Silicon Pixel Detector Research Articles

ElectronCT - an imaging technique using very-high energy electrons

The electronCT technique is an imaging method based on the multiple Coulomb scattering of relativistic electrons and has potential applications in medical and industrial imaging. It utilizes a pencil beam of electrons in the very high energy electron (VHEE, 50–250 MeV) range and a single detection layer for the determination of the beam profile. The technique constitutes a projectional, two-dimensional imaging method and thus also qualifies for the tomographic reconstruction of samples. Given the simplicity of the technical setup and its location behind the sample, the electronCT technique has potential synergies with VHEE radiotherapy, making use of the same electron source for both treatment and diagnostics and thus being a candidate for in situ imaging and patient localization. At the same time, several technical challenges arise from the measurement technique when applied for the imaging of living beings. Measurements performed at the ARES linear particle accelerator at an electron energy of 155 MeV using a mouse phantom and a Timepix3 silicon pixel detector assembly demonstrate the feasibility of this technique. Both projectional and tomographic reconstructions are presented and the potential and limits of the technology are discussed.

Advancements in experimental techniques for measuring dipole moments of short-lived particles at the LHC

ALADDIN is a proposed fixed-target experiment at the LHC for the direct measurement of charm baryon dipole moments. The detector features a spectrometer and a Cherenkov detector, while the experimental technique is based on the phenomena of particle channelling and spin precession in bent crystals. TWOCRYST, a proof-of-principle test at the LHC for the proposed experiment, is planned during the LHC Run 3. Recent channelling efficiency measurements performed at the CERN SPS of bent crystals developed at INFN are presented, marking significant progress towards its realisation. The silicon pixel detector for TWOCRYST is under construction. It will work in the secondary vacuum of a Roman Pot positioned inside the LHC beam pipe. The design, construction and integration of the pixel detector inside the Roman Pot will be discussed, along with the design and perspectives for the proposed ALADDIN experiment.

Design and thermal simulation of the front-end module for STARLIGHT

This paper presents a front-end module emulator for SemiconducTor Array detectoR with Large dynamIc ranGe and cHarge inTegrating readout (STARLIGHT), a versatile hybrid silicon pixel detector with a high frame rate (≥10kHz) and serving as the first charge-integrating pixel detector for XFEL in China. The detector is intended for operation in a vacuum environment, with the front-end module generating a thermal power of up to 5.443 mW/mm2, presenting a significant challenge for thermal management. To assess the thermal management capabilities of the mechanical and PCB designs for the project, a thermal emulator was developed to replicate the heat generated by the ASIC. This was particularly crucial during the early stages of the project when the ASIC was not yet available, achieved by placing copper wires on the PCB. Subsequent thermal simulations were conducted and compared with the results obtained from the thermal emulator. The comparison shows that the experimental results are very close to the thermal simulation results, validating the thermal performance of the STARLIGHT front-end modules. These endeavors not only provide validation but also offer valuable insights to ensure the thermal efficiency of the STARLIGHT front-end modules.

Polarimetry of [formula omitted]-rays converting to [formula omitted] pairs with silicon-pixel-based telescopes

There are serious prospects that the next γ-ray space mission could use a telescope based on silicon pixel detectors. I characterize the potential of such active targets for polarimetry with gamma-ray conversions to pairs and find it excellent both in terms of selection efficiency and of effective polarization asymmetry.

An in-vivo treatment monitoring system for ion-beam radiotherapy based on 28 Timepix3 detectors

Ion-beam radiotherapy is an advanced cancer treatment modality offering steep dose gradients and a high biological effectiveness. These gradients make the therapy vulnerable to patient-setup and anatomical changes between treatment fractions, which may go unnoticed. Charged fragments from nuclear interactions of the ion beam with the patient tissue may carry information about the treatment quality. Currently, the fragments escape the patient undetected. Inter-fractional in-vivo treatment monitoring based on these charged nuclear fragments could make ion-beam therapy safer and more efficient. We developed an ion-beam monitoring system based on 28 hybrid silicon pixel detectors (Timepix3) to measure the distribution of fragment origins in three dimensions. The system design choices as well as the ion-beam monitoring performance measurements are presented in this manuscript. A spatial resolution of 4mm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{4}\\,\\hbox {mm}}$$\\end{document} along the beam axis was achieved for the measurement of individual fragment origins. Beam-range shifts of 1.5mm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${1.5}\\,\\hbox {mm}$$\\end{document} were identified in a clinically realistic treatment scenario with an anthropomorphic head phantom. The monitoring system is currently being used in a prospective clinical trial at the Heidelberg Ion Beam Therapy Centre for head-and-neck as well as central nervous system cancer patients.

Testbeam results of irradiated SiGe BiCMOS monolithic silicon pixel detector without internal gain layer

Samples of the monolithic silicon pixel ASIC prototype produced in 2022 within the framework of the Horizon 2020 MONOLITH ERC Advanced project were irradiated with 70 MeV protons up to a fluence of 1 × 1016 neq/cm2, and then tested using a beam of 120 GeV/c pions. The ASIC contains a matrix of 100 μm pitch hexagonal pixels, read out by low noise and very fast frontend electronics produced in a 130 nm SiGe BiCMOS technology process. The dependence on the proton fluence of the efficiency and the time resolution of this prototype was measured with the frontend electronics operated at a power density between 0.13 and 0.9 W/cm2. The testbeam data show that the detection efficiency of 99.96% measured at sensor bias voltage of 200 V before irradiation becomes 96.2% after a fluence of 1 × 1016 neq/cm2. An increase of the sensor bias voltage to 300 V provides an efficiency to 99.7% at that proton fluence. The timing resolution of 20 ps measured before irradiation rises for a proton fluence of 1 × 1016 neq/cm2 to 53 and 45 ps at HV = 200 and 300 V, respectively.

Towards precise LET measurements based on energy deposition of therapeutic ions in Timepix3 detectors

Objective. There is an increasing interest in calculating and measuring linear energy transfer (LET) spectra in particle therapy in order to assess their impact in biological terms. As such, the accuracy of the particle fluence energy spectra becomes paramount. This study focuses on quantifying energy depositions of distinct proton, helium, carbon, and oxygen ion beams using a silicon pixel detector developed at CERN to determine LET spectra in silicon. Approach. While detection systems have been investigated in this pursuit, the scarcity of detectors capable of providing per-ion data with high spatial and temporal resolution remains an issue. This gap is where silicon pixel detector technology steps in, enabling online tracking of single-ion energy deposition. The used detector consisted of a 300 µm thick silicon sensor operated in partial depletion. Main results. During post-processing, artifacts in the acquired signals were identified and methods for their corrections were developed. Subsequently, a correlation between measured and Monte Carlo-based simulated energy deposition distributions was performed, relying on a two-step recalibration approach based on linear and saturating exponential models. Despite the observed saturation effects, deviations were confined below 7% across the entire investigated range of track-averaged LET values in silicon from 0.77 keV µm−1 to 93.16 keV µm−1. Significance. Simulated and measured mean energy depositions were found to be aligned within 7%, after applying artifact corrections. This extends the range of accessible LET spectra in silicon to clinically relevant values and validates the accuracy and reliability of the measurements. These findings pave the way towards LET-based dosimetry through an approach to translate these measurements to LET spectra in water. This will be addressed in a future study, extending functionality of treatment planning systems into clinical routine, with the potential of providing ion-beam therapy of utmost precision to cancer patients.

The LHCb VELO Upgrade module construction

The LHCb detector has undergone a major upgrade for LHC Run 3. This Upgrade I detector facilitates operation at higher luminosity and utilises full-detector information at the LHC collision rate, critically including the use of vertex information. A new vertex locator system, the VELO Upgrade, has been constructed. The core element of the new VELO are the double-sided pixelated hybrid silicon detector modules which operate in vacuum close to the LHC beam in a high radiation environment. The construction and quality assurance tests of these modules are described in this paper. The modules incorporate 200 μm thick, n-on-p silicon sensors bump-bonded to 130 nm technology ASICs. These are attached with high precision to a silicon microchannel substrate that uses evaporative CO2 cooling. The ASICs are controlled and read out with flexible printed circuits that are glued to the substrate and wire-bonded to the chips. The mechanical support of the module is given by a carbon fibre plate, two carbon fibre rods and an aluminium plate. The sensor attachment was achieved with an average precision of 21 μm, more than 99.5% of all pixels are fully functional, and a thermal figure of merit of 3 Kcm2W-1 was achieved. The production of the modules was successfully completed in 2021, with the final assembly and installation completed in time for data taking in 2022.

Quad-module characterization with the MALTA monolithic pixel chip

The MALTA silicon pixel detector combines a depleted monolithic active pixel sensor (DMAPS) with a fully asynchronous front-end and readout. It features a high granularity pixel matrix with a 36.4 μm symmetric pixel pitch, low power consumption of <1 μW/pixel and low material budget with detector thicknesses as little as 50 μm. It achieves a radiation hardness to 100MRad TID and more than 1 × 10E15 1 MeV neq/cm2 with a time resolution of <2 ns (Pernegger et al., 2023).In order to cover large sensitive areas efficiently with a minimum of power and data connections the development of modules, comprising of up to 4 MALTA detectors, is studied.This contribution presents the beam test performance of parallel and serial powered MALTA 4-chip modules in an effort to characterize the sensor’s chip-to-chip data and power transmission and prepare the production of a first prototype of an ultra-light weight 4-chip module on a flexible circuit with next generation MALTA2 sensors.

Development of pixelated silicon detector for AMS study

A pixelated silicon detector (PSD) has been developed for the position-sensitive detector on a focal plane of an accelerator mass spectrometry (AMS) system in Yamagata University (YU). The YU-AMS system measures the relative abundances of the carbon isotopes 14C, 13C, and 12C for radiocarbon dating. The beam of the rare isotope 14C is transported to the focal plane of the AMS system. When the focal plane detector is position-sensitive to the beam, it can be utilized for beam diagnostics on the AMS beamline to achieve 14C measurement with high accuracy. To investigate the characteristics of the PSD, α particles from 241Am were irradiated on the PSD. A beam test using 14C was also performed to evaluate the size and position of the 14C beam on the focal plane of the YU-AMS system.

Effect of multiple coulomb scattering on the beam tests of silicon pixel detectors

Effect of multiple coulomb scattering on the beam tests of silicon pixel detectors

Design and 3D TCAD simulation of a novel floating-electrode silicon pixel detector

A novel floating-electrode silicon pixel detector has been proposed. The novel configuration of the floating electrode in the silicon pixel detector reduces the size of the collecting cathode and decreases both the capacitance and leakage current of the detector compared to the conventional silicon pixel detector. For the design, we used a 200 × 200 µm2 detector as the model to analyze the impact of varying numbers of floating rings on the electrical performance [Wu et al., AIP Adv. 11(2), 025315 (2021)]. We used Technology Computer Aided Design simulation to compare and analyze the simulated electric field, potential, capacitance, and breakdown voltage of the detector. The results show that decreasing the gap-to-width ratio of the floating electrode, as well as increasing the quantity of floating rings, enhances the detector’s performance.

The data acquisition system for the PANDA Micro-Vertex Detector

The PANDA (antiProton ANnihilation at DArmstadt) experiment will study the strong interaction in annihilation reactions between an antiproton beam and a stationary cluster jet target. The PANDA detector will be composed of several sub-detectors designed for tracking, particle identification and calorimetry. The Micro-Vertex Detector (MVD) is the innermost part of the tracking system surrounding the interaction region, which is designed for precise vertex and tracking detection. It consists of silicon pixel and double-sided microstrip detectors. For the readout of the microstrip sensors an ASIC called ToASt (Torino Asic for Strip readout) is being developed in 0.11 μm CMOS technology at INFN Turin. The ASIC takes advantage of both Time-over-Threshold and Time-of-Arrival methods to accurately measure the event's energy and timestamp. To sustain the acquisition of the microstrip sensors a MDC (Module Data Concentrator) ASIC is under development at KIT. Up to eight ToASt front-ends' data streams are multiplexed, read out and processed by one MDC. The data of several MDCs are collected and processed by the off-detector readout card MMB (MVD Multiplexer Board), also under development at KIT. The processed data is then transferred via 100 GbE optical links to the computing nodes. The ToASt chips have been integrated with the FPGA implementation of the MDC to form the first fully functional detector module. Beam tests have been performed at the COSY facility in Jülich. This paper focuses on the design of MDC ASIC and MMB board, the integration with the ToASt and presents preliminary beam test results.

Resolving soft X-ray photons with a high-rate hybrid pixel detector

Due to their high frame rates and dynamic range, large area coverage, and high signal-to-noise ratio, hybrid silicon pixel detectors are an established standard for photon science applications at X-ray energies between 2 keV and 20 keV. These properties also make hybrid detectors interesting for experiments with soft X-rays between 200 eV and 2 keV. In this energy range, however, standard hybrid detectors are limited by the quantum efficiency of the sensor and the noise of the readout electronics. These limitations can be overcome by utilizing inverse Low-Gain Avalanche Diode (iLGAD) sensors with an optimized X-ray entrance window. We have developed and characterized a prototype soft X-ray iLGAD sensor bonded to the charge integrating 75 µm pixel JUNGFRAU chip. Cooled to −22°C, the system multiplication factor of the signal generated by an impinging photon is ≥ 11. With this gain, the effective equivalent noise charge of the system is ≤5.5 electrons root-mean-square at a 5 µs integration time. We show that by cooling the system below −50°C, single photon resolution at 200 eV becomes feasible with a signal-to-noise ratio better than 5.

Conceptual study of a two-layer silicon pixel detector to tag the passage of muons from cosmic sources through quantum processors

Recent studies in quantum computing have shown that quantum error correction with large numbers of physical qubits are limited by ionizing radiation from high-energy particles. Depending on the physical setup of the quantum processor, the contribution of muons from cosmic sources can constitute a significant fraction of these interactions. As most of these muons are difficult to stop, we perform a conceptual study of a two-layer silicon pixel detector to tag their hits on a solid-state quantum processor instead. With a typical dilution refrigerator geometry model, we find that efficiencies greater than 50% are most likely to be achieved if at least one of the layers is operated at the deep-cryogenic (<1 K) flanges of the refrigerator. Following this finding, we further propose a novel research program that could allow the development of silicon pixel detectors that are fast enough to provide input to quantum error correction algorithms, can operate at deep-cryogenic temperatures, and have very low power consumption.

Relativistic particle measurement in jupiter’s magnetosphere with Pix.PAN

Pix.PAN is a compact cylindrical magnetic spectrometer, intended to provide excellent high energy particle measurements under high rate and hostile operating conditions in space. Its principal design is composed of two Halbach-array magnetic sectors and six Timepix4-based tracking layers; the latest hybrid silicon pixel detector readout ASIC designed. Due to Pix.PAN’s compact and relatively simple design, it has the potential to be used for space missions exploring with measurements of unprecedented precision, high energy particles in radiation belts and the heliophere (solar energetic particles, anomalous and galactic cosmic rays). In this white paper, we discuss the design and expected performance of Pix.PAN for COMPASS (Comprehensive Observations of Magnetospheric Particle Acceleration, Sources, and Sinks), a mission concept submitted to NASA’s Call “B.16 Heliophysics Mission Concept Studies (HMCS)” in 2021 that targets the extreme high energy particle environment of Jupiter’s inner radiation belts. We also discuss PixPAN’s operational conditions and interface requirements. The conceptual design shows that is possible to achieve an energy resolution of<12% for electrons in the range of 10 MeV-1 GeV and<35% for protons between ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim $$\\end{document}200 MeV to a few GeV. Due to the timestamp precision of Timepix4, a time resolution (on an instrument level) of about 100 ps can be achieved for time-of-flight measurements. In the most intense radiation environments of the COMPASS mission, Pix.PAN is expected to have a maximum hit rate of 44MHzcm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\frac{\ ext {MHz}}{\ ext {cm}^2}$$\\end{document} which is below the design limit of 360MHzcm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\frac{\ ext {MHz}}{\ ext {cm}^2}$$\\end{document} of Timepix4. Finally, a sensor design is proposed which allows the instrument to operate with a power budget of 20W without the loss of scientific performance.

The first test of a monolithic silicon pixel detector ASIC for the detection of electromagnetic showers of TeV energy in the FASER experiment at the LHC

The FASER experiment at the LHC is designed to look for new, long-lived fundamental particles. A W-Si preshower detector is currently under construction, with the objective of enabling the discrimination of photon pairs with O(TeV) energies and separation down to 200 μm, extending the discovery potential of the experiment. The detector will be based on a new monolithic silicon pixel sensor in 130 nm SiGe BiCMOS. The first test of the ASIC from a pre-production run shows that the building blocks of the monolithic silicon pixel detector are functional.

TCAD Simulation of X-ray irradiated Si microstrip detector : Impact on full depletion voltage and leakage current

In the intense x-ray radiation environment at synchrotron sources, it is reported that the performance of the silicon pixel detectors degrades with an increasing x-ray dose up to 10 MGy. To study the impact of x-ray irradiation effects in the n-Fz Si microstrip detector, the microscopic radiation damage parameters of x-ray radiation were extracted from the current–voltage, and capacitance-voltage experiments on test Si microstrip detector. The damage parameters are implemented in Synopsys TCAD. In this paper, we have irradiated the test structure up to 10 MGy, and the results on full depletion voltage, and leakage current are compared with the TCAD simulation results. A very good agreement in between experimental and simulation results is observed in the leakage current for the non-irradiated, and 1 MGy irradiated detectors, where for high doses up to 10 MGy, experimental leakage current was fifty times higher than the simulated leakage current at full depletion voltage. The full depletion voltage in 0 MGy detector is also well matched with the simulation result, and further, it shows the full depletion voltage performance of x-ray irradiated detector. Finally, the new detector design specifications and process parameters are proposed for the optimum performance of the radiation hard p+n Si pixel detector equipped with guard rigs at cut edge for the next generation photon science applications.

Monte Carlo and experimental evaluation of a Timepix4 compact gamma camera for coded aperture nuclear medicine imaging with depth resolution

PurposeWe designed a prototype compact gamma camera (MediPROBE4) for nuclear medicine tasks, including radio-guided surgery and sentinel lymph node imaging with a 99mTc radiotracer. We performed Monte Carlo (MC) simulations for image performance assessment, and first spectroscopic imaging tests with a 300 μm thick silicon detector. MethodsThe hand-held camera (1 kg weight) is based on a Timepix4 readout circuit for photon-counting, energy-sensitive, hybrid pixel detectors (24.6 × 28.2 mm2 sensitive area, 55 μm pixel pitch), developed by the Medipix4 Collaboration. The camera design adopts a CdTe detector (1 or 2 mm thick) bump-bonded to a Timepix4 readout chip and a coded aperture collimator with 0.25 mm diameter round holes made of 3D printed 1-mm thick tungsten. Image reconstruction is performed via autocorrelation deconvolution. ResultsGeant4 MC simulations showed that, for a 99mTc source in air, at 50 mm source-collimator distance, the estimated collimator sensitivity (4 × 10−4) is 292 times larger than that of a single hole in the mask; the system sensitivity is 0.22 cps/kBq (2 mm CdTe); the lateral spatial resolution is 1.7 mm FWHM. The estimated axial longitudinal resolution is 8.2 mm FWHM at 40 mm distance. First experimental tests with a 300 μm thick Silicon pixel detector bump-bonded to a Timepix4 chip and a high-resolution coded aperture collimator showed time-over-threshold and time-of-arrival capabilities with 241Am and 133Ba gamma-ray sources. ConclusionsMC simulations and validation lab tests showed the expected performance of the MediPROBE4 compact gamma camera for gamma-ray 3D imaging.

DIMUS: super-compact Dimuonium Spectroscopy collider at Fermilab

While dimuonium (μ + μ -) — the “smallest QED atom” — has not yet been observed, it is of utmost fundamental interest. By virtue of the larger mass, dimuonium has greater sensitivity to beyond the standard model (BSM) effects than its cousins positronium or muonium, both discovered long ago, while not suffering from large QCD uncertainties. Dimuonium atoms can be created in e + e - collisions with large longitudinal momentum, allowing them to decay a small distance away from the beam crossing point and avoid prompt backgrounds. We envision a unique cost-effective and fast-timeline opportunity for copious production of (μ + μ -) atoms at the production threshold via a modest modification of existing Fermilab Accelerator Science and Technology (FAST) facility to arrange collisions of 408 MeV electrons and positrons at a 75° angle. This compact 23 m circumference collider (DIMUS) will allow for precision tests of QED and open the door for searches for new physics coupled to the muon. The FAST facility is perfectly suited for DIMUS as there are existing SRF accelerators and infrastructure, capable of producing high energy, high current electron and positron beams, sufficient for O(1032)cm2 s-1 luminosity and ∼0.5 million dimuons per year. The expansion will require installation of a second SRF cryomodule, positron production and accumulation system, fast injection/extraction kickers and two small circumference intersecting rings. An approximately meter-sized detector with several layers of modern pixelated silicon detector and crystal-based electromagnetic calorimeters will ensure observation of the decays of dimuonium to electron-positron pairs in presence of the Bhabba scattering background. An expansion of the system to include solenoidal magnet outside of the calorimeter system, a layer of steel shielding behind the magnet, and a set of dedicated muon detectors would extend the physics program of DIMUS to include precision studies of rare processes with muons, pions, and η mesons produced in e + e - collisions.