High Energy Physics Detectors Research Articles

Reaching Beyond: Da Vià bringing people together [Women to Watch

As an expert in radiation detectors for high-energy physics and medical applications, Dr. Cinzia Da Vià has dedicated her career to understanding what our world is made of—and how that knowledge can best further humanity. The Italian physicist, who now splits time between Manchester, United Kingdom, and Long Island, New York, has been a leader in her field for decades, achieving work milestones such as codiscovering the “Lazarus effect”; forming the European Platform on Radiation Detectors and Imaging; driving the design of 3D detectors, which contributed to the study of the Higgs boson; and authoring a book.

Method for detector description transformation to Unity and application in BESIII

Detector and event visualization are essential parts of the software used in high-energy physics (HEP) experiments. Modern visualization techniques and multimedia production platforms such as Unity provide impressive display effects and professional extensions for visualization in HEP experiments. In this study, a method for automatic detector description transformation is presented, which can convert the complicated HEP detector geometry from GDML in offline software to 3D modeling in Unity. The method was successfully applied in the BESIII experiment and can be further developed into applications such as event displays, data monitoring, or virtual reality. It has great potential in detector design, offline software development, physics analysis, and outreach for next-generation HEP experiments as well as applications in nuclear techniques for the industry.

Silicon photonic devices for optical data readout in high-energy physics detectors

Silicon photonics is standing out as a potential technology for the development of radiation-tolerant optical transceivers. In this work, we report the preliminary electro-optical characterization of two radiation-hardened-by-design shallow-etched Mach–Zehnder modulators with different doping configurations.

A novel experimental approach to characterize neutron fields at high- and low-energy particle accelerators

The characterization of particle accelerator induced neutron fields is challenging but fundamental for research and industrial activities, including radiation protection, neutron metrology, developments of neutron detectors for nuclear and high-energy physics, decommissioning of nuclear facilities, and studies of neutron damage on materials and electronic components. This work reports on the study of a novel approach to the experimental characterization of neutron spectra at two complex accelerator environments, namely the CERF, a high-energy mixed reference field at CERN in Geneva, and the Bern medical cyclotron laboratory, a facility used for multi-disciplinary research activities, and for commercial radioisotope production for nuclear medicine. Measurements were performed through an innovative active neutron spectrometer called DIAMON, a device developed to provide in real time neutron energy spectra without the need of guess distributions. The intercomparison of DIAMON measurements with reference data, Monte Carlo simulations, and with the well-established neutron monitor Berthold LB 6411, has been found to be highly satisfactory in all conditions. It was demonstrated that DIAMON is an almost unique device able to characterize neutron fields induced by hadrons at 120 GeV/c as well as by protons at 18 MeV colliding with different materials. The accurate measurement of neutron spectra at medical cyclotrons during routine radionuclide production for nuclear medicine applications is of paramount importance for the facility decommissioning. The findings of this work are the basis for establishing a methodology for producing controlled proton-induced neutron beams with medical cyclotrons.

Characterization of radiation damages on Silicon photomultipliers by X-rays up to 100 kGy

Silicon photomultipliers (SiPMs) are highly-sensitive photodetectors emerging as the technology of choice for many applications, including among the others, large high-energy physics experiments and detectors for space instruments, where they are often exposed to a large amount of radiation. In recent years, there has been an increasing interest in assessing the performance deterioration of such detectors after ionizing and non-ionizing radiation, such as protons, neutrons and X or gamma rays. It is therefore interesting to characterize the effect of irradiation on such Geiger-mode detectors, differentiating between the ionizing and non-ionizing energy-loss effects. Moreover, it is interesting to compare the radiation damage effects on several types of SiPMs, to assess the main phenomena and the deterioration mechanisms, aiming to a more radiation tolerant SiPM design.In this work we irradiated several types of SiPM structures, produced in FBK (Trento, Italy), with 40 keV X-rays, at several doses, up to 100 kGy (in silicon), performing both online measurements (after each irradiation step) and offline functional characterization, after one month of room temperature annealing. The SiPMs are made with many different technologies, in particular different layouts, junction polarities, internal structures and starting materials. We studied the variation in the reverse current–voltage curves, distinguishing the effects on multiplied and not-multiplied current components, the primary dark count rate, the correlated noise probabilities and photon detection efficiency. Comparing all the measurement results, knowing the internal structure and the fabrication processes, we were able to extract and distinguish different deterioration mechanisms, also supported by TCAD simulations on the different effects of ionizing radiation inside the microcells.

Picosecond imaging at high spatial resolution using TOFPET2 AISC v2d and microchannel plate detector

Microchannel plate-based detectors provide advantages over their solid-state counterparts for applications where a combination of virtually zero noise photon-counting, large format, short wavelength sensitivity with high resolution timing and imaging are required. Solar-blind applications, Cherenkov detectors for high energy physics, and UV astronomy are such fields. The application to Cherenkov detection is particularly demanding, requiring time resolution below 100 picoseconds combined with imaging and high throughput. This requires the readout to combine high spatial and temporal event resolution at high rates necessitating a parallel readout approach. We describe a readout design comprising a pixellated readout array instrumented using multi-channel fast timing electronics and incorporating charge centroiding to achieve sub-pixel spatial resolution. We present experimental results of the relationship between time-over-threshold and signal amplitude and a centroiding image obtained with an MCP detector using a pixellated readout geometry. The readout was optimised for a fast electronics implementation based on the TOFPET system, a multi-channel all-in-one ASIC originally designed for time-of-flight PET using silicon photomultipliers.

Allpix2 — silicon detector Monte Carlo simulations for particle physics and beyond

Allpix2 is a versatile, open-source simulation framework for silicon pixel detectors. Its goal is to ease the implementation of detailed simulations for both single sensors and more complex setups with multiple detectors. While originally created for silicon detectors in high-energy physics, it is capable of simulating a wide range of detector types for various application scenarios, through its interface to Geant4 to describe the interaction of particles with matter, and the different algorithms for charge transport and digitization. The simulation chain is arranged with the help of intuitive configuration files and an extensible system of modules, which implement the individual simulation steps. Detailed electric field maps imported from TCAD simulations can be used to precisely model the drift behavior of the charge carriers, bringing a new level of realism to the Monte Carlo simulation of particle detectors.Recently, Allpix2 has seen major improvements to its core framework to take full advantage of multi- and many-core processor architectures for simulating events fully parallel. Furthermore, new physics models such as charge carrier recombination in silicon have been introduced, further extending the application range. This contribution provides an overview of the framework and its components, highlighting the versatility and recent developments.

Bias and priors in machine learning calibrations for high energy physics

Machine learning offers an exciting opportunity to improve the calibration of nearly all reconstructed objects in high-energy physics detectors. However, machine learning approaches often depend on the spectra of examples used during training, an issue known as prior dependence. This is an undesirable property of a calibration, which needs to be applicable in a variety of environments. The purpose of this paper is to explicitly highlight the prior dependence of some machine learning-based calibration strategies. We demonstrate how some recent proposals for both simulation-based and data-based calibrations inherit properties of the sample used for training, which can result in biases for downstream analyses. In the case of simulation-based calibration, we argue that our recently proposed Gaussian Ansatz approach can avoid some of the pitfalls of prior dependence, whereas prior-independent data-based calibration remains an open problem.

Upgrading the beam telescopes at the DESY II Test Beam Facility

The DESY II Test Beam Facility is a key infrastructure for modern high energy physics detector development, providing particles with a small momentum spread in a range from 1 to 6GeV to user groups e.g. from the LHC experiments and Belle II as well as generic detector R&D. Beam telescopes are provided in all three test beam areas as precise tracking reference without time stamping, with triggered readout and a readout time of > 115 μs . If the highest available rates are used, multiple particles are traversing the telescopes within one readout frame, thus creating ambiguities that cannot be resolved without additional timing layers. Several upgrades are currently investigated and tested: Firstly, a fast monolithic pixel sensor, the TelePix, to provide precise track timing and triggering on a region of interest is proposed to overcome this limitation. The TelePix is a 180nm HV-CMOS sensor that has been developed jointly by DESY, KIT and the University of Heidelberg and designed at KIT. In this publication, the performance evaluation is presented: The difference between two amplifier designs is evaluated. A high hit detection efficiency of above 99.9% combined with a time resolution of below 4ns at negligible pixel noise rates is determined. Finally, the digital hit output to provide region of interest triggering is evaluated and shows a short absolute delay with respect to a traditional trigger scintillator as well as an excellent time resolution. Secondly, a fast LGAD plane has been proposed to provide a time resolution of a few 10 ps, which is foreseen to drastically improve the timing performance of the telescope. Time resolutions of below 70 ps have been determined in collaboration with the University of California, Santa Barbara.

Recasting LHC searches for long-lived particles with MadAnalysis 5

We present an extension of the simplified fast detector simulator of MadAnalysis 5 – the SFS framework – with methods making it suitable for the treatment of long-lived particles of any kind. This allows users to make use of intuitive Python commands and straightforward C++ methods to introduce detector effects relevant for long-lived particles, and to implement selection cuts and plots related to their properties. In particular, the impact of the magnetic field inside a typical high-energy physics detector on the trajectories of any charged object can now be easily simulated. As an illustration of the capabilities of this new development, we implement three existing LHC analyses dedicated to long-lived objects, namely a CMS run 2 search for displaced leptons in the emu channel (CMS-EXO-16-022), the full run 2 CMS search for disappearing track signatures (CMS-EXO-19-010), and the partial run 2 ATLAS search for displaced vertices featuring a pair of oppositely charged leptons (ATLAS-SUSY-2017-04). We document the careful validation of all MadAnalysis 5 SFS implementations of these analyses, which are publicly available as entries in the MadAnalysis 5 Public Analysis Database and its associated dataverse.

MiniCACTUS: Sub-100 ps timing with depleted MAPS

MiniCACTUS is a monolithic CMOS sensor demonstrator designed for time tagging individual Minimum Ionizing Particles with an accuracy better than 100ps. The sensor features an active array of 2 × 4 pixels surrounded by guard-rings used to bias the high-resistivity substrate, an analog and digital front-end per pixel, a slow control interface and internal programmable biases through DACs. The baseline pixel sizes are 1.0mm2 and 0.5mm2. The sensing element is a deep n-well/p-substrate diode without internal amplification. The analog front-ends and the discriminators for each pixel have been implemented outside the pixel, at the column level. After fabrication, the sensors have been thinned to 200µm and 100µm and then post-processed for backside biasing. As such, this sensor is a demonstrator chip for future large scale timing detectors, like upgrades of timing detectors at LHC, or future high energy physics detector projects. Measurements of noise, response to X and γ-rays are presented, as well as time resolution measurements using β decays from 90Sr. Some preliminary results from a test-beam campaign are also mentioned.

Progress in 3D Silicon Radiation Detectors

In the past few years, there has been an increasing interest toward 3D silicon radiation detectors. Owing to their unique architecture, 3D detectors provide a remarkable radiation hardness at relatively low bias voltage (hence low power dissipation), that makes them the most appealing solution for use in the innermost layers of tracking detectors in High Energy Physics (HEP) experiments. Besides this primary application, the use of 3D sensor technology has been extended also to other fields, like thermal neutron detection and microdosimetry for proton and ion therapy. In this paper, we will review the state of the art and on going efforts in 3D detectors, covering the main design and technological issues, as well as selected results from the experimental characterization and TCAD simulation.

Spectral Response of UV Photodetectors for Barium Fluoride Crystal Readout

Because of its fast scintillation peaked at 220 nm with a decay time of less than 0.6 ns, barium fluoride crystals have attracted broad interest in the community pursuing ultrafast detectors for future high energy physics (HEP) experiments and GHz hard X-ray imaging for future X-ray free-electron laser (XFEL) facilities. A crucial issue for its application is the spectral response of photodetectors down to vacuum ultraviolet (VUV). In this article, we compare quantum efficiency (QE) and photon detection efficiency (PDE) spectra measured for several ultraviolet (UV) photodetectors down to 200 nm. Their figures of merit on the detection efficiency for the fast component and the suppression of the slow component are also discussed.

(Gd,Ce)2O3-Al2O3-SiO2 scintillation glass

Heavy scintillation glass of Gd2O3-Al2O3-SiO2 composition doped with Ce, combining high light yield and fast scintillation kinetics, was developed. The glass samples were prepared at 1500 °C by a melt-quench technique; the resulting glass was colorless and satisfactorily homogeneous. A photoluminescence study showed that a variety of sites for the Ce3+ ion stabilization exists in the glass, but the phenomenon was found less pronounced compared to BaO-Gd2O3-SiO2 glass. The glass has demonstrated ∼4 times faster scintillation kinetics and a minor drop of the light yield related to barium-gadolinium-silica glass, which makes this material of particular interest for large volume detectors in high energy physics, medical imaging, and other applications due to a low-cost production capability.

First steps towards interlocking modular microfluidic cooling substrates (i-MμCS) for future silicon tracking detectors in High Energy Physics (HEP)

In future High Energy Physics detectors, the coverage of large surfaces with silicon pixel chip sensors poses a challenge for the sensors positioning, for their cooling, assembly, and interconnection. The use of a cooling substrate on which the sensors are glued is typically limited by the bulky and complicated hydraulic interconnection between adjacent substrates. In this research, a new type of cooling substrate is presented. Its design is based on microchannels, where additive manufacturing of plastic and ceramic materials has been considered an alternative to the current silicon etching process. A solution to the mechanical and hydraulic interconnection problem is achieved through a modular interlocking concept. Design optimisation was followed having identified three relevant parameters, plug-and-ply, interchangeability and sealing performance, which qualify the substrates interconnection and guaranty their correct positioning. This paper poses the bases to a new substrate category where modularity, re-workability and easy connectivity are the strong points. This concept could find applications also outside High Energy Physics experiments such as hardware cloud computing and medical detectors.

Impact of X-ray induced radiation damage on FD-MAPS of the ARCADIA project

Recent advancements in Monolithic Active Pixel Sensors (MAPS) demonstrated the ability to operate in high radiation environments of up to multiple kGy’s, which increased their appeal as sensors for high-energy physics detectors. The most recent example in such application is the new ALICE inner tracking system, entirely instrumented with CMOS MAPS, that covers an area of about 10 m2. However, the full potential of such devices has not yet been fully exploited, especially in respect of the size of the active area, power consumption, and timing capabilities.The ARCADIA project is developing Fully Depleted (FD) MAPS with an innovative sensor design, that uses a proprietary processing of the backside to improve the charge collection efficiency and timing over a wide range of operational and environmental conditions. The innovative sensor design targets very low power consumption, of the order of 20 mW cm−2 at 100 MHz cm−2 hit flux, to enable air-cooled operations of the sensors. Another key design parameter is the ability to further reduce the power regime of the sensor, down to 5 mW cm−2 or better, for low hit rates like e.g. expected in space experiments. In this contribution, we present a comparison between the detector characteristics predicted with Technology Computer Aided Design (TCAD) simulations and the ones measured experimentally. The comparison focuses on the current-voltage (IV) and capacitance-voltage (CV) characteristics, as well as noise estimated from in-pixel capacitances of passive/active pixel matrices. In view of the targeted applications of this technology, an emphasis is set on the modeling of X-ray induced radiation damage at the Si-SiO2 interface and the impact on the in-pixel sensor capacitance. The so-called new Perugia model has been used in the simulations to predict the sensor performance after total ionizing doses of up to 10 Mrad.

Timing Performance Simulation for 3D 4H-SiC Detector.

To meet the high radiation challenge for detectors in future high-energy physics, a novel 3D 4H-SiC detector was investigated. Three-dimensional 4H-SiC detectors could potentially operate in a harsh radiation and room-temperature environment because of its high thermal conductivity and high atomic displacement threshold energy. Its 3D structure, which decouples the thickness and the distance between electrodes, further improves the timing performance and the radiation hardness of the detector. We developed a simulation software—RASER (RAdiation SEmiconductoR)—to simulate the time resolution of planar and 3D 4H-SiC detectors with different parameters and structures, and the reliability of the software was verified by comparing the simulated and measured time-resolution results of the same detector. The rough time resolution of the 3D 4H-SiC detector was estimated, and the simulation parameters could be used as guideline to 3D 4H-SiC detector design and optimization.

A massively scalable Time-to-Digital Converter with a PLL-free calibration system in a commercial 130 nm process

A 33.6 ps LSB Time-to-Digital converter was designed in 130 nm BiCMOS technology. The core of the converter is a differential 9-stage ring oscillator, based on a multi-path architecture. A novel version of this design is proposed, along with an analytical model of linearity. The model allowed us to understand the source of the performance superiority (in terms of linearity) of our design and to predict further improvements. The oscillator is integrated in a event-by-event self-calibration system that allows avoiding any PLL-based synchronization. For this reason and for the compactness and simplicity of the architecture, the proposed TDC is suitable for applications in which a large number of converters and a massive parallelization are required such as High-Energy Physics and medical imaging detector systems. A test chip for the TDC has been fabricated and tested. The TDC shows a DNL≤1.3 LSB, an INL≤2 LSB and a single-shot precision of 19.5 ps (0.58 LSB). The chip dissipates a power of 5.4 mW overall.

Hardware Implementation Study of Particle Tracking Algorithm on FPGAs

In recent years, the technological node used to implement FPGA devices has led to very high performance in terms of computational capacity and in some applications these can be much more efficient than CPUs or other programmable devices. The clock managers and the enormous versatility of communication technology through digital transceivers place FPGAs in a prime position for many applications. For example, from real-time medical image analysis to high energy physics particle trajectory recognition, where computation time can be crucial, the benefits of using frontier FPGA capabilities are even more relevant. This paper shows an example of FPGA hardware implementation, via a firmware design, of a complex analytical algorithm: The Hough transform. This is a mathematical spatial transformation used here to facilitate on-the-fly recognition of the trajectories of ionising particles as they pass through the so-called tracker apparatus within high-energy physics detectors. This is a general study to demonstrate that this technique is not only implementable via software-based systems, but can also be exploited using consumer hardware devices. In this context the latter are known as hardware accelerators. In this article in particular, the Xilinx UltraScale+ FPGA is investigated as it belongs to one of the frontier family devices on the market. These FPGAs make it possible to reach high-speed clock frequencies at the expense of acceptable energy consumption thanks to the 14 nm technological node used by the vendor. These devices feature a huge number of gates, high-bandwidth memories, transceivers and other high-performance electronics in a single chip, enabling the design of large, complex and scalable architectures. In particular the Xilinx Alveo U250 has been investigated. A target frequency of 250 MHz and a total latency of 30 clock periods have been achieved using only the 17 ÷ 53% of LUTs, the 8 ÷ 12% of DSPs, the 1 ÷ 3% of Block Rams and a Flip Flop occupancy range of 9 ÷ 28%.

Micro-pattern gaseous detectors in high-energy and astroparticle physics

Introduced in the late 70s of the last century, a new generation of position-sensitive sensors named micro-pattern gaseous detectors (MPGDs) allows to detect and localize ionizing radiation with sub-mm accuracy and high-rate capability. Performing and reliable, MPGDs are gradually replacing detection systems based on multiwire proportional chambers, and find applications in particle physics, astrophysics, plasma diagnostics and other fields.