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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
Ablation of irradiated metals by high-intensity pulsed ion beam
X. P. Zhu,M. K. Lei,S. M. Miao,T. C. Ma,Z. H. Dong 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
Surface morphology and roughness of pure Ti irradiated by high-intensity pulsed ion beam (HIPIB) have been investigated by using scanning electronic microscope (SEM) and profilometer, respectively. The HIPIB irradiation was carried out at an accelerating voltage of 220 kV, an ion current density of \symbol{126}250 A/cm$^2$ with 75 ns pulse width under single or multi shots. Craters were formed on the irradiated surfaces and their dimension was expanded with increasing the ion current density. At $<$90 A/cm$% ^2 $, small craters of $\mu $m size were observed on the weakly melted surface. At 90-120 A/cm$^2$, large craters about 10 $\mu $m were found on the obviously melted surface. At 120-250 A/cm$^2$, the surface was severely melted with craters and the size of the craters increased to 20-80 $\mu $m with a wavy feature. At 250 A/cm$^2$ with 1 shot, surface roughness (\textit{% R}$_{\mathit{a}}$) greatly increased to a maximal value of 0.43 $\mu $m from the initial \textit{R}$_{\mathit{a}}$ of 0.18 $\mu $m, in good agreement with the SEM observation. With further increasing the shot number, the \textit{R}$_{\mathit{a}}$ decreased continuously and finally reached 0.06 $% \mu $m with 30 shots, indicating a planar ablated surface. The micro non-uniformity on the surfaces induced a selective ablation under HIPIB irradiation. The locally liquid evaporation and droplet ejection led to a disturbance in the molten surface layer to different scales depending on the ion current densities. On the other hand, the micro non-uniformity disappeared gradually under multi-shot irradiation, resulting in a more uniform ablation due to the diminished selective ablation.
Instability in GIDL Current of Thermally-Nitrided-Oxide N-MOSFET's
Ma, Z. J.,Lai, P. T.,ChEng, Y. C.,Huang, M. Q. 대한전자공학회 1991 ICVC : International Conference on VLSI and CAD Vol.2 No.1
Part of holes created from band-to-band (B-B) tunneling can surmount the Si/SiO₂ interface and are trapped in gate oxide above the deep-depletion drain layer, with the aid of both lateral and vertical fields. As a result, GIDL current decreases due to a lowering of the vertical field. This kind of hole injection depends on voltage difference between the drain and gate rather than the drain voltage, because of a nitridation-induced lowering effect of harrier height for hole injection. A subsequent hot-electron injection can quickly neutralize the trapped holes and make the GIDL current recover, and even increase beyond the original value.
Ma, L D,Wang, J,WEI, C,Kuroiwa, T,Narukawa, T,Ito, N,HIOKI, A,CHIBA, K,Yim, Y H,Lee, K S,Lim, Y R,Turk, G C,Davis, C W,Mester, Z,Yang, L,McCooeye, M,Maxwell, P,Cankur, O,Tokman, N,Coskun, F G BUREAU INTERNATIONAL DES POIDS ET MESURES 2017 METROLOGIA -BERLIN- Vol.54 No.-
<P></P> <P>The CCQM-K97 key comparison was organized by the inorganic analysis working group (IAWG) of CCQM as a follow-up to completed pilot study CCQM-P96 and P96.1 to test the abilities of the national metrology institutes to accurately quantitate the mass fraction of arsenobetaine (AsB) in standard solution and in fish tissue. A pilot study CCQM-P133 was parallelized with this key comparison. National Institute of Metrology (NIM), China and National Metrology Institute of Japan (NMIJ) acted as the coordinating laboratories.</P> <P>Six NMIs participated in CCQM-K97 and two institutes participated in CCQM-P133, and all of them submitted the results. Some NMIs submitted more than one results by different methods. The results were in excellent agreement with each other, and obviously better than those of previous P96 and P96.1. Therefore the calibrant which each NMI used was comparable. It shows that the capabilities of some of the participants have been improved after the previous pilot studies.</P> <H2>Main text</H2> <P> To reach the main text of this paper, click on <A HREF='http://www.bipm.org/utils/common/pdf/final_reports/QM/K97/CCQM-K97.pdf'>Final Report</A>. Note that this text is that which appears in Appendix B of the BIPM key comparison database <A HREF='http://kcdb.bipm.org/'>kcdb.bipm.org/</A>.</P> <P>The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).</P>
Xu, Z.R.,Ma, Y.L.,Hu, C.H.,Xia, M.S.,Guo, T.,Jin, H.L. Asian Australasian Association of Animal Productio 2003 Animal Bioscience Vol.16 No.11
Two hundred forty 1-d-old Arbor Acres broiler chicks were used to investigate the effects of Cu (II)-exchanged montmorillonite (CEM) or montmorillonite on the growth performance, intestinal microflora, bacterial enzyme activities and morphology of broilers. The chicks were assigned randomly into three groups with 80 chicks per treatment. The three dietary treatments were basal diet only (control group), basal diet +1 g $kg^{-1}$ montmorillonite, and basal diet +1 g $kg^{-1}$ CEM. The results showed that the addition of CEM to the diet increased significantly the body weight and feed efficiency, but a similarly significant increase was not found in broilers fed the diet containing montmorillonite. Supplementing the CEM in the diet of broilers also decreased the numbers of Clostridium perfringens and Escherichia coli in the small intestine and cecum. The addition of either CEM or montmorillonite to the diet depressed the activities of $\beta$-glucosidase and $\beta$-glucuronidase in the small intestinal and cecal contents. Data of villus height and crypt depth for duodenum, jejunum and ileum indicated that dietary addition of CEM or montmorillonite improved the small intestinal mucosal morphology.
N. Zhao,M. L. Huang,H. T. Ma,F. Yang,Z. J. Zhang 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.5
The influence of trace rare earth (RE) Ce addition on the microstructure, melting point and wettability ofpure Sn as well as on the soldering reactions in Sn-xCe/Cu(Ni) solder joints was investigated. In bulk SnxCesolders, large β-Sn grains were observed with the Ce addition less than 0.2 wt%; while the β-Sn grainsize decreased markedly when the Ce addition was 0.2 wt%, resulting in a refined microstructure. The additionof trace RE Ce had little effect on the melting temperature of the solders. Smaller wetting angles of SnxCesolders on both Cu and Ni substrates were measured when the samples were reflowed at a higher temperature. The Sn-0.2Ce solder owned the best wettability on Cu substrate. Scallop-like Cu6Sn5 intermetallic compound(IMC) grains formed at the Sn-xCe/Cu interfaces, while a continuous Ni3Sn4 IMC layer formed at eachSn-xCe/Ni interface. With the increase of Ce addition, the interfacial IMC grain size and the interfacialIMC layer thickness on both Cu and Ni substrates decreased gradually. The activity of Sn was lowered with theCe addition, which depressed the growth of the interfacial IMC. In the current study, the Ce addition of0.2 wt% exhibits the optimized performance.
Field dependence of antiferromagnetic domain switching in epitaxial Fe/CoO/MgO(001) systems
Li, Q.,Ma, T. P.,Yang, M.,Sun, L.,Huang, S. Y.,Li, R. W.,Won, C.,Qiu, Z. Q.,Wu, Y. Z. American Physical Society 2017 Physical Review B Vol.96 No.2
<P>Utilizing the magneto-optic Kerr effect and Kerr microscopy measurements, we investigated the antiferro-magnetic (AFM) domain switching process at different magnetic fields in a single-crystalline Fe/CoO bilayer grown on MgO(001) substrate. In spite of the zero-net magnetic moment in the CoO layer, we find that the activation energy barrier of CoO AFM domain switching decreased at larger magnetic field. To separate the different behaviors of domain nucleation and domain wall motion during the CoO spin switching process, a new analytical method was developed. Using this method, we found that the CoO domain nucleation energy barrier exhibited a jump at a critical magnetic field while the CoO domain wall motion experienced only a tiny energy barrier variation. The field-dependent behaviors of the energy barriers were attributed to the formation of a spiral domain wall in the Fe layer during its magnetization reversal and this was supported by micromagnetic simulations.</P>