Upgrade of Control System for the BEPCII

The BEPC will increase its luminosity ten times with upgrade of both the machine and detector,which is the project BEPCII,The project will be started at beginning chine and detector,which is the project BEPCII.The project will be started at beginning of 2002 and finished within 3-4 years.In order to reach the goal of the BEPCII,a number of new equipment will be added in the system,such as the superconducting RF cavities,new magnet power supplies and beam feedback system,and the BEPC control system has to be upgraded.The BEPC control system was built in 1987 and was upgraded in 1994.It is an Open VMS and CAMAC based-system,some equipment is controlled by PCs.We are going to upgrade the existing system by EPICS.Several VME IOCs will be added in the system with feildbus,PLCs for the new equipment control.And we will keep the existing system in use,such as CAMAC hardware ,PC based sub-control and application programs,which will be merged into the EPICS system.Recently the development of the EPICS prototype has been started.Regard some slow control,commercial SCADA product can be chosen as the development tool.We have just finished a prototype with the SCADA product Wizcon.This paper will describe the system design and development issues.

Improved measurement of electron antineutrino disappearance at Daya Bay

We report an improved measurement of the neutrino mixing angle θ13 from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for sin22θ13 with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GWm th were detected in six antineutrino detectors deployed in two near （flux-weighted baselines of 470 m and 576 m） and one far （1648 m） underground experimental halls. Using 139 days of data, 28909 （205308） electron antineutrino candidates were detected at the far hall （near halls）. The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is 0.944± 0.007（stat.） ± 0.003（syst.）. An analysis of the relative rates in six detectors finds sin22θ13=0.089± 0.010（stat.）±0.005（syst.） in a three-neutrino framework.

Influence of Grain Size and Texture on the Yield Asymmetry of Mg-3Al-1Zn Alloy

The yield asymmetry between compression and tension of magnesium alloy Mg-3Al-1Zn（AZ31） with different grain sizes and textures has been studied by tensile and compressive testing of as-cast,as-extruded and equal channel angular pressed（ECAPed） specimens.The significant yield asymmetry（the ratio of yield strength between compression and tension σyc/σyt is ～0.44） was found in as-extruded specimens and the corresponding microstructure evolution during deformation revealed that {10 ˉ 12} tensile twinning is the underlying reason for the large yield asymmetry.Strong texture and grain size are influential factors for large yield asymmetry.The separate contributions of grain size and texture on yield asymmetry were investigated.

Search for electron-antineutrinos associated with gravitational-wave events GW150914,GW151012,GW151226,GW170104,GW170608,GW170814,and GW170817 at Daya Bay

The establishment of a possible connection between neutrino emission and gravitational-wave(GW)bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge.In the Daya Bay experiment,using the data collected from December 2011 to August 2017,a search was per-formed for electron-antineutrino signals that coincided with detected GW events,including GW150914,GW151012,GW151226,GW170104,GW170608,GW 170814,and GW 170817.We used three time windows of±10,±500,and±1000 s relative to the occurrence of the GW events and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates.The detected electron-antineutrino candidates were consistent with the expected background rates for all the three time windows.Assuming monochromatic spectra,we found upper limits(90%confidence level)of the electron-antineutrino fluence of(1.13-2.44)×10^(11)cm^(-2)at 5 MeV to 8.0×10^(7)cm^(-2)at 100 MeV for the three time w indows.Under the assumption of a Fermi-Dirac spectrum,the upper limits were found to be(5.4-7.0)×10^(9)cm^(2)for the three time windows.

Laser transverse modes of spherical resonators:a review [Invited]

The study of structured laser beams has been one of the most active fields of research for decades, particularly in exploring laser beams with orbital angular momentum. The direct generation of structured beams from laser resonators is deeply associated with the formation of transverse modes. The wave representations of transverse modes of spherical cavities are usually categorized into Hermite–Gaussian(HG) and Laguerre–Gaussian(LG)modes for a long time. Enormous experimental results have revealed that the generalized representation for the transverse modes is the Hermite–LG(HLG) modes. We make a detailed overview for the theoretical description of the HLG modes from the representation of the spectral unitary group of order 2 in the Jordan–Schwinger map.Furthermore, we overview how to derive the integral formula for the elliptical modes based on the Gaussian wave-packet state and the inverse Fourier transform. The relationship between the HLG modes and elliptical modes is linked by the quantum Fourier transform. The most striking result is that the HLG modes can be exactly derived as the superposition of the elliptical modes without involving Hermite and Laguerre polynomials.Finally, we discuss the application of the HLG modes in characterizing the propagation evolution of the vortex structures of HG beams transformed by an astigmatic mode converter. This overview certainly provides not only a novel formula for transverse modes, but also a pedagogical insight into quantum physics.

Antineutrino energy spectrum unfolding based on the Daya Bay measurement and its applications

The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era.The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment,in combination with the fission rates of fissile isotopes in the reactor,is used to extract the positron energy spectra resulting from the fission of specific isotopes.This information can be used to produce a precise,data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay.The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method.Consistent results are obtained with other unfolding methods.A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated.Given the reactor fission fractions,the technique can predict the energy spectrum to a 2%precision.In addition,we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.