摘要:

Ion cyclotron range of frequency (ICRF) heating is currently in use on CHS and W7‐AS and is a major element of the heating planned for steady state helical devices. In helical devices, the lack of a toroidal current eliminates both disruptions and the need for ICRF current drive, simplifying the design of antenna structures as compared to tokamak applications. However the survivability of plasma facing components and steady state cooling issues are directly applicable to tokamak devices. Results from LHD steady state experiments should be available on a time scale to strongly influence the next generation of steady state tokamak experiments. The helical plasma geometry provides challenges not faced with tokamak ICRF heating, including the potential for enhanced fast ion losses, impurity accumulation, limited access for antenna structures, and open magnetic field lines in the plasma edge. The present results and near term plans provide the basis for steady state ICRF heating of larger helical devices. An approach which includes direct electron, mode conversion, ion minority and ion Bernstein wave heating addresses these issues. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49515

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Low‐aspect‐ratio tokamaks (LARTs) have received recent attention because of encouraging results from small scale experiments and because of the LART’s potential for attaining high stable &bgr; in next generation devices. For this potential to be realized, efficient methods of non‐inductive heating and current drive required to heat and sustain such plasmas must be found. A typical next generation high &bgr; LART experiment has an unusually large dielectric &ohgr;2pe/&OHgr;2ce∼100, compared to the conventional tokamak value of ∼1. In the high dielectric regime considered here, lower hybrid and electron cyclotron waves have severe accessibility problems. In contrast to these limitations, recent calculations by M. Ono [1] indicate that fast waves in the intermediate frequency regime with &ohgr;≊20&OHgr;ci≪&ohgr;LHexperience sufficient damping on electrons to consider localized power deposition and have a high ion &bgr; accessibility limit. In an attempt to model this regime, ray tracing calculations for NSTX and CDX‐U have been performed and modelling results will be presented for cases of interest. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49516

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In the Tokamak Fusion Test Reactor (TFTR) the mode converted ion Bernstein wave (IBW) has been shown to heat electrons, drive current (both on and off axis), and to interact with fusion products. D‐3He and D‐T‐3He plasmas have been used as mode conversion targets. On‐axis mode conversion heating increased Te(0) from 3 keV to 10 keV with 4 MW of ICRF. On‐axis currents of 125 kA with 2 MW of ICRF, and off axis currents of 100 kA with 4 MW of ICRF, have been driven. A strong interaction of the IBW with fusion products has been observed. Mode conversion current drive (MCCD) for TPX is briefly discussed. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49517

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Ion Bernstein waves (IBWs) have been generated by mode conversion of ion cyclotron range of frequency (ICRF) fast waves in TFTR. The loss rate of fusion products in these discharges can be large, up to 10 times the first orbit loss rate. The losses are observed at the passing/trapped boundary, indicating that passing particles are being moved onto loss orbits either by increase of theirv⊥ due to the wave, by outward transport in minor radius, or both. The lost particles appear to be DD fusion produced tritons heated to ∼1.5 times their birth energy. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49518

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A new scenario for effeicient mode conversion heating, in the ion cyclotron range of frequency, is proposed. Experiments on Tore Supra demonstrate that this new scheme is quite efficient. A detailed analysis of thes mode conversion scenario is carried out, using a new complete 1‐D model and the 3‐D full wave code Alcyon. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49519

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

D(H) minority heating experiments were performed atBT=5.3 T with up to 3.5 MW of RF power. The highest stored energy of 130 kJ was achieved in an ELM‐free H‐mode plasma. The H‐mode power threshold is roughly consistent with the ITER scaling,P/S=0.044n¯eBT, but H‐modes have been obtained at power levels as much as a factor of two below this scaling. H‐factors of up to 1.5 have been observed in ELM‐free H‐mode plasmas. The highest fusion reactivity of 9×1013sec−1was obtained in a PEP H‐mode plasma with lithium pellet injection and on‐axis ICRF heating. These discharges are characterized by highly peaked density and ion temperature profiles, with fusion reactivity enhanced by typically an order of magnitude above similar L‐mode discharges. Effective localized direct electron heating by mode converted IBW was observed in H‐3He plasmas (analogous to D‐T plasmas) at 6.5 T. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49520

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Sawtooth relaxation is suppressed during ELM‐free period by second harmonic minority ICRF heating in 4MA H‐mode experiments with high power NBI heating. TAE modes in high plasma current regime (up to 4MA) are investigated with ICRF heating, where high‐n TAE modes (n more than 10) appear. TAE amplitude increases with increasing toroidal mode number. The ion energy spectrum is measured up to 1 MeV during higher harmonic beam ion acceleration (from 2nd to 5th harmonics). The tail ion temperature increases with increasing harmonic number up to 4th harmonics. The lower hybrid (LH) wave deposition profile (therefore the driven current profile) can be controlled by changing launched wave spectra (phase velocity, spectral width, compound spectra) or changing geometry (launching position, safety factor). It is also demonstrated to drive noninductive current in the opposite direction to the ohmic current by LH waves for enhancement of the current profile controllability. Antenna coupling with a large separatrix‐antenna gap is demonstrated for both fast waves and LH waves and some related issues are discussed. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49522

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Recent RF heating and current drive experiments in the Lower Hybrid (LH) and Ion Cyclotron (IC) frequency ranges are reported. In the 4T improved confinement LHEP regime, steady‐state LHCD operation has been realized with a new ‘‘constant‐flux’’ scenario. A new, reversed shear, 2T improved confinement plasma regime has also been investigated when the core plasma is inaccessible to the LH waves. Stable, LH driven 0.4 MA discharges were obtained withHrlw=2 at &bgr;p=0.8,q0above 2 and with a reduced electron thermal diffusivity in the central reversed shear region. Efficient direct coupling of the fast magnetosonic wave to the electrons for heating and current drive is observed during 48 MHz/2T operation. Fast wave electron heating has produced improved confinement withHr1w=2 at &bgr;p=1.6, and a bootstrap current fraction up to 45%. Fast wave current drive has been observed at the level of 80 kA in a 0.4 MA discharge. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49523

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Simulations of the non‐thermal bremsstrahlung emission based on the resolution of the full two‐dimensional relativistic Fokker‐Planck equation are reported for recent TORE SUPRA and JET LH experiments. From a comparison with standard one‐dimensional treatments, it is shown that the perpendicular electron dynamics plays an important role in the quantitative prediction of the various moments of the fast electron tail. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49560

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Lower hybrid discharges have been realised in Tore Supra using feed‐back control of the primary circuit voltage (Voh) such that the loop voltage was maintained exactly zero near the plasma surface. This new scenario allows the plasma current to float and quickly reach an equilibrium value determined by the current drive efficiency and Lower Hybrid power. Recent experimental results show that, with the new ‘‘constant flux’’ scenario the coupled plasma and primary currents reach a steady state in less than 10 s which is in good agreement with theoretical expectations. A complete analysis of this scenario is presented. ©1996 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.49562

出版商:AIP    

年代:1996

数据来源: AIP