arXiv subjects

H. W. Wang

Publications and source records attributed to H. W. Wang.

At least 19 recordsLinked to original sources

arXiv2024

Burn-in Test and Thermal Performance Evaluation of Silicon Photomultipliers for the JUNO-TAO Experiment

This study evaluates more than 4,000 tiles made of Hamamatsu visual-sensitive silicon photomultipier (SiPM), each with dimensions of 5 $\times$ 5 cm$^2$, intended for the central detector of the Taishan Anti-neutrino Observatory (TAO), a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO) aimed at measuring the reactor anti-neutrino energy spectrum with unprecedented energy resolution. All SiPM tiles underwent a room temperature burn-in test in the dark for two weeks, while cryogenic testing analyzed the thermal dependence of parameters for some sampled SiPMs. Results from these comprehensive tests provide crucial insights into the long-term performance and stability of the 10 square meters of SiPMs operating at -50°C to detect scintillation photons in the TAO detector. Despite some anomalies awaiting further inspection, all SiPMs successfully passed the burn-in test over two weeks at room temperature, which is equivalent to 6.7 years at -50°C. Results are also used to guide optimal SiPM selection, configuration, and operation, ensuring reliability and sustainability in reactor neutrino measurements. This work also provides insights for a rapid and robust quality assessment in future experiments that employ large-scale SiPMs as detection systems.

physics.ins-det↗

arXiv2023

Structural origin of the Jeff=1/2 antiferromagnetic phase in Ga-doped Sr2IrO4

Sr2IrO4 hosts a novel Jeff =1/2 Mott state and quasi-two-dimensional antiferromagnetic order, providing a unique avenue of exploring emergent states of matter and functions that are extraordinarily sensitive to any structural variations. While the correlation between the physical property and lattice structure in Sr2IrO4 has been a focused issue in the past decade, a common perception assumes that the magnetic ordering is essentially determined by the Ir-O-Ir bond angle. Therefore, a delicate modulation of this angle and consequently a major modulation of the magnetic ordering, by chemical doping such as Ga at Ir site, has been extensively investigated and well believed. In this work, however, we present a whole package of structure and magnetism data on a series of single crystal and polycrystalline Sr2Ir1-xGaxO4 samples, revealing the substantial difference in the Néel temperature TN between the two types of samples, and the TN value for the polycrystalline sample x = 0.09 is even 64 K higher than that of the single crystal sample x = 0.09 (deltaTN ~ 64 K at x = 0.09). Our systematic investigations demonstrate the crucial role of the c/a ratio in tuning the interlayer coupling and thereby the Neel point TN, i.e. a higher TN can be achieved as c/a is reduced. The notable differences in structural parameters between the two groups of samples are probably caused by additional strain due to the massive grain boundaries in polycrystalline samples. The present work suggests an additional ingredient of physics that is essential in modulating the emergent properties in Sr2IrO4 and probably other iridates.

cond-mat.str-el↗

arXiv2022

Measurement of the $^{159}$Tb(n, $γ$) cross section at the CSNS Back-n facility

The stellar (n, $γ$) cross section data for the mass numbers around A $\approx$ 160 are of key importance to nucleosynthesis in the main component of the slow neutron capture process, which occur in the thermally pulsing asymptotic giant branch (TP--AGB). The new measurement of (n, $γ$) cross sections for $^{159}$Tb was performed using the C$_6$D$_6$ detector system at the back streaming white neutron beam line (Back-n) of the China spallation neutron source (CSNS) with neutron energies ranging from 1 eV to 1 MeV. Experimental resonance capture kernels were reported up to 1.2 keV neutron energy with this capture measurement. Maxwellian-averaged cross sections (MACS) were derived from the measured $^{159}$Tb (n, $γ$) cross sections at $kT$ = 5 $\sim$ 100 keV and are in good agreement with the recommended data of KADoNiS-v0.3 and JEFF-3.3, while KADoNiS-v1.0 and ENDF-VIII.0 significantly overestimate the present MACS up to 40$\%$ and 20$\%$, respectively. A sensitive test of the s-process nucleosynthesis was also performed with the stellar evolution code MESA. Significant changes in abundances around A $\approx$ 160 were observed between the ENDF/B-VIII.0 and present measured rate of $^{159}$Tb(n, $γ$)$^{160}$Tb in the MESA simulation.

nucl-ex↗

arXiv2022

Neutron capture measurement and resonance parameter analysis of natSm

Multiple isotopes of samarium element are the isotopes produced by the s process, and 154Sm is produced by the r process. In addition, 144Sm is p nuclei in nuclear astrophysics. The measurement of these can help us to better understand the results of relevant photonuclear reaction experiments. On the other hand, 149Sm is a 235U fission product with a 1% yield, its cross sections are important to reactor neutronics. In this work, the neutron capture yield of the natural samarium target was measured at the back-streaming white neutron beamline (Back-n) of the China Spallation Neutron Source (CSNS), and the resonance parameters were analyzed by SAMMY code. The resonance peaks and the neutron separation energies contributed by the different isotopes are considered individually. The results of the capture yield found signs of the possibility of two resonance peaks at 8 eV, which awaits further experimental examination. Cross-section was calculated according to resonance parameters and was compared with other experimental results and evaluation databases of ENDF/B-VIII.0 and CENDL-3.2. A clear difference between ENDF/B VIII.0 and CENDL-3.2 database appears at 23.2 eV, the experimental result at this energy is smaller than data of ENDF/B VIII.0 database but CENDL-3.2 database. Most of the controversial experimental results invariably come from the samarium 149 isotope.

nucl-ex↗

arXiv2022

p-process chaser detector in $n$-$γ$ coincidences

We propose two types of neutron-$γ_1$-$γ_2$ triple coincidence detectors (not constructed) to chase gamma transitions to produce p-nuclei following the neutron emission in the $(γ, n)$ reaction. Neutrons are detected with 24 $^3$He counters embedded in a polyethylene moderator in Type I detector and with 6 liquid scintillation detectors in Type II detector, respectively. $γ$ rays are detected with two high-purity germanium detectors and four LaBr$_3$(Ce) detectors. The detector which is referred to as p-process chaser detector is used to search for mediating states in $^{180}$Ta through which the isomeric and ground states in $^{180}$Ta are thermalized in the p-process. A search is made for both resonant states and unresolved states in high nuclear-level-density domain.

physics.ins-det↗

arXiv2020

Anisotropic behavior of TiB2 nanoparticles reinforced 2024Al composites rolling sheet

The in-plane anisotropy (IPA) of mechanical properties existed in plate products is often undesired since it limits the industrial application and increases the difficulty of material processing. It is thus one of the important factors which requires strict control during the manufacture of high-performance aluminum alloy plates. The anisotropic behavior of TiB2/2024Al composite rolling sheet under different heat treatment is studied in this article. T4 heat treated specimen shows good isotropy of yield strength and its texture components are significantly weakened compared with traditional Al alloys. The evolution of microstructures for T4 specimen was studied. The submicron TiB2 particles increase the driving force of recrystallization during rolling process and static recrystallization (SRX) is stimulated, thus induces texture randomization. Anisotropic behavior of yield strength occurs in specimen after T3 heat treatment. It is supposed that the difference in the activation of slip system under different loading direction gives rise to this anisotropy.

cond-mat.mtrl-sci↗

arXiv2019

Nuclear probes of an out-of-equilibrium plasma at the highest compression

We report the highest compression reached in laboratory plasmas using eight laser beams, E$_{laser}$$\approx$12 kJ, $τ_{laser}$=2 ns in third harmonic on a CD$_2$ target at the ShenGuang-II Upgrade (SGII-Up) facility in Shanghai, China. We estimate the deuterium density $ρ_D$= 2.0 $\pm$ 0.9 kg/cm$^{3}$, and the average kinetic energy of the plasma ions less than 1 keV. The highest reached areal density $Λρ_{D}$=4.8 $\pm$ 1.5 g/cm$^{2}$ was obtained from the measured ratio of the sequential ternary fusion reactions (dd$\rightarrow$t+p and t+d$\rightarrow$$α$+n) and the two body reaction fusions (dd$\rightarrow$$^3$He+n). At such high densities, sequential ternary and also quaternary nuclear reactions become important as well (i.e. n(14.1 MeV) + $^{12}$C $\rightarrow$ n'+$^{12}$C* etc.) resulting in a shift of the neutron (and proton) kinetic energies from their birth values. The Down Scatter Ratio (DSR-quaternary nuclear reactions) method, i.e. the ratio of the 10-12MeV neutrons divided by the total number of 14.1MeV neutrons produced, confirms the high densities reported above. The estimated lifetime of the highly compressed plasma is 52 $\pm$ 9 ps, much smaller than the lasers pulse duration.

physics.plasm-ph↗

arXiv2018

Structural transitions in hybrid improper ferroelectric Ca$_3$Ti$_2$O$_7$ tuned by site-selective iso-valent substitutions: a first-principles study

Ca$_3$Ti$_2$O$_7$ is an experimentally confirmed hybrid improper ferroelectric material, in which the electric polarization is induced by a combination of the coherent TiO$_6$ octahedral rotation and tilting. In this work, we investigate the tuning of ferroelectricity of Ca$_3$Ti$_2$O$_7$ using iso-valent substitutions on Ca-sites. Due to the size mismatch, larger/smaller alkaline earths prefer $A$'/$A$ sites respectively, allowing the possibility for site-selective substitutions. Without extra carriers, such site-selected iso-valent substitutions can significantly tune the TiO$_6$ octahedral rotation and tilting, and thus change the structure and polarization. Using the first-principles calculations, our study reveals that three substituted cases (Sr, Mg, Sr+Mg) show divergent physical behaviors. In particular, (CaTiO$_3$)$_2$SrO becomes non-polar, which can reasonably explain the suppression of polarization upon Sr substitution observed in experiment. In contrast, the polarization in (MgTiO$_3$)$_2$CaO is almost doubled upon substitutions, while the estimated coercivity for ferroelectric switching does not change. The (MgTiO$_3$)$_2$SrO remains polar but its structural space group changes, with moderate increased polarization and possible different ferroelectric switching paths. Our study reveals the subtle ferroelectricity in the $A_3$Ti$_2$O$_7$ family and suggests one more practical route to tune hybrid improper ferroelectricity, in addition to the strain effect.

cond-mat.mtrl-sci↗

arXiv2017

A data acquisition system based on ROOT and waveform digital technology for Photo-Neutron Source

The data acquisition system is based on ROOT and waveform digital technology, including neutron detector, waveform digitizer, PCI card, optical fiber, computer, reaction target device, stepper motor, data acquisition software and control target software. It achieves to acquire and record the waveform information of signal measured by the detector using a waveform digitizer. The specific target position is changed by the stepper motor which is remotely controlled by the data acquisition software and control target software. It is implemented by the exchange of information between the data acquisition software and the control target software. The system realizes to automatically open files and change targets at fixed intervals. It is capable of data compression by removing the data those are not signals, and automatic alarm when the beam is lost.

physics.ins-det↗

arXiv2016

The decay characteristic of $^{22}$Si and its ground-state mass significantly affected by three-nucleon forces

The decay of the proton-rich nucleus $^{22}$Si was studied by a silicon array coupled with germanium clover detectors. Nine charged-particle groups are observed and most of them are recognized as $β$-delayed proton emission. A charged-particle group at 5600 keV is identified experimentally as $β$-delayed two-proton emission from the isobaric analog state of $^{22}$Al. Another charged-particle emission without any $β$ particle at the low energy less than 300 keV is observed. The half-life of $^{22}$Si is determined as 27.5 (18) ms. The experimental results of $β$-decay of $^{22}$Si are compared and in nice agreement with shell-model calculations. The mass excess of the ground state of $^{22}$Si deduced from the experimental data shows that three-nucleon (3N) forces with repulsive contributions have significant effects on nuclei near the proton drip line.

nucl-ex↗

arXiv2016

Proton-proton correlations in distinguishing the two-proton emission mechanism of $^{23}$Al and $^{22}$Mg

The proton-proton momentum correlation functions ($C_{pp}(q)$) for kinematically complete decay channels of $^{23}$Al $\rightarrow$ p + p + $^{21}$Na and $^{22}$Mg $\rightarrow$ p + p + $^{20}$Ne have been measured at the RIKEN RI Beam Factory. From the very different correlation strength of $C_{pp}(q)$ for $^{23}$Al and $^{22}$Mg, the source size and emission time information were extracted from the $C_{pp}(q)$ data by assuming a Gaussian source profile in the correlation function calculation code (CRAB). The results indicated that the mechanism of two-proton emission from $^{23}$Al was mainly sequential emission, while that of $^{22}$Mg was mainly three-body simultaneous emission. By combining our earlier results of the two-proton relative momentum and the opening angle, it is pointed out that the mechanism of two-proton emission could be distinguished clearly.

nucl-ex↗

arXiv2016

Beta-decay study of $T_z=-2$ proton-rich nucleus $^{20}$Mg

The $β$ decay of the drip-line nucleus $^{20}$Mg gives important information on resonances in $^{20}$Na, which are relevant for the astrophysical $rp$-process. A detailed $β$ decay spectroscopic study of $^{20}$Mg was performed by a continuous-implantation method. A detection system was specially developed for charged-particle decay studies, giving improved spectroscopic information including the half-life of $^{20}$Mg, the excitation energies, the branching ratios, and the log $ft$ values for the states in $^{20}$Na populated in the $β$ decay of $^{20}$Mg. A new proton branch was observed and the corresponding excited state in $^{20}$Na was proposed. The large isospin asymmetry for the mirror decays of $^{20}$Mg and $^{20}$O was reproduced, as well. However, no conclusive conclusion can be draw about the astrophysically interesting 2645~keV resonance in $^{20}$Na due to the limited statistics.

nucl-ex↗

arXiv2015

Different mechanism of two-proton emission from proton-rich nuclei $^{23}$Al and $^{22}$Mg

Two-proton relative momentum ($q_{pp}$) and opening angle ($θ_{pp}$) distributions from the three-body decay of two excited proton-rich nuclei, namely $^{23}$Al $\rightarrow$ p + p + $^{21}$Na and $^{22}$Mg $\rightarrow$ p + p + $^{20}$Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at $q_{pp}\sim20$ MeV/c as well as a peak in $θ_{pp}$ around 30$^\circ$ are seen in the two-proton break-up channel from a highly-excited $^{22}$Mg. In contrast, such peaks are absent for the $^{23}$Al case. It is concluded that the two-proton emission mechanism of excited $^{22}$Mg is quite different from the $^{23}$Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.

nucl-ex↗

arXiv2015

New measurement of the excited states in $^{11}$B via the elastic resonance scattering of $^{10}$Be + p

The elastic resonance scattering protons decayed from $^{11}$B to the ground state of $^{10}$Be were measured using the thick-target technique in inverse kinematics at the Heavy Ion Research Facility in Lanzhou (HIRFL). The obtained excitation functions were well described by a multichannel R-matrix procedure under the kinematics process assumption of resonant elastic scattering. The excitation energy of the resonant states ranges from 13.0 to 17.0 MeV, and their resonant parameters such as the resonant energy E$_{x}$, the spin-parity J$^π$, and the proton-decay partial width $Γ_p$ were determined from R-matrix fits to the data. Two of these states around E$_{x}$ = 14.55 MeV [J$^π$ = (3/2$^+$, 5/2$^+$), $Γ_p$ = 475 $\pm$ 80 keV] and E$_{x}$ = 14.74 MeV [J$^π$ = 3/2$^-$, $Γ_p$ = 830 $\pm$ 145 keV], and a probably populated state at E$_x$ = 16.18 MeV [J$^π$ =(1/2$^-$, 3/2$^-$), $Γ_p$ $<$ 60 keV], are respectively assigned to the well-known states in $^{11}$B at 14.34 MeV, 15.29 MeV, and 16.43 MeV. The isospin of these three states were previously determined to be T = 3/2, but discrepancies exist in widths and energies due to the current counting statistics and energy resolution. We have compared these states with previous measurements, and the observation of the possibly populated resonance is discussed.

nucl-ex↗

arXiv2014

Examination of the role of the $^{14}$O($α$,$p$)$^{17}$F reaction rate in type I x-ray bursts

The $^{14}$O($α$,$p$)$^{17}$F reaction is one of the key reactions involved in the breakout from the hot-CNO cycle to the rp-process in type I x-ray bursts (XRBs). The resonant properties in the compound nucleus $^{18}$Ne have been investigated through resonant elastic scattering of $^{17}$F+$p$. The radioactive $^{17}$F beam was separated by the CNS Radioactive Ion Beam separator (CRIB) and bombarded a thick H$_2$ gas target at 3.6 MeV/nucleon. The recoiling light particles were measured by three $Δ$E-E silicon telescopes at laboratory angles of $θ$$_{lab}$$\approx$3$^\circ$, 10$^\circ$ and 18$^\circ$, respectively. Five resonances at $E_{x}$=6.15, 6.28, 6.35, 6.85, and 7.05 MeV were observed in the excitation functions, and their spin-parities have been determined based on an $R$-matrix analysis. In particular, $J^π$=1$^-$ was firmly assigned to the 6.15-MeV state which dominates the thermonuclear $^{14}$O($α$,$p$)$^{17}$F rate below 2 GK. As well, a possible new excited state in $^{18}$Ne was observed at $E_{x}$=6.85$\pm$0.11 MeV with tentative $J$=0 assignment. This state could be the analog state of the 6.880 MeV (0$^{-}$) level in the mirror nucleus $^{18}$O, or a bandhead state (0$^+$) of the six-particle four-hole (6$p$-4$h$) band. A new thermonuclear $^{14}$O($α$,$p$)$^{17}$F rate has been determined, and the astrophysical impact of multiple recent rates has been examined using an XRB model. Contrary to previous expectations, we find only modest impact on predicted nuclear energy generation rates from using reaction rates differing by up to several orders of magnitude.

nucl-ex↗

arXiv2014

PandaX: A Liquid Xenon Dark Matter Experiment at CJPL

PandaX is a large upgradable liquid-xenon detector system that can be used for both direct dark-matter detection and $^{136}$Xe double-beta decay search. It is located in the Jinping Deep-Underground Laboratory in Sichuan, China. The detector operates in dual-phase mode, allowing detection of both prompt scintillation, and ionization charge through proportional scintillation. The central time projection chamber will be staged, with the first stage accommodating a target mass of about 120\,kg. In stage II, the target mass will be increased to about 0.5\,ton. In the final stage, the detector can be upgraded to a multi-ton target mass. In this paper a detailed description of the stage-I detector design and performance results established during the commissioning phase is presented.

physics.ins-det↗

arXiv2014

Investigation of thermonuclear $^{18}$Ne($α$,$p$)$^{21}$Na rate via resonant elastic scattering of $^{21}$Na+$p$

The $^{18}$Ne($α$,$p$)$^{21}$Na reaction is thought to be one of the key breakout reactions from the hot CNO cycles to the rp-process in type I x-ray bursts. In this work, the resonant properties of the compound nucleus $^{22}$Mg have been investigated by measuring the resonant elastic scattering of $^{21}$Na+$p$. An 89 MeV $^{21}$Na radioactive beam delivered from the CNS Radioactive Ion Beam Separator bombarded an 8.8 mg/cm$^2$ thick polyethylene (CH$_{2}$)$_{n}$ target. The $^{21}$Na beam intensity was about 2$\times$10$^{5}$ pps, with a purity of about 70% on target. The recoiled protons were measured at the center-of-mass scattering angles of $θ_{c.m.}$$\approx$175.2${^\circ}$, 152.2${^\circ}$, and 150.5${^\circ}$ by three sets of $ΔE$-$E$ telescopes, respectively. The excitation function was obtained with the thick-target method over energies $E_x$($^{22}$Mg)=5.5--9.2 MeV. In total, 23 states above the proton-threshold in $^{22}$Mg were observed, and their resonant parameters were determined via an $R$-matrix analysis of the excitation functions. We have made several new $J^π$ assignments and confirmed some tentative assignments made in previous work. The thermonuclear $^{18}$Ne($α$,$p$)$^{21}$Na rate has been recalculated based on our recommended spin-parity assignments. The astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the $^{18}$Ne($α$,$p$)$^{21}$Na rate significantly affects the peak nuclear energy generation rate, reaction fluxes, as well as the onset temperature of this breakout reaction in these astrophysical phenomena.

astro-ph.SR↗

arXiv2014

Properties of resonant states in 18Ne relevant to key 14O(alpha,p)17F breakout reaction in type I x-ray bursts

The $^{14}$O($α$,$p$)$^{17}$F reaction is one of the key reactions involved in the breakout from the hot-CNO cycle to the rp-process in type I x-ray bursts. The resonant properties in the compound nucleus $^{18}$Ne have been investigated through resonant elastic scattering of $^{17}$F+$p$. The radioactive $^{17}$F beam was separated by the CNS Radioactive Ion Beam separator (CRIB) and bombarded a thick H$_2$ gas target at 3.6 MeV/nucleon. The recoiling light particles were measured by using three $Δ$E-E silicon telescopes at laboratory angles of $θ$$_{lab}$$\approx$3$^\circ$, 10$^\circ$ and 18$^\circ$, respectively. Five resonances at $E_{x}$=6.15, 6.28, 6.35, 6.85, and 7.05 MeV were observed in the excitation functions. Based on an $R$-matrix analysis, $J^π$=1$^-$ was firmly assigned to the 6.15-MeV state. This state dominates the thermonuclear $^{14}$O($α$,$p$)$^{17}$F rate below 1 GK. We have also confirmed the existence and spin-parities of three states between 6.1 and 6.4 MeV. As well, a possible new excited state in $^{18}$Ne was observed at $E_{x}$=6.85$\pm$0.11 MeV and tentatively assigned as $J$=0. This state could be the analog state of the 6.880 MeV (0$^{-}$) level in the mirror nucleus $^{18}$O, or a bandhead state (0$^+$) of the six-particle four-hole (6$p$-4$h$) band. A new thermonuclear rate of the $^{14}$O($α$,$p$)$^{17}$F reaction has been determined, and its astrophysical impact has been examined within the framework of one-zone x-ray burst postprocessing calculations.

nucl-ex↗