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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
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.
Liu L.N.,Zheng W.M.,Zhang X.J.,Yang H.,Yuan S.,Mao Y.Z.,Zhang W.,Zhu G.H.,Wang L.,Qin C.M.,Zhao Y.P.,Cheng Y.,Zhang K. 한국원자력학회 2024 Nuclear Engineering and Technology Vol.56 No.1
Ion cyclotron range of frequency (ICRF) heating system is an important auxiliary heating method in the experimental Advanced Superconducting Tokamak (EAST). In EAST, several megawatts of power are transmitted with coaxial transmission lines and coupled to the plasma. For the long pulse and high power operation of the ICRF waves heating system, it is very important to effectively control the power and initial phase of the ICRF signals. In this paper, a power and phase feedback control system is described based on field programmable gate array (FPGA) devices, which can realize complicated algorithms with the advantages of fast running and high reliability. The transmitted power and antenna phase are measured by a power and phase detector and digitized. The power and phase feedback control algorithms is designed to achieve the target power and antenna phase. The power feedback control system was tested on a dummy load and during plasma experiments. Test results confirm that the feedback control system can precisely control ICRF power and antenna phase and is robust during plasma variations.
Yin, L. H.,Yang, J.,Tong, P.,Luo, X.,Park, C. B.,Shin, K. W.,Song, W. H.,Dai, J. M.,Kim, K. H.,Zhu, X. B. Royal Society of Chemistry 2016 Journal of Materials Chemistry C Vol.4 No.47
<P>We report a systematic study on the magnetic, magnetocaloric (MC), specific heat and magnetoelectric (ME) properties of the single crystals of rare-earth orthochromites, RCrO3 (R = Dy, Nd, Er, Tb). Interesting stair-like metamagnetic transitions were observed for the first time in TbCrO3 crystals. Intrinsic large anisotropy in the magnetic and ME properties were also revealed in all of the RCrO3 crystals. The reorientation/ordering of the rare earth R3+ spins was observed to be accompanied with large MC, rotating MC and ME effects. These behaviors are found be closely related to the R-R and R-Cr interactions in these chromites. In particular, the ME effect can be ascribed to the spin phonon coupling. All these results suggest the essential and unique role of 4f electrons of rare earth ions in these chromites.</P>
Ye, S.,Zhu, L.,Kim, I.J.,Yang, S.h.,Oh, W.C. Korean Society of Industrial and Engineering Chemi 2016 Journal of industrial and engineering chemistry Vol.43 No.-
<P>This study improved the electrochemical performance of electrochemical double-layer capacitor (EDLC) with an activated carbon (MSP20)-based electrode by adding a small amount of expanded graphene (EG) and styrene-butadiene rubber (SBR). The prepared EG was characterized via X-ray diffraction (XRD) spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy. Finally, the electrochemical performance of graphene was examined in an electrolyte solution of tetraethylammonium tetrafluoroborate ((C2H5)(4)NBF4, TEABF(4)) in propylene carbonate (C4H6O3, PC). The capacitive performance of EDLC was evaluated with the same charge on the positive and negative electrodes by conducting cyclic voltammetry,charge and discharge measurements, electrochemical impedance spectroscopy and electron spin resonance analysis. (C) 2016 Published by Elsevier B.V. on behalf of The Korean Society of Industrial and Engineering Chemistry.</P>
Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser
Gerber, S.,Yang, S.-L.,Zhu, D.,Soifer, H.,Sobota, J. A.,Rebec, S.,Lee, J. J.,Jia, T.,Moritz, B.,Jia, C.,Gauthier, A.,Li, Y.,Leuenberger, D.,Zhang, Y.,Chaix, L.,Li, W.,Jang, H.,Lee, J.-S.,Yi, M.,Dakovs American Association for the Advancement of Scienc 2017 Science Vol.357 No.6346
<P><B>A deeper look into iron selenide</B></P><P>In the past 10 years, iron-based superconductors have created more puzzles than they have helped resolve. Some of the most fundamental outstanding questions are how strong the interactions are and what the electron pairing mechanism is. Now two groups have made contributions toward resolving these questions in the intriguing compound iron selenide (FeSe) (see the Perspective by Lee). Gerber <I>et al.</I> used photoemission spectroscopy coupled with x-ray diffraction to find that FeSe has a very sizable electron-phonon interaction. Quasiparticle interference imaging helped Sprau <I>et al.</I> determine the shape of the superconducting gap and find that the electron pairing in FeSe is orbital-selective.</P><P><I>Science</I>, this issue p. 71, p. 75; see also p. 32</P><P>The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a “coherent lock-in” measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure. Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.</P>
Molecular Characterization and Expression Patterns of Porcine Eukaryotic Elongation Factor 1 A
Wang, H.L.,Wang, H.,Zhu, Z.M.,Yang, S.L.,Fen, S.T.,Li, Kui Asian Australasian Association of Animal Productio 2006 Animal Bioscience Vol.19 No.7
The eukaryotic elongation factor 1 A (EEF1A) participates in protein synthesis by forming the eEF1A GTP tRNA complex to deliver aminoacyl-tRNA to the A site of ribosomes. This study described cDNA sequences and partial genomic structure of porcine EEF1A1. The porcine EEF1A1 gene encoded a protein with 462 amino acids, which shared complete homology with human, chimpanzee and dog. The temporal expression pattern showed the diversity of EEF1A1 level in mRNA was relatively minor in prenatal embryo skeletal muscle, however, the expression decreased during aging after birth in skeletal muscle of the Chinese Tongcheng pig. The spatial expression patterns indicated that the gene expressed in skeletal muscle, heart, lung, liver, kidney, fat and spleen. In addition, we assigned the gene to porcine chromosome 1 using a radiation hybrid panel.
Leakage Currents of a Fast Switching Thyristor Made by Proton Irradiation Method
E.D. Kim,C.L. Zhang,S.C. Kim,N.K. Kim,J.Z. Zhu,B.F. Yang 전력전자학회 2004 ICPE(ISPE)논문집 Vol.- No.-
A thyristor with a VRRM of 1,600V was made with 200μm of N-base width from 60Ω·cm NTD-Si wafer and the proton irradiation was employed for improving its switching performance. This study showed that 4.7MeV-proton irradiation gives a narrow distribution of induced defects in the middle of N-drift region with its width of 10μm, which resulted in a superior trade-off relation between its static and dynamic characteristics. It was found that 3.7MeV and 5.9MeV protons remarkably increased the forward leakage current IDRM and the reverse leakage current IRRM, respectively. The increased IDRM and IRRM are attributed to the induced defects in the depletion layers of thyristor junctions J2 and J1, respectively.