通讯机构：
[Song Feng] S;School of Nuclear Science and Technology, University of South China, Hengyang, China
关键词：
Neutron total cross section;CLLB scintillator;Geant4;Pulse shape discrimination (PSD)
摘要：
To reduce the experimental uncertainty in the
$$^{235}$$
U resonance energy region and improve the detection efficiency for neutron total cross section measurements compared with those obtained with the neutron total cross section spectrometer(NTOX), a dedicated lithium-containing scintillation detector has been developed on the Back-n beam line at the China Spallation Neutron Source. The Fast Scintillator-based Neutron Total Cross Section (FAST)spectrometer has been designed based on a Cs
$$_{2}$$
LiLaBr
$$_{6}$$
(CLLB) scintillator considering the
$$\gamma$$
-ray flash and neutron environment on the Back-n beam line. The response of the CLLB scintillator to neutrons and
$$\gamma$$
-rays was evaluated with different
$$^6$$
Li/
$$^7$$
Li abundance ratios using Geant4. The neutron-
$$\gamma$$
discrimination performance of the CLLB has been simulated considering different scintillation parameters, physical designs, and light readout modes. A cubic
$$^6$$
Li-enriched (
$$>90\%$$
) CLLB scintillator, which has a thickness of 4-9 mm and side length of no less than 50 mm to cover the
$$\Phi$$
50 mm neutron beam at the spectrometer position, has been proposed coupling to a side readout SiPM array to construct the FAST spectrometer. The developed simulation techniques for neutron-
$$\gamma$$
discrimination performance could provide technical support for other neutron-induced reaction measurements on the Back-n beam line.
通讯机构：
[Chen, X.] S;School of Nuclear Science and Technology, China
关键词：
triply heavy baryons;holographic QCD;potential energy
摘要：
Using gauge/gravity duality, we study the potential energy and the melting of triply heavy baryon at finite temperature and chemical potential in this paper. First, we calculate the three-quark potential and compare the results with quark-antiquark potential. With the increase of temperature and chemical potential, the potential energy will decrease at large distances. It is found that the three-quark potential will have an endpoint at high temperature and/or large chemical potential, which means triply heavy baryons will melt at enough high temperature and/or large chemical potential. We also discuss screening distance which can be extracted from the three-quark potential. At last,we draw the melting diagram of triply heavy baryons in the T-μ plane.
摘要：
为快速准确地实现碳离子治疗计划的三维剂量验证,采用有机玻璃PMMA(聚甲基丙烯酸甲酯)为电离室室壁和水等效模体,设计了一种三维电离室阵列,并通过Geant4软件对三维电离室阵列的结构设计进行了深入研究与验证.首先通过模拟不同能量碳离子束在水和PM M A模体中沉积的剂量分布,计算了PM M A模体的水等效厚度系数;然后研究了三维电离室阵列中电离腔室间的距离及信号导线对其剂量测量准确度的影响;最后模拟并验证了碳离子束在三维电离室阵列中沉积的剂量分布.结果表明:PM M A模体的水等效厚度系数为1.151;相邻电离腔室间的信号串扰主要来源于前侧的电离腔室,且串扰程度与电离腔室间距呈反比,间距为1 mm时串扰程度占电离腔室内剂量的3％,间距为30 m m时串扰影响可完全消除;信号导线对后侧电离腔室内剂量的干扰影响约为1％.将碳离子束在三维电离室阵列中沉积的剂量分布与PM M A模体中的剂量分布进行对比,碳离子束的射程具有良好的一致性,偏差为0.5 mm.
作者机构：
[Chen, Pengju; Tang, Xian] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Xiao, Peng; Li, Yang] Cent South Univ, Powder Met Res Inst, Changsha 410083, Peoples R China.;[Li, Yang] Cent South Univ, Nat Key Lab Sci & Technol High Strength Struct Ma, Changsha 410083, Peoples R China.
通讯机构：
[Yang Li] P;Powder Metallurgy Research Institute, Central South University, Changsha, China<&wdkj&>National Key Laboratory of Science and Technology on High-strength Structural Materials, Central South University, Changsha, China
关键词：
Yb2Si2O7;mullite;tri-layer;sol-gel;burner rig test
摘要：
The corrosion behavior of environmental barrier coatings (EBCs) directly affects the service life and stability of ceramic matrix composite (CMC) structural parts in the aero-engines. The silicon carbide (SiC) whisker toughening phase and c-AlPO_4 bonding phase are firstly used to improve the service life of novel tri-layer Yb_2Si_2O_7/mullite/SiC EBCs in the burner rig test. The formation of penetrating cracks in Yb_2Si_2O_7/mullite/SiC coating caused the failure of coating at 1673 K. The SiC whiskers in mullite middle coating significantly inhibited the formation of penetrating cracks in Yb_2Si_2O_7/mullite/SiC coating, and efficiently prevented the oxidation of carbon fiber reinforced silicon carbide (C_f/SiC) samples for 360-min thermal cycles (24 times) with a weight loss of 6.19×10~(-3) g·cm~(-2). Although c-AlPO_4 particles further improved the service life of SiC_w-mullite (SM) coating, the overflow of PO_x gas aggravated the formation and expansion of cracks in the Yb_2Si_2O_7 outer coating, and caused the service life of overall Yb_2Si_2O_7/c-AlPO_4-SiC_w-mullite (ASM)/SiC coating to be slightly lower than that of Yb_2Si_2O_7/SM/SiC coating. This study guides the design of modified tri-layer EBCs with long service life in high-temperature and high-speed gas environment.
作者机构：
[朱恩平; 王婷; 刘紫静; 赵鹏程; 王天石] School of Nuclear Science and Technology, University of South China, Hengyang;421001, China;[朱恩平; 王婷; 刘紫静; 赵鹏程; 王天石] 421001, China
通讯机构：
School of Nuclear Science and Technology, University of South China, Hengyang, China
作者机构：
[Luo, W.; Luo, W; Lan, H. -Y.; Qin, T. -T.] Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;[Wang, W. -M.] Renmin Univ China, Beijing Key Lab Optoelect Funct Mat & Micronano D, Beijing 100872, Peoples R China.;[Wang, W. -M.] Renmin Univ China, Dept Phys, Beijing 100872, Peoples R China.
通讯机构：
[Luo, W ] U;[Wang, WM ] R;Univ South China, Sch Nucl Sci & Technol, Hengyang 421001, Peoples R China.;Renmin Univ China, Beijing Key Lab Optoelect Funct Mat & Micronano D, Beijing 100872, Peoples R China.;Renmin Univ China, Dept Phys, Beijing 100872, Peoples R China.
摘要：
Aneutronic fusion reactions such as proton–boron fusion could efficiently produce clean energy with quite low neutron doses. However, as a consequence, conventional neutron spectral methods for diagnosing plasma ion temperature would no longer work. Therefore, finding a way to probe the ion temperature in aneutronic fusion plasmas is a crucial task. Here, we present a method to realize ultrafast in situ probing of 11B ion temperature for proton–boron fusion by Doppler broadening of the nuclear resonance fluorescence (NRF) emission spectrum. The NRF emission is excited by a collimated, intense γ-ray beam generated from submicrometer wires irradiated by a recently available petawatt (PW) laser pulse, where the γ-ray beam generation is calculated by three-dimensional particle-in-cell simulation. When the laser power is higher than 1 PW, five NRF signatures of a 11B plasma can be clearly identified with high-resolution γ-ray detectors, as shown by our Geant4 simulations. The correlation between the NRF peak width and 11B ion temperature is discussed, and it is found that NRF emission spectroscopy should be sensitive to 11B ion temperatures Ti > 2.4 keV. This probing method can also be extended to other neutron-free-fusion isotopes, such as 6Li and 15N.
