Silicon Tracker Research Articles

Determination of the natural frequencies of ultralight carbon fiber trusses for silicon tracking systems

In this work a method is developed to determine the natural frequency of highly-irradiated ultralight carbon fiber trusses. This method is based both in experimental acoustic measurements and the ANSYS-based modeling of the trusses. The structures under study are sensor supporting trusses widely used in silicon inner trackers of large experimental setups at LHC, FAIR and NICA.

Nonresonant central exclusive production from CMS+TOTEM

The central exclusive production of charged hadron pairs in pp collisions at a center-of-mass energy of 13[Formula: see text]TeV is examined, based on data collected in a special high-[Formula: see text] run of the LHC. Events are selected by requiring both scattered protons detected in the TOTEM Roman pots, exactly two oppositely charged identified particles in the CMS silicon tracker, and the energy–momentum balance of these four particles. The nonresonant continuum processes are studied with the invariant mass of the centrally produced two-pion system in the resonance-free region, [Formula: see text][Formula: see text]GeV or [Formula: see text][Formula: see text]GeV. Differential cross sections as functions of the azimuthal angle between the surviving protons, squared four-momenta, and two-hadron invariant mass are measured in a wide region of scattered protons with transverse momentum between 0.2 and 0.8[Formula: see text]GeV and for pion rapidities [Formula: see text]. A rich structure of interactions related to double pomeron exchange emerges. The parabolic minimum in the distribution of the two-proton azimuthal angle is observed for the first time. It can be understood as an effect of additional pomeron exchanges between the protons, and of the interference between the bare and the rescattered amplitudes. After model tuning, various physical quantities related to the pomeron cross section, proton–pomeron and hadron–pomeron form factors, trajectory slopes and intercepts, as well as coefficients of diffractive eigenstates of the proton are determined.

Identification of positrons and electrons at TeV energy scale using the AMS tracker, time-of-flight counters, and electromagnetic calorimeter

The Alpha Magnetic Spectrometer, AMS, is successfully collecting data since its installation on the International Space Station on May 19, 2011. One of the main AMS objectives is the measurement of cosmic ray positrons and electrons at the highest energies. We present a new technique for the identification of electrons and positrons, which is used in the AMS data analysis in the energy range up to a few TeV. The focus of this article is on the rejection of the proton background using the AMS silicon tracker, the time-of-flight counters, and the electromagnetic calorimeter.

Characterization of Tracking Modules Based on DSSD Sensors at the SC-1000 Accelerator for the BM@N Project

The results of studying characteristics of modules based on double-sided microstrip silicon sensors, which are designed to create the wide-aperture Silicon Tracking System for the BM@N facility, are presented. The main module features are the use of fast readout electronics based on the STS-XYTER chip and the application of ultralight (0.23% X0) aluminum microcables for transmitting analog signals from the sensor strips to the input channels of the readout electronics. The results of testing different configurations of tracking modules on the extracted beam of protons at the SC-1000 accelerator in the PNPI are presented. The stable operation of readout electronics is demonstrated at loads close to the maximum values of 360 kHz s–1 cm–2. The signal-to-noise ratio was no less than 23. The measured coordinate resolution of the modules within the beam telescope was 17 ± 0.4 μm, and the detector efficiency of recording for protons with energy of 1 GeV was no less than 99%.

The high count-rate self-triggering Silicon Tracking System of the CBM experiment at FAIR: Design, series assembly, upgrade options

The Compressed Baryonic Matter (CBM) experiment is a stationary target spectrometer with hadron and lepton identification. It is under construction at the Facility for Antiproton and Ion Research (FAIR) that is being realized next to the GSI grounds in Darmstadt, Germany. CBM will investigate QCD matter at highest, up to supernova core-collaps baryonic densities (Ablyazimov et al., 2017). This will be done in collisions of nuclear beams with targets at center of mass energies sNN=2.9–4.9 GeV. Because of the long beam extraction technique employed at FAIR’s SIS100 synchrotron, CBM’s data collection can be based on streaming time-stamped detector data into a compute farm. Event determination and physics analysis are performed there online, allowing for collision rates up to 10 MHz. CBM’s core tracking detector is the Silicon Tracking System, operating 8 tracking stations based on double-sided silicon microstrip sensors and self-triggering front-end electronics in a 1 Tm dipole magnetic field (Heuser et al., 2013).

From 3D to 5D tracking: SMX ASIC-based double-sided micro-strip detectors for comprehensive space, time, and energy measurements

We present the recent development of a lightweight detector capable of accurate spatial, timing, and amplitude resolution of charged particles. The technology is based on double-sided double-metal p+ – n – n+ micro-strip silicon sensors, ultra-light long aluminum-polyimide micro-cables for the analogue signal transfer, and a custom-developed SMX read-out ASIC capable of measurement of the time (Δt ≲ 5 ns) and amplitude. Dense detector integration enables a material budget > 0.3 % X 0. A sophisticated powering and grounding scheme keeps the noise under control.In addition to its primary application in Silicon Tracking System of the future CBM experiment in Darmstadt, our detector will be utilized in other research applications.

A Lightweight Algorithm to Model Radiation Damage Effects in Monte Carlo Events for High-Luminosity Large Hadron Collider Experiments.

Radiation damage significantly impacts the performance of silicon tracking detectors in Large Hadron Collider (LHC) experiments such as ATLAS and CMS, with signal reduction being the most critical effect; adjusting sensor bias voltage and detection thresholds can help mitigate these effects, generating simulated data that accurately mirror the performance evolution with the accumulation of luminosity, hence fluence, is crucial. The ATLAS and CMS collaborations have developed and implemented algorithms to correct simulated Monte Carlo (MC) events for radiation damage effects, achieving impressive agreement between collision data and simulated events. In preparation for the high-luminosity phase (HL-LHC), the demand for a faster ATLAS MC production algorithm becomes imperative due to escalating collision, events, tracks, and particle hit rates, imposing stringent constraints on available computing resources. This article outlines the philosophy behind the new algorithm, its implementation strategy, and the essential components involved. The results from closure tests indicate that the events simulated using the new algorithm agree with fully simulated events at the level of few %. The first tests on computing performance show that the new algorithm is as fast as it is when no radiation damage corrections are applied.

CNN-based track reconstruction study for gamma-ray pair telescope

MeV Gamma-ray Telescope (MGT) is a conceptual mission aimed at improving the detection sensitivity of gamma-ray astronomy in the MeV energy range. It consists of three sub-detectors: Gamma-ray Conversion silicon tracker, CALOrimeter and Anti-Coincident Detector. In this paper, a track reconstruction algorithm based on Convolutional Neural Networks (CNN) is developed for MGT. In order to train and test the model, Geant4 simulation is used and generates a large number of gamma-ray events at nine energy points in the energy band from 0.5 GeV to 10 GeV. Finally, the reconstruction results of angular resolution, position resolution and acceptance are shown. The testing results indicate that the angular resolution of MGT significantly improves in the 0.5∼10 GeV range compared with Fermi-LAT.

Investigation of proton radiation damage effects on the n-Fz DSSSD for the Phase I Upgrade of new Si Tracker at the R3B experiment

Radiation hard Double Sided Silicon Strip Detectors are used at the Silicon Tracker for the detection of two-dimensional position andenergy measurement of the incident protons in the R3B experiment at FAIR. Double Sided Silicon Strip Detectors were fabricated by Micron Semiconductor Ltd., U.K. and the first set of experimental measurements havebeenperformed on the non-irradiated detectors in order to understand the macroscopic performance of the detectors for the tracker. This study is extended to the performance of the irradiated detectors in the proton radiation environmentusing proton radiation damage model. The detectors were irradiated with 23 MeV protons up to an expected fluence of 8 × 1014 neq cm-2, which is one order higher than expected fluence at an initial phase0 of the experiment. The performance characteristics of the detectors on the full depletion voltage, leakage current, and charge collection efficiency were extrapolated using SRH and CCE modelling, which is usually implemented in device TCAD. The results on the detectors were compared with the available experimental data on the detectors. A very good comparison between experimental data and calculated resulthave been recorded for non-irradiated and irradiated detectors. The agenda is to propose a proton radiation hard Double Sided Silicon Strip Detector design on the basis of the present study for the phase 1 upgrade of the experiment.

The LHCb Upgrade I

The LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software.

AstroPix4 — a novel HV-CMOS sensor developed for space based experiments

For the proposed space based gamma-ray observatory All-sky Medium-Energy Gamma-ray Observatory eXplorer (AMEGO-X), a silicon tracker based on a novel High Voltage-CMOS (HV-CMOS) sensor called AstroPix, is currently being developed. Preliminary measurements with the first full reticle prototype AstroPix3 show that the power target of 1.5 mW/cm2 can currently not be reached due to the digital consumption of 3.08 mW/cm2, while the analog power consumption of 1.04 mW/cm2 and a break down voltage of over 350 V look promising. Based on these results, the design changes in AstroPix4, submitted in May 2023, are presented, containing changes to the time stamp generation and readout architecture. A digital power consumption below 0.25 mW/cm2 is expected by removing the fast 200 MHz clock used to measure the time-over-threshold (ToT) and an LVDS receiver. A maximum resolution of 3.125 ns for time-of-arrival (ToA) and ToT is reached by adding per-pixel Flash-Time-to-Digital Converter (TDCs) controlled by a global delay-locked loop (DLL).

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.

The DMAPS upgrade of the Belle II vertex detector

Abstract The SuperKEKB collider will undergo a major upgrade to reach the target luminosity of 6 × 1035 cm-2 s-1 during the long shutdown (LS2) foreseen to start around year 2027. We are developing a new vertex detector (VTX) to replace the current one (VXD). This new pixel silicon tracker aims to be both more robust against the higher level of machine background and more performant in terms of precision on the decay vertices and standalone track finding efficiency. The baseline layout consists of two layers composing the inner part (iVTX) and three outer layers (oVTX), all arranged in a barrel-shaped geometry, with minimal material budget. All layers will be equipped with dedicated depleted monolithic active CMOS pixel sensors (DMAPS) named OBELIX, designed in the TowerJazz 180 nm technology. This paper will review all the aspects of the project: the detector specifications and the baseline design, the expected improved performance, the OBELIX features and its design status, including the tests of the forerunner chip TJ-Monopix2, and the fabrication and tests for the iVTX and oVTX ladder prototypes.

The commissioning status of the intermediate silicon tracker of sPHENIX

The sPHENIX project is a new collider experiment at the Relativistic Heavy Ion Collider (RHIC) in Brookhaven National Laboratory (BNL). It aims to study the Quark-Gluon Plasma and cold Quantum Chromodynamics (QCD) by measuring photons, jets, jet correlations, and the Upsilon family with high precision. To achieve these goals, a precise tracking system is necessary. The tracking system of the sPHENIX detector consists of the MVTX, INTT, TPC, and TPOT. INTT is a two-layer barrel silicon tracker that plays a unique role among the sPHENIX tracking detectors. It is capable of bridging the tracks of MVTX and TPC. In addition, its precise timing resolution enables INTT to associate individual tracks with events to eliminate pile-up events. The INTT barrel installation and cabling were completed in March 2023. We have since commissioned and confirmed the detector responses. The INTT status, and performance evaluated by beam and cosmic rays are described in this proceedings.

STAR forward detector upgrade status and performance

An upgrade to the STAR detector system at forward rapidities has been completed before the RHIC RUN 2022. It consists of the Forward Tracking System (FTS) and the Forward Calorimeter System (FCS). The Forward Tracking System is composed of a Silicon Tracker and a small-strip Thin Gap Chamber Tracker. The Forward Calorimeter System contains an Electromagnetic Calorimeter and a Hadronic Calorimeter. These systems cover the pseudorapidity region of 2.5 < η < 4, providing detection capabilities for neutral pions, photons, electrons, jets, and charged hadrons. This enables the STAR experiment to study cold QCD physics at very high and low regions of Bjorken x and to explore the longitudinal structure of the initial state in relativistic heavyion collisions by measuring the decorrelations at large η. This proceeding will introduce the STAR forward upgrade, its current status, and its performance during the STAR Run22.

The “green” use of fluorocarbons in Cherenkov detectors and silicon tracker cooling systems: challenges and opportunities in an unfolding era of alternatives

Saturated fluorocarbons (SFCs) of form CnF(2n+2) are chosen for their optical properties as Cherenkov radiators, with C4F10 and CF4 currently used at CERN in the COMPASS and LHCb ring imaging Cherenkov detectors. Their non-conductivity, non-flammability and radiation-resistance also make SFCs ideal coolants: C6F14 liquid cooling is used in all LHC experiments, while C3F8 is used for the evaporative cooling of TOTEM and the ATLAS silicon tracker. These fluids, however, have high global warming potentials (5000–10000*GWPCO2), and represented around 36% of CERN’s CO2-equivalent emissions in 2018. There is thus an impetus to reduce their use, losses in purification and wastage through leaks, through improved monitoring and closed circulation system design. Newer spur-oxygenated fluoro-ketones, for example from the 3 M NOVEC® range, with CnF2nO structures, can offer similar performance to SFCs with but with very low, or zero GWP. Although these fluids do not yet exist in large quantities over the full CnF2 “matrix” the radiation tolerance and thermal performance of NOVEC 649 (C6F12O) was sufficiently promising for it to be chosen as a C6F14 replacement for cooling silicon photomultipliers. Additionally, subject to optical testing, NOVEC 5110 (C5F10O) could (if blended with nitrogen) replace both C4F10 and CF4 in Cherenkov detectors. Lighter molecules (for example C2F4O, with similar thermodynamics to C2F6)—if and when available in industrial quantities—might allow lower temperature operation than evaporative CO2 in future silicon trackers operated at very high luminosity. Ultrasonic gas mixture analysis is very sensitive to concentration changes of a heavy vapour in a light carrier, and is used—in the only such fluorocarbon coolant leak monitoring system operating at LHC—for real-time monitoring of C3F8 coolant leaks from the ATLAS pixel and SCT silicon trackers into their nitrogen-flushed environmental volumes. A typical C3F8 sensitivity of better than 10−5 is achieved. Advanced new ultrasonic algorithms allow measurement of the concentrations of a pair of gases of particular interest on top of a varying known baseline of other gases. The technique is thus of considerable value in leak monitoring and could be used to blend fluoro-ketones with nitrogen or argon to reduce the GWP “load” of large volume atmospheric pressure gas Cherenkov radiators without the recourse to higher-pressure noble gas approaches. This paper outlines an approach to GWP reduction with fluoro-ketone fluids and the blending of heritage SFCs or fluoro-ketones with lighter gases using ultrasonic monitoring and control. Possible avenues for the use of fluoro-ketones in liquid phase and evaporative cooling of silicon trackers are discussed.

A commentary on the NIM A paper by G. Ambrosi et al. on the spatial resolution of the silicon tracker of the Alpha Magnetic Spectrometer

A commentary on the NIM A paper by G. Ambrosi et al. on the spatial resolution of the silicon tracker of the Alpha Magnetic Spectrometer

Quantum Algorithms for Charged Particle Track Reconstruction in the LUXE Experiment

The LUXE experiment is a new experiment in planning in Hamburg, which will study quantum electrodynamics at the strong-field frontier. LUXE intends to measure the positron production rate in this unprecedented regime using, among others, a silicon tracking detector. The large number of expected positrons traversing the sensitive detector layers results in an extremely challenging combinatorial problem, which can become computationally expensive for classical computers. This paper investigates the potential future use of gate-based quantum computers for pattern recognition in track reconstruction. Approaches based on a quadratic unconstrained binary optimisation and a quantum graph neural network are investigated in classical simulations of quantum devices and compared with a classical track reconstruction algorithm. In addition, a proof-of-principle study is performed using quantum hardware.

Functional characterization of modules for the Silicon Tracking System of the CBM experiment

The CBM experiment is a fixed-target heavy-ion physics experiment at the future FAIR facility, designed to explore the QCD phase diagram at high baryon-net densities and moderate temperatures. To address its complex physics program, the experiment is conceived to operate at beam–target interaction rates up to 10 MHz with self-triggered front-end electronics and free-streaming readout architecture. The Silicon Tracking System (STS) of CBM is the main charged-particle tracker, capable of delivering time-stamped hits for online tracking and event building, and momentum measurement inside a superconducting dipole magnet. The functional unit of the STS is the detector module, a device assembled from a double-sided silicon microstrip sensor connected via a stack of microcables to a pair of front-end boards carrying the readout electronics. The assembly and successful operation of STS modules, produced with close-to-final components, was an important milestone achieved in recent years. The systematic study of the modules’ performance is also necessary for optimizing the assembly procedure and ensuring high production yield. This work reports a series of tests, which aim to evaluate the module’s operation and establish the basic criteria for quality control. It summarizes the procedures and results of different measurements performed with the modules, starting with noise estimation and charge amplitude calibration, resulting in the linearization of the channel’s ADC and a homogeneous threshold distribution. Those results were verified using a radioactive source. Additionally, first conclusions concerning the assembly yield in terms of number of functional channels were obtained. These studies represent a fundamental step towards the series production readiness for the final STS detector.

Study of Proton Radiation Damage Effects in Si microstrip Detector for New and Fast Tracking System of pCT

A new and fast radiation hard p-Si micro strip detector requires for the high proton imaging performance using the Proton Computed Tomography (pCT) system. Silicon trackers of the pCT have been measured the actual proton dose delivered to the cancer patient during the medical treatment. In this paper, several proton cancer doses up to 9.62x 1014 neq,/cm2 are used for the SRH modelling of the full depletion voltage and leakage current at 293 K of the Si micro-strip detector using microscopic radiation damage model. Radiation hard thin (150μm) p-type MCz Si micro strip detector design is proposed for the pCT that can work up to 800V for very high-irradiated proton cancer doses.