The small angle neutron scattering （SANS） instrument is presently being constructed at Chinese Spal- lation Neutron Source （CSNS） in China, and the biological shielding design is needed to prevent the instrument f...The small angle neutron scattering （SANS） instrument is presently being constructed at Chinese Spal- lation Neutron Source （CSNS） in China, and the biological shielding design is needed to prevent the instrument from causing excessive dose rates in accessible locations. In this paper, the study of shielding design for SANS that relies on Monte Carlo simulation is introduced. Beam line shielding calculations are performed considering both scenarios of closed versus open TO chopper. The basic design scheme of the beam stop is discussed. The size of the TO chopper rotor is also estimated.展开更多
The decay channel ψ′→ π 〉＋π^-J/ψ（J/ψ 〉 γp^-p） is studied using a sample of 1.06 × 10^8 ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the p...The decay channel ψ′→ π 〉＋π^-J/ψ（J/ψ 〉 γp^-p） is studied using a sample of 1.06 × 10^8 ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the p^-p invariant mass spectrum. The enhancement can be fitted with an S-wave Breit-Wigner resonance function with a resulting peak mass of M = 1861-13^＋6 （stat）-26^＋7 （syst） MeV/c^2 and a narrow width that is Г 〈 38 MeV/c^2 at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with well established mesons.展开更多
The China Spallation Neutron Source（CSNS） is driven by protons whose energies are about 1.6 GeV.At such high energies, the spallation neutrons lead to the formation of large amounts of helium, hydrogen and new heavi...The China Spallation Neutron Source（CSNS） is driven by protons whose energies are about 1.6 GeV.At such high energies, the spallation neutrons lead to the formation of large amounts of helium, hydrogen and new heavier species in the form of transmutation products. These hydrogen, helium and transmutation products have a critical effect on the mechanical properties on the one hand and exacerbate the displacement radiation damage on the other hand. In this paper, the background hydrogen/helium concentrations and the maximum hydrogen/helium concentrations near cracks in a tungsten target for CSNS have been calculated at temperatures of 100 and 300 by applying a theoretical model. For the CSNS tungsten target plate, we find the maximum hydrogen concentration near the tips of cracks ranges from 3.0×10^（-2）–2×10^（-1）, which exceeds the hydrogen background concentration by 1.2–1.8 times; the maximum helium concentration near the tips of cracks ranges from 3.0×10^（-4）- 1.2×10^（-3）, which exceeds the helium background concentration by 2- 4 times; the maximum hydrogen/helium concentration increases with the increase of the transfer length across the surfaces of the target and it decreases with the increase of temperature.展开更多
基金Supported by National Natural Science Foundation of China(91026009,11174358,11075203)
文摘The small angle neutron scattering （SANS） instrument is presently being constructed at Chinese Spal- lation Neutron Source （CSNS） in China, and the biological shielding design is needed to prevent the instrument from causing excessive dose rates in accessible locations. In this paper, the study of shielding design for SANS that relies on Monte Carlo simulation is introduced. Beam line shielding calculations are performed considering both scenarios of closed versus open TO chopper. The basic design scheme of the beam stop is discussed. The size of the TO chopper rotor is also estimated.
基金Supported by Ministry of Science and Technology of China (2009CB825200)National Natural Science Foundation of China(NSFC) (10625524,10821063,10825524,10835001,10935007)+6 种基金Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program,CAS (KJCX2-YW-N29,KJCX2-YW-N45)100 Talents Program of CASIstituto Nazionale di Fisica Nucleare,Italy,Russian Foundation for Basic Research (08-02-2221, 08-02-92200-NSFC-a)Siberian Branch of Russian Academy of Science,joint project No 32 with CAS,Chinese University of Hong Kong Focused Investment Grant (3110031)U. S. Department of Energy(DE-FG02-04ER41291,DE-FG02-91ER40682,DE-FG02-94ER40823)WCU Program of National Research Foundation of Korea(R32-2008-000-10155-0)the A.P. Sloan Foundation
文摘The decay channel ψ′→ π 〉＋π^-J/ψ（J/ψ 〉 γp^-p） is studied using a sample of 1.06 × 10^8 ψ′ events collected by the BESIII experiment at BEPCII. A strong enhancement at threshold is observed in the p^-p invariant mass spectrum. The enhancement can be fitted with an S-wave Breit-Wigner resonance function with a resulting peak mass of M = 1861-13^＋6 （stat）-26^＋7 （syst） MeV/c^2 and a narrow width that is Г 〈 38 MeV/c^2 at the 90% confidence level. These results are consistent with published BESII results. These mass and width values do not match with well established mesons.
基金Supported by National Science Foundation of China(51371195,11174358)
文摘The China Spallation Neutron Source（CSNS） is driven by protons whose energies are about 1.6 GeV.At such high energies, the spallation neutrons lead to the formation of large amounts of helium, hydrogen and new heavier species in the form of transmutation products. These hydrogen, helium and transmutation products have a critical effect on the mechanical properties on the one hand and exacerbate the displacement radiation damage on the other hand. In this paper, the background hydrogen/helium concentrations and the maximum hydrogen/helium concentrations near cracks in a tungsten target for CSNS have been calculated at temperatures of 100 and 300 by applying a theoretical model. For the CSNS tungsten target plate, we find the maximum hydrogen concentration near the tips of cracks ranges from 3.0×10^（-2）–2×10^（-1）, which exceeds the hydrogen background concentration by 1.2–1.8 times; the maximum helium concentration near the tips of cracks ranges from 3.0×10^（-4）- 1.2×10^（-3）, which exceeds the helium background concentration by 2- 4 times; the maximum hydrogen/helium concentration increases with the increase of the transfer length across the surfaces of the target and it decreases with the increase of temperature.
