Semiconductor Tracker Research Articles

Operation and performance of the ATLAS semiconductor tracker in LHC Run 2

The semiconductor tracker (SCT) is one of the tracking systems for charged particles in the ATLAS detector. It consists of 4088 silicon strip sensor modules.During Run 2 (2015–2018) the Large Hadron Collider delivered an integrated luminosity of 156 fb-1 to the ATLAS experiment at a centre-of-mass proton-proton collision energy of 13 TeV. The instantaneous luminosity and pile-up conditions were far in excess of those assumed in the original design of the SCT detector.Due to improvements to the data acquisition system, the SCT operated stably throughout Run 2.It was available for 99.9% of the integrated luminosity and achieved a data-quality efficiency of 99.85%.Detailed studies have been made of the leakage current in SCT modules and the evolution of the full depletion voltage, which are used to study the impact of radiation damage to the modules.

Measurements of sensor radiation damage in the ATLAS inner detector using leakage currents

Non-ionizing energy loss causes bulk damage to the silicon sensors of the ATLAS pixel and strip detectors. This damage has important implications for data-taking operations, charged-particle track reconstruction, detector simulations, and physics analysis. This paper presents simulations and measurements of the leakage current in the ATLAS pixel detector and semiconductor tracker as a function of location in the detector and time, using data collected in Run 1 (2010–2012) and Run 2 (2015–2018) of the Large Hadron Collider. The extracted fluence shows a much stronger |z|-dependence in the innermost layers than is seen in simulation. Furthermore, the overall fluence on the second innermost layer is significantly higher than in simulation, with better agreement in layers at higher radii. These measurements are important for validating the simulation models and can be used in part to justify safety factors for future detector designs and interventions.

Development of the front end amplifier circuit for the ATLAS ITk silicon strip detector

We present the development of the front end amplifiercircuit for the ABCStar readout ASIC designed for the upgraded ATLAS Inner Tracker (ITk) detector. The amplifier is intended to work with siliconstrip sensors of moderate length between 1.9 cm and 5.5 cm dependent on position in the detector. The final circuit is implemented in a commercial 130 nm CMOS process tolerant up to the total ionizing doses (TID) predicted for the lifetime of the detector, that is maximum of 66 Mrad (660 kGy) (Si) for the endcap region. The final architecture and the performance of the circuit is presented in the context of a long development program which started soon after the construction of the present ATLAS Semi-Conductor Tracker (SCT) detector.

In situ radiation damage studies of optoelectronics in the ATLAS SemiConductor Tracker

This paper presents results on in situ measurements of radiation damage for the on-detector optoelectronics for the ATLAS SemiConductor Tracker. The results come from proton-proton collisions in LHC during operation in 2016, 2017 and 2018. The results for both p - i - n diodes and VCSELs are given and compared to expectations from beam tests of devices from the same wafer, before the start of LHC operation. The VCSELs show evidence for some radiation damage as expected from earlier studies. The magnitude of the damage is compared with simple extrapolations from test beam data. The p - i - n diodes do show significant radiation damage as expected from test beam studies.

The ATLAS Fast TracKer—Architecture, Status and High-Level Data Quality Monitoring Framework

The Fast Tracker (FTK) is a highly parallel processor dedicated to a quick and efficient reconstruction of tracks in the Pixel and Semiconductor Tracker (SCT) detectors of the ATLAS experiment at LHC. It is designed to identify charged particle tracks with transverse momentum above 1 GeV and reconstruct their parameters at an event rate of up to 100 kHz. The average latency of the processing is below 100 μs at the expected collision intensities. This performance is achieved by using custom ASIC chips with associative memory for pattern matching, while modern FPGAs calculate the track parameters. This paper describes the architecture, the current status and a High-Level Data Quality Monitoring framework of the FTK system. This monitoring framework provides an online comparison of the FTK hardware output with the FTK functional simulation, which is run on the pixel and SCT detector data at a low rate, allowing the detection of non-expected outputs of the FTK system.

A compact, high resolution tracker for cosmic ray muon scattering tomography using semiconductor sensors

A semiconductor tracker for muon scattering tomography is presented. The tracker contains silicon strip sensors with an 80 μm pitch, precision mechanics and integrated cooling. The electronic readout of the sensors is performed by a scalable, inexpensive, flexible, FPGA-based system, which is demonstrated to achieve an event rate of 30 kHz. The tracker performance is compared with a Geant4 simulation. A scattering angle resolution compatible with 1.5 mrad at the 4 GeV average cosmic ray muon energy is demonstrated. Images of plastic, iron and lead samples are obtained using an Angle Statistics Reconstruction algorithm. The images demonstrate good contrast between low and high atomic number materials.

Alternative glues for the production of ATLAS silicon strip modules for the Phase-II upgrade of the ATLAS Inner Detector

The Phase-II upgrade of the ATLAS detector for the High Luminosity Large Hadron Collider (HL-LHC) includes the replacement of the current Inner Detector with an all-silicon tracker consisting of pixel and strip detectors. The current Phase-II detector layout requires the construction of 20,000 strip detector modules consisting of sensor, circuit boards and readout chips, which are connected mechanically using adhesives. The adhesive used initially between readout chips and circuit board is a silver epoxy glue as was used in the current ATLAS SemiConductor Tracker (SCT). However, this glue has several disadvantages, which motivated the search for an alternative. This paper presents a study of six ultra-violet (UV) cure glues and a glue pad for possible use in the assembly of silicon strip detector modules for the ATLAS upgrade. Trials were carried out to determine the ease of use, thermal conduction and shear strength. Samples were thermally cycled, radiation hardness and corrosion resistance were also determined. These investigations led to the exclusion of three UV cure glues as well as the glue pad. Three UV cure glues were found to be possible better alternatives than silver loaded glue. Results from electrical tests of first prototype modules constructed using these glues are presented.

Noise evaluation of silicon strip super-module with ABCN250 readout chips for the ATLAS detector upgrade at the High Luminosity LHC

Toward High Luminosity LHC (HL-LHC), the whole ATLAS inner tracker will be replaced, including the semiconductor tracker (SCT) which is the silicon micro strip detector for tracking charged particles. In development of the SCT, integration of the detector is the important issue. One of the concepts of integration is the “super-module” in which individual modules are assembled to produce the SCT ladder.A super-module prototype has been developed to demonstrate its functionality. One of the concerns in integrating the super-modules is the electrical coupling between each module, because it may increase intrinsic noise of the system. To investigate the electrical performance of the prototype, the new Data Acquisition (DAQ) system has been developed by using SEABAS. The electric performance of the super-module prototype, especially the input noise and random noise hit rate, was investigated by using SEABAS system.

Operation and performance of the ATLAS semiconductor tracker

The semiconductor tracker is a silicon microstrip detector forming part of the inner tracking system of the ATLAS experiment at the LHC. The operation and performance of the semiconductor tracker during the first years of LHC running are described. More than 99% of the detector modules were operational during this period, with an average intrinsic hit efficiency of (99.74±0.04)%. The evolution of the noise occupancy is discussed, and measurements of the Lorentz angle, δ-ray production and energy loss presented. The alignment of the detector is found to be stable at the few-micron level over long periods of time. Radiation damage measurements, which include the evolution of detector leakage currents, are found to be consistent with predictions and are used in the verification of radiation background simulations.

Performance and operation experience of the ATLAS SemiConductor Tracker

We report on the operation and performance of the ATLAS Semi-Conductor Tracker(SCT), which has been functioning for 3 years in a high luminosity,high radiation environment. The SCT is constructed of 4088 silicondetector modules, for a total of 6.3 million strips. Each moduleoperates as a stand-alone unit, mechanically, electrically, opticallyand thermally. The modules are mounted into two types of structures:one barrel, made of 4 cylinders, and two end-cap systems made of 9disks. The SCT silicon micro-strip sensors are processed in the planarp-in-n technology. The signals are processed in the front-end ABCD3TAASICs, which use a binary readout architecture. Data is transferredto the off-detector readout electronics via optical fibres. We find99.3% of the SCT modules are operational, the noise occupancy andhit efficiency exceed the design specifications; the alignment is veryclose to the ideal to allow on-line track reconstruction and invariantmass determination. We will report on the operation and performance ofthe detector including an overview of the issues encountered. Weobserve a significant increase in leakage currents from bulk damagedue to non-ionizing radiation and make comparisons with thepredictions. We will also cover the time evolution of the keyparameters of the strip tracker, including the evolution of noise andgain, the measurement of the Lorentz angle and the tracking efficiencyin the harsh LHC environment. Valuable lessons for future siliconstrip detector projects will be presented.

Performance and operation experience of the ATLAS Semiconductor Tracker

We report on the operation and performance of the ATLAS Semi-Conductor Tracker (SCT), which has been functioning for 3 years in the high luminosity, high radiation environment of the Large Hadron Collider at CERN. We also report on the few improvements of the SCT foreseen for the high energy run of the LHC. We find 99.3% of the SCT modules are operational, the noise occupancy and hit efficiency exceed the design specifications; the alignment is very close to the ideal to allow on-line track reconstruction and invariant mass determination. We will report on the operation and performance of the detector including an overview of the issues encountered. We observe a significant increase in leakage currents from bulk damage due to non-ionizing radiation and make comparisons with the predictions.

Single event upset studies using the ATLAS SCT

Single Event Upsets (SEU) are expected to occur during high luminosity running of the ATLAS SemiConductor Tracker (SCT). The SEU cross sections were measured in pion beams with momenta in the range 200 to 465 MeV/c and proton test beams at 24 GeV/c but the extrapolation to LHC conditions is non-trivial because of the range of particle types and momenta. The SEUs studied occur in the p-i-n photodiode and the registers in the ABCD chip. Other possible locations for SEU were not investigated in this study. Comparisons between predicted SEU rates and those measured from ATLAS data are presented. The implications for ATLAS operation are discussed.

ATLAS silicon microstrip tracker operation and performance

The Semi-Conductor Tracker (SCT) is one of the key precision tracking devices in the ATLAS experiment at CERN Large Hadron Collider (LHC). The SCT was constructed of 4088 modules for a total of 6.3 million silicon strips and was installed into the ATLAS experiment in 2007. The SCT has been fully operational since then, and achieves a good tracking performance from the startup of the LHC operation.

ATLAS silicon microstrip tracker operation and performance

The Semi-Conductor Tracker (SCT) is a silicon strip detector and one of the key precision tracking devices of the Inner Detector of the ATLAS experiment at CERN LHC. The SCT is constructed of 4088 silicon detector modules for a total of 6.3million channels. Each module is designed, constructed and tested to operate as a stand-alone unit, mechanically, electrically, optically and thermally. The modules are mounted into two types of structures: one barrel (4 cylinders) and two end-cap systems (9 disks on each). The current results from the successful operation of the SCT Detector at the LHC and its status after three years of operation will be presented. The operation of the detector including an overview of the main issues encountered is reported. The main emphasis is given to the tracking performance of the SCT and the data quality during the >2 years of data taking of proton–proton collision data at 7TeV (and short periods of heavy ion collisions). The SCT has been fully operational throughout all data taking periods, delivering high quality tracking data.

ATLAS Silicon Microstrip Tracker operation and performance

The Semi-Conductor Tracker (SCT) is a silicon strip detector and oneof the key precision tracking devices in the Inner Detector (ID) of the ATLASexperiment at CERN LHC. SCT has been installed inside the ATLAS experimentalcavern since 2007 and has been operational ever since. Calibration data has beentaken regularly and analysed to determine the performance of the system.The current results from the successful operation of the SCT detector and itsstatus after three years of operation are presented. We report on the operationof the detector including an overview of recent system updates, issues weencountered and the observation of significant increases in leakage currents (asexpected) from bulk damage due to non-ionising radiation. The main emphasis isgiven to the tracking performance of the SCT and the data quality. The running experience can be used to extract valuable lessons for futuresilicon strip detector projects.

ATLAS silicon microstrip tracker operation and performance

The Semi-Conductor Tracker is a silicon microstrip detector at the heart of the ATLAS experiment at the CERN Large Hadron Collider. Together with the rest of the ATLAS Inner Detector it provides vital precision tracking information of charged particles. In this paper the performance and operational status of the Semi-Conductor Tracker in the last two years of ATLAS data taking are reviewed.

The COBRA double beta decay experiment

The COBRA experiment is searching for double beta decay using CdZnTe semiconductor detectors. The main focus is on the isotope 116Cd. In addition to pure energy measurements, pixelisation allows also for tracking capabilities. This kind of semiconductor tracker is unique in the field. The current status of the experiment is shown including the latest half-life limits.

The ATLAS semi-conductor tracker operation and performance

The Semi-Conductor Tracker (SCT) is a silicon strip detector and one of the key precision tracking devices in the Inner Detector of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The SCT was installed and commissioned within ATLAS in 2007, and has been used to exploit fully the physics potential of the LHC since the first proton–proton collisions at 7TeV were delivered in 2009. In this paper, its operational status throughout data taking up to the end of 2011 is presented, and its tracking performance is reviewed.

The ATLAS SemiConductor Tracker operation and performance

The ATLAS SemiConductor Tracker (SCT) is a key precision tracking detector in the ATLAS experiment at CERN's Large Hadron Collider.The SCT is composed of 4088 planar p-in-n silicon micro-strip detectors. The signals from the strips are processed in the front-end ABCD3TA ASICs, which operate in binary readout mode; data are transferred to the off-detector readout electronics via optical fibres.The SCT was completed in 2007. An extensive commissioning phasefollowed, during which calibration data were collected and analysed todetermine the noise performance of the system, and further performanceparameters of the detector were determined using cosmic ray data, bothwith and without magnetic field. After the commissioning phase, theSCT was ready for the first LHC proton-proton collisions in December2009.From the beginning of data taking, the completed SCT has been in verygood shape with more than 99% of its 6.3 million strips operational;the detector is well timed-in and the operational channels are 99.9%efficient in data acquisition. The noise occupancy and hit efficiencyare better than the design specifications. The detector geometry ismonitored continuously with a laser-based alignment system and isstable to the few-micron level; the alignment accuracy as determinedby tracks is near specification and improving as statisticsincrease. The sensor behaviour in the 2T solenoidal magnetic fieldhas been studied by measuring the Lorentz angle. Radiation damage inthe silicon is monitored by periodic measurements of the leakagecurrent; these measurements are in reasonable agreement withpredictions.

The ATLAS SCT grounding and shielding concept and implementation

This paper describes the design and implementation of the grounding and shielding system for the ATLAS SemiConductor Tracker (SCT). The mitigation of electromagnetic interference and noise pickup through power lines is the critical design goal as they have the potential to jeopardize the electrical performance. We accomplish this by adhering to the ATLAS grounding rules, by avoiding ground loops and isolating the different subdetectors. Noise sources are identified and design rules to protect the SCT against them are described. A rigorous implementation of the design was crucial to achieve the required performance. This paper highlights the location, connection and assembly of the different components that affect the grounding and shielding system: cables, filters, cooling pipes, shielding enclosure, power supplies and others. Special care is taken with the electrical properties of materials and joints. The monitoring of the grounding system during the installation period is also discussed. Finally, after connecting more than four thousand SCT modules to all of their services, electrical, mechanical and thermal within the wider ATLAS experimental environment, dedicated tests show that noise pickup is minimised.