SUNIST-05
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SUNIST The 3rd IAEA TCM on Spherical Torus and the 11th STW, St. Petersburg Preliminary experiment of plasma current startup by ECR wave on SUNIST spherical tokamak HE Yexi, ZHANG Liang, *FENG Chunhua, FU Hongjun, GAO Zhe, TAN Yi, WANG Wenhao, *WANG Long, *YANG Xuanzong, XIE Lifeng yexihe@mail.tsinghua.edu.cn, 86-10-62791874 (o), 86-10-62782658 (fax) SUNIST United Laboratory Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China *Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China This work was supported by JSPS-CAS Core-University Program on Plasma and Nuclear Fusion, the National Nature and Science Fund of China (Grant numbers: 10275041 and 10375089) , and International Atomic Energy Agency (Research contract No. 12935/R0) . SUNIST- Sino UNIted Spherical Tokamak SUNIST UNIST OUTLINE SUNIST spherical tokamak Preliminary result Remained questions SUNIST UNIST SUNIST spherical tokamak SUNIST United Laboratory SUNIST United Laboratory founded in 2004, consists of Department of Engineering Physics, Tsinghus University (DEP) ; Institute of Physics, Chinese Academy of Science (IOP) and keeping very close collaboration with Southwestern Institute of Physics (SWIP) and Institute of Plasma Physics, Chinese Academy of Science (IPPAS). Members of SUNIST Laboratory He, Yexi Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-1062791874(lab), 86-10-62782658(fax), yexihe@mail.tsinghua.edu.cn (e-mail) Yang, Xuanzong Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China 86-1082649132(office), xzyang@aphy.iphy.ac.cn (e-mail) Wang, Long Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China 86-1082649137(office), wanglong@aphy.iphy.ac.cn (e-mail) Feng, Chunhua Institute of Physics, Chinese Academy of Science, Beijing 100080, P.R.China 86-1082649132(office), chfeng@aphy.iphy.ac.cn (e-mail) Gao, Zhe Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-1062776446(lab), 86-10-62782658(fax), gaozhe@mail.tsinghua.edu.cn (e-mail) Wang, Wenhao Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-10-62776446(lab), 86-10-62782658(fax), whwang@mail.tsinghua.edu.cn (e-mail) Xie, Lifeng Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R.China, 86-1062776446(lab), 86-10-62782658(fax), xielf@mail.tsinghua.edu.cn (e-mail) SUNIST SUNIST spherical tokamak SUNIST spherical tokamak SUNIST main parameters: major radius R 0.3m minor radius a 0.23m Aspect ratio A ~1.3 elongation κ ~1.6 toroidal field （R0） BT 0.15T plasma current IP 0.05MA flux (double swing) ΔΦ 0.06Vs SUNIST UNIST SUNIST spherical tokamak SUNIST spherical tokamak magnets and power supply Vacuum vessel and BV magnet assembling toroidal magnet pre-assembling Cross section and designed magnetic surface coil turn L(mH) R(mW) ID(kA) VC(V) Capacitor(mF) TF 24 508 4.72 9.4 200 2560(1280) HF 236 519 17.8 13 3000 13.3/1280 EF 26 684 15 1.5 1200/120 1(2)/476(18.8) SUNIST SUNIST spherical tokamak SUNIST spherical tokamak main parameters – vacuum vessel: outer diameter inner diameter height volume surface area 1.2 0.13 1.2 ~1 ~ 2.3 m m m m3 m2 vacuum pumps: TMP (1000l//s) Sputtering Ti pump (200l/s) wall conditioning: baking: PTC（Curie point 160 0C) glowing discharge, siliconization background pressure: ~ 6×10-5 Pa leaking rate on cross seal: ≯2×10-7 Pam3/s vacuum and vacuum vessel SUNIST SUNIST spherical tokamak SUNIST spherical tokamak Diagnostics electromagnetic probes: diagnostics and data acquisition 2 Rogowski probes, 9 flux loops (4 inside vessel) 15 2-D minor probes (13 in one poloidal cross section) electrostatic probes: sets of movable 4 probes for Isi, Φ, and Vtoroidal Data acquisition: 48 channel ADC: 32ch new, 16ch used in CT-6B SUNIST SUNIST spherical tokamak Typical Discharge SUNIST UNIST OUTLINE SUNIST spherical tokamak Preliminary result Remained questions SUNIST Preliminary result Typical discharge of ECR startup Microwave: Pout < 100kW, t pulse ~ 30 ms, f = 2.45 GHz background pressure ~ 110-4 Pascal hydrogen pressure ~ 110-2 Pascal during discharge SUNIST Preliminary result Discharge with a group of plasma current peaks SUNIST Preliminary result Dependence of plasma current on vertical field SUNIST Preliminary result Electrode arrangement SUNIST Preliminary result Typical discharge with electrode assistance SUNIST Preliminary result Plasma current counteracted by electrode current SUNIST Preliminary result One special discharge with electrode assistance SUNIST Preliminary result Performances of preliminary ECR current startup Plasma current is just spikes ~ hundreds millisecond of bottom width when the plasma existed during wave injecting from the lightening signal. The dependence of driven IP on vertical field is consistent with the toroidal plasma current by vertical field drift effect in ECR plasma. IP could increase above 10% (Fig. 7) in co-direction, IP would be counteracted more obviously (Fig.8), in counterdirection with electrode discharge assistance. We obtained one special discharge that the currents of plasma and electrode are cutoff and extended to wave timescale. SUNIST UNIST OUTLINE SUNIST spherical tokamak Preliminary result Remained questions SUNIST Remained questions Remained questions This kind of plasma current spike is impossible to develop to typical ST plasma current. It is necessary to rearrange launch system of microwave for better coupling to plasma. SUNIST Remained questions Remained questions The discharge shown in Fig. 9 suggests that there is a discharge regime with no limitations of density cut off on ECR current startup and Ii-sat with electrode discharge assistance. The questions are why this regime exists and how to find it for developing it from occasional event to reproducible discharge. SUNIST Remained questions Remained questions In preliminary experiments, the background pressure of vacuum vessel increased from less than 110-4 Pascal up to a balanced value, ~ 310-4 Pascal. Driven plasma current decreased with the increase of background pressure just like to scan fuelling gas to higher pressure. It is necessary to control wall condition for further experiments. SUNIST The 3rd IAEA TCM on Spherical Torus and the 11th STW, St. Petersburg Preliminary experiment of plasma current startup by ECR wave on SUNIST spherical tokamak THANKS SUNIST- Sino UNIted Spherical Tokamak SUNIST A questions about central solenoid - Is it impossible to keep? hard mode save mode too high J CS,then stress,thermal load in high F neutron problem moderate J CS, just operating very short time operation mode conclusion Impossible to keep ?
