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Merging Start-up and Sustainment Experiments on UTST

15 th Intl. Workshop on Spherical Tori 2009, Madison, WI, Oct. 22, 2009. Merging Start-up and Sustainment Experiments on UTST. T. Yamada 1 , R. Imazawa 2 , S. Kamio 1 , R. Hihara 1 , K. Abe 1 , M. Sakumura 1 , Q. H. Cao 1 , H. Sakakita 3 , H. Koguchi 3 , S. Kiyama 3 ,

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Merging Start-up and Sustainment Experiments on UTST

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  1. 15th Intl. Workshop on Spherical Tori 2009, Madison, WI, Oct. 22, 2009 Merging Start-up and Sustainment Experiments on UTST T. Yamada1, R. Imazawa2, S. Kamio1, R. Hihara1, K. Abe1, M. Sakumura1, Q. H. Cao1, H. Sakakita3, H. Koguchi3, S. Kiyama3, Y. Hirano3, T. Oosako1, H. Kobayashi1, T. Wakatsuki4, B. I. An4, Y. Nagashima1, M. Inomoto1, A. Ejiri1, Y. Takase1 and Y. Ono1 1Graduate School of Frontier Sciences, The University of Tokyo 2Graduate School of Engineering, The University of Tokyo 3National Institute of Advanced Industrial Science and Technology 4Graduate School of Science, The University of Tokyo

  2. Outline Overview of the UTST experiment Recent progress of the UTST experiment 290-ch. simultaneous measurement PF + Acceleration coils Neutral Beam Injection Summary

  3. Overview of the UTST experiment

  4. Objective of the UTST Plasma Merging technique (Hongo campus) RF heating technique UTST (Kashiwa campus) NB injection from AIST TST-2 (Takase-Ejiri Lab.)

  5. Generating a High b ST By magnetic reconnection, the magnetic field energy is converted to the plasma kinetic energy, and the plasma b is increased up to 50%. Two Merging STs

  6. Double Null Merging (DNM) Method PF coils generate plasmas Ion heating by Magnetic Reconnection Merging High b ST Null-points formed PF At UTST, DNM start-up is performed by outer PF coils.

  7. The UTST Plasma Merging Device PF1 (8 turns) ACC1 (4 turns) Pickup coil array Bt: 64 channels Bz: 64 channels EF1 (8 turns) PF2 (3 turns) Pickup coil array Bt: 81 channels Bz: 81 channels 2 m PF3 (3 turns) EF2 (8 turns) CS (95 turns) ACC2 (4 turns) TF (8 turns) Washer gun (for pre-ionization) PF4 (8 turns) 0.7 m

  8. Typical Discharge of theUTST Plasma Washer gun is used for pre-ionization. Gas (H2) Anode Cathode Plasma Washers Insulator Two main discharge scenarios. DNM start-up discharge (PF). DNM start-up + CS assist discharge (PF + CS). Seed plasma in a spiral magnetic field.

  9. a. PF discharge TF (/turn) EF (/turn) Plasma current (CW) Washer gun PF (/turn) Plasma current up to 40 kA was obtained by DNM method, by using PF coils.

  10. b. PF+CS discharge Plasma current (CW) TF (/turn) EF (/turn) current[kA] Washer gun CS (/turn) PF (/turn) Plasma current reached 170 kA by using the CS coil to assist the DNM start-up (PF) discharge.

  11. Recent progress of the UTST experiment

  12. 1. Two-dimensional Pickup Coil Arrays Expansion of the digitizer made it possible to measure all the 290 channels simultaneously. By using Bt and Bz pickup coil arrays, many variables can be calculated. Pickup coil array Bt: 64 chs. Bz: 64 chs. Pickup coil array Bt: 81 chs. Bz: 81 chs. Glass tube An Example of poloidal flux, Y, produced by EF coils, measured by the pickup coils.

  13. Improvement of the measurement Precision of Bz and Btmeasurement has been improved. q and Dq are measured by generating toroidal or vertical magnetic fields. Bz and Bt are reconstructed by Good agreement between Bz with Bt and Bz w/o Bt.

  14. a. Results on PF discharge Two STs are merged together to form a single ST Fast camera images

  15. (Movies)

  16. b. Results on PF + CS discharge Fast camera images 4.73 ms 4.74 ms 4.72 ms 4.70 ms 4.71 ms The merged plasma reached up to 170 kA.

  17. (Movies)

  18. 2. PF discharge + Acceleration coils By using acceleration coils on PF discharge, current sheet was observed. Acceleration coils increase the plasma merging speed. ACC1 Current sheet ?! PF + CS + ACC is under preparation. ACC2 To be reported in APS DPP, PP8.00099 (Atlanta, GA).

  19. 3. Neutral Beam Injection A general view of the experiment device UTST NB 160 mm NB's acceleration electrode (concave type, F = 1250 mm) Neutralization chamber Jointed to UTST Ion source

  20. Neutral Beam Injection Neutral beam power Test of the neutral beam device and test injection into the UTST device have been finished. Higher density will be required for effective results. 10 ms 500 kW Top view of NB and UTST UTST NB Fast camera image Plasma current focus

  21. Summary • Plasma startup by double null merging method was successfully observed in the UTST plasma merging experiment. Plasma current up to 40 kA was achieved, and the merging of magnetic surfaces was observed. • With CS assist, plasma current reached 170 kA. • By using Acceleration coils, current sheet was observed. • Neutral beam injection has just started. Future Works • Pre-ionization at the upper region is needed for balancing STs. • Power supplies to the coils will be increased. • More diagnostics.

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