A miniaturized neutron spin flipper based on a high-TC superconductor film,developed at the China Spallation Neutron Source(CSNS),is presented.A neutron spin flipper is an essential component for performing polarized ...A miniaturized neutron spin flipper based on a high-TC superconductor film,developed at the China Spallation Neutron Source(CSNS),is presented.A neutron spin flipper is an essential component for performing polarized neutron experiments and,as such,constitutes a high priority for developing CSNS’s polarized neutron capability.To provide the beamlines with a universal neutron spin flipper operating over a wide wavelength band,the neutron spin flipper utilizes non-adiabatic spin flipping during transit through opposite magnetic fields that are mutually shielded by the superconductor Meissner effect.A compact vacuum heat shield and a low-power consumption sterling refrigerator maintained the superconducting condition while reducing the size and power input of the flipper.The prototype device was tested at the CSNS BL-20,which demonstrated a flipping efficiency of 99%at 4 A°.展开更多
In this work,we perform a statistical investigation towards 50 high-mass clumps using data from the Bolocam Galactic Plane Survey(BGPS)and Millimetre Astronomy Legacy Team 90-GHz survey(MALT90).Eleven dense molecu...In this work,we perform a statistical investigation towards 50 high-mass clumps using data from the Bolocam Galactic Plane Survey(BGPS)and Millimetre Astronomy Legacy Team 90-GHz survey(MALT90).Eleven dense molecular lines(N2H^+(1–0),HNC(1–0),HCO^+(1–0),HCN(1–0),HN^(13)C(1–0),H^(13)CO^+(1–0),C2H(1–0),HC3N(10–9),SiO(2–1),^(13)CS(2–1)and HNCO(4(4,0)-3(0,3)))are detected.N2H^+ and HNC are shown to be good tracers for clumps in various evolutionary stages since they are detected in all the fields.The detection rates of N-bearing molecules decrease as the clumps evolve,but those of O-bearing species increase with evolution.Furthermore,the abundance ratios[N2H^+]/[HCO^+]and log([HC3N]/[HCO^+])decline with log([HCO^+])as two linear functions,respectively.This suggests that N^+2H^+ and HC3N transform to HCOas the clumps evolve.We also find that C2H is the most abundant molecule with an order of magnitude 10^(-8).In addition,three new infall candidates,G010.214–00.324,G011.121–00.128 and G012.215–00.118(a),are discovered to have large-scale infall motions and infall rates with an order of magnitude 10^(-3)M⊙yr^(-1).展开更多
High-entropy alloy layer up to 150 lm in thickness was formed on H13 substrate with a metallurgical bonding at the coating/substrate interface. Simple solid solution phases were formed in the coating layer with a typi...High-entropy alloy layer up to 150 lm in thickness was formed on H13 substrate with a metallurgical bonding at the coating/substrate interface. Simple solid solution phases were formed in the coating layer with a typical microstructure composed of both dendrite and interdendrite. The microstructure at the top of the cladding zone consists of equiaxed grains while that at the bottom consists of columnar grains. The coating layer exhibits great enhancement in microhardness and wear resistance compared with the H13 substrate.展开更多
The Al0. 5CoCrCuFeNi high-entropy alloy powders with simple face-centered-cubic (FCC) solid solution structure were introduced into the surface layer of a low carbon steel during laser surface alloying. A high perfo...The Al0. 5CoCrCuFeNi high-entropy alloy powders with simple face-centered-cubic (FCC) solid solution structure were introduced into the surface layer of a low carbon steel during laser surface alloying. A high performance surface layer with extremely fine martensite as the dominant phase was obtained, resulting in a great improvement in microhardness, wear resistance, and corrosion resistance. The great enhancement of microhardness and wear resistance of the laser alloyed layer is mainly due to the formation of extremely fine martensite hard phase, the solid solution strengthening of the alloying e!.ements in supersaturated a-Fe solid solution, and the existence of size effect and strain effect under rapid solidification. The enhancement of corrosion resistance is due to the alloying of Al, Co, Ni, Cr and Cu in the laser alloyed layer.展开更多
基金supported by the National Key Research and Development Program of China(No.2020YFA0406000)the National Natural Science Foundation of China(Nos.12075265 and U2032219)+2 种基金The 3He spin filter implemented in the experiment was developed within the Scientific Instrument Developing Project of the Chinese Academy of Sciences(No.ZDKYYQ20190004)the Dongguan Introduction Program of Leading Innovative and Entrepreneurial Talents(No.20191122)The magnetic field simulation and analysis work were supported by Guangdong Natural Science Funds for Distinguished Young Scholars.
文摘A miniaturized neutron spin flipper based on a high-TC superconductor film,developed at the China Spallation Neutron Source(CSNS),is presented.A neutron spin flipper is an essential component for performing polarized neutron experiments and,as such,constitutes a high priority for developing CSNS’s polarized neutron capability.To provide the beamlines with a universal neutron spin flipper operating over a wide wavelength band,the neutron spin flipper utilizes non-adiabatic spin flipping during transit through opposite magnetic fields that are mutually shielded by the superconductor Meissner effect.A compact vacuum heat shield and a low-power consumption sterling refrigerator maintained the superconducting condition while reducing the size and power input of the flipper.The prototype device was tested at the CSNS BL-20,which demonstrated a flipping efficiency of 99%at 4 A°.
基金supported by the National Natural Science Foundation of China(Nos.11363004 and 11403042)supported by the National Key Basic Research Program of China(No.2015CB857100)
文摘In this work,we perform a statistical investigation towards 50 high-mass clumps using data from the Bolocam Galactic Plane Survey(BGPS)and Millimetre Astronomy Legacy Team 90-GHz survey(MALT90).Eleven dense molecular lines(N2H^+(1–0),HNC(1–0),HCO^+(1–0),HCN(1–0),HN^(13)C(1–0),H^(13)CO^+(1–0),C2H(1–0),HC3N(10–9),SiO(2–1),^(13)CS(2–1)and HNCO(4(4,0)-3(0,3)))are detected.N2H^+ and HNC are shown to be good tracers for clumps in various evolutionary stages since they are detected in all the fields.The detection rates of N-bearing molecules decrease as the clumps evolve,but those of O-bearing species increase with evolution.Furthermore,the abundance ratios[N2H^+]/[HCO^+]and log([HC3N]/[HCO^+])decline with log([HCO^+])as two linear functions,respectively.This suggests that N^+2H^+ and HC3N transform to HCOas the clumps evolve.We also find that C2H is the most abundant molecule with an order of magnitude 10^(-8).In addition,three new infall candidates,G010.214–00.324,G011.121–00.128 and G012.215–00.118(a),are discovered to have large-scale infall motions and infall rates with an order of magnitude 10^(-3)M⊙yr^(-1).
基金financially supported by the National Natural Science Foundation of China (No. 50401006)the Fundamental Research Funds for the Central Universities (No. N120409003)the University Students’ Innovation Plan of China (No. 130066)
文摘High-entropy alloy layer up to 150 lm in thickness was formed on H13 substrate with a metallurgical bonding at the coating/substrate interface. Simple solid solution phases were formed in the coating layer with a typical microstructure composed of both dendrite and interdendrite. The microstructure at the top of the cladding zone consists of equiaxed grains while that at the bottom consists of columnar grains. The coating layer exhibits great enhancement in microhardness and wear resistance compared with the H13 substrate.
基金Item Sponsored by National Natural Science Foundation of China(50401006)Fundamental Research Funds for Central Universities of China(N120409003)
文摘The Al0. 5CoCrCuFeNi high-entropy alloy powders with simple face-centered-cubic (FCC) solid solution structure were introduced into the surface layer of a low carbon steel during laser surface alloying. A high performance surface layer with extremely fine martensite as the dominant phase was obtained, resulting in a great improvement in microhardness, wear resistance, and corrosion resistance. The great enhancement of microhardness and wear resistance of the laser alloyed layer is mainly due to the formation of extremely fine martensite hard phase, the solid solution strengthening of the alloying e!.ements in supersaturated a-Fe solid solution, and the existence of size effect and strain effect under rapid solidification. The enhancement of corrosion resistance is due to the alloying of Al, Co, Ni, Cr and Cu in the laser alloyed layer.