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Measurement of divertor heat flux at the end-cell of the GAMMA 10

OS2012/PMIF2012 Aug.28,2012 Tsukuba(Japan). Measurement of divertor heat flux at the end-cell of the GAMMA 10. H. Matsuura a , H. Takeda b , K. Ichimura b , K. Hosoi b , Y. Nakashima b , M. Sakamoto b , M. Shoji c , K. Nagaoka c , T. Imai b

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Measurement of divertor heat flux at the end-cell of the GAMMA 10

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  1. OS2012/PMIF2012 Aug.28,2012 Tsukuba(Japan) Measurement of divertor heat flux at the end-cell of the GAMMA 10 H. Matsuuraa, H. Takedab, K. Ichimurab, K. Hosoib, Y. Nakashimab, M. Sakamotob, M. Shojic, K. Nagaokac, T. Imaib aRadiation Research Center, Osaka Prefecture University bPlasma Research Center, University of Tsukuba cNational Institute for Fusion Science

  2. Contents of my presentation • Why is plasma heat flux(energy flux) important? • What is thermal probe and how is it used ? • What is necessary for GAMMA 10 (or ITER) plasma heat flux measurement? • What did we do?What have we obtained? • What is left for future work?

  3. PSI and heat(Energy) flux New J. Phys. 11 (2009) 115012 • Plasma medicine and biomaterial treatment • Plasma CVD and etching • Space vehicles, such as Hayabusa • Divertor design and ELM control Plasma heat flux is important in wide PSI field.

  4. Classical thermal probe

  5. Concept of thermal probe ( or solid calorimeter)

  6. Measurement of heat flux change Heat flux change due to H-mode, detachment, plug ECH, and so on is more interesting than steady state heat flux or total heat load per a discharge shot. How about heat flux? LHD results( presented at ITC21)

  7. What is necessary for determination of q(t) as like in LHD experiment? • Fitting procedure of measured TC data with response function model with physical causality • Response function of probe/calorimeter sensor with appropriate modeling • A small sensor with fast response (small thermal diffusion time) and good SN ratio

  8. Here we assume the infinite slab model with only plasma irradiation boundary.

  9. Heat sink boundary Heat sink Kurihara, Kado (OS2006)

  10. qsink=0 GAMMA 10 Calorimeter tip

  11. Comparison of boundary condition Red: perfect sink boundary,Blue: perfect isolation boundary,Magenta: infinite boundary probe tip Plasma pulse

  12. GAMMA10 Calorimeter system The west end-mirror region, together withthe location of the diagnostic equipment installed for this experiment.

  13. Response of the old sensor The heat-flux density is evaluated from the differencebetween the temperature of the calorimeter tip measuredjust before the discharge and that measured immediately after thedischarge. • Was Temperature evolution of TC data sufficiently traced? In FY 2010 experiment, time response of calorimeter sensor was slow, and data recorder also worked slowly. Calorimetric estimation One division is 16[min], nearly equal shot interval

  14. Improvement of sensor

  15. Response of TC signal

  16. TC signal noise During and just after discharge, there exist large noises in TC signal. They come from RF power,magnetic field induction, .... Noise at t=400-2000ms is well compensated with no plasma shot data.

  17. Comparison of the response for box heat pulse with two model 2MW/m2, 100ms 1MW/m2, 150ms heat sink boundary model thermal isolation boundary model Temperature at x=2,6,12[mm] is estimeted with two boundary model. Present (isolation boundary) model reproduces well the TC data.

  18. Conclusion(What we did.) • We develop a new fitting procedure of measured TC data, and demonstrate with LHD probe data. • We expand response function model to be applicable to small sensors in GAMMA10. • We construct a new calorimeter sensor and test it in FY2012 experiment.

  19. What is left for future work? • Determination of the TC noise origin and reduction of it. ( Isolation Amplifier used in Heliotron J experiment may be effective.) • Cross check of heat flux estimation • Determination of heat flux evolution with plug ECH or ICRF additional heating • Diagnostic as a thermal probe (for example, divertor Ti measurement)

  20. Thank you for kind attention. Any questions and comments are welcome. This work is partially performed with the support and under the auspices of the NIFS Collaborative Research Program. (NIFS12KUGM071/NIFS12KUHL047)

  21. Sheath heat transmission factor

  22. HDP analysis(H-J) (Presented at ITC18/ITC19)

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