arXiv subjects

H. Sun

Publications and source records attributed to H. Sun.

At least 37 records · Page 2Linked to original sources

arXiv2024

Probing a Magnetar Origin for the population of Extragalactic Fast X-ray Transients detected by Chandra

Twenty-two extragalactic fast X-ray transients (FXTs) have now been discovered from two decades of Chandra data (analyzing ~259 Ms of data), with 17 associated with distant galaxies (>100 Mpc). Different mechanisms and progenitors have been proposed to explain their properties; nevertheless, after analyzing their timing, spectral parameters, host-galaxy properties, luminosity function, and volumetric rates, their nature remains uncertain. We interpret a sub-sample of nine FXTs that show a plateau or a fast-rise light curve within the framework of a binary neutron star (BNS) merger magnetar model. We fit their light curves and derive magnetar (magnetic field and initial rotational period) and ejecta (ejecta mass and opacity) parameters. This model predicts two zones: an orientation-dependent free zone (where the magnetar spin-down X-ray photons escape freely to the observer) and a trapped zone (where the X-ray photons are initially obscured and only escape freely once the ejecta material becomes optically thin). We argue that six FXTs show properties consistent with the free zone and three FXTs with the trapped zone. This sub-sample of FXTs has a similar distribution of magnetic fields and initial rotation periods to those inferred for short gamma-ray bursts (SGRBs), suggesting a possible association. We compare the predicted ejecta emission fed by the magnetar emission (called merger-nova) to the optical and near-infrared upper limits of two FXTs, XRT 141001 and XRT 210423 where contemporaneous optical observations are available. The non-detections place lower limits on the redshifts of XRT 141001 and XRT 210423 of z>1.5 and >0.1, respectively. If the magnetar remnants lose energy via gravitational waves, it should be possible to detect similar objects with the current advanced LIGO detectors out to a redshift z<0.03, while future GW detectors will be able to detect them out to z=0.5.

astro-ph.HE↗

arXiv2023

The Lobster Eye Imager for Astronomy Onboard the SATech-01 Satellite

The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July 2022. In this paper, we introduce the design and on-ground test results of the LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide field-of-view (FoV) of 346 square degrees (18.6 degrees * 18.6 degrees) of the X-ray imager is realized. An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons, and four large-format complementary metal-oxide semiconductor (CMOS) sensors, each of 6 cm * 6 cm, are used as the focal plane detectors. The instrument has an angular resolution of 4 - 8 arcmin (in FWHM) for the central focal spot of the point spread function, and an effective area of 2 - 3 cm2 at 1 keV in essentially all the directions within the field of view. The detection passband is 0.5 - 4 keV in the soft X-rays and the sensitivity is 2 - 3 * 10-11 erg s-1 cm-2 (about 1 mini-Crab) at 1,000 second observation. The total weight of LEIA is 56 kg and the power is 85 W. The satellite, with a design lifetime of 2 years, operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes. LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation, and by optimizing the working setups of the instrumental parameters. In addition, LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band, albeit limited useful observing time available.

astro-ph.IM↗

arXiv2023

SOLPS-ITER numerical evaluation about the effect of drifts in a divertor configuration of ASDEX-Upgrade and a limiter configuration of J-TEXT

The High Field High Density Region (HFSFD) has been experimentally observed in both divertor and limiter tokamak devices. In order to numerically reproduced the HFSHD region in the limiter tokamak device J-TEXT, we first performed SOLPS-ITER simulations on the J-TEXT limiter tokamak with the activation of drifts, which is associated with the HFSHD region. The validated physical models, which is from ASDEX Upgrade (AUG) divertor modelling including full drifts and currents, were applied. Through a gas puffing rate scan, both attached and detached regimes were numerically obtained in the AUG divertor and J-TEXT limiter. The key plasma parameters in the J-TEXT limiter are evaluated with and without drifts that have a qualitative performance like AUG except the roll-overment of the total ion flux at the targets. The drift effects on the target profiles are investigated in which the maximum electron temperature at the outer targets is 15eV and 5eV respectively. When the outer targets are attached in the J-TEXT limiter and AUG divertor, the drifts result in the partial detachment of the inner targets. In the detached regimes, the drifts decrease the electron temperature on AUG divertor targets. However, for the J-TEXT limiter, the electron temperature only decreases at the far SOL region. The effect of drifts on the neutral density is also presented.

physics.plasm-ph↗

arXiv2022

A 40 Gbps Optical Transceiver for Particle Physics Experiments

We present the design and the test results of a quad-channel optical transceiver module (QTRx) possibly for future particle physics experiments. The transmitters of QTRx, each at 10 Gbps, are based on a Quad-channel VCSEL Diode array Driver (QLDD) and 1 x 4 VCSEL array. The receivers of QTRx, with data rates of 2.56 Gbps or 10 Gbps per channel, are based on a Quad-channel Trans-Impedance and limiting Amplifier (QTIA) and 1 x 4 photodiode array of GaAs or InGaAs. QTRx is 20 mm x 10 mm x 5 mm and couples to an MT fiber connector. Test results indicate that QTRx achieves the design goals with a power consumption of 124 mW per transmitter channel at 10 Gbps and 120 mW at 2.56 Gbps for the receiver channel with an on-chip charge pump. The sensitivities of QTIA are -17 dBm at 2.56 Gbps and -8 dBm at 10 Gbps, respectively. Further improvements with a gold-finger interface and a more compact optical lens are being designed.

physics.ins-det↗

arXiv2022

A prototype optical link board with redundancy design for the ATLAS liquid argon calorimeter Phase-2 upgrade

A prototype optical-link board has been developed for the ATLAS Liquid Argon Calorimeter Phase-2 upgrade. The board consists of 24 lpGBT chips and 8 VTRx+ modules and demonstrates the full optical link design of the future front-end board. The board has 22 simplex optical links to transmit detector data, which are emulated in FPGAs and injected through 6 FMC connectors, to the off-detector electronics. The board implements 2 duplex optical links for clocks, control, and monitoring with redundant design to improve the system reliability. Data transmission and all redundant designs have been verified. A fiber routing scheme, in which 2 or 3 VTRx+ modules are re-connected to the front panel with an MPO connector, has been prototyped.

physics.ins-det↗

arXiv2022

A radiation tolerant clock generator for the CMS Endcap Timing Layer readout chip

We present the test results of a low jitter Phase Locked Loop (PLL) prototype chip for the CMS Endcap Timing Layer readout chip (ETROC). This chip is based on the improved version of a clock synthesis circuit named ljCDR from the Low-Power Gigabit Transceiver (lpGBT) project. The ljCDR is tested in its PLL mode. An automatic frequency calibration (AFC) block with the Triple Modular Redundancy (TMR) register is developed for the LC-oscillator calibration. The chip was manufactured in a 65 nm CMOS process with 10 metal layers. The chip has been extensively tested, including Total Ionizing Dose (TID) testing up to 300 Mrad and Single Event Upset (SEU) testing with heavy ions possessing a Linear energy transfer (LET) from 1.3 to 62.5 MeV*cm^2/mg.

physics.ins-det↗

arXiv2022

QTIA, a 2.5 or 10 Gbps 4-Channel Array Optical Receiver ASIC in a 65 nm CMOS Technology

The Quad transimpedance and limiting amplifier (QTIA) is a 4-channel array optical receiver ASIC, developed using a 65 nm CMOS process. It is configurable between the bit rate of 2.56 Gbps and 10 Gbps per channel. QTIA offers careful matching to both GaAs and InGaAs photodiodes. At this R&D stage, each channel has a different biasing scheme to the photodiode for optimal coupling. A charge pump is implemented in one channel to provide a higher reverse bias voltage, which is especially important to mitigate radiation effects on the photodiodes. The circuit functions of QTIA successfully passed the lab tests with GaAs photodiodes.

physics.ins-det↗

arXiv2022

Triaxially strained suspended graphene for large-area pseudo-magnetic fields

Strain-engineered graphene has garnered much attention recently owing to the possibilities of creating substantial energy gaps enabled by pseudo-magnetic fields. While theoretical works proposed the possibility of creating large-area pseudo-magnetic fields by straining monolayer graphene along three crystallographic directions, clear experimental demonstration of such promising devices remains elusive. Herein, we experimentally demonstrate a triaxially strained suspended graphene structure that has the potential to possess large-scale and quasi-uniform pseudo-magnetic fields. Our structure employs uniquely designed metal electrodes that function both as stressors and metal contacts for current injection. Raman characterization and tight-binding simulations suggest the possibility of achieving pseudo-magnetic fields over a micrometer-scale area. Current-voltage measurements confirm an efficient current injection into graphene, showing the potential of our devices for a new class of optoelectronic applications. We also theoretically propose a photonic crystal-based laser structure that obtains strongly localized optical fields overlapping with the spatial area under uniform pseudo-magnetic fields, thus presenting a practical route towards the realization of graphene lasers.

cond-mat.mes-hall↗

arXiv2022

A 20 Gbps PAM4 Data Transmitter ASIC for Particle Physics Experiments

We present the design and test results of a novel data transmitter ASIC operating up to 20.48 Gbps with 4-level Pulse-Amplitude-Modulation (PAM4) for particle physics experiments. This ASIC, named GBS20, is fabricated in a 65 nm CMOS technology. Two serializers share a 5.12 GHz Phase Locked Loop (PLL) clock. The outputs from the serializers are combined into a PAM4 signal that directly drives a Vertical-Cavity-Surface-Emitting-Laser (VCSEL). The input data channels, each at 1.28 Gbps, are scrambled with an internal 27-1 Pseudo-Random Binary Sequence (PRBS), which also serves as a frame aligner. GBS20 is tested to work at 10.24 and 20.48 Gbps with a VCSEL-based Transmitter-Optical-Subassembly (TOSA). The power consumption of GBS20 is below 238 mW and reduced to 164 mW in the low-power mode.

physics.ins-det↗

arXiv2021

In-pixel automatic threshold calibration for the CMS Endcap Timing Layer readout chip

We present the implementation and verification of an in-pixel automatic threshold calibration circuit for the CMS Endcap Timing Layer (ETL) in the High-Luminosity LHC upgrade. The discriminator threshold of the ETL readout chip (ETROC) needs to be calibrated regularly to mitigate the circuit baseline change. Traditional methods need a lot of communication through a slow control system hence are time-consuming. This paper describes an in-pixel automatic scheme with improvements in operating time and usability. In this scheme, a sample-accumulation circuit is used to measure the average discriminator output. A binary successive approximation and linear combination scan are applied to find the equivalent baseline. The actual calibration procedure has been first implemented in FPGA firmware and tested with the ETROC front-end prototype chip (ETROC0). The calibration circuit has been implemented with Triple Modular Redundancy (TMR) and verified with Single Event Effects (SEEs) simulation. A complete calibration process lasts 35 ms with a 40 MHz clock. In the worst case, the dynamic and static power consumption are estimated to be 300 uW and 10.4 uW, respectively. The circuit design, implemented in a 65 CMOS technology, will be integrated into ETROC2, the next iteration of the ETROC with a 16x16 pixel matrix.

physics.ins-det↗

arXiv2021

Characterization of the CMS Endcap Timing Layer readout chip prototype with charge injection

We present the characterization of a readout Application-Specific Integrated Circuit (ASIC) for the CMS Endcap Timing Layer (ETL) of the High-Luminosity LHC upgrade with charge injection. The ASIC, named ETROC and developed in a 65 nm CMOS technology, reads out a 16x16 pixel matrix of the Low-Gain Avalanche Detector (LGAD). The jitter contribution from ETROC is required to be below 40 ps to achieve the 50 ps overall time resolution per hit. The analog readout circuits in ETROC consist of the preamplifier and the discriminator. The preamplifier handles the LGAD charge signal with the most probable value of around 15 fC. The discriminator generates the digital pulse, which provides the Time-Of-Arrival (TOA, leading edge) and Time-Over-Threshold (TOT, pulse width) information. The prototype of ETROC (ETROC0) that implements a single channel of analog readout circuits has been evaluated with charge injection. The jitter of the analog readout circuits, measured from the discriminator's leading edge, is better than 16 ps for a charge larger than 15 fC with the sensor capacitance. The time walk resulting from different pulse heights can be corrected using the TOT measurement. The time resolution distribution has a standard deviation of 29 ps after the time-walk correction from the charge injection. At room temperature, the preamplifier's power consumption is measured to be 0.74 mW and 1.53 mW per pixel in the low- and high-power mode, respectively. The measured power consumption of the discriminator is 0.84 mW per pixel. With the ASIC alone or the LGAD sensor, The characterization performances fulfill the ETL's challenging requirements.

physics.ins-det↗

arXiv2021

Quality control tests of the front-end optical link components for the ATLAS Liquid Argon Calorimeter Phase-1 upgrade

We present the procedures and results of the quality control tests for the front-end optical link components in the ATLAS Liquid Argon Calorimeter Phase-1 upgrade. The components include a Vertical-Cavity Surface-Emitting Laser (VCSEL) driver ASIC LOCld, custom optical transmitter/transceiver modules MTx/MTRx, and a transmitter ASIC LOCx2. LOCld, MTx, and LOCx2 each contain two channels with the same structure, while MTRx has a transmitter channel and a receiver channel. Each channel is tested at 5.12 Gbps. A total of 5341 LOCld chips, 3275 MTx modules, 797 MTRx modules, and 3198 LOCx2 chips are qualified. The yields are 73.9%, 98.0%, 98.4%, and 61.9% for LOCld, LOCx2, MTx, and MTRx, respectively.

physics.ins-det↗

arXiv2021

Characterization and quality control test of a gigabit cable receiver ASIC (GBCR2) for the ATLAS Inner Tracker Detector upgrade

We present the characterization and quality control test of a gigabit cable receiver ASIC prototype, GBCR2, for the ATLAS Inner Tracker pixel detector upgrade. GBCR2 equalizes and retimes the uplink electrical signals from RD53B through a 6 m Twinax AWG34 cable to lpGBT. GBCR2 also pre-emphasizes downlink command signals through the same electrical connection from lpGBT to RD53B. GBCR2 has seven uplink channels each at 1.28 Gbps and two downlink channels each at 160 Mbps. The prototype is fabricated in a 65 nm CMOS process. The characterization of GBCR2 has been demonstrated that the total jitter of the output signal is 129.1 ps (peak-peak) in the non-retiming mode or 79.3 ps (peak-peak) in the retiming mode for the uplink channel and meets the requirements of lpGBT. The total power consumption of all uplink channels is 87.0 mW in the non-retiming mode and 101.4 mW in the retiming mode, below the specification of 174 mW. The two downlink channels consume less than 53 mW. A quality control test procedure is proposed and 169 prototype chips are tested. The yield is about 97.0%.

physics.ins-det↗

arXiv2021

Graphene-based Distributed 3D Sensing Electrodes for Mapping Spatiotemporal Auricular Physiological Signals

Underneath the ear skin there are richly branching vascular and neural networks that ultimately connecting to our heart and brain. Hence, the three-dimensional (3D) mapping of auricular electrophysiological signals could provide a new perspective for biomedical studies such as diagnosis of cardiovascular diseases and neurological disorders. However, it is still extremely challenging for current sensing techniques to cover the entire ultra-curved auricle. Here, we report a graphene-based ear-conformable sensing device with embedded and distributed 3D electrodes which enable full-auricle physiological monitoring. The sensing device, which incorporates programable 3D electrode thread array and personalized auricular mold, has 3D-conformable sensing interfaces with curved auricular skin, and was developed using one-step multi-material 3D-printing process. As a proof-of-concept, spatiotemporal auricular electrical skin resistance (AESR) mapping was demonstrated. For the first time, 3D AESR contours were generated and human subject-specific AESR distributions among a population were observed. From the data of 17 volunteers, the auricular region-specific AESR changes after cycling exercise were observed in 98% of the tests and were validated via machine learning techniques. Correlations of AESR with heart rate and blood pressure were also studied using statistical analysis. This 3D electronic platform and AESR-based new biometrical findings show promising biomedical applications.

eess.SP↗

arXiv2020

Effects of cluster correlations on fragment emission in 12C + 12C at 50 MeV/nucleon

The effects of cluster correlations have been studied in the $^{12}$C + $^{12}$C reaction at 50 MeV/nucleon, using three AMD models, the AMD (AMD/D) without any additional cluster correlations, AMD/D-COALS with nucleon correlations based on a coalescence prescription for light cluster formations with $A\leq4$ and AMD-Cluster with an extended cluster correlation in two-nucleon collision processes and a special treatment for intermediate fragment formation with A $\le 9$. The angular distributions and energy spectra of fragments have been simulated and compared with the available experimental data. It is found that the cluster correlations take a crucial role to describe the productions of light charged particles (LCPs) and intermediate mass fragments (IMFs), and the AMD-cluster studied here provides a consistent overall reproduction of the experimental data. It is also shown that the significant effects of the secondary decay processes are involved for the fragment production besides the dynamical productions in the AMD stage. Detailed LCP and IMF production mechanisms involved in the intermediate energy heavy ion collisions are discussed.

nucl-th↗

arXiv2020

A novel quad-channel 10 Gbps CMOS VCSEL array driver with integrated charge pumps

We present a novel design and the test results of a 4-channel driver for an array of Vertical-Cavity Surface-Emitting Lasers (VCSELs). This ASIC, named cpVLAD and fabricated in a 65 nm CMOS technology, has on-chip charge pumps and is for data rates up to 10 Gbps per channel. The charge pumps are implemented to address the issue of voltage margin of the VCSEL driving stage in the applications under low temperature and harsh radiation environment. Test results indicate that cpVLAD is capable of driving VCSELs with forward voltages of up to 2.8 V using 1.2 V and 2.5 V power supplies with a power consumption of 94 mW/channel.

physics.ins-det↗

arXiv2020

Optical transceivers for event triggers in the ATLAS phase-I upgrade

The ATLAS phase-I upgrade aims to enhance event trigger performance in the Liquid Argon (LAr) calorimeter and the forward muon spectrometer. The trigger signals are transmitted by optical transceivers at 5.12 Gbps per channel in a radiation field. We report the design, quality control in production and ageing test of the transceivers fabricated with the LOCld laser driver and multi-mode 850 nm vertical-cavity surface-emitting laser (VCSEL). The modules are packaged in miniature formats of dual-channel transmitter (MTx) and transceiver (MTRx) for the LAr. The transmitters are also packaged in small form-factor pluggable (SFP) for the muon spectrometer. In production, the LOCld chips and VCSELs in TOSA package were examined before assembly. All of the modules were tested and selected during production for quality control based on the eye-diagram parameters measured at 5.12 Gbps. The yield is 98 % for both the MTx and MTRx on a total 4.7k modules. The uniformity of transmitter channels of a MTx was assured by choosing the TOSA components with approximately equal light powers. The ageing effect is monitored in burn-in of a small batch of transmitter modules with bit-error test and eye-diagrams measured periodically. The observables are stable with the light power degradation within 5 % over a period of more than 6k hours.

physics.ins-det↗

arXiv2020

A 4-Channel 10-Gbps/ch CMOS VCSEL Array Driver with on-chip Charge-pumps

We present the design and test results of a 4-channel 10-Gbps/ch Vertical-Cavity Surface-Emitting Laser array driver, the cpVLAD. With on-chip charge-pumps to extend the biasing headroom for the VCSELs needed for low temperature operation and mitigation of the radiation effects. The cpVLAD was fabricated in a 65-nm CMOS technology. The test results show that the cpVLAD is capable of driving VCSELs with forward bias voltages as high as 2.8 V from a 2.5 V power supply. The power consumption of the cpVLAD is 94 mW/ch.

physics.ins-det↗