS colloidal quantum dots (PbS CQDs) which improve the absorption rate of infrared light. The generated photovoltage is amplified and converted in situ by CNT TFT. Notably, under infrared radiation of 1300 nm, the noise equivalent current reach up to 1.25*10−13A/Hz1/2. At a drain-source bias (Vds)= -0.1 V. The device exhibits detectivity of 5.6*1013 Jones and a fast response of 0.57 ms. The silicon-based ROIC is implemented by CMOS 0.18um process, with a power supply voltage of 1.8 V. It mainly includes a programmable integrator, a sampling and holding circuit, and a 10bit/2.5 MHz successive approximation analog-to-digital converter (SAR ADC). The programmable integrator has four levels of integral gain to meet the application requirements of different infrared light intensities. The experiment results show that the imaging function of the overall photodetector is correct, laying the foundation for the development of carbon-silicon based heterojunction integrated photodetector in the future.

WASA: a low power and high integration readout ASIC for TPCs in 65 nm CMOS

The paper presents the development of a low-power and high-integration readout ASIC (WASA) for time projection chambers (TPCs). Each channel of the ASIC consists of the analog front-end, a waveform sampling ADC and digital signal processing circuits. To reduce power consumption, a simple CR-RC shaper and a digital trapezoid filter are adopted to achieve comparable performance to a CR-RC4 shaper with much lower power. Trigger logic and data buffer have also been integrated to reduce the data bandwidth. A 16-channel prototype chip was fabricated in a 65 nm CMOS process and was tested. The test results were consistent with the simulation. At 40 MSPS sampling rate, the power consumption of the chip was only 4.94 mW per channel, including 1.38 mW from the analog front-end, 0.83 mW from the waveform sampling ADC and 2.73 mW from digital logics. The equivalent noise charge of 569 e+14.8 e/pF has been achieved. The measured dynamic range was 120 fC and the integral nonlinearity was less than 0.74%. More design details and test results will be given in this paper.

Probing the potential of CdZnTe for high-energy high-flux 2D X-ray detection using the XIDer incremental digital integrating readout

The latest synchrotron radiation sources have the capability to produce X-ray beams with a photon flux that can be up to three orders of magnitude higher than previous-generation facilities, and that are not manageable by the currently available 2D photon-counting pixel detectors. The construction of new detectors that exceed the limitations of existing devices is a critical strategic need. Developing such detectors is a challenge in terms of readout electronics as well as sensor material, particularly in the case of devices intended to operate at X-ray energies above 30 keV. The approach adopted at the ESRF to deal with this major difficulty is twofold: the use of a novel semiconductor material with improved electrical properties, high-flux CdZnTe, and the investigation of a specific readout scheme, incremental digital integration, via the XIDer project in collaboration with the University of Heidelberg. Incremental digital integration is a method intended to be less sensitive to variations of the dark current than the conventional charge integration readout. However, this readout scheme requires that the leakage current from the sensor material stays below a certain threshold to reduce the leakage contributions. This paper introduces the ESRF strategy and few examples of the methods employed to evaluate the performance and leakage current behavior of high-flux CdZnTe pixelated sensors. These examples illustrate the first results obtained with this material under moderate to very high X-ray irradiation fluxes of up to 1012 photons/mm2/s.

Exploring the time-resolving capabilities of XIDer assemblies

The XIDer R&D project, between the European Synchrotron Radiation Facility (ESRF) and Heidelberg University, is developing state-of-the-art detectors for the high-energy, high-flux beamlines of the ESRF Extremely Brilliant Source (EBS). In particular, the XIDer detector aims to tackle the significant challenges posed by time-resolved experiments analysing the pattern of diffracted or scattered X-rays.To fulfil the needs of these experiments, a novel on-chip incremental digital integration readout scheme with per-pixel digital data output has been implemented. The EBS beam operates with different time structures: from a near-100% duty cycle X-ray beam to an up to 5.7MHz pulsed X-ray beam. For the latter EBS mode, the XIDer ASIC has been designed to have a fast front-end and memory storage cells, such that the pulsed EBS beam can be exploited by time-resolved experiments. Recent measurements of the time-resolving capabilities of XIDer ASICs hybridised cadmium telluride and cadmium zinc telluride sensors are presented.

Bi2S3Electron Transport Layer Incorporation for High-Performance Heterostructure HgTe Colloidal Quantum Dot Infrared Photodetectors

Infrared photodetectors (PDs) based on epitaxial semiconductors occupy the majority of the market, but their high cost from material growth and device integration limits their application fields. Colloidal quantum dots (CQDs) provide a high potential candidate for infrared PDs due to their unique infrared sensitivity, tunable physical and chemical properties, and good compatibility with readout integration circuits. In particular, HgTe CQD PDs have demonstrated a wide detection range from short-wave to long-wave infrared. Although significant progress has been achieved in HgTe CQD infrared PDs, they are still in the primary stage of QD synthesis and prototype device fabrication. Here, we develop a new p–i–n photodiode from the traditional p–i device structure. Bismuth sulfide (Bi2S3) films were adopted as the electron transport layer, which could favor uniform absorber deposition, superior charge extraction, and suppressed interfacial loss. The Bi2S3-based photodiodes have achieved a room-temperature dark current density as low as 1.6 × 10–5 A/cm2 at −400 mV. Furthermore, their specific detectivity (D*) achieves ∼1011 Jones at room temperature.

A Chemoresistive Gas Sensor Readout Integrated Circuit With Sensor Offset Cancellation Technique

A Chemoresistive Gas Sensor Readout Integrated Circuit With Sensor Offset Cancellation Technique

XIDER: a novel X-ray detector for the next generation of high-energy synchrotron radiation sources

Next-generation sources of synchrotron radiation pose significant challenges for 2D pixelated X-ray detectors, such as at the ESRF Extremely Brilliant Source (EBS), the first fourth-generation high-energy synchrotron facility. In particular, scattering and diffraction experiments require fast detectors with a high dynamic range, from single photon sensitivity to pile-up conditions under very high photon fluxes. Furthermore, in the case of high-energy applications, the high-Z sensor materials needed for efficient photon detection introduce other difficulties. Leakage current, bias- and flux-induced polarisation, and afterglow all must be carefully managed for the detector system to reach the required specifications. The XIDER project aims to fulfil the needs of the above-mentioned applications by implementing a novel incremental digital integration readout scheme. XIDER detectors seek to operate efficiently under the high-flux EBS beam of up to 100 keV photons, with a time resolution that can cope with near-continuous and pulsed beams. Simultaneously, non-constant leakage current contributions can be removed for noise-free single photon detection, resulting in a very high dynamic range. This contribution presents the recent developments of the XIDER project, including the first characterisation measurements with cadmium telluride sensors.

Spectral and directional sensitive composition characterization of mixed-radiation fields with the miniaturized radiation camera MiniPIX Timepix2

The semiconductor pixel detector Timepix2 is operated with highly integrated readout electronics as a miniaturized and portable MiniPIX TPX2 radiation camera for radiation imaging and spectral-sensitive particle tracking in wide field-of-view. The device provides room-temperature operation, ease of use (single USB 2.0 port), online response with single track visualization, fast frame readout (up to 60 fps) and double per-pixel response for detailed measurements with per-pixel energy and counting or energy and timing sensitivity. We evaluate the response and applicability of a MiniPIX TPX2 camera with the Timepix2 ASIC chip equipped with a 300 µm thick silicon sensor for wide-range composition and spectral characterization of mixed-radiation fields. Measurements were performed in high-energy proton radiotherapy environments with protons of selected energies in the range 225–70 MeV and water-equivalent targets of varying configuration (size, dimension, geometry). High-resolution pattern recognition and spectral-tracking analysis of the single particle tracks in the pixelated detector enable to resolve and classify all detected signals according particle species, direction and energy loss. Based on the experimental calibrations performed with well-defined radiation fields together with quantum imaging visualization of single particle tracks, ten broad-range particle-event classes are resolved. Mixed-radiation fields are thus analyzed according particle-event types in wide range of deposited energy, linear-energy-transfer LET, particle fluxes and dose rates. The spatial distribution over the detector sensor matrix of the distinguished groups can be visualized as well as the directional mapping of energetic charged particles.

Development of a compact and cost-effective PET detector module for a small-animal PET system with FESA ASIC

Due to the high cost and large channel number in positron emission tomography (PET) systems, the integration level and cost performance must be considered in the construction of commercial PET systems. In this paper, a highly integrated readout electronic system was designed and implemented based on a self-developed FESA (Front End for SiPM Arrays) readout ASIC; a compact cost-effective detector module with four lined up detector heads was built, and its performance was evaluated. Each detector head consisted of a 24× 24 LYSO crystal array (each crystal element had dimensions of 0.99 × 0.99 × 15 mm3), one end coupling to an 8 × 8 silicon photomultiplier array (SiPM array with dimensions of 3.2 × 3.2 mm2 each), and the other end covered with a 1 mm thick light guide layer. Since the front-end FESA readout chip employed a row-column summing circuit to reduce the readout channels from 64 to 16, we tried a new depth encoding method based on a single-end readout with the structure. The test results showed that the average coincidence time resolution (CTR), energy resolution, and depth of interaction (DOI) resolution of the detector are 413 ps, 15.7%, and 5.2 mm, respectively, while the crystal array in the detector head with 9-to-1 coupling can be clearly separated in the flood image. Compared with the detector head without the depth encoding ability, the clearness of the flood image was slightly decreased, but the energy resolution and time performance remained the same. We also implemented a central control board that connected all detector modules via fiber connections. The data from the detector modules could be collected over the connections, and the system central clock could be precisely distributed; therefore, the compactness of the electronics system was further enhanced.

Broadband Graphene Field-Effect Coupled Detectors: From Soft X-Ray to Near-Infrared

Here, we report a broadband graphene-silicon field-effect coupled detector (FCD) sensitive to photons spanning from soft X-ray to Near-Infrared region. Unlike traditional charge-coupled devices (CCD) relying on serial charge transfer between potential wells, the FCD integrates photo-sensing, charge integration, field-effect amplification, and random readout in one pixel. The charge integration in the potential well of the semiconductor substrate and field-effect coupled amplification in graphene transistor result in a highly sensitive broadband response. In the X-ray region, the device displays a high sensitivity of 1088 CGy <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">air</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> and a fast response time < ~5 ms. Linear array imaging reveals the potential of our devices for array-based broadband imaging. Our FCD offers a viable strategy to monolithically integrate 2D materials into conventional solid-state imaging technology, exploring the next-generation broadband photodetectors for high-quality imaging and super vision technology.

First results on SiSeRO devices: a new x-ray detector for scientific instrumentation

We present an evaluation of an on-chip charge detector, called the single electron sensitive read out (SiSeRO), for charge-coupled device image sensor applications. It uses a p-channel metal-oxide-semiconductor field-effect transistor (p-MOSFET) transistor at the output stage with a depleted internal gate beneath the p-MOSFET. Charge transferred to the internal gate modulates the source-drain current of the transistor. We have developed a drain current readout module to characterize the detector. The prototype sensor achieves a charge/current conversion gain of 700 pA per electron, an equivalent noise charge (ENC) of 15 electrons (e − ) root mean square, and a full width half maximum of 230 eV at 5.9 keV. Further, we discuss the SiSeRO working principle, the readout module developed at Stanford, and the first characterization test results of the SiSeRO prototypes. While at present only a proof-of-concept experiment, in the near future we plan to use next generation sensors with improved noise performance and an enhanced readout module. In particular, we are developing a readout module enabling repetitive non-destructive readout of the charge, which can in principle yield subelectron ENC performance. With these developments, we eventually plan to build a matrix of SiSeRO amplifiers to develop an active pixel sensor with an on-chip application specific integrated circuit-based readout system. Such a system, with fast readout speeds and subelectron noise, could be effectively utilized in scientific applications requiring fast and low-noise spectro-imagers.

Design of Prototype Readout Integrated Circuit for Time-of- Arrival and Time-over-Threshold Measurement for Hybrid Pixel X-ray Detectors in 28 nm CMOS

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Monte Carlo simulations for XIDer, a novel digital integration X-ray detector for the next generation of synchrotron radiation sources

This work presents the first simulation results of the incremental digital integration readout, a charge-integrating front-end scheme with in-pixel digitisation and accumulation. This novel readout concept is at the core of the XIDer (X-ray Integrating Detector) project, which aims to design 2D pixelated X-ray detectors optimised for high energy scattering and diffraction applications for the next generation of synchrotron radiation sources such as the ESRF Extremely Brilliant Source (EBS). The digital integration readout and the XIDer detector open the possibilities for high-duty-cycle operation under very high photon flux, fast frame-rate and high dynamic range with single-photon sensitivity in the 30–100 keV energy range. The readout method allows for noise-free effective X-ray detection. The digital integration concept is currently under investigation to evaluate the impact of main critical design parameters to identify the strengths and weaknesses of the readout scheme and consequently to propose refinements in the final implementation. Simulations have been performed with a dedicated Monte Carlo simulation tool, X-DECIMO, a modular Python package designed to recreate the complete detection chain of X-ray detectors for synchrotron radiation experiments. Losses and non-linearities of the readout scheme are simulated and quantified. In addition to presenting simulation results for this novel readout scheme, this work underlines the potential of the approach and some of its limitations.

Development of a portable thermostatic γ spectrometer

This paper presents the design and evaluation of a portable γ spectrometer with an automatic constant temperature function. The γ spectrometer includes a detector consisting of a CsI(Na) crystal coupled with a silicon photomultiplier (SiPM) array and highly integrated readout electronics. The performance of the crystal and SiPM changes with temperature. To solve this problem, we design a thermoelectric cooler-based unit to keep the temperature constant. Experiments are conducted to evaluate the performance of the γ spectrometer under different temperatures. The test results show that when the external temperature range is 2–38 °C, the temperature inside the spectrometer remains constant at 20 ± 0.07 °C. Because of the constant temperature, the peak drift for 662 keV is reduced to 1.80 channels, and the energy resolution for 662 keV remains around 8.20%.

Design and Implementation of a Portable High-Performance Gamma-Ray Camera

With the growing number of facilities applying nuclear technology in China, a high-performance portable gamma-ray camera that uses well-developed gamma-ray imaging techniques is increasingly required. To fulfill this requirement, we have designed a camera using a self-supported mask, a CsI(Na) array coupled to a silicon photomultiplier (SiPM) rather than the traditional position-sensitive photomultiplier tube (PSPMT) and a highly integrated readout circuit. In addition, with the elimination of multi-Compton events in the crystal array based on a row/column readout circuit incorporated into the data processing method, the peak-to-valley ratio of the flood source map and the image quality quantified by the contrast-to-noise ratio index of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs were improved significantly by 25.8% from 9.8 to 12.3 and 14.8% from 38.7 to 45.0, respectively.

A single-hole spin qubit

Qubits based on quantum dots have excellent prospects for scalable quantum technology due to their compatibility with standard semiconductor manufacturing. While early research focused on the simpler electron system, recent demonstrations using multi-hole quantum dots illustrated the favourable properties holes can offer for fast and scalable quantum control. Here, we establish a single-hole spin qubit in germanium and demonstrate the integration of single-shot readout and quantum control. We deplete a planar germanium double quantum dot to the last hole, confirmed by radio-frequency reflectrometry charge sensing. To demonstrate the integration of single-shot readout and qubit operation, we show Rabi driving on both qubits. We find remarkable electric control over the qubit resonance frequencies, providing great qubit addressability. Finally, we analyse the spin relaxation time, which we find to exceed one millisecond, setting the benchmark for hole quantum dot qubits. The ability to coherently manipulate a single hole spin underpins the quality of strained germanium and defines an excellent starting point for the construction of quantum hardware.

Direct polymer microcantilever fabrication from free-standing dry film photoresists

Traditionally, polymeric microcantilevers are assembled by a multitude of process steps comprising liquid spin-coated photoresists and rigid substrate materials. Polymer microcantilevers presented in this work rely instead on commercially available dry film photoresists and allowed an omittance of multiple fabrication steps. Thin, 5 μm thick dry film photoresists are thermally laminated onto prepatterned silicon substrates that contain AFM compatible probe bodies. Partially suspended dry film resists are formed between these probe bodies, which are patterned to yield microcantilevers using conventional photolithography protocols. A limited amount of thermal cycling is required, and sacrificial probe-release layers are omitted as microcantilevers form directly through resist development. Even 1 mm long polymeric cantilevers were fabricated this way with superior in-plane alignment. The general effects of post-exposure bake (PEB) and hardbake protocols on cantilever deflection are discussed. Generally, higher PEB temperatures limit out-of-plane cantilever bending. Hardbake improved vertical alignment only of high-PEB temperature cantilevers, while surprisingly worsening the alignment of low-PEB temperature cantilevers. The mechanism behind the latter is likely explained by complex interactions between the resist and the substrate related to differences in thermal expansion, heat conduction, as well as resist cross-linking gradients. We present furthermore multilayer structures of dry film resists, specifically cylindrical dry film resist pillars on the polymer cantilever, as well as the integration of metal structures onto the polymer cantilever, which should enable in future integrated piezoresistive deflection readout for various sensing applications. Finally, cantilever spring constants were determined by measuring force–displacement curves with an advanced cantilever calibration device, allowing also the determination of both, dry film resist cantilever density and Young’s modulus.