Global Energetics of Solar Powerful Events on 2017 September 6

Solar flares and coronal mass ejections(CMEs)are thought to be the most powerful events on the Sun.They can release energy as high as~10^(32)erg in tens of minutes,and also can release solar energetic particles(SEPs)into interplanetary space.We explore global energy budgets of solar major eruptions that occurred on 2017 September 6,including the energy partition of a powerful solar flare,and the energy budget of the accompanying CME and SEPs.In the wavelength range shortward of~222 nm,a major contribution of the flare radiated energy is in the soft X-ray(SXR)0.1-7 nm domain.The flare energy radiated at wavelengths of Lyαand mid-ultraviolet is larger than that radiated in the extreme ultraviolet wavelengths,but it is much less than that radiated in the SxR waveband.The total flare radiated energy could be comparable to the thermal and nonthermal energies.The energies carried by the major flare and its accompanying CME are roughly equal,and they are both powered by the magnetic free energy in the NOAA AR 12673.Moreover,the CME is efficient in accelerating SEPs,and the prompt component(whether it comes from the solar flare or the CME)contributes only a negligible fraction.

JUNO sensitivity on proton decay p→νK^(+)searches

The Jiangmen Underground Neutrino Observatory(JUNO)is a large liquid scintillator detector designed to explore many topics in fundamental physics.In this study,the potential of searching for proton decay in the p→νK^(+)mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification.Moreover,the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals.Based on these advantages,the detection efficiency for the proton decay via p→νK^(+)is 36.9%±4.9%with a background level of 0.2±0.05(syst)±0.2(stat)events after 10 years of data collection.The estimated sensitivity based on 200 kton-years of exposure is 9.6×1033 years,which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies.

Measurement of the differential cross sections and angle-integrated cross sections of the ~6Li(n,t)~4 He reaction from 1.0 eV to 3.0 MeV at the CSNS Back-n white neutron source

The^6 Li(n,t)~4 He reaction was measured as the first experiment involving neutron-induced charged particle emission reactions at the CSNS(China Spallation Neutron Source)Back-n white neutron source.The differential cross-sections of the^6 Li(n,t)~4 He reaction at 15 detection angles ranging from 19.2°to 160.8°are obtained from 1.0 eV to 3.0 MeV at 80 neutron energy points;for 50 energy points below 0.1 MeV they are reported for the first time.The results indicate that the anisotropy of the emitted tritium is noticeable above E_n=100 eV.The angle-integrated cross-sections are also obtained.The present differential cross-sections agree in general with the previous evaluations,but there are some differences in the details.More importantly,the present results indicate that the cross-sections of the^6 Li(n,t)~4 He reaction might be overestimated by most evaluations in the 0.5-3.0 MeV region,although they are recommended as standards below 1.0 MeV.

The C_(6)D_(6)detector system on the Back-n beam line of CSNS

Introduction The neutron capture cross sections are very important in the field of nuclear device design and basic physics research.Hydrogen-free liquid scintillator such as C_(6)D_(6)detectors are widely used in the neutron capture cross-sectional measurements for the low neutron sensitivity and fast time response.The Back-n white neutron source at China Spallation Neutron Source is the first spallation white neutron source in China,and it is suitable for neutron capture cross-sectional measurement.Materials and methods A C_(6)D_(6)detector system was built in the Back-n experimental station.The pulse height weighting technique was used to determine the system’s detection efficiency.The response to gamma rays of the C_(6)D_(6)detector was measured,and the energy resolution function was determined.Monte Carlo simulation with Geant4 code was carried out to get the weighting function of this C_(6)D_(6)detector system.Additionally,the systematic uncertainty of the weighting function was also determined.Conclusion According to the experimental and simulation results,this C_(6)D_(6)detector system can be used to measure neutron capture cross section.

Sub-percent precision measurement of neutrino oscillation parameters with JUNO

JUNO is a multi-purpose neutrino observatory under construction in the south of China.This publication presents new sensitivity estimates for the measurement of the △m_(31)^(2),△m_(21)^(2),sin^(2)θ_(12),and sin^(2)θ_(13) oscillation parameters using reactor antineutrinos,which is one of the primary physics goals of the experiment.The sensitivities are obtained using the best knowledge available to date on the location and overburden of the experimental site,the nuclear reactors in the surrounding area and beyond,the detector response uncertainties,and the reactor antineutrino spectral shape constraints expected from the TAO satellite detector.It is found that the △m_(21)^(2) and sin^(2)θ_(12) oscillation parameters will be determined to 0.5%precision or better in six years of data collection.In the same period,the △m_(31)^(2) parameter will be determined to about 0.2%precision for each mass ordering hypothesis.The new precision represents approximately an order of magnitude improvement over existing constraints for these three parameters.

Feasibility and physics potential of detecting ^(8)B solar neutrinos at JUNO

The Jiangmen Underground Neutrino Observatory(JUNO)features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector.Some of JUNO's features make it an excellent location for^8B solar neutrino measurements,such as its low-energy threshold,high energy resolution compared with water Cherenkov detectors,and much larger target mass compared with previous liquid scintillator detectors.In this paper,we present a comprehensive assessment of JUNO's potential for detecting^8B solar neutrinos via the neutrino-electron elastic scattering process.A reduced 2 MeV threshold for the recoil electron energy is found to be achievable,assuming that the intrinsic radioactive background^(238)U and^(232)Th in the liquid scintillator can be controlled to 10^(-17)g/g.With ten years of data acquisition,approximately 60,000 signal and 30,000 background events are expected.This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter,which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework.IfDelta m^(2)_(21)=4.8times10^(-5);(7.5times10^(-5))eV^(2),JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3sigma(2sigma)level by measuring the non-zero signal rate variation with respect to the solar zenith angle.Moreover,JUNO can simultaneously measureDelta m^2_(21)using^8B solar neutrinos to a precision of 20% or better,depending on the central value,and to sub-percent precision using reactor antineutrinos.A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of Delta m^2_(21)reported by solar neutrino experiments and the KamLAND experiment.

Design,construction,and offline calibration of ARPolar prototype for SXFEL facility

Purpose The polarization characteristics of photoelectrons are critical for free-electron laser(FEL)experiments.Several FEL facilities have operated an eTOF-alike polarimeter based on the angular distribution of photoelectrons.The purpose of this paper is to introduce the design,construction and offline test of the prototype angular resolved polarimeter(ARPolar-CORE)for the Shanghai Soft X-ray Facility(SXFEL).This paper describes the overall design of this instrument,covering the main chamber,detector assemblies,and electronics.Methods To validate the performance of the instrument,the detectors and electronics were tested offline and calibrated.Moreover,based on the measured pulse shape obtained from the offline tests,a comprehensive numerical analysis is presented to evaluate the performance of the instrument.Results and conclusion The results show that the fluctuation in the electron charges is less than 0.8%under the SXFEL working conditions,corresponding to a linear polarity of 0.988±0.0175 for linearly and horizontally polarized FEL pulses.The analysis also indicates that a 0.16 eV mean square error is fully feasible for 645 eV FEL pulses.