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Observation of the topological surface state in the nonsymmorphic topological insulator KHgSb
Liang, A. J.,Jiang, J.,Wang, M. X.,Sun, Y.,Kumar, N.,Shekhar, C.,Chen, C.,Peng, H.,Wang, C. W.,Xu, X.,Yang, H. F.,Cui, S. T.,Hong, G. H.,Xia, Y.-Y.,Mo, S.-K.,Gao, Q.,Zhou, X. J.,Yang, L. X.,Felser, C. American Physical Society 2017 Physical review. B Vol.96 No.16
<P>Topological insulators represent unusual topological quantum states, typically with gapped bulk band structure but gapless surface Dirac fermions protected by time-reversal symmetry. Recently, a distinct kind of topological insulator resulting from nonsymmorphic crystalline symmetry was proposed in the KHgX (X = As, Sb, Bi) compounds. Unlike regular topological crystalline insulators, the nonsymmorphic glide-reflection symmetry in KHgX guarantees the appearance of an exotic surface fermion with hourglass shape dispersion (where two pairs of branches switch their partners) residing on its (010) side surface, contrasting to the usual two-dimensional Dirac fermion form. Here, by using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structures of KHgSb on both (001) and (010) surfaces and reveal the unique in-gap surface states on the (010) surface with delicate dispersion consistent with the 'hourglass Fermion' recently proposed. Our experiment strongly supports that KHgSb is a nonsymmorphic topological crystalline insulator with hourglass fermions, which serves as an important step to the discovery of unique topological quantum materials and exotic fermions protected by nonsymmorphic crystalline symmetry.</P>
Thermal analysis and optimization of the new ICRH antenna Faraday Screen in EAST
Q.C. Liang,L.N. Liu,W. Zhang,X.J. Zhang,S. Yuan,Y.Z. Mao,C.M. Qin,Y.S. Wang,H. Yang Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.7
In Experimental Advanced Superconducting Tokamak (EAST) experiments, to achieve long pulse and high-power ICRH system operation, a new kind of ICRH antenna has been designed. One of the most critical factors in limiting the operation of long pulse and high power is the intense heat load in the front face of the ICRH antenna, especially the Faraday Screen (FS). Therefore, the cooling channels of FS need to be designed. According to thermal-hydraulic analysis, the FS tubes are divided into several groups to achieve more excellent water cooling capability. The number of series and parallel tubes in one group is chosen as six. This antenna went into service in the spring of 2021, and it is delightful that the temperature distribution of the FS tube is below 400 ℃ in 14.5 s and 1.8 MW ICRH system operation. However, the active water-cooling design was not carried out on the upper and lower plates of FS, which led to severe ablations on that region under long pulse and high power operation, and the temperature is up to 800. Therefore, the upper and lower side plates of the FS were designed with water cooling based on thermal-hydraulic analysis. During the 2022 winter experiments, the temperature of ICRH antenna FS was lower than 400 in the pulse of 200s and the power of 1 MW operation.
Y. Q. Ning,B. C. Xie,C. Zhou,H. Q. Liang,M. W. Fu 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.2
Strain-rate sensitivity (SRS) is an important parameter to describe the thermodynamic behavior in plasticdeformation process. In this research, the variation of SRS associated with steady-state DRX in P/Msuperalloys was quantitatively investigated. Based on the theoretical analysis and microstructural observationof the alloy after deformation, the SRS coefficient was employed to identify the deformation mechanismof the alloy. Meanwhile, the corresponding relationship between SRS coefficient m, stress exponent nand deformation mechanism was revealed. The stress exponent n in the Arrhenius constitutive model of P/Msuperalloys was calculated. In addition, it is found there is a relatively stable stress exponent range (n = 4-6),indicating that dislocation evolution played as the major hot deformation mechanism for P/M FGH4096superalloy. Furthermore, the Bergstrom model and Senkov model were used and combined together to estimatethe SRS coefficient in the steady-state DRX and the m value maintains at 0.2-0.22, which are consistentwith the microstructural evolution during hot deformation process. The SRS coefficient distribution mapand power dissipation efficiency distribution map were finally constructed associated with the microstructuralevolution during hot deformation, which can be used to optimize the processing parameters of thesuperalloys.
Activation of antiferromagnetic domain switching in exchange-coupled Fe/CoO/MgO(001) systems
Li, Q.,Chen, G.,Ma, T. P.,Zhu, J.,N'Diaye, A. T.,Sun, L.,Gu, T.,Huo, Y.,Liang, J. H.,Li, R. W.,Won, C.,Ding, H. F.,Qiu, Z. Q.,Wu, Y. Z. American Physical Society 2015 Physical review. B, Condensed matter and materials Vol.91 No.13
Liu L.N.,Liang Q.C.,Yang H.,Zhang X.J.,Yuan S.,Mao Y.Z.,Zhang W.,Zhu G.H.,Wang L.,Qin C.M.,Zhao Y.P.,Cheng Y.,Zhang K. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.10
To operate the ion cyclotron resonance heating (ICRH) antennas in a better heating state and produce relatively low impurities, it is necessary to control the antenna spectrum by changing the antenna phasing. As the electrical length of the antenna feeding transmission lines is changing as a matter of the standing wave pattern at the ceramic supports, 90 elbows, T-connectors and antenna loops, we chose to measure the current at the grounding points of the antenna loops by antenna strap probe. The voltage drops along a small, several millimeter-long paths at the end of the antenna loops give a signal that is proportional to the current in the antenna loop. Through the simulation of the antenna strap probe and the actual measurement of the antenna phasing under vacuum conditions, the reliability of the antenna strap probe based diagnostic system have been successfully proved. Moreover, this system was successfully applied to the ICRH daily experiments in the spring of 2021. In the near future, the active realtime feedback control of the antenna phasing system will be developed based on this diagnostic system in the EAST tokamak.
Antiferromagnetic spin reorientation transition in epitaxial NiO/CoO/MgO(001) systems
Zhu, J.,Li, Q.,Li, J. X.,Ding, Z.,Liang, J. H.,Xiao, X.,Luo, Y. M.,Hua, C. Y.,Lin, H.-J.,Pi, T. W.,Hu, Z.,Won, C.,Wu, Y. Z. American Physical Society 2014 Physical review. B, Condensed matter and materials Vol.90 No.5
Improvement of lower hybrid current drive systems for high-power and long-pulse operation on EAST
Wang M.,Liu L.,Zhao L.M.,Li M.H.,Ma W.D.,Hu H.C.,Wu Z.G.,Feng J.Q.,Yang Y.,Zhu L.,Chen M.,Zhou T.A.,Jia H.,Zhang J.,Cao L.,Zhang L.,Liang R.R.,Ding B.J.,Zhang X.J.,Shan J.F.,Liu F.K.,Ekedahl A.,Gonich 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.11
Aiming at high-power and long-pulse operation up to 1000 s, some improvements have been made for both 2.45 GHz and 4.6 GHz lower hybrid (LH) systems during the recent 5 years. At first, the guard limiters of the LH antennas with graphite tiles were upgraded to tungsten, the most promising material for plasma facing components in nuclear fusion devices. These new guard limiters can operate at a peak power density of 12.9 MW/m2 . Strong hot spots were usually observed on the old graphite limiters when 4.6 GHz system operated with power >2.0 MW [B. N. Wan et al., Nucl. Fusion 57 (2017) 102019], leading to a reduction of the maximum power capability. With the new limiters, 4.6 GHz LH system, the main current drive (CD) and electron heating tool for EAST, can be operated with power >2.5 MW routinely. Long-pulse operation up to 100 s with 4.6 GHz LH power of 2.4 MW was achieved in 2021 and the maximal temperature on the guard limiters measured by an infrared (IR) camera was about 540 C, much below the permissible value of tungsten material (~1200 C). A discharge with a duration of 1056 s was achieved and the 4.6 GHz LH energy injected into the plasma was up to 1.05 GJ. Secondly, the fully-activemultijunction (FAM) launcher of 2.45 GHz system was upgraded to a passive-active-multijunction (PAM), for which the density of optimum coupling was relatively low (below the cut-off value). Good coupling with reflection coefficient ~3% has been achieved with plasma-antenna distance up to 11 cm for the new PAM. Finally, in order to eliminate the effect of ion cyclotron range of frequencies (ICRF) wave on 4.6 GHz LH wave coupling, the location of the ICRF launcher was changed to a port that is located 157.5 toroidally from the 4.6 GHz LH system and is not magnetically connected