Readout Channels Research Articles

Application of the VMM ASIC for SiPM-based calorimetry

Highly integrated multichannel readout electronics is crucial in contemporary particle physics experiments. A novel silicon photomultiplier readout system based on the VMM3a ASIC was developed, for the first time exploiting this chip for calorimetric purposes. To extend the dynamic range the signal from each SiPM channel was processed by two electronics channels with different gain. A fully operational prototype system with 256 SiPM readout channels allowed the collection of data from a prototype of the ALICE Forward Hadron Calorimeter (FoCal-H Prototype 2). The design and the test beam results using high energy hadron beams are presented and discussed, confirming the applicability of VMM3a-based solutions for energy measurements in a high rate environment.

Optimization of the Pixel Design for Large Gamma Cameras Based on Silicon Photomultipliers.

Most single-photon emission computed tomography (SPECT) scanners employ a gamma camera with a large scintillator crystal and 50-100 large photomultiplier tubes (PMTs). In the past, we proposed that the weight, size and cost of a scanner could be reduced by replacing the PMTs with large-area silicon photomultiplier (SiPM) pixels in which commercial SiPMs are summed to reduce the number of readout channels. We studied the feasibility of that solution with a small homemade camera, but the question on how it could be implemented in a large camera remained open. In this work, we try to answer this question by performing Geant4 simulations of a full-body SPECT camera. We studied how the pixel size, shape and noise could affect its energy and spatial resolution. Our results suggest that it would be possible to obtain an intrinsic spatial resolution of a few mm FWHM and an energy resolution at 140 keV close to 10%, even if using pixels more than 20 times larger than standard commercial SiPMs of 6 × 6 mm2. We have also found that if SiPMs are distributed following a honeycomb structure, the spatial resolution is significantly better than if using square pixels distributed in a square grid.

An FPGA-based parallel deconvolution application envisaging high-energy calorimeters operating under severe pile-up conditions

Signal pileup may arise when the system response time is larger than what would be required by the event rate in the application. In this condition, information superposition occurs, and signal estimation is deteriorated due to such information distortion. For online applications, mitigating such a pileup distortion usually requires embedded digital signal processing, which often involves FPGA-based designs when high event rates are a concern. Recently, high-energy particle experiments started facing an unprecedented increase in pileup conditions, which demanded new approaches for signal estimation. This work proposes a dedicated parallel signal processing system embedded on an FPGA platform that implements different filtering techniques for online energy reconstruction in calorimeters (energy measurement) operating under severe pileup conditions. Each designed filter is an inverse approximation of the calorimeter readout channel's impulse response, performing deconvolution of the incoming signals. Such a deconvolution approach for energy estimation was recently introduced, and the proposed filters were implemented in this work. Evaluation of the digital system design was performed using a data set that considers a typical high-energy calorimeter front-end response, as high-luminosity particle collider experiments produce high pileup distortions in calorimeter signals when processing the subproducts of the collisions. As the Large Hadron Collider (LHC) provides the most demanding conditions in terms of signal pileup, the acquisition system of the proposed solution is synchronous with its collision rate (40 MHz). The results showed that the proposed implementation may be applied as a preprocessing (pileup reduction) step in calorimeter instrumentation and could reduce the signal pileup within the fast response time required by such experiments.

Large area tiles of position-sensitive silicon photomultipliers

Silicon photomultipliers (SiPMs) are highly sensitive photodetectors emerging as the technology of choice for many applications. In FBK, we developed a position sensitive SiPM technology, called “linearly graded” (LG-SiPM), which is based on an avalanche-current position-weighted partitioning approach. In particular, we recently developed a new version of LG-SiPM with a larger chip area (10 × 10 mm2) and based on NUV-HD technology, having a peak photon detection efficiency at 420 nm. These SiPMs have been characterized in terms of noise, detection efficiency and position resolution.We also developed tiles of 2x2 and 3x3 elements with such SiPMs, reaching very large sensitive areas of about 20 × 20 mm2 and 30 × 30 mm2. In such large area tiles we implemented a “smart channel” configuration, being able to have just 6 output channels and 8 channels respectively, with a position resolution below 0.5 mm. These detectors provide great advantages in all application requiring position resolution but with a small number of readout channels and reduced system complexity.

Position-Sensitive Silicon Photomultiplier Arrays with Large-Area and Sub-Millimeter Resolution.

Silicon photomultipliers (SiPMs) are solid-state single-photon-sensitive detectors that show excellent performance in a wide range of applications. In FBK (Trento, Italy), we developed a position-sensitive SiPM technology, called "linearly graded" (LG-SiPM), which is based on an avalanche-current weighted-partitioning approach. It shows position reconstruction resolution below 250 μm on an 8 × 8 mm2 device area with four readout channels and minimal distortions. A recent development in terms of LG-SIPM is a larger chip version (10 × 10 mm2) based on FBK NUV-HD technology (near-ultraviolet sensitive), with a peak photon detection efficiency at 420 nm. Such a large-area detector with position sensitivity is very interesting in applications like MR-compatible PET, high-energy physics experiments, and readout of time-projection chambers, gamma and beta cameras, or scintillating fibers, with a reduced number of channels. These SiPMs were characterized in terms of noise, photon detection efficiency, and position resolution. We also developed tiles of 2 × 2 and 3 × 3 LG-SiPMs, reaching very large sensitive areas of 20 × 20 mm2 and 30 × 30 mm2. We implemented a "smart-channel" configuration, which allowed us to have just six output channels for the 2 × 2 elements and eight channels for the 3 × 3 element tiles, preserving a position resolution below 0.5 mm. These kinds of detectors provide a great advantage in compact and low-power applications by maintaining position sensitivity over large areas with a small number of channels.

A hardware/firmware-based switching gate multiplexing method for pulse mode radiation detectors

We present a hardware/firmware-based switching gate multiplexing method for pulse mode radiation detectors that can combine many detector signals into two readout channels. One readout channel passes the signal of the multiplexed detector that “fired” first, and the other channel provides a variable-width logic pulse, i.e., a pulse width modulation (PWM) signal, that identifies the active detector. The multiplexed output pulse is produced by passing the first active detector’s signal to a fan-in circuit by gating on the corresponding channel for a fixed duration while blocking all other detector signals. It does this using individual analog switches for all the detector signals. Each switch is controlled by a fixed width logic pulse that is triggered by the arrival of the first active detector pulse. Both the fixed width logic pulse and the PWM signal are generated using a field-programmable gate array (FPGA). To demonstrate the proposed multiplexing method, a prototype four-channel multiplexer was developed for use with four NaI(Tl) detectors. The performance of the multiplexer was evaluated in terms of its ability to retain energy resolution, timing resolution, and original pulse shape. The proposed multiplexing method showed very little degradation in energy resolution and timing resolution or alteration of pulse shape. The switching gate feature of the proposed method enables the multiplexer output to have very low noise contribution from the inactive channels. This multiplexing technique also has the unique capability of isolating and recovering the first active detector’s output pulse in cases where there is overlap between pulses from different detectors in a single digitized record. These features make the proposed hardware/firmware-based switching gate multiplexing method very promising for application to large radiation detector networks.

Nanoparticle ZnS:Ag/6LiF—a new high count rate neutron scintillator with pulse shape discrimination

A neutron sensitive scintillator employing nanoparticles of ZnS:Ag has been developed for the first time. Pulse shape differences between neutron and gamma signals were observed in this material and neutron-gamma discrimination was applied. With initial signal processing parameters, gamma sensitivities of 8.5×10−6 to 60Co gammas were achieved. The average primary decay of neutron scintillation in nanoparticle ZnS:Ag/6LiF was measured to be 18ns, and afterglow was significantly suppressed in comparison to standard ZnS:Ag/6LiF scintillators that employ micron sized ZnS:Ag. Fast decay times and minimal afterglow indicate potential for use in high count rate capability applications. Prospective count rate capabilities were investigated here as proof of concept, with rates of 1.12Mcps measured for a single readout channel with less than 3.5% count loss. This is approximately 70 times greater than the count rate capability of the current standard ZnS:Ag/6LiF scintillation detectors. With improvements to signal processing and scintillator composition, nanoparticle ZnS:Ag/6LiF could be a promising candidate for future high rate capability neutron detectors.

Front-end electronics development of large-area SiPM arrays for high-precision single-photon time measurement

TRopIcal DEep-sea Neutrino Telescope (TRIDENT) plans to incorporate silicon photomultipliers (SiPMs) with superior time resolution in addition to photomultiplier tubes (PMTs) into its detection units, namely hybrid Digital Optical Modules (hDOMs), to improve its angular resolution. However, the time resolution significantly degrades for large-area SiPMs due to the large detector capacitance, posing significant challenges for the readout electronics of SiPMs in hDOM. We analyzed the influences of series and parallel connections when constructing a large-area SiPM array and designed a series-parallel connection SiPM array with differential output. We also designed a high-speed pre-amplifier based on transformers (MABA-007159) and radio frequency amplifiers (BGA2803), and an analog multi-channel summing circuit based on operational amplifiers (LMH6629). We measured the single photon time resolution (SPTR) of a 4 × 4 SiPM (Hamamatsu S13360-3050PE) array (12 × 12 mm2) of approximately 300 ps FWHM. This front-end readout design enables the large-area SiPM array to achieve high-precision single photon time measurement in one readout channel.

10Boron-film-based gas detectors at ESS

The development of detectors for the European Spallation Source is an important parallel element to the effort put into the design and construction of the neutron source and instruments. The 10Boron-film-based detector developments that started over a decade ago as basic detector concepts have now reached technical maturity after intense prototyping work and numerous testing campaigns. Several of the ESS beamlines that will soon enter the commissioning phase started welcoming the detector systems built with the 10B-film converter technology. The real-size demonstrators evolved in the last 2–3 years into a diverse suite of gas proportional counters for use in diffraction, reflectometry and small-angle scattering studies in spite of the operational complexity posed by the requirements for large-area coverage, low material budget and robustness for operation in the high-flux and high-radiation environment of ESS. The detectors are now being shipped to ESS or undergoing the last performance and calibration tests before being handed over to the instrument teams for installation in the host beamlines. A common feature of these detector systems is the very large number of readout channels that they are instrumented with in order to fulfill the demanding requirements for sensitivity, spatial resolution and count-rate capability. Across all of the detector types that will operate at ESS, the integration, testing and commissioning of the read-out technologies and software tools for data reduction, calibration and analysis are the focus of the detector and integration teams. These will yield a wealth of knowledge about their operation as well as initial results on the in-situ performance, a very important asset to ensure rapid commissioning of the detectors when neutrons from the ESS source become available. In this paper we will give an overview of the 10B-film-based detector technologies included in the ESS detector suite that are currently facing the transition from the production phase to installation and integration with the other beamline components, which comes with its own specific challenges of both organizational and technical nature.

Design of the CMS High Granularity Calorimeter trigger primitive generator system

The High Luminosity phase of the LHC (HL-LHC) is planned to begin data taking in 2029, with the instantaneous luminosity expected to increase to 4 times its current value and the average number of particle interactions per bunch crossing increasing by approximately 3.5 times its current value. The current endcap calorimeters in the CMS detector will be replaced by a novel high granularity calorimeter (HGCAL) that will have fine segmentation in both the transverse and longitudinal directions and will be the first such calorimeter specifically optimised for particle flow reconstruction to operate at a colliding-beam experiment. The Level 1 trigger of the CMS experiment will combine the calorimeter data with tracking information to allow particle-flow techniques to be used. The high granularity of the calorimeter leads to about six million readout channels in total, concentrated in one million trigger cells, sampled for the L1 trigger at a rate of 40 MHz. The trigger data volumes will be an order of magnitude above those currently handled in CMS, posing significant challenges for data manipulation and processing. In addition, the trigger algorithms must be able to efficiently reject the huge background rate in the forward region of the detector due to the high pileup environment. The status of the HGCAL trigger architecture and design, as well as the algorithms developed in order to tackled these major issues, is presented here. The data flow is described from the formation and preselection of trigger cells on detector to the generation of two types of trigger primitives off detector, projective towers of energy in the (η, ϕ) plane and three-dimensional clusters of particles. Particle flow will use these 3D clusters, and their formation is described and followed by recent developments in the optimization of their transverse size.

CMS HGCAL electronics vertical integration system tests

In preparation for the High-Luminosity phase of the CERN Large Hadron Collider, the Compact Muon Solenoid collaboration will replace the existing endcap calorimeters with the High Granularity Calorimeter. Considering both endcaps, this novel sub-detector will have around six million readout channels, pushing approximately 108 Tbit s-1 of usable data between the detector front-end (on-detector) electronics and the back-end (off-detector) electronics. Given the scale and complexity of the endcap calorimeter upgrade project, the electronics testing must be carefully planned. The strategy has been to split the efforts between vertical (start-to-end) and horizontal (parallelisation) test systems wherever possible. An important milestone was the development and operation of a test system that prototypes a complete vertical slice of the future endcap electronics system. For the first time, a version of a test system consisting of the full vertical electronics readout chain was successfully operated in a beam test, where it was used to acquire real physics data.

New generation B-Field and RAD-tolerant DC/DC power converter for on-detector operation

The increase in the number of readout channels in new detectors, like the Micro Pattern Gas Detectors (MPGD), in the order of several millions, requires a large amount of electrical power to supply the front-end electronics, up to hundreds kW. If this power is generated at long distances from the detector, the voltage drop on the connection cables puts serious constraints to the supply current, to the wire cross-section and to the power distribution. A large amount of voltage drop on the cables, apart an increased power dissipation on wire resistance, determines regulation issues on the load in case of current transients. To mitigate these problems, a new generation DC/DC converter, working in a heavily hostile environment and with a power density greater than 200 W/dm3, was developed. It is modular, with up to four independent modules, eight channels each, collected in a water-cooled crate, and can supply the load with an adjustable 10 to 12 V output up to 170 W per channel. In this contribution, the design constraints of such a converter are analysed, taking as a basis the environmental, electrical and mechanical requirements of the ATLAS New Small Wheel (NSW) project. Thermal considerations require the converter to be water-cooled, and the dimensional constraints impose the adoption of an innovative design to convey the dissipated heat towards the heat exchanger. The control and monitoring system allows for the full remote management of the converter. Main electrical parameters were measured and are reported. The converter was also characterized in a harsh working environment, with radiation tests in the CERN CHARM facility beyond the limits estimated for ten years operation in ATLAS, and with magnetic field tests in various orientations, using different magnets at CERN up to 1.3 T. A better common mode noise filtering design improvement was implemented after the first characterization. Final performance measurements after the modifications are also reported.

Electronics design for a muon imaging system using triangular plastic scintillators with WLS fiber readouts

Muon imaging technology has developed rapidly over the past decades with extensive applications. In many cases, plastic scintillator detectors are preferred because of their high cost performance, ease of processing and robustness in harsh environments. To reduce imaging time and improve imaging quality, detectors tend to have large areas and high position resolutions. The challenge to the electronics for such detectors is to maintain the scale of electronics acceptable while improving the high position resolution of the detector. In this paper, the basic detector unit is a triangular strip of plastic scintillator, each embedded with two wavelength-shifting (WLS) fibers read out by the silicon photomultipliers (SiPMs). Since the hit position of muon on the detector is determined by the splitting ratio of the scintillation light on two adjacent scintillator strips, it is necessary the readout electronics has high linearity and low noise. The possibility of the electronics channel multiplexing on the same detector plane is fully explored so that four WLS fibers can be read out by one SiPM realizing 2:1 readout channel compression. Furthermore, since multiple electronics modules are connected by a daisy chain structure, the electronics system is very scalable with its data acquisition system (DAQ) independent of detector size. In addition to detailing the position encoding readout scheme, the design of electronics module and the DAQ system, the electronics system has been implemented and applied to a prototype detector for performance evaluation. Using scintillator strips with 11 mm pitch size, the position resolution of the detector reaches 1.49 mm, which demonstrates that the designed electronics is suitable for the new detector structure, and the combination of the two has a good application prospect in muon imaging.

Using Deep Neural Networks to Improve the Precision of Fast-Sampled Particle Timing Detectors

Measurements from particle timing detectors are often affected by the time walk effect caused by statistical fluctuations in the charge deposited by passing particles. The constant fraction discriminator (CFD) algorithm is frequently used to mitigate this effect both in test setups and in running experiments, such as the CMS-PPS system at the CERN’s LHC. The CFD is simple and effective but does not leverage all voltage samples in a time series. Its performance could be enhanced with deep neural networks, which are commonly used for time series analysis, including computing the particle arrival time. We evaluated various neural network architectures using data acquired at the test beam facility in the DESY-II synchrotron, where a precise MCP (MicroChannel Plate) detector was installed in addition to PPS diamond timing detectors. MCP measurements were used as a reference to train the networks and compare the results with the standard CFD method. Ultimately, we improved the timing precision by 8% to 23%, depending on the detector's readout channel. The best results were obtained using a UNet-based model, which outperformed classical convolutional networks and the multilayer perceptron.

Microwave quantum diode

The fragile nature of quantum circuits is a major bottleneck to scalable quantum applications. Operating at cryogenic temperatures, quantum circuits are highly vulnerable to amplifier backaction and external noise. Non-reciprocal microwave devices such as circulators and isolators are used for this purpose. These devices have a considerable footprint in cryostats, limiting the scalability of quantum circuits. As a proof-of-concept, here we report a compact microwave diode architecture, which exploits the non-linearity of a superconducting flux qubit. At the qubit degeneracy point we experimentally demonstrate a significant difference between the power levels transmitted in opposite directions. The observations align with the proposed theoretical model. At − 99 dBm input power, and near the qubit-resonator avoided crossing region, we report the transmission rectification ratio exceeding 90% for a 50 MHz wide frequency range from 6.81 GHz to 6.86 GHz, and over 60% for the 250 MHz range from 6.67 GHz to 6.91 GHz. The presented architecture is compact, and easily scalable towards multiple readout channels, potentially opening up diverse opportunities in quantum information, microwave read-out and optomechanics.

Position-sensitive hybrid particle detector based on discrete-time readout

In this work a new readout scheme for scintillator-based detectors, using discrete time differences through a delay line is proposed, reducing the readout channels while maintaining the spatial resolution. A prototype was built using plastic scintillator blocks and MPPC sensors. Currently, the prototype produces discrete distributions with a dispersion <1.1ns which allows discriminating the different positions. The estimated spatial resolution is σ=1.456mm. This value presents a better resolution than that of Time-of-Flight detectors and of the order of Segmented detectors, but uses fewer readout channels. It is expected to improve this resolution using interpolation effects and testing with larger scale instruments.

A finely segmented semi-monolithic detector tailored for high-resolution PET.

Preclinical research and organ-dedicated applications use and require high (spatial-)resolution positron emission tomography (PET) detectors to visualize small structures (early) and understand biological processes at a finer level of detail. Researchers seeking to improve detector and image spatial resolution have explored various detector designs. Current commercial high-resolution systems often employ finely pixelated or monolithic scintillators, each with its limitations. We present a semi-monolithic detector, tailored for high-resolution PET applications with a spatial resolution in the range of 1mm or better, merging concepts of monolithic and pixelated crystals. The detector features LYSO slabs measuring (24×10×1)mm3, coupled to a 12×12 readout channel photosensor with 4mm pitch. The slabs are grouped in two arrays of 44 slabs each to achieve a higher optical photon density despite the fine segmentation. We employ a fan beam collimator for fast calibration to train machine-learning-based positioning models for all three dimensions, including slab identification and depth-of-interaction (DOI), utilizing gradient tree boosting (GTB). The data for all dimensions was acquired in less than 2h. Energy calculation was based on a position-dependent energy calibration. Using an analytical timing calibration, time skews were corrected for coincidence timing resolution (CTR) estimation. Leveraging machine-learning-based calibration in all three dimensions, we achieved high detector spatial resolution: down to 1.18mm full width at half maximum (FWHM) detector spatial resolution and 0.75mm mean absolute error (MAE) in the planar-monolithic direction, and 2.14mm FWHM and 1.03mm MAE for DOI at an energy window of (435-585)keV. Correct slab interaction identification in planar-segmented direction exceeded 80%, alongside an energy resolution of 12.7% and a CTR of 450ps FWHM. The introduced finely segmented, high-resolution slab detector demonstrates appealing performance characteristics suitable for high-resolution PET applications. The current benchtop-based detector calibration routine allows these detectors to be used in PET systems.

A 32-Channel Readout ASIC for X-Ray Spectrometry and Tracking in the GAPS Experiment

A 32-Channel Readout ASIC for X-Ray Spectrometry and Tracking in the GAPS Experiment

Comparison of readout systems for high-rate silicon photomultiplier applications

Recent years have shown an increased use of silicon photomultipliers (SiPM) in experiments as they are of reasonable cost, have relatively low power consumption and are easily available in a variety of form factors allowing for a large number of readout channels. At the same time, experiments are generating data at increasingly high rates requiring the use of more efficient readout systems. In this work, the dead time, efficiency, dynamic range, coincidence time resolution and energy resolution of five different readout systems at various stages of maturity are evaluated to determine the best system for acquiring data from a detector in a high rate experiment. Additional functionalities of the systems are also discussed.

Homogeneous electroanalysis coupled with colorimetry dual-mode sensing of silver ion in water based on target-inhibited peroxidase activity of Pt@ZIF-8 nanozyme

Electrochemical sensing is the commonly used method for the detection of heavy metal silver ion (Ag+), while the conventional electrochemical sensors generally require the existence of electrode modifications and even electrodeposition step coupled with a single-mode readout. Herein, by preparing ZIF-8 organometallic frame load with platinum nanoparticles (Pt@ZIF-8) as nanozyme and o-phenylenediamine (OPD) as colorless substance, taking advantage of the superior peroxidase activity of Pt@ZIF-8 that can catalyze the oxidation of OPD to product electroactive/yellow 2,3-diaminophenazinc and the target-inhibited effect towards nanozyme activity from Ag+, a homogeneous electroanalysis coupled with colorimetry (HEA-CM) dual-mode sensing platform was designed for the first time to detect Ag+. Furthermore, the colorimetric images were converted on a smartphone to digital signals for the quantitative analysis. The designed strategy could offer multiple advantages such as electrodeposition-free, modification-free and dual channel readout. After investigating the sensing mechanism and experimental parameters, the analytical performance of the designed strategy was evaluated, obtaining extremely low detection limit (0.034 nM), reliable recovery rate (99.61 %-101.6 %) and wide linearity. This work offered an effective method for the simple, sensitive, rapid, accurate and multiplexed determination of Ag+, and also opened a new pathway for the detection of other heavy metals based on HEA-CM dual-mode strategy.