Modelling of ICRH induced current and rotation

Johnson, T.; Hellsten, T.; Eriksson, L.‐G.; Laxåbäck, Martin; Bergkvist, Tommy

doi:10.1063/1.1638082

Cited by 1 publication

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The creation of high-energy ions with wide banana orbits results in losses as the wall intercepts the drift orbits of the ions. These losses are more important for symmetric spectra and for counter-current propagating waves than for interactions with co-current propagating waves [24]. The losses become smaller as the plasma current increases and are likely to be one of the reasons why the first successful ICRH experiments were obtained in tokamaks with sufficiently large currents to confine the high-energy ions, such as PLT [55].…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…In the first method, the drift term in the collision operator described in section 2.3 is used to correct the transport. The second method is based on finding stationary solutions by recycling lost ions by adding them as thermal ones near the plasma boundary simulating physical recycling or gas puffing [53,24]. The discontinuities at the end points of the RF trajectories, defined by equation (9), when the interactions between the wave and the particle cease, make it difficult to satisfy reciprocity.…”

Section: Self-consistent Simulations With the Selfo Codementioning

confidence: 99%

“…The de-trapped orbits may reside entirely on the low field side of the resonance. They are limited in energy because of the Doppler shifted resonances on the low field side of the orbit disappear as the energy increases above a critical value [24] or by the wall intercepting the orbit.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of finite drift orbit width and RF-induced spatial transport on plasma heated by ICRH

Hellsten¹,

Johnson²,

Carlsson

et al. 2004

Nucl. Fusion

View full text Add to dashboard Cite

The effects of RF-induced transport and orbit topology of resonant ions are analysed for high power ion cyclotron resonance heating (ICRH). These effects are found to play important roles in the details of the high-energy part of the distribution function, and affect the driven current and momentum transfer to the background plasma. The finite drift orbit width broadens the power deposition and leads to losses of high-energy ions intercepted by the wall. RF-induced transport of resonant ions across magnetic flux surfaces appears due to the toroidal acceleration of resonant ions interacting with waves having a finite toroidal mode number. Heating with waves propagating parallel to the current leads to a drift of the turning points of trapped resonant ions towards the midplane. As the turning points meet, the orbits will de-trap, preferentially into co-current passing orbits, which may ultimately be displaced to the low field side of the magnetic axis. Ions with such orbits are a typical feature in plasmas heated with directed toroidal mode spectra of waves propagating parallel to the plasma current. These ions will be subjected to a strong RF diffusion partly caused by the focusing of the wave field and partly by the Doppler shifted cyclotron resonance, as it approaches tangency with the drift orbit. The resonance condition puts a limitation on the achievable energy for these ions, which is more severe than for corresponding trapped ions. This results in a rather flat tail up to a critical energy, above which the tail rapidly decays. Heating with waves propagating anti-parallel with the plasma current curtails the energy of the trapped ions due to a vertical outward drift of the turning points of the trapped ions. Heating with symmetric spectra, in particular with waves with low magnitude of the toroidal mode numbers, gives rise to high-energy trapped ions with wide orbits, of which the maximum energy is either restricted by the fact that the RF diffusion vanishes due to cancellation of the perpendicular acceleration over a gyro orbit or by the drift orbits being intercepted by the wall. In the steady state the main source for momentum transfer to the bulk plasma comes from the finite momentum of the wave for heating with asymmetric spectra. For heating with symmetric spectra the enhanced losses of high-energy trapped ions can produce a net counter-current torque on the plasma.

show abstract

Section: Conclusion and Discussionmentioning

confidence: 99%

Section: Self-consistent Simulations With the Selfo Codementioning

confidence: 99%