Future High Energy Physics Research Articles

Calorimeters for Precision Timing Measurements in High Energy Physics

Current and future high energy physics particle colliders are capable to provide instantaneous luminosities of 1034 cm-2s-1 and above. The high center of mass energy, the large number of simultaneous collision of beam particles in the experiments and the very high repetition rates of the collision events pose huge challenges. They result in extremely high particle fluxes, causing very high occupancies in the particle physics detectors operating at these machines. To reconstruct the physics events, the detectors have to make as much information as possible available on the final state particles. We discuss how timing information with a precision of around 10 ps and below can aid the reconstruction of the physics events under such challenging conditions. High energy photons play a crucial role in this context. About one third of the particle flux originating from high energy hadron collisions is detected as photons, stemming from the decays of neutral mesons. In addition, many key physics signatures under study are identified by high energy photons in the final state. They pose a particular challenge in that they can only be detected once they convert in the detector material. The particular challenge in measuring the time of arrival of a high energy photon lies in the stochastic component of the distance to the initial conversion and the size of the electromagnetic shower. They extend spatially over distances which propagation times of the initial photon and the subsequent electromagnetic shower which are large compared to the desired precision. We present studies and measurements from test beams and a cosmic muon test stand for calorimeter based timing measurements to explore the ultimate timing precision achievable for high energy photons of 10 GeV and above. We put particular focus on techniques to measure the timing with a precision of about 10 ps in association with the energy of the photon. For calorimeters utilizing scintillating materials and light guiding components, the propagation speed of the scintillation light in the calorimeter is important. We present studies and measurements of the propagation speed on a range of detector geometries. Finally, possible applications of precision timing in future high energy physics experiments are discussed.

Future Prospects of di-jet Production Constraining Δg(x) at Low x in Polarized p + p Collisions at RHIC

One of the main objectives of the high-energy spin physics program at RHIC at BNL is the precise determination of the polarized gluon distribution function, Δg(x). Polarized [Formula: see text] collisions at [Formula: see text] GeV and at [Formula: see text] GeV at RHIC provide an unique way to probe the proton spin structure. Inclusive measurements, such as inclusive jet and hadron production, have so far been the prime focus of various results at [Formula: see text] GeV constraining Δg(x) for 0.05 < x < 0.2. A recent global analysis provides for the first time evidence of a non-zero value of the gluon polarization [Formula: see text]. First results of di-jet production at [Formula: see text] GeV by the STAR collaboration will allow a better constraint of the underlying event kinematics. Extending the current program to smaller values of x is a key goal for the future high-energy spin physics program at RHIC. Forward di-jet production measurements at STAR beyond the current acceptance from -1 < η < +2 to +2.5 < η < +4, in particular those carried out at [Formula: see text] GeV, provides access to low x values at the level of 10-3 where current uncertainties of Δg(x) remain very large. Those measurements will eventually be complemented by a future Electron-Ion Collider facility probing Δg(x) in polarized [Formula: see text] collisions.

The Associative Memory Serial Link Processor for the Fast TracKer (FTK) at ATLAS

The Fast TracKer (FTK) is an extremely powerful and very compact processing unit, essential for efficient Level 2 trigger selection in future high-energy physics experiments at the LHC. FTK employs Associative Memories (AM) to perform pattern recognition; input and output data are transmitted over serial links at 2 Gbit/s to reduce routing congestion at the board level.Prototypes of the AM chip and of the AM board have been manufactured and tested, in preparation of the imminent design of the final version.

Status and perspectives of pixel sensors based on 3D vertical integration

This paper reviews the most recent developments of 3D integration in the field of silicon pixel sensors and readout integrated circuits. This technology may address the needs of future high energy physics and photon science experiments by increasing the electronic functional density in small pixel readout cells and by stacking various device layers based on different technologies, each optimized for a different function. Current efforts are aimed at improving the performance of both hybrid pixel detectors and of CMOS sensors. The status of these activities is discussed here, taking into account experimental results on 3D devices developed in the frame of the 3D-IC consortium. The paper also provides an overview of the ideas that are being currently devised for novel 3D vertically integrated pixel sensors.

Response of Inorganic Scintillators to Neutrons of 3 and 15 MeV Energy

In the perspective of the development of future high energy physics experiments, homogeneous calorimeters based on inorganic scintillators can be considered for the detection of hadrons (e.g., calorimeter based on dual-readout technique). Although of high importance in the high energy physics framework as well as for homeland security applications, the response of these inorganic scintillators to neutrons has been only scarcely investigated. This paper presents results obtained using five common scintillating crystals (of size around 2×2×2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ), namely lead tungstate (PbWO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ), bismuth germanate (BGO), cerium fluoride (CeF ), Ce-doped lutetium-yttrium orthosilicate (LYSO:Ce) and lutetium aluminum garnet (LuAG:Ce) in a pulsed flux of almost mono-energetic (~3 MeV and ~15 MeV) neutrons provided by the Van de Graff accelerator SAMES of CEA Valduc. Energy spectra have been recorded, calibrated and compared with Geant4 simulations computed with different physics models. The neutron detection efficiency for these crystals has been estimated and compared with simulation.

Three-dimensional diamond detectors: Charge collection efficiency of graphitic electrodes

Implementation of 3D-architectures in diamond detectors promises to achieve unreached performances in the radiation-harsh environment of future high-energy physics experiments. This work reports on the collection efficiency under β-irradiation of graphitic 3D-electrodes, created by laser pulses in the domains of nanoseconds (ns-made-sensors) and femtoseconds (fs-made-sensors). Full collection is achieved with the fs-made-sensors, while a loss of 25%–30% is found for the ns-made-sensors. The peculiar behaviour of ns-made sensors has been explained by the presence of a nano-structured sp3-carbon layer around the graphitic electrodes, evidenced by micro-Raman imaging, by means of a numerical model of the charge transport near the electrodes.

A Study on Radiation Damage in PWO-II Crystals

We report in this paper an investigation on radiation hardness of 20 cm long PWO-II crystals produced at BTCP for the proposed PANDA experiment at FAIR. The optical and scintillation properties of PWO-II crystals, such as transmittance, light output and light response uniformity, were measured before and after γ-ray irradiations at different dose rates. PWO-II crystals are compared to PWO crystals used in the CMS experiment. Progresses are observed in the light output and the radiation hardness for PWO-II crystals. Its use for crystal calorimeters in future high energy physics experiments is discussed. To maintain crystal precision, a precision light monitoring system is mandatory to follow variations of crystal transparency in situ.

How Photonic Crystals Can Improve the Timing Resolution of Scintillators

Photonic crystals (PhCs) and quantum optics phenomena open interesting perspectives to enhance the light extraction from scintillating media with high refractive indices as demonstrated by our previous work. By doing so, they also influence the timing resolution of scintillators by improving the photostatistics. The present contribution will demonstrate that they are actually doing much more. Indeed, photonic crystals, if properly designed, allow the extraction of fast light propagation modes in the crystal with higher efficiency, therefore contributing to increasing the density of photons in the early phase of the light pulse. This is of particular interest to tag events at future high-energy physics colliders, such as CLIC, with a bunch-crossing rate of 2 GHz, as well as for a new generation of time-of-flight positron emission tomographs (TOFPET) aiming at a coincidence timing resolution of 100 ps FWHM. At this level of precision, good control of the light propagation modes is crucial if we consider that in a 2 × 2 × 20-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> LSO crystal, the time spread (peak to peak) of extracted photons can be as large as 400 ps considering simple light bouncing only. This paper presents a detailed analysis of the light propagation and extraction modes in a LSO crystal combining the LITRANI light ray tracing and the CAMFR PhC simulation codes. Ongoing measurement results are shown with an attempt to unfold the contribution from the improved photostatistics that result from the total enhanced light output on one side and from the improved contribution of fast propagation mode extraction on the other side. Some results are also shown on a new and more industrial process to produce PhCs by the use of nano-imprint technology.

Ultra-low-power radiation hard ADC for particle detector readout applications

Radiation hard analog to digital converter (ADC) has been designed for future high energy physics experiments. The ADC has been designed in a commercial 130 nm CMOS process and it achieves 12-bit resolution, 25 MS/s sampling speed, 15 mW power consumption and hardness to at least 1.8 Megarad(Si) of total ionizing dose (TID). 16 ADC channels will be placed on one packaged silicon chip. The readout of the Liquid Argon Calorimeter of the ATLAS detector in the planned High-Luminosity Large Hadron Collider is one possible application for this ADC.

Development, Design and Characterization of a Novel Protocol and Interfaces for the Control and Readout of Front-End Electronics in High Energy Physics Experiments

The new FF-LYNX communication protocol, aiming at the fulfillment of non-homogeneous latency and bandwidth requirements of future High Energy Physics experiments, as well as its implementation into IP Cores available for ASICs development, are described in this paper. The first test-chip implementing FF-LYNX IP-Cores has been designed in the IBM 130 nm CMOS technology, adopting radiation hardening techniques. Transmitter and Receiver interfaces, designed in three different speed options, 4 × F, 8 × F and 16 × F (F=reference clock frequency), as well as different rad-hard FIFOs, constitute the overall architecture of the testchip. A detailed analysis of the area, power consumption and speed has been performed besides the functional characterization, by means of a configurable test-bed. X-ray irradiation tests have been carried out at CERN facilities to verify the Total Ionization Dose hardness of the interfaces, with their full functionality up to 40 Mrad(SiO2).

Quality of Long LSO/LYSO Crystals

Because of their high stopping power (X0 = 1.14 cm) and fast (t = 40 ns) and bright (4 times of BGO) scintillation cerium doped silicate based heavy crystal scintillators (LSO and LYSO) have attracted a broad interest in the high energy physics community pursuing precision electromagnetic calorimeter for future high energy physics experiments. Their excellent radiation hardness against γ-rays, neutrons and charged hadrons also makes them a preferred material for calorimeters to be operated in a severe radiation environment, such as the HL-LHC. The optical and scintillation properties and its radiation hardness against γ-ray irradiations up to 1 Mrad are presented for the first 2.5 × 2.5 × 28 cm LYSO sample. An absorption band was found at the seed end of this sample and three other long samples, which was traced back to a bad seed crystal used in the corresponding crystal growth process. Significant progresses in optical and scintillation properties were achieved for large size LYSO crystals after eliminating this absorption band. Their application in future HEP experiments at HL-LHC are discussed.

A Study on Radiation Damage in BGO and PWO-II Crystals

We report in this paper an investigation on radiation damage in 20 cm long BGO crystals produced at SIC as well as 20 cm long PWO-II crystals produced at BTCP for the proposed Panda experiment at GSI. The optical and scintillation properties of BGO and PWO-II crystals, such as transmittance, light output and light response uniformity, were measured before and after γ-ray irradiations at different dose rates. BGO crystals produced recently are compared to crystals used in the L3 experiment at LEP which was produced in early eighties. PWO-II crystals are compared to crystals used in the CMS experiment. Progresses are observed in the radiation hardness for both crystals. Their use for crystal calorimeters in future high energy physics experiments is discussed. To maintain crystal precision, a precision light monitoring system is mandatory to trace variations of crystal transparency in situ for a BGO or PWO crystal calorimeter in radiation environment.

A Roadmap For Geant4

The Geant4 simulation toolkit is now in the 14th year of its production phase. Geant4 is the choice of most current and near future high energy physics experiments as their simulation engine, and it is also widely used in astrophysics, space engineering, medicine and industrial application domains. Geant4 is a “living” code under continuous development; improvement of physics quality and computational speed is still a priority for Geant4. It is evolving and being enriched with new functionalities. On the other hand, the simulation paradigm that prevailed during the foundation of Geant4 is now being rethought because of new technologies in both computer hardware and software. The Geant4 Collaboration has identified many options and possibilities. Geant4 has accommodated some of these by providing a multi-threading prototype based on event-level parallelism. In this article we discuss the past, present and future of the Geant4 toolkit.

Quality of a 28 cm Long LYSO Crystal and Progress on Optical and Scintillation Properties

Because of their high stopping power and fast and bright scintillation, cerium doped LSO and LYSO crystals have attracted a broad interest in the physics community pursuing precision electromagnetic calorimeter for future high energy physics experiments. Their excellent radiation hardness against γ -rays, neutrons and charged hadrons also makes them a preferred material for calorimeters to be operated in a severe radiation environment, such as the HL-LHC. An effort was made at SIPAT to grow 25 X <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (28 cm) long LYSO crystals for high energy physics applications. In this paper, the optical and scintillation properties and its radiation hardness against γ -ray irradiations up to 1 Mrad are presented for the first 2.5×2.5×28 cm LYSO sample. An absorption band was found at the seed end of this sample and three other long samples, which was traced back to a bad seed crystal used in the corresponding crystal growth process. Significant progresses in optical and scintillation properties were achieved for large size LYSO crystals after eliminating this absorption band.

Acceleration in the linear non-scaling fixed-field alternating-gradient accelerator EMMA

In a fixed-field alternating-gradient (FFAG) accelerator, eliminating pulsed magnet operation permits rapid acceleration to synchrotron energies, but with a much higher beam-pulse repetition rate. Conceived in the 1950s, FFAGs are enjoying renewed interest, fuelled by the need to rapidly accelerate unstable muons for future high-energy physics colliders. Until now a ‘scaling’ principle has been applied to avoid beam blow-up and loss. Removing this restriction produces a new breed of FFAG, a non-scaling variant, allowing powerful advances in machine characteristics. We report on the first non-scaling FFAG, in which orbits are compacted to within 10 mm in radius over an electron momentum range of 12–18 MeV/c. In this strictly linear-gradient FFAG, unstable beam regions are crossed, but acceleration via a novel serpentine channel is so rapid that no significant beam disruption is observed. This result has significant implications for future particle accelerators, particularly muon and high-intensity proton accelerators.

Characterization of a commercial 65 nm CMOS technology for SLHC applications

The radiation characteristics with respect to Total Ionizing Dose (TID) and Single-Event Upsets (SEUs) of a 65 nm CMOS technology have been investigated. Single transistor structures of a variety of dimensions and several basic circuits were designed and fabricated. The circuits include a 64-kbit shift-register, a 56-kbit SRAM and a ring-oscillator. The test chips were irradiated up to 200 Mrad with an X-ray beam and the corresponding transistor threshold shifts and leakage currents were measured. Heavy-ion beam irradiation was performed to assess the SEU sensitivity of the digital parts. Overall, our results give the confidence that the chosen 65 nm CMOS technology can be used in future High Energy Physics (HEP) experiments even without Hardness-By-Design (HBD) solutions, provided that constant monitoring of the TID response is carried out during the full manufacturing phase of the circuits.

A Gigabit Transceiver for Data Transmission in Future High Energy Physics Experiments

The transmission of data from detectors in future high energy experiments will be driven by a number of requirements. In many cases, raw bandwidth is the strongest of these but other needs such as diverse functionality, compactness, low power and radiation resistance are equally important. The GigaBit-Transceiver project has been launched to provide a solution to these problems. The aim is to deliver a chip-set to build a bidirectional optical link transmitting and receiving serial data at 4.8 Gigabit/s. The project is based on three integrated circuits; a trans-impedance amplifier to receive signals from a photo-diode, a laser driver, and a transceiver containing a high-speed serialiser and de-serialiser. All of these have been successfully prototyped, and this paper will focus on the design and results from the serialiser/deserialiser prototype. This has been designed in commercial 130 nm CMOS with particular emphasis on enhancing its immunity to single-event-effects. The specific design features to achieve this will be described. The chip has been fully characterized in the lab, and jitter and bit-error-rate measurements are presented. The custom packaging of the chip will also be described together with the next steps foreseen in the project.

Characterisation of Glasgow/CNM Double-Sided 3D Sensors

3D detectors are proposed as an alternative to planar silicon technology to withstand the high radiation environments in planned future high energy physics experiments. Here we review the characterization of double-sided 3D detectors designed and built at CNM and the University of Glasgow. A non-irradiated sensor is characterized in a pion test-beamutilizing the Timepix telescope. The charge collection and detection efficiency across the unit pixel are shown. Area of inefficiency can be found at the columnar electrodes at perpendicular angles of beam incidence while the pixels are shown to be fully efficient at angles greater than ten degrees. A reduction in charge sharing compared to the planar technology is also demonstrated. Charge collection studies on irradiated devices with a Sr-90 source show higher charge collection efficiency for 3D over planar sensors at significantly lower applied bias. The sub-pixel response is probed by a micro-focused laser beam demonstrating areas of charge multiplication at high bias voltages.

Characterisation of micro-strip and pixel silicon detectors before and after hadron irradiation

The use of segmented silicon detectors for tracking and vertexing in particle physics has grown substantially since their introduction in 1980. It is now anticipated that roughly 50,000 six inch wafers of high resistivity silicon will need to be processed into sensors to be deployed in the upgraded experiments in the future high luminosity LHC (HL-LHC) at CERN. These detectors will also face an extremely severe radiation environment, varying with distance from the interaction point. The volume of required sensors is large and their delivery is required during a relatively short time, demanding a high throughput from the chosen suppliers. The current situation internationally, in this highly specialist market, means that security of supply for large orders can therefore be an issue and bringing additional potential vendors into the field can only be an advantage. Semiconductor companies that could include planar sensors suitable for particle physics in their product lines will, however, need to prove their products meet all the stringent technical requirements. A semiconductor company with very widespread experience of producing science grade CCDs (including deep depletion devices) has adapted their CCD process to fabricate for the first time several wafers of pixel and micro-strip radiation hard sensors, suitable for future high energy physics experiments. The results of the pre-irradiation characterization of devices fabricated with different processing parameters and the measurements of charge collection properties after different hadron irradiation doses up to those anticipated for the (larger area) outer pixel layers at the high-luminosity LHC (HL-LHC) are presented and compared with results from more established particle physics suppliers.

Architectural modeling of pixel readout chips Velopix and Timepix3

We examine two digital architectures for front end pixel readout chips, Velopix and Timepix3. These readout chips are developed for tracking detectors in future high energy physics experiments. They must incorporate local intelligence in pixels for time-over-threshold measurement and sparse readout. In addition, Velopix must be immune to single-event upsets in its digital logic.The most important requirements for both chips are pixel size, timing resolution, low power and high-speed sparse readout. We describe the transaction level architectural models of the chips using SystemVerilog. The correctness of the models is ensured using Open Verification Methodology. We will also discuss the advantages gained from transaction level modeling.