Constraints on symmetry energy and n/p effective mass splitting with improved quantum molecular dynamics model

A new version of improved quantum molecular dynamics model that includes standard Skyrme interactions has been developed.Based on the new code,four commonly used parameter sets,SLy4,SkI2,SkM*and Gs are adopted in the improved quantum molecular dynamics model and the isospin sensitive observables,namely isospin transport ratios,single and double ratios of the yields of neutrons and protons are investigated.The isospin transport ratios are strongly sensitive to the slope of symmetry energy,and are not very sensitive to the nucleon effective mass splitting.On the other hand,the high energy neutrons and protons yields ratios from reactions at different incident energies provide a good observable to the momentum dependence of nucleon effective mass splitting.By comparing our calculations with the data,we find that the constrained L value(the slope of density dependence of symmetry energy) is about ~46 MeV when the Skyrme type interaction is considered in transport models,and the isospin diffusion data prefer to mn*>mp*,but it is not a strong constraint with deep χ2minimum.

Three-dimensional electric field calculations for wire chamber using element refinement method in ANSYS

Finite element analysis(FEA) method was employed to perform three-dimensional(3D) electric field simulations for gas detectors with multiple wire electrodes.A new element refinement method developed for use in conjunction with the FEA program ANSYS allows successful meshing of the wires without physically inputting the wires in the chamber geometry. First, we demonstrate a model with only one wire, for which we calculate the potential distributions on the central plane and the end-cap region. The results are compared to the calculations obtained using GARFIELD, a two-dimensional program that uses the nearly exact boundary element method. Then we extend the method to same model, but with seven wires.Our results suggest that the new method can be applied easily to the 3D electric field calculations for complicated gas detectors with many wires and complicated geometry such as multiwire proportional chambers and time projection chambers.

Proton Spectroscopic Factors Deduced from Helium-3 Global Phenomenological and Microscopic Optical Model Potentials

Global phenomenological GDP08 and microscopic hefium-3 optical model potentials have been recently derived. We evaluate these two potential sets by comparing the elastic scattering data of 25 MeV 3He on 160, 180, 19F, 23Na, 24Mg, 25Mg, 26Mg, 27A1, 28Si, 30Si, 31p, 32S, 34S, 35Cl, 3761, and 39K isotopes. Using the deuteron angular distributions calculated with the distorted wave Born approximation model, we extract the ground-state proton spectroscopic factors from （3He, d） reactions on the same set of nuclei. The extracted proton spectroscopic factors are compared with the large-basis shell-model calculations.

Nitrogen Desorption and Positron Sensitive Defect of CVD Diamond

The chemical vapor deposition (CVD) process can produce single or poly-crystalline diamond samples of high purity or with controlled doping concentrations. The defect type in the CVD diamonds can be changed by heating the samples. Controlling the defect type can be used to create devices for quantum diamond switches that could be used in radiation sensors and quantum information technology. Eight samples of CVD diamonds were analyzed with Doppler broadening of positron annihilation radiation (DBAR) before and after annealing in high vacuum with an electron gun. Between temperatures of 1700 - 1850 K, nitrogen was liberated from the diamond sample. At these high temperatures, the surface was graphitized and a change in the color and transparency of the diamond was observed. Some of the samples were analyzed with DBAR during periods with and without light. The defect properties were observed to change depending on the time exposure to the positron beam and were then regenerated by exposure to light. The DBAR data is compared to photoluminescence data and a time varying defect state is discussed for detector and optical grade type II CVD diamonds.

NSCL/MSU ECR离子源项目进展报告(英文)

Since the last ECR Workshop,NSCL/MSU has been involved in a vigorous ECR ion source R&D program,which resulted in the construction of an off-line test ECR ion source(ARTEMIS-B)for new beam development and ion optics studies.Also the design and partial completion of a 3rd generation,fully supercon- ducting ECR ion source,SuSI has been accomplished.This paper is an overview of the construction projects and the different R&D activities performed with the existing ion sources.These activities include development of metallic ion beam production methods using evaporation with resistive and inductive ovens and sputtering of very refractory metals.Ion optics developments include testing different focusing elements(magnetic solenoid lens,electrostatic quadrupole triplet lens,Einzel lens,electrostatic double doublet quadrupole combined with an octupole lens),and different beam forming and diagnostics devices.The detailed results will be presented at the workshop in separate talks and posters.

NSCL从ECR离子源向CCF注入的离子束流动力学研究(英文)

The Coupled Cyclotron Facility (CCF) has been operating at the NSCL since 2001,providing up to 160MeV/u heavy ion beams for nuclear physics experiments.Recent steps,particularly the improvement of the ECR-to-K500 injection line,were taken to improve the CCF performance.For that purpose an off-line ECR source,ARTEMIS-B,was built and used to investigate the impact on beam brightness under various source operating conditions,different initial focusing systems and current analysis dipole.Beam dynamics simulations including space-charge and 3D electrostatic field effects were performed and beam diagnostics including emittance scanner were used,leading to a better understanding of the CCF beam injection process. New initial electrostatic focusing elements such as a large-bore quadrupole triplet and a quadrupole double- doublet with compensating octupole were tested,and a new beam tuning procedure was established to improve the beam brightness for the CCF.Following these efforts,a significant increase of primary beam power out of the CCF has been achieved.

NSCL的离线ECR离子源ARTEMIS-B的研究与发展(英文)

This paper reviews recent experimental work done with the off line source ARTEMIS-B at the NSCL.This source was built during the year 2005 and provides opportunities for off line development that can benefit the Coupled Cyclotron Facility(CCF)operation while minimizing the time taken away from the nuclear experimental program.The Artemis-B setup includes many beam diagnostics and a detailed description of the emittance scanner(Allison)and emittance measurement method is presented.A first beam dynamics study indicates that the analysis magnet has strong field aberrations and that the beam size in the dipole must be small in order to avoid significant beam brightness degradation.A second study compares beam brightness for different focusing systems between the ECR ion source and the analyzing magnet.Two electrostatic devices:a quadrupole triplet and a double quadrupole doublet have been tested successively and compared to a magnetic focusing solenoid.The experimental results tend to indicate a better beam brightness at smaller emittance for the electrostatic devices,although emittances measured for each focusing element were for a large part dependant on the tuning procedure developed to minimize the effects of the analyzing magnet.

NSCL溅射金属离子产生研究进展(英文)

Production of metallic ion beams in support of the experimental program at the Coupled Cyclotron Facility at the NSCL required the development of ion sputtering feed of metallic molybdenum,nickel,uranium, and zirconium for use with the ARTEMIS ion source.The production of high intensity lower to medium charge state ions required high material consumption,posing some significant difficulties in reliable long term beam stability.Resultant and ongoing hardware and technique developments to resolve these difficulties will be presented in this poster along with interesting effects of the ion source solenoid field polarity on the sputtering process.

Discovery of Nuclei at and Beyond the Proton Dripline

In contrast to the neutron dripline the proton dripline has been reached almost across the whole nuclear chart. However, because of the Coulomb barrier relatively long-lived isotopes can exist beyond the proton dripline. It is estimated that about 200 new isotopes at and beyond the proton dripline should be able to be discovered in the future. A brief review of the discovery of proton-rich nuclides as well as an outlook for the discovery potential in the future is presented.

Gammasphere上裂变丰中子核核结构若干前沿领域的新进展(Ⅰ:第一和第二部分)(英文)

(第一和第二部分):使用Gammasphere多探测器系统对252Cf裂变源瞬发γ射线进行γ-γ-γ和γ-γ(θ)符合测量,裂变丰中子原子核核结构若干前沿领域的深入研究获得了新的进展。高达5.7×1011以上的三重和更高重符合事件的数据统计,以及更少压缩的三维数据为宽广未知丰中子核区的寻找和研究提供了有利的条件。在具有重要物理意义的若干丰中子核区首次建立,或显著扩展了一批包括转晕态和转晕附近能态的高自旋能级纲图。在偶-偶丰中子核110,112Ru和108Mo中鉴别出了手征对称破缺结构。丰中子110,112Ru附近核的三轴形变基态具有最低的能量,在它们之中已确认了接近最大值的三轴形变。在这些Ru和Mo同位素中观察到的手征双线能带展示出手征破缺的一切特征,特别是其理想的能量简并,表明它们在迄今已报道的手征破缺结构中,具有最好的手征特性。研究了手征结构从具有γ软度的108Ru到具有大三轴形变的110,112Ru的过渡。斜轴推转(TAC)和随机相近似(RPA)理论计算成功地拟合了在这些偶-偶丰中子核中观察到的手征双线能带的特性,并指定其为软手征振动态。在这些偶-偶核中观察到的手征破缺不可能归纳为奇-奇核中那样的简化的几何图像。前者来自闭壳外所有中子的相互作用。对双幻核132Sn附近N=83同中素链的系统研究为这个极富吸引力的核区提供了大量新的谱学信息。N=83同中素135Te(Z=52),136I(Z=53),137Xe(Z=54),138Cs(Z=55)和139Ba(Z=56)的最新能级信息,特别是首次建立的138Cs高自旋能级纲图和壳模型理论计算表明,Z=50质子闭壳外少数g7/2价质子激发同N=82中子闭壳外之唯一f7/2价中子的耦合对该核区能级结构具有关键作用。观察到了132Sn和208Pb附近核区谱学信息的相似性和相对应的三粒子和五粒子态。在135Te中观察到了磁转动,这是在双幻核132Sn附近观察到的首例磁转动。

Observatory science with eXTP

In this White Paper we present the potential of the enhanced X-ray Timing and Polarimetry(eXTP) mission for studies related to Observatory Science targets. These include flaring stars, supernova remnants, accreting white dwarfs, low and high mass X-ray binaries, radio quiet and radio loud active galactic nuclei, tidal disruption events, and gamma-ray bursts. eXTP will be excellently suited to study one common aspect of these objects: their often transient nature. Developed by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s.

Dense matter with eXTP

In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry(eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Sciences, the eXTP mission is expected to be launched in the mid 2020 s.