Time Of Flight System Research Articles

Development and test of a real-size MRPC for CBM-TOF

In the CBM (Compressed Baryonic Matter) experiment constructed at the Facility for Anti-proton and Ion Research (Fair) at GSI, Darmstadt, Germany, MRPC(Multi-gap Resistive Plate Chamber) is adopted to construct the large TOF (Time-of-Flight) system to achieve an unprecedented precision of hadron identification, benefiting from its good time resolution, relatively high efficiency and low construction price. Aiming at CBM TOF, we've developed a kind of double-ended readout strip MRPC which applies low resistive glass to keep good performance of time resolution under high-rate condition. There are 24 strips on one counter, and each is carefully designed to match the 100 Ω impedance of PADI electronics. The prototype of this strip MRPC has been tested with cosmic ray, a 98% efficiency and 60ps time resolution is gotten. In order to further examine the performance of the detector working under higher particle flux rate, the prototype has been tested in the 2014 October GSI beam time and 2015 February CERN beam time. In both beam times a relatively high rate of 1 kHz/cm2 was obtained. The calibration is done with CBM ROOT, and an efficiency of 97% and time resolution of 48ps are obtained. All these results show that the real-size prototype is fully capable of the requirement of the CBM-TOF, and new designs such as self-sealed are modified into the strip counter prototype to obtain even better performance.

An overview of depth cameras and range scanners based on time-of-flight technologies

Time-of-flight (TOF) cameras are sensors that can measure the depths of scene-points, by illuminating the scene with a controlled laser or LED source, and then analyzing the reflected light. In this paper, we will first describe the underlying measurement principles of time-of-flight cameras, including: (i) pulsed-light cameras, which measure directly the time taken for a light pulse to travel from the device to the object and back again, and (ii) continuous-wave modulated-light cameras, which measure the phase difference between the emitted and received signals, and hence obtain the travel time indirectly. We review the main existing designs, including prototypes as well as commercially available devices. We also review the relevant camera calibration principles, and how they are applied to TOF devices. Finally, we discuss the benefits and challenges of combined TOF and color camera systems.

Development of the MRPC for the TOF system of the MultiPurpose Detector

The Multipurpose Detector (MPD) [1] is designed to study of hot and dense baryonic matter in collisions of heavy ions over the atomic mass range 1–197 at the centre of mass energy up to √SNN = 11 GeV (for Au79+). The MPD experiment will be carried out at the JINR accelerator complex NICA [2] which is under construction. The barrel part of the MPD consists of various detectors surrounding the interaction point. It includes a precise tracking system (time projection chamber (TPC) and silicon inner tracker (IT)) and high-performance particle identification system based on time-of-flight (TOF) and calorimeter (ECal). The triple-stack multigap resistive plate chamber is chosen as an active element of the TOF. It provides good time resolution and long term stability. This article presents parameters of the MRPC obtained using the deuteron beam of JINR accelerator Nuclotron. The time resolution is 0∼4 ps with efficiency of 99%. Rate capability studies resulted with a time resolution of 60 ps and efficiency higher than 90% on the beam with particle flux densities up to 2 kHz/cm2.

Bayesian Time-of-Flight for Realtime Shape, Illumination and Albedo.

We propose a computational model for shape, illumination and albedo inference in a pulsed time-of-flight (TOF) camera. In contrast to TOF cameras based on phase modulation, our camera enables general exposure profiles. This results in added flexibility and requires novel computational approaches. To address this challenge we propose a generative probabilistic model that accurately relates latent imaging conditions to observed camera responses. While principled, realtime inference in the model turns out to be infeasible, and we propose to employ efficient non-parametric regression trees to approximate the model outputs. As a result we are able to provide, for each pixel, at video frame rate, estimates and uncertainty for depth, effective albedo, and ambient light intensity . These results we present are state-of-the-art in depth imaging. The flexibility of our approach allows us to easily enrich our generative model. We demonstrate this by extending the original single-path model to a two-path model, capable of describing some multipath effects. The new model is seamlessly integrated in the system at no additional computational cost. Our work also addresses the important question of optimal exposure design in pulsed TOF systems. Finally, for benchmark purposes and to obtain realistic empirical priors of multipath and insights into this phenomena, we propose a physically accurate simulation of multipath phenomena.

Experimental verification of a method to create a variable energy neutron beam from a monoenergetic, isotropic source using neutron elastic scatter and time of flight

An experiment was performed to determine the neutron energy of near-monoergetic deuterium–deuterium (D–D) neutrons that elastically scatter in a hydrogenous target. The experiment used two liquid scintillators to perform time of flight (TOF) measurements to determine neutron energy, with the start detector also serving as the scatter target. The stop detector was placed 1.0m away and at scatter angles of π/6, π/4, and π/3rad, and 1.5m at a scatter angle of π/4rad. When discrete 1ns increments were implemented, the TOF peaks had estimated errors between −21.2 and 3.6% relative to their expected locations. Full widths at half-maximum (FWHM) ranged between 9.6 and 20.9ns, or approximately 0.56–0.66MeV. Monte Carlo simulations were also conducted that approximated the experimental setup and had both D–D and deuterium–tritium (DT) neutrons. The simulated results had errors between −17.2 and 0.0% relative to their expected TOF peaks when 1ns increments were applied. The largest D–D and D–T FWHMs were 26.7 and 13.7ns, or approximately 0.85 and 4.98MeV, respectively. These values, however, can be reduced through manipulation of the dimensions of the system components. The results encourage further study of the neutron elastic scatter TOF system with particular interest in application to active neutron interrogation to search for conventional explosives.

The ATLAS Forward Proton Detector (AFP)

The ATLAS Forward Proton (AFP) detector will identify events in which one or two protons emerge intact from the proton-proton collisions at the LHC. Tracking and timing detectors will be placed 2–3 mm from the beam, 210 m away from the ATLAS interaction point. The silicon-based tracker will provide momentum measurement, while the time of flight system is used to reduce the background from multiple proton-proton collisions. The study of soft and hard diffractive events at low luminosities (μ≈1) is the core of the AFP physics program. This paper presents an overview of the project with particular emphasis on the qualification of the pixel and timing systems.

Recent developments in time-of-flight PET.

While the first time-of-flight (TOF)-positron emission tomography (PET) systems were already built in the early 1980s, limited clinical studies were acquired on these scanners. PET was still a research tool, and the available TOF-PET systems were experimental. Due to a combination of low stopping power and limited spatial resolution (caused by limited light output of the scintillators), these systems could not compete with bismuth germanate (BGO)-based PET scanners. Developments on TOF system were limited for about a decade but started again around 2000. The combination of fast photomultipliers, scintillators with high density, modern electronics, and faster computing power for image reconstruction have made it possible to introduce this principle in clinical TOF-PET systems. This paper reviews recent developments in system design, image reconstruction, corrections, and the potential in new applications for TOF-PET. After explaining the basic principles of time-of-flight, the difficulties in detector technology and electronics to obtain a good and stable timing resolution are shortly explained. The available clinical systems and prototypes under development are described in detail. The development of this type of PET scanner also requires modified image reconstruction with accurate modeling and correction methods. The additional dimension introduced by the time difference motivates a shift from sinogram- to listmode-based reconstruction. This reconstruction is however rather slow and therefore rebinning techniques specific for TOF data have been proposed. The main motivation for TOF-PET remains the large potential for image quality improvement and more accurate quantification for a given number of counts. The gain is related to the ratio of object size and spatial extent of the TOF kernel and is therefore particularly relevant for heavy patients, where image quality degrades significantly due to increased attenuation (low counts) and high scatter fractions. The original calculations for the gain were based on analytical methods. Recent publications for iterative reconstruction have shown that it is difficult to quantify TOF gain into one factor. The gain depends on the measured distribution, the location within the object, and the count rate. In a clinical situation, the gain can be used to either increase the standardized uptake value (SUV) or reduce the image acquisition time or administered dose. The localized nature of the TOF kernel makes it possible to utilize local tomography reconstruction or to separate emission from transmission data. The introduction of TOF also improves the joint estimation of transmission and emission images from emission data only. TOF is also interesting for new applications of PET-like isotopes with low branching ratio for positron fraction. The local nature also reduces the need for fine angular sampling, which makes TOF interesting for limited angle situations like breast PET and online dose imaging in proton or hadron therapy. The aim of this review is to introduce the reader in an educational way into the topic of TOF-PET and to give an overview of the benefits and new opportunities in using this additional information.

Gamma-quanta onboard identification in the GAMMA-400 experiment using the counting and triggers signals formation system.

GAMMA-400 (Gamma Astronomical Multifunctional Modular Apparatus) will be the new generation satellite gamma-observatory. Gamma-telescope GAMMA-400 consists of anticoincidence system (top and lateral sections - ACtop and AClat), the converter-tracker (C), time-of-flight system (2 sections S1 and S2), position-sensitive calorimeter CC1 makes of 2 strips layers and 2 layers of CsI(Tl) detectors, electromagnetic calorimeter CC2 composed of CsI(Tl) crystals, neutron detector ND, scintillation detectors of the calorimeter (S3 and S4) and lateral detectors of the calorimeter (LD). All detector systems ACtop, AClat, S1-S4, LD consist of two BC-408 based sensitive layers of 1 cm thickness each. Three apertures provide events registration both from upper and lateral directions. The main aperture provides the best angular (all strip layers information analysis) and energy (energy deposition in the all detectors studying) resolution. Gamma-telescope GAMMA-400 is optimized for the gamma-quanta and charged particles with energy 100 GeV detection with the best parameters in the main aperture. Triggers in the main aperture will be formed using information about particle direction provided by time of flight system and presence of charged particle or backsplash signal formed according to analysis of energy deposition in combination of both layers anticoincidence systems ACtop and AClat individual detectors. For double-layer ACtop taking into account both amplitude and temporal trigger marker onboard analysis only 2.8% photons will be wrongly recognized as electrons or protons for 100 GeV particles. The part of charged particles mistakenly identified as gammas is ∼10-5 using described algorithms. For E∼3 GeV less than 3% photons will be wrongly recognized as charged particles and fraction of wrongly identified charged particles will be also ∼10-5. In the additional aperture the particles identification is provided by analysis of signals corresponding to energy deposition in the individual detectors S2, S3 and fast signals from CC1 individual detectors discriminators. Low energy (0.2 - 10 MeV) photons in the lateral aperture recognizing by using simple anticoincidence signals from the individual detectors of LD. Gamma-quanta of higher energies are identified using energy deposition in the individual detectors of S3, S4, LD and fast signals from CC2 individual detectors discriminators. The results of anticoincidence system individual detectors thresholds modelling are discussed.

P/π+ response of single layer THGEM detector in Ar+3% iC4H10**Supported by National Natural Science Foundation of China (11265003, U1431109, 11205240) and State Key Laboratory of Particle Detection and Electronics

In this work, we study the response of a single layer Thick Gaseous Electron Multiplier (THGEM) detector to p/π+ at the E3 line of the Beijing Test Beam Facility. The THGEM detector drift gap used in this study is 4 mm, and the gain of the detector operated in Ar+3% iC4H10 is about 2000. p/π+ particles at momenta between 500 MeV/c and 1000 MeV/c are distinguished by a Time Of Flight system. Our results show that at the measured momenta, detection efficiencies for p are from 93% to 99%, and for π+ in the range of 82%–88%. Meanwhile, simple Geant4 simulations also have been done, and are consistent with the amplitude spectra of the beam test results. We preliminarily study the feasibility of the THGEM detector as a sampling element for a Digital Hadronic Calorimeter (DHCAL), which may provide support for the possible application of a THGEM detector in the Circular Electron Positron Collider (CEPC) HCAL.

Avalanche photodiode based time-of-flight mass spectrometry.

This study reports on the performance of Avalanche Photodiodes (APDs) as a timing detector for ion Time-of-Flight (TOF) mass spectroscopy. We found that the fast signal carrier speed in a reach-through type APD enables an extremely short timescale response with a mass or energy independent <2 ns rise time for <200 keV ions (1-40 AMU) under proper bias voltage operations. When combined with a microchannel plate to detect start electron signals from an ultra-thin carbon foil, the APD comprises a novel TOF system that successfully operates with a <0.8 ns intrinsic timing resolution even using commercial off-the-shelf constant-fraction discriminators. By replacing conventional total-energy detectors in the TOF-Energy system, APDs offer significant power and mass savings or an anti-coincidence background rejection capability in future space instrumentation.

Fast differential discrimination approach to improve time resolution with multiple returns for time-of-flight system.

A differential discrimination approach has been proposed in this paper to make fast discrimination from multi-returns in time-of-flight (TOF) systems. The time resolution of classical direct discrimination in a laser TOF system has been analyzed. A theoretical model of the differential discriminator has been established. As theoretical calculations and numerical simulations have shown, time resolution can be improved by using a differential discriminator instead of a classical direct discriminator, especially with large-amplitude signals. However, the relationship between the time resolution and the amplitude is not monotonic. The time resolution decreases as the amplitude decreases when the signals are small. But, through further analysis and simulations, a method to find an appropriate parameter, which can optimize the relationship curve, has been proposed. The theory and the simulations were verified by electrical circuit experiments, and the optical circuit experiments taken with two close targets of about 8.3m. The FWHM of the laser is about 1.9ns. The measured time resolution was better than 2.2ns when the amplitude is 30mV.

Study of the timing performance of micro-channel plate photomultiplier for use as an active layer in a shower maximum detector

We continue the study of micro-channel plate photomultiplier (MCP-PMT) as the active element of a shower maximum (SM) detector. We present test beam results obtained with Photek 240 and Photonis XP85011 MCP-PMTs devices. For proton beams, we obtained a time resolution of 9.6ps, representing a significant improvement over past results using the same time of flight system. For electron beams, the time resolution obtained for this new type of SM detector is measured to be at the level of 13ps when we use Photek 240 as the active element of the SM. Using the Photonis XP85011 MCP-PMT as the active element of the SM, we performed time resolution measurements with pixel readout, and achieved a TR better than 30ps, The pixel readout was observed to improve upon the TR compared to the case where the individual channels were summed.

Picosecond timing of high-energy heavy ions with semiconductor detectors

Construction of new accelerating facilities to investigate reactions with heavy ions requires upgrading of the Time-of-Flight (TOF) systems for on-line ion identification. The requested time resolution of the TOF system developed for Super FRagment Separator in the frame of the FAIR program at GSI, Germany, is in the range of tens of picoseconds, which can be realized by using planar silicon detectors. Such resolution will allow characterization of relativistic ions from Lithium to Uranium. However, fast timing of heavy ions with semiconductor detectors is expected to be limited by the so-called plasma effect due to a high concentration of electron–hole pairs in tracks. Here the results of the experiment with relativistic 197Au ions (the energy of 920MeV per nucleon) obtained with Si detectors are described, which showed the TOF time resolution around 14psrms. The physical mechanism of charge collection from high-density penetrating tracks of relativistic heavy ions is considered and the analysis of timing characteristics is performed taking into account track polarization. Polarization is shown to have a strong influence on the formation of the leading edge of the detector current response generated by relativistic heavy ions, which allows us to explain the observed high time resolution.

Preliminary measurements on the new TOF system installed at the AMS beamline of INFN-LABEC

A high resolution time of flight (TOF) system has been developed at LABEC, the 3MV Tandem accelerator laboratory in Florence, in order to improve the sensitivity of AMS measurements on carbon samples with ultra-low concentration and also to measure other isotopes, such as 129I. The system can be employed to detect and identify residual interfering particles originated from the break-up of molecular isobars. The set-up has been specifically designed for low energy heavy ions: it consists of two identical time pick-off stations, each made up of a thin conductive foil and a Micro-Channel Plate (MCP) multiplier. The beamline is also equipped with a silicon detector, installed downstream the stop TOF station.In this paper the design of the new system and the implemented readout electronics are presented. The tests performed on the single time pick-off station are reported: they show that the maximum contribution to the timing resolution given by both the intrinsic MCP resolution and the electronics is ⩽500ps (FWHM). For these tests, single particle pulsed beams of 2–5MeV protons and 10MeV 12C3+ ions, to simulate typical AMS conditions, were used.The preliminary TOF and TOF-E (TOF-energy) measurements performed with carbon beams after the installation of the new system on the AMS beam line are also discussed. These measurements were performed using the foil–MCP as the start stage and a silicon detector as the stop stage. The spectra acquired with carbon ions suggest the presence of a small residual background from neighboring masses reaching the end of the beamline with the same energy as the rare isotope.

Particle IDentification with the ALICE Time-Of-Flight detector at the LHC

The main physics goal of ALICE (A Large Ion Collider Experiment) is the study of the physics of strongly interacting matter at extreme energy densities, where the formation of a new phase of matter, the Quark-GluonPlasma (QGP), is expected. One of the most important aspect of ALICE is the Particle IDentification (PID) performed by combining different identification techniques. The time measurement with the Time-Of-Flight (TOF) detector, in conjunction with the momentum and track length measured by the tracking detectors is used to calculate the particle mass in the intermediate momentum range from 0.3 up to a few GeV/c. The TOF system covers an area of 141 m2 and consists of Multi-gap Resistive Plate Chambers (MRPC), that allow excellent performances in terms of intrinsic time resolution (of the order of few tens of ps) and overall efficiency (close to 100%).The ALICE TOF system has shown very stable operation during the firstthree years of collisions at the LHC, reaching the design goal of 80ps time resolution. The performance and main physics results will bereported.

The TOF-RPC for the BGO-EGG experiment at LEPS2

We have developed Resistive Plate Chambers (RPCs) and the FEEsfor the Time-of-Flight (TOF) system of the BGO-EGG experiment at LEPS2.The TOF system has an excellent time resolution of 50 ps with large readout strips of 2.5 × 100 cm2.The large readout strip and the signal combining technique enable us to cover the area of 6.4 m2with only 256 channels of the readout electronics.The details of the RPC and the FEE are described in this article.

Effects of sample injection amount and time-of-flight mass spectrometric detection dynamic range on metabolome analysis by high-performance chemical isotope labeling LC-MS.

In chemical isotope labeling (CIL) LC-MS, relative metabolite quantification is done by measuring the peak ratio of a (13)C2-/(12)C2-labeled peak pair for a given metabolite present in two comparative samples. The dynamic range of peak ratio measurement does not need to be very large, as only subtle changes of metabolite concentrations are encountered in most metabolomic studies where relative metabolome quantification of different groups of samples is performed. However, the absolute concentrations of different metabolites can be very different, requiring a technique to provide a wide detection dynamic range to allow the detection of as many peak pairs as possible. In this work, we demonstrated that controlling the sample injection amount into LC-MS was critical to achieve the optimal detectability while avoiding sample carry-over problem. In addition, the use of a high-dynamic-range TOF system increased the number of peak pairs detected, compared to a conventional TOF system. We also investigated the ionization and detection saturation factors limiting the dynamic range of detection. This article is part of a Special Issue entitled: Protein dynamics in health and disease. Guest Editors: Pierre Thibault and Anne-Claude Gingras.

Investigation of the distance error induced by cycle-to-cycle jitter in a correlating time-of-flight distance measurement system

Time-of-flight (TOF) range sensors acquire distances by means of an optical signal delay measurement. As the signal travels at the speed of light, distance resolutions in the subcentimeters range require a time measurement resolution that is in the picoseconds range. However, typical clock synthesizers and digital buffers possess cycle-to-cycle jitter values of up to hundreds of picoseconds, which can potentially have a noticeable impact on the TOF system performances. In this publication, we investigate the influence of two common types of cycle-to-cycle jitter distributions on the measured distance. This includes a random Gaussian distribution, which is caused by, e.g., stochastic noise sources, and a discrete jitter distribution, which is found when timing constraints fail in synchronous digital designs. It was demonstrated that a Gaussian cycle-to-cycle jitter has only a negligible impact on the performance of the TOF distance sensors up to a standard deviation of 1 ns of the Gaussian jitter distribution. However, even the discrete cycle-to-cycle jitter investigated in its simplest form lowers the distance precision of the TOF sensor by a factor of 2.86, i.e., the standard deviation increases from 2.9 to 8.3 mm.

P61: Implementation of a systematic toxicological screening method for post-mortem analysis using a UPLC-QToF MS system

Introduction General unknown screening (GUS) is the procedure used by toxicologists in order to unambiguously identify the xenobiotics involved in an intoxication case. Due to its high specificity, GC-MS was long considered the gold standard for GUS in clinical and forensic toxicology. Still, GC-MS is poorly suited for the detection of several xenobiotics and their more hydrophilic metabolites. Here we describe the optimization and implementation of a comprehensive high-resolution drug screen in biological matrices using a Waters UPLC XEVO G2 QToF MS system. We also examined the transferability of the high-resolution spectral lists established on mirror systems by comparing our data against two other instruments of the same model and manufacturer using the same chromatographic separation (Humbert et al., 2012; Rosano et al., 2013). Methods Drugs and metabolites were extracted from spiked matrices using SPE cartridges or liquid-liquid extraction. Extracts were sequentially injected into a UPLC coupled to a hybrid quadrupole- time of flight system (MSe) in positive and negative ESI mode. Data was collected using MSe acquisition which performs two sets of acquisition simultaneously and compared to a list containing the exact mass, the retention time and the exact mass fragments as previously described (Humbert et al., 2012; Rosano et al., 2013). In order to optimize the extraction procedure, we modeled different approaches (reverse phase SPE, mixed-mode cation exchange SPE and liquid-liquid extraction) using 18 different xenobiotics frequently encountered in toxicological investigations. Results The most efficient extraction process was chosen using the following criteria: ion suppression, recovery and the limit of detection. Based on our data, mixed-mode cation exchange SPE demonstrated the best overall performance and was selected to be compared to our reference GC-MS screening method. We then evaluated the recoveries, ion suppression and the limits of detections for 225 xenobiotics which are part of our GC-MS screen. Overall our transferability study showed few discrepancies in mass or fragments generated. Retention time reproducibility was 99% using a retention time tolerance of 0.4min and 96% using a 0.3 window. Finally, we performed a comparison between the test LC-QToF method and our reference GC-MS method on real samples to evaluate its performance; several cases will be presented. In summary, these cases demonstrated that the LC-QTOF method was able to identify more xenobiotics in the following categories: benzodiazepine and stimulant metabolites (7-amino-clonazepam, 4-methylamphetamine and desmethyl-diphenhydramine), anti hypertensive drugs metabolite (OH-propranolol), antiretroviral drugs (such as ritonavir and darunavir) and hydrophilic anticonvulsant pregabalin. Conclusion Overall, the LC-QToF method demonstrates increased sensitivity compared to GC-MS and should be more specific. Our evaluation of the transferability of lists between labs indicates that retention variability could be an issue for a small fraction of compounds. Also, in order to detect some families of xenobiotics, such as barbiturates and NSAIDS, the addition of a second injection (using negative ionization) was necessary.

Monte Carlo tuning for the BESIII time-of-flight system

Using experimental data, Monte Carlo tuning is implemented for performance parameters associated with the scintillation counters and readout electronics of the BESIII time-of-flight (TOF) system, as part of the full simulation model. The implementation of the tuning is described for simulations designed to reproduce the performance of a number of TOF system parameters, including pulse height, hit efficiency, time resolution, dead channels and background. In addition, comparisons with experimental data are presented.