Tokamak physics

Mission

• develop an integral understanding of the physics of the burning ITER plasma core, including the fast particles generated by the fusion reactions and the magneto-hydrodynamic (MHD) stability of the plasma
• develop the physics and technology for Tokamak MHD stability control
• develop an active MHD feed-back control system for ITER based on Electron Cyclotron Heating and Current Drive
   

Annual report 2009 – Description Tokamak physics group

Reseach Programme

The programme of the Tokamak Physics (TP) group is directed at ITER burn control and is carried out in collaboration with the Plasma Diagnostics (PD) group and the Computational Plasma Physics–High Temperature (CPP-HT) group of the FOM-Insitute DIFFER. The focus is on the development of a state-of-the-art MHD controller employing Electron Cyclotron Heating and Current Drive (ECH&CD) as an actuator and Electron Cyclotron Emission as a sensor for feed-back control. This includes theoretical modelling of the controller, experimental work on control diagnostics and the development of high power mm-wave equipment. Experiments are planned on the European Tokamak facilities ASDEX Upgrade, MAST and ToreSupra. In the long term, the group intends to play a key role in ITER plasma scenario development, core parameter control and MHD control, through the technical and scientific development of the ITER Upper Port Launcher (UPL) for MHD control and the subsequent scientific exploitation of the UPL and the Upper Port Viewer (UPV) on ITER.

The programme is funded by the ITER-NL program (2010-2013), supporting the development of high-power mm-wave systems and remote handling, the new FOM program 120 “MHD control in Burning Plasmas” funding the plasma science activities and the development of advanced control schemes, the EFDA goal oriented training (GOT) programme, providing grants for three positions for the development of remote handling and the use of 2D optics for plasma control and the NWO Centre of Excellence, funding the development of electron cyclotron wave physics and technology. 

For background information, see sub-page Background
 

Current activities:

The current activities of the group include:

• MHD and plasma control
• Remote handling

Highlights:

Proof of Principle of MHD feed-back control by Electron Cyclotron Waves 

The proof of principle of the line-of-sight feed-back control system for real-time, autonomous suppression and stabilization of tearing modes in a Tokamak was demonstrated on TEXTOR; see B.A. Hennen et al., Plasma Phys and Contr. Fus.52 (2010) p.20. The system is based on ECE sensing of tearing modes and actuation by a steerable ECW launcher. The fast detection of the m/n = 2/1 tearing modes and the retrieval of their location, rotation frequency and phase allowed set-points to be established for real time alignment of the ECW launcher with the centre of the tearing mode and forward this signal in closed loop to the gyrotron source to modulate the power in sync with the rotation of the instability. 

Prototype development of an MHD controller 

A mock-up of the AUG mm-wave launcher was built in order to characterise its mechanical properties. Data obtained served as input for a simulator used to optimise the launcher. Real time control of the fast diplexer (FADIS) cavity was achieved by an adjustable mirror enabling switching, merging and toggling of the high power mm-wave beams. A continuous high power in-line electron cyclotron emission (ECE) system was designed and built for real-time MHD instability control at AUG. 

Control oriented modelling 

A method for real-time identification of Tokamak crash-periods has been developed based on b-spline wavelets in limit cycles. The method will be applied for saw-tooth instability analysis. A combined Kadomtsev-Porcelli model has been set-up to simulate the saw-tooth cycle. A controller has been defined based on in-line ECE sensing and three actuators; power, heat-current drive efficiency and deposition radius.
The Rutherford equation for magnetic island evolution has been linearised with respect to the control actuator settings on power, heat-current drive efficiency and deposition radius. An extreme seeking algorithm is implemented for control of the island size.  

Optical diagnostics for plasma control 

2D visual data has been employed for optical boundary reconstruction of Tokamak plasmas, yielding a robust plasma boundary, also under conditions where the standard magnetic interpretation is beset by large error bars. Reliable plasma boundary reconstruction is needed for physics interpretation and for real time control of the plasma position and shape. 

Remote Handling 

Remote handling compatibility analyses have been carried out for the ITER Upper Port ECH system, the Equatorial Port ECH system and the Upper Port Charge Exchange Spectroscopy diagnostics system.
A visualisation and simulation facility has been built for the development of remote handling procedures and for remote maintenance in the ITER Hot Cell Facility. A physics engine is used to emulate the forces encountered, which are fed-back into a master station for control
 

Scientific papers 2009:

1. D. J. Thoen et al., Development and testing of a fast Fourier transform high dynamic-range spectral diagnostics for millimeter wave characterization. Review of Scientific Instruments 80, no. 10 (2009): 103504.
2. Bongers, W.A. et al. A remotely steered millimetre wave launcher for electron cyclotron heating and current drive on ITER. Fusion Engineering and Design In Press, Corrected Proof, (2009).
3.  Bertelli, N. & Westerhof, E. Consequences of finite transport on the effectiveness of ECCD for neoclassical tearing mode stabilization in ITER. Nuclear Fusion 49, (2009). 
4. 
   De Lazzari, D. & Westerhof, E. On the merits of heating and current drive for tearing mode stabilization. Nuclear Fusion 49, 075002 (2009). 
5. Ronden, D. et al. Finalization of the conceptual design of the remote steering ECH launcher for ITER. Fusion Engineering and Design 84, 1645-1648 (2009). 
6. Koning, J. et al. Maintenance implications of critical components in ITER CXRS upper port plug design. Fusion Engineering and Design 84, 1091-1094 (2009). 
7. Hennen, B. et al. A closed-loop control system for stabilization of MHD events on TEXTOR. Fusion Engineering and Design 84, 928-934 (2009). 
8. Heidinger, R. et al. Conceptual design of the ECH upper launcher system for ITER. Fusion Engineering and Design 84, 284-289 (2009). 
9. Heemskerk, C. et al. Applying principles of Design For Assembly to ITER maintenance operations. Fusion Engineering and Design 84, 911-914 (2009). 
10. Elzendoorn, B. et al. Analysis of the ITER ECH Upper Port Launcher remote maintenance using virtual reality. Fusion Engineering and Design 84, 733-735 (2009). 
11. Bongers, W.A. et al. Magnetic Island Localization for NTM Control by ECE Viewed Along the Same Optical Path of the ECCD Beam. Fusion Science and Technology 55, 188-203 (2009). 

Conference contributions:

1. M.R. de Baar et al. Remote Handling for ITER, Dutch Robotics, 26 May 2009, Eindhoven, the Netherlands
2. M.R. de Baar et al. A tearing mode track-and-suppress system for TEXTOR, 5th IAEA Technical Meeting on “ECRH Physics and Technology for Large Fusion Devices” 18-20 February 2009, Gandinaghar, India
3. C. Heemskerk et al. Analysis of Port Plug maintenance procedures in the ITER Hot Cell Facility using Virtual Reality, Poster presented at HOTLAB conference 2009, Prague, Czech Republic, 20-23 September 29
4. D. De Lazzari et al. On the Merits of Heating and Current Drive for Tearing Modes Stabilization, 36th EPS Conference on Plasma Physics June 29 - July 3, 2009, Sofia, BulgariaE. Westerhof et al. Physics aspects limiting the achievable localization of the EC driven current in ITER, 5th IAEA Technical Meeting on “ECRH Physics and Technology for Large Fusion Devices” 18-20 February 2009, Gandinaghar, India
5. N. Bertelli et al. The effect of the radial diffusion on the effectiveness of ECCD for neoclassical tearing mode stabilization in ITER, The 8th Topical Conference on Radio Frequency Power in Plasmas, 24-26 June 2009, Gent, Belgium
6. N. Bertelli et al. The effect of anomalous radial transport on electron cyclotron current drive for neoclassical tearing mode stabilization in ITER, 13th European Fusion Theory Conference, 12-15 October 2009, Riga, Latvia
7. W.A. Bongers et al. ECE System on ASDEX-Upgrade Placed Inline at the High Power Waveguide based Transmission System, IRMMW-THz, 21-25 September 2009 , Busan, Korea
8. D.J. Thoen et al. FFT based Diagnostic for Spectral Characterization of Scattered Millimeter Waves in Tokamaks, IRMMW-THz , 21-25 September 2009, Busan, Korea

Personnel of the Tokamak Physics group