Szczecin, 23 March 2006 Meeting with Dr. B. Green Dr. B. Green (Euratom) and Prof. A. Gałkowski (Association Euratom-IPPLM). Selected Collaboration Issues on Energetic Particle Effects in Tokamaks. M. Lisak , P. Sandquist, D. Anderson Swedish Fusion Association Euratom-VR
Szczecin, 23 March 2006
Meeting with Dr. B. Green Dr. B. Green (Euratom) and
Prof. A. Gałkowski (Association Euratom-IPPLM)
Selected Collaboration Issues on
Energetic Particle Effects in Tokamaks
M. Lisak, P. Sandquist, D. Anderson
Swedish Fusion Association Euratom-VR
Chalmers University of Technology, Göteborg
Yu. Kravtsov, S. Berczyński, P. Berczyński
Szczecin University of Technology and Martitime
University of Szczecin
Why we should study fast particle effects
in fusion plasmas?
Alpha particles in a burning plasma with Q>10 (fa >60%) can have an affect on
ITER oriented physics R&D
e. Fast particle physics
“Most of the research issues listed above (with the exception of disruption
studies) are linked to the presence of a population of fast particles. For the
investigation of fast particle effects it is not necessary to work with the Alpha
particles generated in DT operation: simulations are possible, e.g. by using
ICRH minority heating or negative NBI.”
RESEARCH TOPICS WITHIN COLLABORATION BETWEEN CHALMERS AND THE SZCZECIN CONSORTIUM
regimes is a problem to be solved on the way to design and construction of
an ignition device
(3.5 MeV alpha particles)
velocity distribution function of fast particles
Studies of instabilities and confinement of energetic ions on JET serve as a framework for the implementation of innovative fast ion diagnostics in next step burning plasma devices such as ITER.
Local WKB analysis estimates the linear growth rate and the instability threshold
Diffusion of the fast particle velocity distribution function anomalous ion relaxation in velocity space, anomalous fast ion losses, outward flux of lower energy ions.
- The mode amplitude evolves according to
- Steady-state, oscillating and explosive solutions depending on
- Bifurcations at single-mode saturation can be analyzed
- Formation of a long-lived coherent nonlinear structure is possible
- Resonance overlap can indicate strong nonlinear regime
- Multi-mode scenarios with marginal stability are interesting:
Full life-cycle of EPMs, starting from instability threshold: So far, described only the initial phase.
Fishbones: Transition from an explosive growth to a slowly growing MHD structure (i.e. island near q=1 surface).
General aim of work: Development and experimental evaluation of theoretical models for fast particle effects in MHD phenomena.
In particular, effects of supra-thermal electrons and NBI and ICRH- accelerated ions on sawteeth have to be validated against JET data.
Participation in upcoming JET experimental campaigns C15-C17 on fast particle experiments is planned (P. Sandquist).
Participation in the Integrated Modelling Project 2: Non-Linear MHD and Disruptions, where redistribution of fast ions during sawtooth activity will be studied. Presentation on the subject was given (M. Lisak) at the Sawtooth Workshop at JET on 16-17 February 2006.
Sawtooth oscillations are one of the most typical form of MHD activity in a tokamak plasma. They appear in the form of oscillations of X-ray radiation, temperature, density and current in the central plasma region and are shaped like the teeth of a saw. The internal kink-mode is considered to be responsible for the sawtooth oscillations.
The sawtooth oscillation
The core of a tokamak is subject to relaxation oscillations when q<1
Fast Electron Bremsstrahlung in Low-Density, Grassy Sawtoothing Plasmas
Low density, ICRH-only heated
plasmas on JET show transitions to a ’grassy’ sawtooth regime
At the time of the transition, the
electric field on axis is close to the critical electric field for runaway production
supra-thermal electrons might play a role in the transition.
(P. Sandquist, S. Sharapov, M. Lisak et al, contribution at EPS 2005)
Tomographic reconstructions of FEB emission of supra-thermal electrons (left), fast ion FEB energies (right) and intermediate energies (middle).
General kinetic Fokker-Planck theory of relativistic electrons is being developed.
Thank you !