High Rate Environment Research Articles

Pure CsI electromagnetic calorimeter design for the Super Tau-Charm Facility

The Super Tau-Charm Facility (STCF) is a high-luminosity electron-positron collider proposed in China. It will operate in the energy region of 2–7 GeV with a peak luminosity of at least 0.5×1035 cm−2 s−1, providing an excellent platform for studying the tau-charm physics. The STCF detector includes an electromagnetic calorimeter (EMC), which plays a crucial role in the accurate measurement of photon energy. To address the challenge of achieving superior photon energy resolution in the high-rate environment caused by the high luminosity, a fast-response EMC based on pure CsI crystals is proposed for the STCF experiment. In this paper, we present the conceptual design of a pure CsI EMC for STCF. The light yield of a pure CsI unit designed for the STCF EMC was measured using cosmic rays. Without considering the mechanical structures of the EMC and the sub-detectors in front of the EMC, the performance of the pure CsI based EMC was studied through Geant4 simulations incorporating the measured light yield, and the EMC design was optimized based on the results. The simulation was carried out under the condition of 100 p.e./MeV light yield and the high background environment anticipated in the STCF experiment. By employing a waveform fitting method, an energy resolution of better than 2.5% for 1 GeV photons was achieved, which satisfies the major performance requirement for the STCF EMC. However, validation studies should be conducted, including the contribution of different types of experimental backgrounds and the accuracy of the background counting rate.

Performance of a fast timing micro-pattern gaseous detector for future collider experiments

The fast timing MPGD is a micro-pattern gaseous detector conceived for achieving sub-nanosecond time resolution while maintaining the ability to instrument large areas in high-rate environments; applications of such technology are perspected in high-energy physics experiments at future colliders and medical diagnostics with time-of-flight methods. This work shows the systematic studies carried on an FTM prototype on the performance of GEM foils coated with resistive DLC films, whose development is essential for the FTM operation. The resistive foil performance has been tested with several gas mixtures and compared with the results obtained on conductive foils. The results show that the performance of the FTM is presently limited by the technology of manufacturing of DLC-coated GEM foils, with high gains reachable exclusively in isobuthane-based mixtures.

Floating Rate Notes in High Rate Environment and the Stock Market Response

Previous study finds that the firms with inferior growth options tend to issue callable bonds. Typically, these firms are characterized by stock underperformance. Previous study also finds that the floating rate as a superior alternative to the call provision, which is restrictive, when the interest rates are likely to fall. We study the long-term stock performance of floating rate notes (FRNs) issuing firms, issued when the interest rates are high. Stock overperformance would suggest floating rate as a preferred choice by the firms with high growth options rather the call option. We find that the FRNs are generally investment grade with extremely rare presence of a call option. We perform the analysis using Buy and hold abnormal return (BHAR) as the proxy for the long-term stock overperformance/underperformance. A sample of floating rate notes issued (1654) from 1992 to 2007, a period of high interest rates, reveals significant overperformance by the floating rate notes issuing firms in the high-rate paradigm. High growth firms, in the high-rate environment, significantly benefit from the floating rate provision which is less restrictive and less costly than the call option, which typically provides call protection period and pays a call premium. Floating rate provision better mitigates the interest rate risk for the firms in the high-rate environment. We find that the smaller, high growth, higher leverage, less profitable firms with greater agency issues benefit more from issuing FRNs in the high-rate environment. Our study has relevance to the stock portfolio construction and performance. We also perform a comparative analysis using the sample of floating rate notes issued (270) during 2008 to 2018, a period of low interest rates, and find stock underperformance. The implications are that the call option likely is a better choice for the firm since the firm preserves the right to forego exercising the option.

Pixelated resistive Micromegas detector for high-rate environment

The R&D work reported in this paper has been devoted to the production and test of pixelated resistive micromegas detectors able to track particles in a high-rate environment, up to 10 MHz/cm2, keeping a stable gain and a good spatial resolution. To pursue our goal, we had to reduce the occupancy by increasing the detector granularity and this has been done by changing the read-out anodes from the usual strips to pads. This minor change in the electrodes layout drastically increased the difficulty of implementing a resistive structure to protect the anodes from sparking. We present the results of the tests performed on four prototypes, with different protection schemes, showing it is possible to reach the desired rate with high gain, high efficiency and good position resolution. The response to X-rays from low (55Fe source) to high (X-rays generator) rates, as well as to beams of ionizing particles is reported.

Performance of photosensors in a high-rate environment for gas Cherenkov detectors

The solenoidal large intensity device (SoLID) at Jefferson Lab will push the boundaries of luminosity for a large-acceptance detector, which necessitates the use of a light-gas threshold Cherenkov counter for online event selection. Due to the high luminosity, the single-photon background rate in this counter can exceed 160 kHz/cm2 at the photosensors. Therefore, it is essential to validate the high-rate limits of the planned photosensors and readout electronics in order to mitigate the risk of failure. We report on the design and an early set of studies carried out using a small Cherenkov counter in a high-rate environment up to 60 kHz/cm2, in Hall C at Jefferson Lab. Commercially available multi-anode photomultipliers (MaPMT) and low-cost large-area picosecond photodetectors (LAPPD) were tested using the JLab FADC250 modules for readout. The test beam results show that the MaPMT array and the internal stripline LAPPD can detect and identify single-electron and pair-production events in high-rate environments. Due to its higher quantum efficiency, the MaPMT array provided a better separation between the single-electron and the pair-production events compared to the internal stripline LAPPD. A GEANT4 simulation confirms the beam test performance of our counter device.

Characterization of mixed Bi4(Ge[formula omitted]Si[formula omitted])3O12 for crystal calorimetry at future colliders

Bismuth germanate (BGO) is a well known high density scintillating material widely used in many applications such as high energy physics and medical imaging. Bismuth silicate (BSO) features properties similar to BGO in terms of stopping power and Cherenkov photon yield with a lower scintillation light output but faster decay time, thus being more attractive for applications in high-rate environments. Mixed crystals such as Bi4(GexSi1−x)3O12 (BGSO, with x varying from 0 to 1) make it possible to optimize decay time and light yield based on the detector needs.A characterization campaign of the optical and scintillation properties of two sets of BGSO mixed crystals with Ge fraction varying from 0 to 100% was performed. A coincidence time resolution (CTR) at 511 keV of 208 ±2 ps FWHM was measured for a 2 × 2 × 3 mm3 pixel with 40% Ge, while the optimum value obtained for the effective decay time is 49.9 ±1.8 ns for a 6 × 6 × 0.7 mm3 plate-shaped sample with 30% Ge. Furthermore the smallest slow decay time component achieved is 101 ±2 ns and is obtained for the plate-shaped sample with 30% Ge, while the largest is 236 ±5 ns for a pure BGO sample with the same geometry.In addition we demonstrated the possibility to efficiently separate the Cherenkov and scintillation light produced in a pure BSO sample. Such a technique could be exploited in a crystal-based dual-readout calorimeter to improve the energy resolution for hadronic showers and jets.

Development and performance of a fast timing micro-pattern gaseous detector (FTM) for future collider experiments and medical diagnostics

The fast timing MPGD is a micro-pattern gaseous detector conceived for achieving sub-nanosecond time resolution while maintaining the ability to instrument large areas in high-rate environments; applications of such technology are perspected in high-energy physics experiments at future colliders and medical diagnostics with time-of-flight methods. The work presented is a set of systematic studies carried on an FTM prototype on the performance of GEM foils coated with resistive DLC films, whose development is essential for the FTM operation. The resistive foil performance has been tested with several gas mixtures and compared with the results obtained on conductive foils. The results show that the performance of the FTM is presently limited by the technology of manufacturing of DLC-coated GEM foils, with high gains reachable exclusively in isobutane-based mixtures.

CsI calorimeter for the J-PARC KOTO experiment

An electromagnetic calorimeter made of undoped CsI crystals is used in the J-PARC KOTO experiment to search for new physics beyond the standard model with the KL→π0νν̄ decay. The calorimeter is designed to operate in vacuum of 0.1 Pa and in a high-rate environment where the counting rate due to KL decays is O(100) kHz. A special method to calibrate the calorimeter during the data taking without using a tracking system for charged particles is reported. The energy, position, and timing resolutions of the calorimeter were evaluated in several beam tests, and the resolutions satisfy the required performance. The energy resolution with the total energy E is 0.66⊕1.81∕E[GeV]% in the inner region of the calorimeter.

Influence of hole geometry on gas gain in GEM detectors

Gas electron multipliers (GEMs) belong to the most modern and advanced technologies in the field of gaseous detectors. Detectors, based on the GEM technology, enjoy great popularity in various fields of physics. Especially in the field of high-energy physics, GEMs are well-appreciated thanks to their flexibility in geometry, resistance to aging and excellent performance in high-rate environments. The core of the detector consists of thin foils with an etched pattern of holes. The detection principle relies on electron multiplication inside the holes, where a high electric field is present. New etching techniques have been used for the production of large-size (0.3 m2 - 0.4 m2) GEM foils needed for high-energy physics experiments. The new techniques result in different hole geometries. To better understand the gas gain dependence on the hole geometry, several measurements have been performed with a triple-GEM detector, and have been complemented by GARFIELD++ simulations. The results are compared with other recent studies.

Aging studies of Triple-GEM detectors for future upgrades of the CMS endcap muon system at the HL-LHC

Concurrently with the high-luminosity LHC (HL-LHC) upgrade, the Compact Muon Solenoid (CMS) experiment is renovating some of its subsystems. In particular, in the muon spectrometer region, Triple-GEM detectors will be installed to cope with the high-rate environment and to maintain the actual performance of the detector. In this work we summarize the aging tests performed to validate the Triple-GEM technology for the CMS purpose. Furthermore the tests and results completed to amplify the knowledge of the aging issue in Triple-GEMs and gaseous detectors in general are presented, with some hint for future test to perform.

FPGA Implementation of SPI Bus Communication Based on State Machine Method

The SPI bus is a synchronous serial interface data bus with full duplex, few signal lines, simple protocol, and fast transmission speed. Based on these characteristics, parallel high-speed computing with FPGA is used to meet device expansion and experiment in high-rate environments. This paper introduces the structure and working principle of SPI communication bus, analyzes its timing structure and four working modes, and uses this state machine method to realize its SPI bus communication function on FPGA. The module circuit of SPI is written by Verilog hardware description language, and the waveform is simulated in vivado simulator. After the simulation waveform analysis, the feasibility of the state machine method is verified.

RPC detectors with semiconductive electrodes: efficiency and time resolution measurements

A new particle detector with sub-nanosecond time resolution capable of working in high-rate environment (rate capability of the order of MHz cm2) is under developmnet. Semi-conductive electrodes with resistivity ρ up to 108 Ωcm have been used to improve the RPC [1,2] rate capability. In this paper efficiency and time resolution of three different detector structures are presented.

The integrated low-level trigger and readout system of the CERN NA62 experiment

The integrated low-level trigger and data acquisition (TDAQ) system of the NA62 experiment at CERN is described. The requirements of a large and fast data reduction in a high-rate environment for a medium-scale, distributed ensemble of many different sub-detectors led to the concept of a fully digital integrated system with good scaling capabilities. The NA62 TDAQ system is rather unique in allowing full flexibility on this scale, allowing in principle any information available from the detector to be used for triggering. The design concept, implementation and performances from the first years of running are illustrated.

Fast Timing for High-Rate Environments with Micromegas

The current state of the art in fast timing resolution for existing experiments is of the order of 100 ps on the time of arrival of both charged particles and electromagnetic showers. Current R&D on charged particle timing is approaching the level of 10 ps but is not primarily directed at sustained performance at high rates and under high radiation (as would be needed for HL-LHC pileup mitigation). We demonstrate aMicromegas based solution to reach this level of performance. The Micromegas acts as a photomultiplier coupled to a Cerenkovradiator front window, which produces sufficient UV photons to convert the ∼100 ps single-photoelectron jitter into a timing response of the order of 10-20 ps per incident charged particle. A prototype has been built in order to demonstrate this performance. The first laboratory tests with a pico-second laser have shown a time resolution of the order of 27 ps for ∼50 primary photoelectrons, using a bulk Micromegas readout.

Design, construction and performance tests of a prototype micromegas chamber with two readout planes in a common gas volume

In this paper, the design and the performance of a prototype detector based on MicroMegas technology with two detection planes in a common gas volume is discussed. The detector is suited for the forward region of LHC detectors, addressing the high-rate environment and limited available space. Each detection plane has an active area of 9×9cm2 with a two-dimensional strip readout and is separated by a common gas region with a height of 14mm. A micro-mesh, working as a cathode, is placed in the middle of the common gas volume separating it into two individual cells. This setup allows for an angle reconstruction of incoming particles with a precision of ∼2mrad. Since this design reduces the impact of multiple scattering effects by the reduced material budget, possible applications for low energy beam experiments can be envisioned. The performance of the prototype detector has been tested with a 4.4GeV electron beam, provided by the test beam facility at DESY.

Upgrade of In-Beam Charged Particle Detector for the KOTO Experiment

The KOTO experiment aims at measuring the branching ratio of the decay. Since the decay is highly suppressed in the Standard Model, it is sensitive to new physics beyond the standard model. In the KOTO experiment, two photons from the π0 in the final state are detected by an electromagnetic calorimeter, and the absence of extra particles except for the escaping neutrinos is ensured by the surrounding veto counters. As one of the veto counters, an in-beam charged particle detector, composed of 3-mm thick plastic scintillators, covered the beam hole of the calorimeter. It was operating in a high-rate environment with a single counting rate of 10 MHz, which caused 10% loss to the signal. To reduce the hits by neutral particles, the detector has been upgraded to a thin-gap wire chamber. Keeping a high detection efficiency over 99.6% for penetrating charged particles, a 65% reduction of the single counting rate was achieved, corresponding to 40% recovery of acceptance for .

First large volume characterization of the QIE10/11 custom front-end integrated circuits

The CMS experiment at the CERN Large Hadron Collider (LHC) will upgrade the photon detection and readout systems of its barrel and endcap hadron calorimeters (HCAL) through the second long shutdown of the LHC in 2018. A central feature of this upgrade is the development of two new versions of the QIE (Charge Integrator and Encoder), a Fermilab-designed custom ASIC for measurement of charge from detectors in high-rate environments. These most recent additions to the QIE family feature 17-bits of dynamic range with 1% digitization precision for high charge and a time-to-digital converter (TDC) with half nanosecond resolution all with 16 bits of readout per bunch crossing. For the first time, the CMS experiment has produced and characterized in great detail a large volume of chips. The characteristics and performance of the new QIE and their related chip-to-chip variations as measured in a sample of 10,000 chips is described.

QIE10: a new front-end custom integrated circuit for high-rate experiments

We present results on a new version of the QIE (Charge Integrator and Encoder), a custom Application Specific Integrated Circuit (ASIC) designed at Fermilab. Developed specifically for the measurement of charge from photo-detectors in high-rate environments, this most recent addition to the QIE family features 3 fC sensitivity, 17-bits of dynamic range with logarithmic response, a Time-to-Digital Converter (TDC) with sub-nanosecond resolution, and internal charge injection. The device is capable of dead-timeless operation at 40 MHz, making it ideal for calorimetry at the Large hadron Collider (LHC). We present bench measurements and integration studies that characterize the performance, radiation tolerance measurements, and plans for deployment in the Atlas and CMS detectors as part of the Phase 1 and Phase 2 upgrades.

Pattern recognition in a high-rate GEM-TPC

A pattern recognition software for a continuously operating high-rate Time Projection Chamber with Gas Electron Multiplier amplification (GEM-TPC) has been designed and tested. Space points are delivered by a track-independent clustering algorithm. A true 3-dimensional track follower combines them to helical tracks, without constraints on the vertex position. Fast helix fits, based on a conformal mapping on the Riemann sphere, are the basis for deciding whether points belong to one track. To assess the performance of the algorithm in a high-rate environment, pp interactions at a rate of 2 × 107 s−1, the maximum rate foreseen for PANDA, have been simulated. The pattern recognition is capable of finding different kinds of track topologies with high efficiency and provides excellent seed values for track fitting or online event selection. The feasibility of event deconvolution has been demonstrated: Different techniques to retain the tracks from an event with known time from other tracks in the TPC are presented in this paper.

A digital method for separation and reconstruction of pile-up events in germanium detectors

The problem of pulse pile-up is very often encountered in precise measurements of γ-rays using germanium detectors. The standard method of treating the pile-up events is to identify and reject them using an appropriate electronic system. Digital acquisition techniques now allow the recording of waveforms of pile-up events that can be analyzed and the contributing single pulses recovered, rather than simply tolerating the losses associated with pile-up. In this paper, a method for the off-line digital processing of pile-up events from germanium detectors is demonstrated. The method is based on an appropriate fitting of the detector signals, shaped with a suitable digital pulse shaper. It is shown that the method is able to recover the pile-up events with good accuracy even when the constituent signals are in close proximity. The method is very useful for γ-ray spectroscopy in nuclear physics experiments, where the low intensity signals can be lost due to the pile-up in a high-rate environment.