Precise Timing Information Research Articles

Design and Implementation of a Global Positioning System (GPS) for Constraint-Free Applications

The implementation and evaluation of a GPS/GSM module for positioning, tracking, and remote communication applications are examined in this work. The Global Navigation Satellite System (GNSS) provides precise location and timing information through a network of satellites. Specifically, the study focuses on the performance of a SIM808 GPS/GSM module in various operational conditions and constraints. Trilateration tests were conducted at twelve locations, revealing a time-to-first-fix (TTFF) ranging from 102.4 to 163.2 seconds; position differentiation accuracy, as determined by the Haversine Equation, indicated deviations of up to 7.52% in constrained scenarios; altitude measurements exhibited an error of about 4.14 meters, while lateral distance differentiation indicated deviations of up to 30.99% in specific instances. The deviations affecting the efficacy of the module are such as signal strength, satellite visibility, and receiver quality. Thus, the findings highlight the module's potential for applications requiring remote monitoring, control, and IoT deployments. Further improvements and considerations for practical implementations are suggested based on the outcomes of the evaluation.

Low gain avalanche detectors for precision timing in the CMS MTD endcap timing layer

The MIP Timing Detector (MTD) of the Compact Muon Solenoid (CMS) is designed to provide precision timing information (with resolution of ∼40 ps per layer) for charged particles, with hermetic coverage up to a pseudo-rapidity of |η| = 3. This upgrade will reduce the effects of pile-up expected under the High-Luminosity LHC running conditions and brings new and unique capabilities to the CMS detector. The time information assigned to each track will enable the use of 4D reconstruction algorithms and will further discriminate in the time domain interaction vertices within the same bunch crossing to recover the track purity of vertices in current LHC conditions. The endcap region of the MTD, called the Endcap Timing Layer (ETL) will be instrumented with silicon-based low gain avalanche detectors (LGADs), covering the high radiation pseudo-rapidity region between |η| = 1.6 and 3.0. Each endcap will be instrumented with a two-disk system of LGADs, read out by Endcap Timing Readout Chips (ETROCs), being designed for precision timing measurements. We will present an overview of the MTD ETL design, which is detailed in the MTD technical design report. We will also present the R&D and test beam studies that were instrumental for achieving the ETL design, characterization of the LGAD sensors, as well as recent progress on the development of the ETROC readout electronics.

Light detection and cosmic rejection in the ICARUS LArTPC at Fermilab

The ICARUS-T600 detector is a 760-ton Liquid Argon Time Projection Chamber (LArTPC) currently operating at Fermilab as the Far Detector in the Short Baseline Neutrino (SBN) program. The SBN program is composed of three LArTPCs with a central goal of testing the sterile neutrino hypothesis. After operating for 3-years in the Gran Sasso Underground Laboratory, the ICARUS detector was shipped to CERN where it was outfitted with 360 8” Photomultiplier Tubes (PMTs) for a new optical detection system. The PMT system detects fast scintillation light from charged particles interacting in the Liquid Argon, generating the trigger signal for the full detector and allows 3D reconstruction of events. Now operating at shallow depth, the detector is exposed to a high flux of cosmic rays that can fake neutrino interactions. To mitigate this effect a Cosmic Ray Tagger (CRT) and a 3-meter-thick concrete were installed. Precise timing information from both the PMT and CRT subsystems can help to identify whether an interaction originated from inside or outside of the ICARUS cryostat. This paper reviews a method for cosmogenic background reduction and timing calibration of the CRT and PMT light detection systems in ICARUS.

Low Gain Avalanche Detectors for the ATLAS High Granularity Timing Detector: Laboratory and test beam campaigns

The High Granularity Timing Detector (HGTD) is designed for the mitigation of pile-up effects in the ATLAS forward region and for bunch per bunch luminosity measurements. HGTD, based on Low Gain Avalanche Detector (LGAD) technology and covering the pseudorapidity region between 2.4 and 4.0, will provide high precision timing information to distinguish between collisions occurring close in space but well-separated in time. Apart from being radiation resistant, LGAD sensors should deliver 30 ps time resolution per track for a minimum-ionizing particle (35 ps per hit) at the start of lifetime, increasing to 50 ps per track (70 ps per hit) at the end of HL-LHC operation. Each readout cell has a transverse size of 1.3×1.3 mm2 leading to a highly granular detector with about 3 millions of readout electronics channels. A dedicated ASIC for the HGTD detector, ALTIROC, is being developed in several phases producing prototype versions of 2×2, 5×5 and 15×15 channels. HGTD modules are hybrids of the LGAD and ALTIROC connected through flip-chip bump bonding process. Several test beam campaigns have been conducted at DESY and CERN SPS between 2021 and 2022. A summary of the results from LGAD-alone and hybrids will be presented.

The development of a laser system for use in the timing performance measurements of CMS HGCAL silicon modules

For optimal operations in the high radiation and pileup environment of the HL-LHC, the CMS-HGCAL requires precise timing information at the level of 30 ps (RMS) for a particle shower. The time measurement in silicon detector modules is performed using a per-channel time-of-arrival discriminator coupled with charge measurement to correct for the time-walk. The module design includes access holes in the PCB and in the sensor passivation to enable infrared laser light to be injected directly into the sensor cells. We present the calibration and timing-in of the system used to perform measurements.

Activeness: A Novel Neural Coding Scheme Integrating the Spike Rate and Temporal Information in the Spiking Neural Network

In neuromorphic computing, the coding method of spiking neurons serves as the foundation and is crucial for various aspects of network operation. Existing mainstream coding methods, such as rate coding and temporal coding, have different focuses, and each has its own advantages and limitations. This paper proposes a novel coding scheme called activeness coding that integrates the strengths of both rate and temporal coding methods. It encompasses precise timing information of the most recent neuronal spike as well as the historical firing rate information. The results of basic characteristic tests demonstrate that this encoding method accurately expresses input information and exhibits robustness. Furthermore, an unsupervised learning method based on activeness-coding triplet spike-timing dependent plasticity (STDP) is introduced, with the MNIST classification task used as an example to assess the performance of this encoding method in solving cognitive tasks. Test results show an improvement in accuracy of approximately 4.5%. Additionally, activeness coding also exhibits potential advantages in terms of resource conservation. Overall, activeness offers a promising approach for spiking neural network encoding with implications for various applications in the field of neural computation.

Cosmic time calibrator for wireless sensor network

Time synchronization of sensor nodes is critical for optimal operation of wireless sensor networks (WSNs). Since clocks incorporated into each node tend to drift, recurrent corrections are required. Most of these correction schemes involve clients periodically receive RF timing signals from a time server. However, an RF-based scheme is prone to glitches or failure unless operating in a region with almost entirely unobstructed space; hence it only operates well in a limited range of environments. For example, GPS requires open-sky environments. Moreover, the precision of land-based RF schemes is limited to a few micro seconds. In this work, we report on a more versatile and new type of recurrent clock resynchronization scheme called cosmic time calibrator (CTC) and its development and testing. CTC utilizes cosmic-ray muon signals instead of RF signals. Muons are penetrative and continuously precipitating onto the Earth’s surface, and they tend to travel linearly through encountered matter at approximately the speed of light in vacuum. Therefore, muons themselves can periodically transfer the precise timing information from node to node; hence, the performance of the inter-nodal communication device such as Wi-Fi or Bluetooth is minimized/unnecessary for an online/offline WSN analysis. The experimental results have indicated that a resynchronization frequency and precision of 60 Hz and ± 4.3 ns (S.D.) can be achieved. Modelling work of the WSN-based structural health monitoring of aerospace structures has shown that CTC can contribute to the development of new critical and useful applications of WSN in a wider range of environments.

TRICK: A tracking ring imaging CherenKov detector

TRICK is a project funded by the INFN CSN5 Young grant 2020. It will use an innovative 5D technique to provide information about 3D position, time, and ID of the incoming particles. The proposed idea is based on the well-known technology of GEM-based TPC together with conventional Aerogel proximity focussing RICH in a single box. Both parts, TPC and RICH, will be read out simultaneously and instrumented with the same TIGER ASIC developed for the BESIII CGEM-IT detector. By combining information from both systems, the TRICK technique will improve the performance of each instrument: precise time information will help the extraction of the TPC position, while tracking will help the rings identification, by measuring the expected centre, also in a magnetic field. The TRICK-box prototype, instrumented with triple-GEM and Hamamatsu H12700 MA-PMT, aims to achieve a spatial resolution of 100 μm, time resolution below 1 ns, and 3σ separation for π/K up to 4 GeV.This paper introduces the project and focuses on the initial studies with the prototype, the preparation of the first cosmic stand, and the next steps.

Common Android Smartphones and Apps for Cost-Efficient GNSS Data Collection: An Overview

Global Navigation Satellite System (GNSS) sensors are increasingly considered as major sources of precise Position, Navigation, and Timing (PNT) information. Android-based smartphones contain inbuilt GNSS sensors, and they now contribute to a major global GNSS market segment. Various hardware and Android-based applications (App) developments are witnessed to best exploit the current multi-constellation, multi-frequency GNSS environment. Since Android version 7.0 (Nougat) and Location Application Programming Interface (API) 24, recording GNSS raw data in the smartphone became possible. This paper describes the potential of commercial Smartphones and reviews the capabilities of Android Apps for cost-efficient GNSS measurements for the geospatial community and a novel classification of the Apps based on their capabilities and usability. Results on the positioning capability of common smartphones using real-time data show the achievable modest solution precision, and these are suitable for use of the devices in geomatics applications, improved App development, and for IoT-based system and infrastructure development.

Sequential displaced vertices: Novel collider signature for long-lived particles

In this paper, we point out a novel signature of physics beyond the Standard Model which could potentially be observed both at the Large Hadron Collider (LHC) and at future colliders. This signature, which emerges naturally within many proposed extensions of the Standard Model, results from the multiple displaced vertices associated with the successive decays of unstable, long-lived particles along the same decay chain. We call such a sequence of displaced vertices a ``tumbler.'' We examine the prospects for observing tumblers at the LHC and assess the extent to which tumbler signatures can be distinguished from other signatures of new physics which also involve multiple displaced vertices within the same collider event. As part of this analysis, we also develop a procedure for reconstructing the masses and lifetimes of the particles involved in the corresponding decay chains. We find that the prospects for discovering and distinguishing tumblers can be greatly enhanced by exploiting precision timing information such as would be provided by the CMS timing layer at the high-luminosity LHC. Our analysis therefore provides strong additional motivation for continued efforts to improve the timing capabilities of collider detectors at the LHC and beyond.

Fast Beam Condition Monitor of the CMS experiment at HL-LHC

To achieve the challenging target of 1% precision for luminosity measurement at the high-luminosity LHC (HL-LHC) with instantaneous luminosity up to 7.5×1034 cm−2 s−1, the CMS experiment will employ multiple luminometers with orthogonal systematics. A key component of the proposed system is a standalone luminometer, the Fast Beam Condition Monitor (FBCM), which is fully independent of the central trigger and data acquisition and hence is able to operate outside of CMS data taking periods at 40 MHz providing bunch-by-bunch luminosity measurement with 1 s time granularity. FBCM will be placed inside the cold volume of the tracker as it utilizes silicon-pad sensors with an asynchronous read-out. A zero-hit-counting algorithm will be used to measure luminosity. FBCM will also provide precise timing information with a few ns precision enabling the measurement of beam-induced background. We report on the optimization of the design and the expected performance of FBCM.

Overview of CNM LGAD results: boron Si-on-Si and epitaxial wafers

Low Gain Avalanche Detectors (LGADs) are n-on-p silicon sensors with an extra p-layer below the collection electrode which provides signal amplification. When the primary electrons reach the amplification region new electron-hole pairs are created that enhance the generated signal. The moderate gain of these sensors, together with the relatively thin active region, provide precise time information for minimum ionizing particles. To mitigate the effect of pile-up at the HL-LHC the ATLAS and CMS experiments have chosen the LGAD technology for the High Granularity Timing Detector (HGTD) and for the End-Cap Timing Layer (ETL), respectively. A full characterization of recent productions of LGAD sensors fabricated at CNM has been carried out before and after neutron irradiation up to 2.5 × 1015 neq/cm2. Boron-doped sensors produced in epitaxial and Si-on-Si wafers have been studied. The results include their electrically characterization (IV and bias voltage stability) and performance studies (charge and time resolution) for single pad devices with a Sr-90 radioactive source set-up. The behaviour of the Inter-Pad region for irradiated 2 × 2 LGAD arrays, using the Transient Current Technique (TCT), is shown. The results indicate that the Si-on-Si devices with higher resistivity perform better than the epitaxial ones.

On Privacy Risks of Watching YouTube over Cellular Networks with Carrier Aggregation

One's core values, personality, and social status may be reflected in the watch history of online video streaming services such as YouTube. Unfortunately, several prior research work demonstrates that man-in-the-middle or malware-assisted attackers can accurately infer the titles of encrypted streaming videos by exploiting the inherent correlation between the encoded video contents and the traffic rate changes. In this paper, we present a novel video-inference attack called Moba that further exacerbates the problem by only requiring the adversary to simply eavesdrop the broadcast messages of a primary cell of a targeted user's cellular phone. Our attack utilizes a side channel in modern cellular networks that leaks the number of actively transmitting cells for each user. We show that this seemingly harmless system information leakage can be used to achieve practical video-inference attacks. To design effective video-inference attacks, we augment the coarse-grained side-channel measurements with precise timing information and estimate the traffic bursts of encrypted video contents. The Moba attack considers an adversary-chosen set of suspect YouTube videos, from which a targeted user may watch some videos during the attack. We confirm the feasibility of Moba in identifying the exact YouTube video title (if it is from the suspect set) via our over-the-air experiments conducted in LTE-Advanced networks in two countries. Moba can be effective in verifying whether a targeted user watches any of the suspect videos or not; e.g., precision of 0.98 is achieved after observing six-minutes of a single video play. When further allowed to observe multiple video plays, Moba adversary is able to identify whether the targeted user frequently watches the suspect videos with a probability close to one and a near-zero false positive rate. Finally, we present a simple padding-based countermeasure that significantly reduces the attack effectiveness without sacrificing any cellular radio resources.

A High-Granularity Timing Detector for the ATLAS Phase-II upgrade

The increase of the particle flux at the HL-LHC with instantaneous luminosities up to L=7.5 × 10 34 cm −2 s −1 will have a severe impact on the ATLAS detector reconstruction and trigger performance. The end-cap and forward region where the liquid Argon calorimeter has coarser granularity and the inner tracker has poorer momentum resolution will be particularly affected. A High Granularity Timing Detector will be installed in front of the liquid Argon end-cap calorimeters to help in charged-particle reconstruction and luminosity measurement. This low angle detector is introduced to augment the new all-silicon Inner Tracker in the pseudo-rapidity range from 2.4 to 4.0. Two silicon-sensor double-sided per end-cap will provide precision timing information for minimum-ionizing particles with a resolution as good as 30 ps per track in order to assign each particle to the correct vertex. Readout cells have a size of 1.3 mm × 1.3 mm, leading to a highly granular detector with 3.7 million channels. The Low Gain Avalanche Detectors technology has been chosen as sensor as it provides excellent timing performance. The requirements and overall specifications of the High Granularity Timing Detector are presented as well as the technical design and the project status. The on-going R&D effort carried out to study the sensors, the readout ASIC, and the other components, supported by laboratory and test beam results, are also presented.

Prospects of charge signal analyses in liquid xenon TPCs with proportional scintillation in the liquid phase

As liquid xenon TPCs increase in target mass while pursuing the direct detection of WIMP dark matter, the technical challenges arising due to their size call for new solutions and open the discussion on alternative detector concepts. Proportional scintillation in liquid xenon allows for a single-phase design evading problems related to the liquid-gas interface and the precise gas gap required in a dual-phase TPC.Aside from a different scintillation mechanism, the successful detection- and analysis scheme of state-of-the-art experiments is maintained in this approach.We study the impact on charge signal analysis in a single-phase detector of DARWIN dimensions, where the fast timing of the proportional scintillation signal allows for the precise identification of the single electrons in the ionisation signal.Such a discrete electron-counting approach can lead to a better signal resolution for low energies when compared to the classical dual-phase continuous method.The absence of the liquid-gas interface can further benefit the S2-only energy resolution significantly. This can reduce the uncertainties from the scintillation and signal-detection process to a level significantly below the irreducible fluctuation in the primary ionisation. Exploiting the precise electron arrival time information can further allow for a powerful single vs. multiple site interaction discrimination with 93% rejection efficiency and 98% signal acceptance. This outperforms the design goal of the DARWIN observatory by a reduction factor of 4.2 in non-rejected multiple site neutron events.

Radiation hardness characterization of low gain avalanche detector prototypes for the high granularity timing detector

The high granularity timing detector (HGTD) is a crucial component of the ATLAS phase II upgrade to cope with the extremely high pile-up (the average number of interactions per bunch crossing can be as high as 200). With the precise timing information (<i>σ<sub>t</sub></i>～30 ps) of the tracks, the track-to-vertex association can be performed in the “4-D” space. The Low Gain Avalanche Detector (LGAD) technology is chosen for the sensors, which can provide the required timing resolution and good signal-to-noise ratio. Hamamatsu Photonics K.K. (HPK) has produced the LGAD with thicknesses of 35 μm and 50 μm. The University of Science and Technology of China(USTC) has also developed and produced 50 μm LGADs prototypes with the Institute of Microelectronics (IME) of Chinese Academy of Sciences. To evaluate the irradiation hardness, the sensors are irradiated with the neutron at the JSI reactor facility and tested at USTC. The irradiation effects on both the gain layer and the bulk are characterized by <i>I</i>-<i>V</i> and <i>C</i>-<i>V</i> measurements at room temperature (20 ℃) or −30 ℃. The breakdown voltages and depletion voltages are extracted and presented as a function of the fluences. The final fitting of the acceptor removal model yielded the <i>c</i>-factor of 3.06×10<sup>−16</sup> cm<sup>−2</sup>, 3.89×10<sup>−16</sup> cm<sup>−2</sup> and 4.12×10<sup>−16</sup> cm<sup>−2</sup> for the HPK-1.2, HPK-3.2 and USTC-1.1-W8, respectively, showing that the HPK-1.2 sensors have the most irradiation resistant gain layer. A novel analysis method is used to further exploit the data to get the relationship between the <i>c</i>-factor and initial doping density.

Timed protocol analysis of interconnected mobile IoT devices

With the emergence of the Internet of Things (IoT), application developers can rely on a variety of protocols and Application Programming Interfaces (APIs) to support data exchange between IoT devices. However, this may result in highly heterogeneous IoT interactions in terms of both functional and non-functional semantics. To map between heterogeneous functional semantics, middleware connectors can be utilized to interconnect IoT devices via bridging mechanisms. In this paper, we make use of the Data eXchange (DeX) connector model that enables interoperability among heterogeneous IoT devices. DeX interactions, including synchronous, asynchronous and streaming, rely on generic post and get primitives to represent IoT device behaviors with varying space/time coupling. Nevertheless, non-functional time semantics of IoT interactions such as data availability/validity, intermittent connectivity and application processing time, can severely affect response times and success rates of DeX interactions. We introduce timing parameters for time semantics to enhance the DeX API. The new DeX API enables the mapping of both functional and time semantics of DeX interactions. By precisely studying these timing parameters using timed automata models, we verify conditions for successful interactions with DeX connectors. Furthermore, we statistically analyze through simulations the effect of varying timing parameters to ensure higher probabilities of successful interactions. Simulation experiments are compared with experiments run on the DeX Mediators (DeXM) framework to evaluate the accuracy of the results. This work can provide application developers with precise design time information when setting these timing parameters in order to ensure accurate runtime behavior.

Time Resolution of BC422 Plastic Scintillator Read Out by a SiPM

Plastic scintillators are widely used in particle detectors when precise timing information is required. As a basis for comparing different detectors we use such a characteristic as the time resolution per 1MeV detected energy, i.e. the expected time resolution assuming the deposited energy in the scintillator equals to 1MeV and all the scintillation light is collected to the photosensor. In this work we measure this parameter with BC422 plastic scintillator read out by different SiPMs. The best obtained value is about 6ps, which is almost a factor of 3 better compared to our earlier result from 2012. Such an improvement represents the progress in the development of SiPMs made over these years and, driven by this progress, an improved knowledge and know-how on such detectors.

Point Positioning Capability of Compact, Low-Cost GNSS Modules: A Case Study

Global Navigation Satellite System (GNSS) provides precise Position, Velocity, and Timing (PVT) information. Various types of receivers of varying cost and complexity are used for collection and use of GNSS data. Currently, cost-effective, compact, low power consuming, multi-constellation enabled, single, or dual-frequency GNSS modules are being increasingly available having the capability of providing modest position solution accuracy. This paper presents the results of GPS, BeiDou, and GPS + BeiDou hybrid positioning capabilities of few commercially available modules based on systematic analysis from data collected during two time periods from two locations of India using geodetic and commercial patch antennas w.r.t. the reference points created through PPP (Precise Point Positioning). The results are compared with those provided a survey-grade GNSS receiver. It is witnessed that, selected single frequency module can provide 3-4m 2DRMS (Distance Root Means Square) precision and their dual frequency counterparts can provide 2DRMS solution precision around 3 m in GPS-only operation, around 7 m in BeiDou-only operation and around 3.5 m in case of GPS + BeiDou hybrid operation. The performance of the compact modules clearly presents the cost-performance benefit of the compact modules for real-time applications and the results of this study would help in understanding the capabilities of these modules for mass-market applications.

Evolution of PET Detectors and Event Positioning Algorithms Using Monolithic Scintillation Crystals

The use of monolithic scintillator-based photon detectors in positron emission tomography (PET) has emerged as an attractive alternative to traditional pixelated array designs. Monolithic-based detector designs employ the scintillation light distribution (LD) shape to provide a single 3-D photon interaction position per event, enabling high spatial resolution throughout the crystal volume. Since there are no intercrystal gaps, monolithic designs provide higher intrinsic detection efficiency compared to pixelated designs. However, in order to make the monolithic detector design practical for clinical PET systems, some major drawbacks need to be addressed, such as the time-consuming and complex calibration procedures to obtain precise spatial and timing information. This article gives a historical review of monolithic-based PET detectors, a description of their main advantages and challenges, describes the state-of-the-art, including their use in current commercial system, and ends with a future prospective.