28th IAEA Fusion Energy Conference (FEC 2020)

WEST Actively Cooled Load Resilient Ion Cyclotron Resonance Heating Results

13 May 2021, 17:35

17m

Virtual Event

Rapporteur Fusion Energy Technology TECH/3 Divertor and Heating

Speaker

Dr Julien Hillairet (CEA, IRFM, F-13108 St-Paul-Lez-Durance, France )

Description

WEST Actively Cooled Load Resilient Ion Cyclotron Resonance Heating Results

J.Hillairet¹, J.- M.Bernard¹, L.Colas¹, F.Durand¹, W.Helou^1,11, G.Lombard¹, P.Mollard¹, G.Urbanczyk^1,2, Y.Song², Q.Yang², Z.Chen^1,2, Y.Wang², H.Xu², S.Yuan², Y.Zhao², F.Durodié³, E.Lerche³, C.Bourdelle¹, J.-M. Delaplanche¹, C.Desgranges¹, R.Dumont¹, A.Ekedahl¹, M.Goniche¹, C.Guillemaut¹, G.T.Hoang¹, P.Maget¹, R.Volpe¹, N.Bertelli⁴, V.Bobkov⁵, C.Klepper⁶, C.Lau⁶, B.Lu⁷, E.Martin⁶, R.Maggiora⁸, D.Milanesio⁸, M.Ono⁴, R.Ragona³, S.Shiraiwa⁴, K.Vulliez⁹, G.Wallace¹⁰, and WEST Team

1. CEA, IRFM, F-13108 St-Paul-Lez-Durance, France
2. Institute of Plasma Physics, CAS, Hefei, Anhui 230031, PR China
3. Laboratory for Plasma Physics, Royal Military Academy, 1000 Bruxelles, Belgium
4. Princeton Plasma Physics Laboratory, Princeton, NJ 08543, USA.
5. Max-Planck Institut für plasmaphysik, Boltzmannstraße 2, 85748 Garching, Germany
6. Oak Ridge National Laboratory, 1 Bethel Valley Rd, Oak Ridge, TN 37830
7. Southwestern Institute of Physics (SWIP), PO Box 432, Chengdu 610041, PR China
8. Politecnico di Torino, Department of Electronics and Telecommunications
9. CEA, Direction de l'Energie Nucléaire, Université de Montpellier, DE2D, SEAD, Laboratoire d’Etanchéité, F-30207 Bagnols-sur-Cèze, France.
10. MIT Plasma Science and Fusion Center, Cambridge, MA, 02139, USA
11. ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex, France

ELM-resilient antenna with the capability of operating in long-pulse operation is mandatory for Ion Cyclotron Resonance Heating (ICRH) system of ITER and next step fusion machines. The Associated Laboratory CEA-ASIPP had designed in collaboration with ERM, and manufactured three actively water-cooled and ELM-resilient multi-megawatt antennas for WEST [1]-[6] (Fig1). This paper reports on the successful design, manufacturing and operation of these antennas on WEST.

The intrinsic load tolerance property of the WEST ICRH antennas [5], already demonstrated during commissioning and first plasma experiments [7], has been confirmed in the 2019 experimental campaign and is in good agreement with RF modelling (Fig2). An automatic matching algorithm has been implemented and successfully used during operations [1]. Due to the antenna load-resilience, variations in plasma scenario parameters such as fluctuations of the fast wave cut-off layer or minor changes in resonance layer location do not affect the antenna operation significantly. Moreover, the operation of the antennas is quite straightforward, as once the antenna tuning capacitors have been set up for a given frequency, the antenna accepts small capacitance deviations from ideal match point.

Long pulse high power operation requires dedicated protections from the generator to the antenna [1]. For this purpose, several interlocks are used in the WEST ICRH system [2]. Sub-Harmonic Arc Detector (SHAD) and reflected power interlocks stop generators from feeding an antenna within 10 µs, then re-apply power after 30 ms. The RF power is real-time controlled in order not to exceed the antenna maximum electric field (2 kV/mm) or the maximum voltages and currents thresholds at the capacitors (30 kV or 915 A peak values respectively). The new optical arc detectors looking inside the antenna have been qualified and found to trigger mostly during the conditioning phases. These optical detectors are particularly essential to protect the low impedance sections of the antenna, where arcs may not trigger other safety systems. The pressure level inside the antenna is monitored from an auxiliary pumping system. RF power is cut if pressure is above a safety threshold of 3.5x10-3 Pa until pressure recovers. Abnormal events can also be detected from the antenna voltage measurements and additional interlocks have been added for safer operation. RF power is stopped within 10 µs in case of voltages lower than 10 kV (for power larger than 100 kW) or if voltages relative differences are higher than 50%. Thanks to all of these security systems and despite the higher power levels achieved, no damage has been observed on the three antenna front-faces after the WEST 2019 experimental campaign.

The commissioning phase was relatively short, of about two days for each antenna to reach 1 to 1.5 MW. After this commissioning phase, all three antennas have been operated simultaneously on WEST plasmas, leading to 5.8 MW coupled ICRH power after around 50 plasma discharges (close to 2 MW per antenna). All antennas are equipped with dedicated gas puffing valves in order to improve the coupling conditions. However, due to the present WEST pumping system capabilities, no major coupling improvement has been observed for the limited level of gas flux injected by these valves so far. In combined operation with the Lower Hybrid Current Drive (LHCD) system, a total injected RF power of up to 9.2 MW has been achieved [8].

References
[1] W.Helou et al., to appear in AIP Conference Proceedings, 2020
[2] J.Hillairet et al., AIP Conference Proceedings, 2015, vol. 1689, p.070005, doi: 10/ggc294.
[3] Q.Yang et al., Proc 10th Asia plasma and fusion association conference, Gandhinagar, India, 2015.
[4] Z.Chen et al., Fusion Engineering and Design, vol. 94, p. 82‑89, 2015, doi: 10/f7bvfh.
[5] W.Helou et al., Fusion Engineering and Design, vol. 96‑97, p.473‑476, oct. 2015, doi: 10/ggc25r.
[6] K.Vulliez et al., Fusion Engineering and Design, vol. 96‑97, p.611‑615, oct. 2015, doi: 10/ggc2zv.
[7] J.-M.Bernard et al., Fusion Engineering and Design, vol. 146, p.1778‑1781, doi: 10/ggc269.
[8] J.Bucalossi, this conference

Presentation materials

IAEA_2021_ICRH_WEST_Hillairet_4-3_V1.pdf

TECH-3-5R_Hillairet_summary_slide.pptx