High density internal transport barriers for burning plasma operation
2005
A tokamak plasma with internal transport barriers (ITBs) is the best candidate for a steady ITER operation, since the high energy confinement allows working at plasma currents (Ip) lower than the reference scenario. To build and sustain an ITB at the ITER high density (10 20 m −3 ) and largely dominant electron (e − ) heating is not trivial in most existing tokamaks. FTU can instead meet both requests, thanks to its radiofrequency heating systems, lower hybrid (LH, up to 1.9 MW) and electron cyclotron (EC up to 1.2 MW). By the combined use of them, ITBs are obtained up to peak densities ne0 > 1.3 × 10 20 m −3 , with central e − temperatures Te0 ≈ 5.5 keV, and are sustained for as long as the heating pulse is applied (>35 confinement times, τE) .A tne0 ≈ 0.8 × 10 20 m −3 Te0 can be larger than 11 keV. Almost full current drive (CD) and an overall good steadiness is attained within about one τE, 20 times faster than the ohmic current relaxation time. The ITB extends over a central region with an almost flat or slightly reversed q profile and qmin ≈ 1.3 that is fully sustained by off-axis lower hybrid current drive. Consequent to this is the beneficial good alignment of the bootstrap current, generated by the ITB large pressure gradients, with the LH driven current. Reflectometry shows a clear change in the turbulence
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
20
References
2
Citations
NaN
KQI