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Li, S.

Publications and source records attributed to Li, S..

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Reflectivity and PDE of VUV4 Hamamatsu SiPMs in liquid xenon

Considering reflective properties of materials and photodetection efficiency (PDE) of photodetectors is important for optimizing energy resolution and sensitivity of the next generation neutrinoless double beta decay, direct detection dark matter, and neutrino oscillation experiments that will use noble liquid gases, such as nEXO, DARWIN, DarkSide-20k, and DUNE . Little information is currently available about reflectivity and PDE in liquid noble gases, because such measurements are difficult to conduct in a cryogenic environment and at short enough wavelengths. Here we report a measurement of specular reflectivity and relative PDE of Hamamatsu VUV4 silicon photomultipliers (SiPMs) with 50 μ m micro-cells conducted with xenon scintillation light ( ~ 175 nm) in liquid xenon. The specular reflectivity at 15 o incidence of three samples of VUV4 SiPMs is found to be 30.4 ± 1.4%, 28.6 ± 1.3%, and 28.0 ± 1.3%, respectively. The PDE at normal incidence differs by ± 8% (standard deviation) among the three devices. The angular dependence of the reflectivity and PDE was further measured for one of the SiPMs. Both the reflectivity and PDE decrease as the angle of incidence increases. This is the first measurement of an angular dependence of PDE and reflectivity of a SiPM in liquid xenon.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Impact Behavior of Polyetheretherketone/Nickel Foam Co-continuous Composites

In this study, we prepared eight types of polyetheretherketone/nickel (PEEK/Ni) foam co-continuous phase composites (named “PEEK-Nis”) in which virgin PEEK was infiltrated into homologous hollow Ni structures by using hot pressing. Their Charpy impact behavior was investigated in accordance with ISO: 179-1, and the effect of the structure of the foam Ni on the impact properties of the PEEK-Nis was also studied. Compared with unfilled PEEK, the Ni prisms can effectively disperse, transfer, and absorb the energy of the pendulum, further improve the impact toughness of the PEEK-Nis and eventually lead to different fracture modes. The impact toughness of PEEK-Nis was mainly affected by Ni volume fraction, coating thickness, and pores per inch (PPI) value, which are mutually restricted. When the Ni content was less than 8.5%, the impact toughness of PEEK-Nis increased with an increase in PPI value. When the Ni content was between 8.5 and 18%, the impact toughness of PEEK-Nis increased with the coating thickness. When the Ni content exceeded 18%, the impact toughness decreased dramatically possibly because of the mechanical mismatch of the two-phase materials in PEEK-Nis. For further optimization, PEEK-NiB-2 was fabricated and had the most reasonable structure of the reinforcing phase. Among all PEEK-Nis, PEEK-NiB-2 exhibited the best impact toughness, with a value over two times that of unfilled PEEK.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Characterization of the Hamamatsu VUV4 MPPCs for nEXO

In this paper we report on the characterization of the Hamamatsu VUV4 (S/N: S13370-6152) Vacuum Ultra-Violet (VUV) sensitive Silicon Photo-Multipliers (SiPMs) as part of the development of a solution for the detection of liquid xenon scintillation light for the nEXO experiment. Various SiPM features, such as: dark noise, gain, correlated avalanches, direct crosstalk and Photon Detection Efficiency (PDE) were measured in a dedicated setup at TRIUMF. SiPMs were characterized in the range 163 K = T = 233 K. At an over voltage of 3.1 ± 0.2 V and at T = 163 K we report a number of Correlated Avalanches (CAs) per pulse in the 1µs interval following the trigger pulse of 0.161±0.005. At the same settings the Dark-Noise (DN) rate is 0.137 ± 0.002 Hz/mm2. Both the number of CAs and the DN rate are within nEXO specifications. The PDE of the Hamamatsu VUV4 was measured for two different devices at T = 233 K for a mean wavelength of 189 ± 7 nm. At 3.6 ± 0.2 V and 3.5 ± 0.2 V of over voltage we report a PDE of 13.4 ± 2.6 % and 11 ± 2%, corresponding to a saturation PDE of 14.8 ± 2.8 % and 12.2±2.3%, respectively. Both values are well below the 24 % saturation PDE advertised by Hamamatsu. More generally, the second device tested at 3.5 ± 0.2 V of over voltage is below the nEXO PDE requirement. The first one instead yields a PDE that is marginally close to meeting the nEXO specifications. This suggests that with modest improvements the Hamamatsu VUV4 MPPCs could be considered as an alternative to the FBKLF SiPMs for the final design of the nEXO detector.

Gallina, G↗
DOE OSTI2019

Simulation of charge readout with segmented tiles in nEXO

nEXO is a proposed experiment to search for the neutrino-less double beta decay (0νββ) of 136 Xe in a tonne-scale liquid xenon time projection chamber (TPC). The nEXO TPC will be equipped with charge collection tiles to form the anode. In this work, the charge reconstruction performance of this anode design is studied with a dedicated simulation package. A multi-variate method and a deep neural network are developed to distinguish simulated 0νββ signals from backgrounds arising from trace levels of natural radioactivity in the detector materials. These simulations indicate that the nEXO TPC with charge-collection tiles shows promising capability to discriminate the 0νββ signal from backgrounds. Furthermore, the estimated half-life sensitivity for 0νββ decay is improved by 20 32)% with the multi-variate (deep neural network) methods considered here, e sensitivity estimated in the nEXO pre-conceptual design report.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Measurement of the cosmic ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite

The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is essential to understand the source and acceleration of cosmic rays in the Milky Way. This work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2 1 / 2 years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to ~100 TeV with high statistics. The measured spectrum validates the spectral hardening at ~300 GeV found by previous experiments and reveals a softening at ~13.6 TeV, with the spectral index changing from ~2.60 to ~2.85. Our result implies the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

A high precision calibration of the nonlinear energy response at Daya Bay

A high precision calibration of the nonlinearity in the energy response of the Daya Bay Reactor Neutrino Experiment’s antineutrino detectors is observed. The energy nonlinearity originates from the particle-dependent light yield of the scintillator and charge-dependent electronics response. The nonlinearity model is constrained by γ calibration points from deployed and naturally occurring radioactive sources, the β spectrum from 12 B decays, and a direct measurement of the electronics nonlinearity with a new flash analog-to-digital converter readout system. With this beind said, less than 0.5% uncertainty in the energy nonlinearity calibration is achieved for positrons of kinetic energies greater than 1 MeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Density changes in low pressure gas targets for electron scattering experiments

A system of modular sealed gas target cells has been developed for use in electron scattering experiments at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). This system was initially developed to complete the MARATHON experiment which required, among other species, tritium as a target material. Thus far, the cells have been loaded with the gas species 3 H, 3 He, 2 H, 1 H and 40 Ar and operated in nominal beam currents of up to 22.5 μA in Jefferson Lab's Hall A. While the gas density of the cells at the time of loading is known, the density of each gas varies uniquely when heated by the electron beam. To extract experimental cross sections using these cells, density dependence on beam current of each target fluid must be determined. In this study, data from measurements with several beam currents within the range of 2.5 to 22.5 μA on each target fluid are presented. In addition, expressions for the beam current dependent fluid density of each target are developed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

First measurement of the Ar ( e , e ' ) X cross section at Jefferson Laboratory

The success of the ambitious programs of both long- and short-baseline neutrino-oscillation experiments employing liquid-argon time-projection chambers will greatly rely on the precision with which the weak response of the argon nucleus can be estimated. In the E12-14-012 experiment at Jefferson Lab Hall A, we have studied the properties of the argon nucleus by scattering a high-quality electron beam off a high-pressure gaseous argon target. Here, we present the measured 40 Ar(e,e') double differential cross section at incident electron energy E = 2:222 GeV and scattering angle = 15:541 deg. The data cover a broad range of energy transfers, where quasi-elastic scattering and delta production are the dominant reaction mechanisms. The result for argon is compared to our previously reported cross sections for titanium and carbon, obtained in the same kinematical setup.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Design and Beam Test Results for the sPHENIX Electromagnetic and Hadronic Calorimeter Prototypes

The super Pioneering High Energy Nuclear Interaction eXperiment (sPHENIX) at the Relativistic Heavy Ion Collider (RHIC) will perform high precision measurements of jets and heavy flavor observables for a wide selection of nuclear collision systems, elucidating the microscopic nature of strongly interacting matter ranging from nucleons to the strongly coupled quark-gluon plasma. A prototype of the sPHENIX calorimeter system was tested at the Fermilab Test Beam Facility as experiment T-1044 in the spring of 2016. The electromagnetic calorimeter (EMCal) prototype is composed of scintillating fibers embedded in a mixture of tungsten powder and epoxy. The hadronic calorimeter (HCal) prototype is composed of tilted steel plates alternating with plastic scintillator. Results of the test beam reveal the energy resolution for electrons in the EMCal is $2.8\%\oplus~15.5\%/\sqrt{E}$ and the energy resolution for hadrons in the combined EMCal plus HCal system is $13.5\%\oplus 64.9\%/\sqrt{E}$. These results demonstrate that the performance of the proposed calorimeter system satisfies the sPHENIX specifications.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗