Heating experiments on the FT Tokamak in the lower hybrid frequency range

Alladio, F.; Barbato, Emanuele; Bardotti, G.; Bartiromo, R.; Bracco, G.; Buceti, G.; Buratti, P.; Crisanti, F.; Angelis, R. De; Marco, F. De; Pretis, M. de; Frigione, D.; Gasparotto, M.; Giannella, R.; Grolli, M.; Lenoci, M.; Mancuso, Salvatore; Mazzitelli, G.; Pericoli, V.; Pieroni, L.; Podda, S.; Righetti, Giulia; Romanelli, M.; Santini, F.; Segrè, S. E.; Tuccillo, A. A.; Zanza, V.

doi:10.1088/0741-3335/26/1a/314

Cited by 19 publications

(40 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At somewhat higher densities, also deuterium tails appear. The presence of the minority H absorption justifies the observed ion mass independence of the density limit for the electron heating regime [139]. Both in H 2 and in D 2 discharges, this limit was always close to 5 X 10 19 rrf 3 .…”

Section: Ion Heating Modesupporting

confidence: 62%

“…for 0.5 < n e < 1.5 X 10 14 cm' 3 . At low current in FT [139], as well as in other experiments [140], this range is quite reduced since the onset of decay instability occurs close to the density limit for electron absorption. In FT the ion heating regime is characterized by enhanced neutron emission in a D 2 plasma (with ATi ss 200 eV at P R F = 200 kW) and by the presence of ion tails measured by charge exchange analysis [138].…”

Section: Ion Heating Modementioning

confidence: 64%

“…4.4, the knee where the plateau of the hydrogen spectrum starts is around 6 keV. According to the quasi-linear theory [132], this should correspond [148).…”

Section: Ion Heating Modementioning

confidence: 99%

See 2 more Smart Citations

High magnetic field tokamaks

et al. 1986

View full text Add to dashboard Cite

A review of existing high magnetic field tokamaks is presented. The results obtained, especially in the research areas concerning confinement, impurity control and heating, are discussed and compared with those of tokamaks at lower toroidal field. New devices, either proposed or under construction, are surveyed. Advantages and difficulties of such machines in exploring the approach to ignition are examined.

show abstract

Section: Ion Heating Modesupporting

confidence: 62%

Section: Ion Heating Modementioning

confidence: 64%

See 1 more Smart Citation

High magnetic field tokamaks

et al. 1986

View full text Add to dashboard Cite

show abstract

“…In previous electron Landau-heating experiments only 100-200 kW of rf power was injected, mostly at lower densities, and the associated electron heating was modest. 2 "" 4 The present experiments indicate the potential attractiveness of lower hybrid rf heating of fusion-grade plasmas.…”

mentioning

confidence: 65%

High-Power Electron Landau-Heating Experiments in the Lower Hybrid Frequency Range in a Tokamak Plasma

et al. 1984

View full text Add to dashboard Cite

The effectiveness of plasma heating by electron Landau interaction in the lower hybrid range of frequencies in tokamak plasmas is demonstrated. Upon injection of 850 kW of rf power at a density of n e -1.4x 10 14 cm -3 , an electron temperature increase of 1.0 keV and an ion temperature increase of 0.8 keV was achieved. These results are compared with transport and ray-tracing code predictions.PACS numbers: 52.50. Gj, 52.40.Db In this Letter experimental results are presented which demonstrate for the first time that substantial electron Landau heating in the lower hybrid frequency range 1 can be achieved in magnetically confined high-temperature (T e ~ T { > 1 keV) and high-density (« e > lxlO 14 cm" 3 ) plasmas. In the present experiments ///LH(0)^.2 [where AH(0) is the lower hybrid frequency at the plasma center] so that direct ion Landau heating by the waves can be excluded. 1 Bulk ion heating is achieved by collisional equilibration between electrons and ions. In previous electron Landau-heating experiments only 100-200 kW of rf power was injected, mostly at lower densities, and the associated electron heating was modest. 2 "" 4 The present experiments indicate the potential attractiveness of lower hybrid rf heating of fusion-grade plasmas.The experiments were carried out in the Alcator C tokamak (major radius R = 64 cm, minor radius a = 16.5 cm), at magnetic fields in the range B T ~ 7-11 T. Three types of limiter materials were used: molybdenum, graphite, and silicon-carbidecoated graphite. The lower hybrid waves were launched by two 4x4 waveguide arrays located 180° relative to each other around the torus. 5 Each array was fed by four 250-kW, 4.6-GHz Varian klystrons, and adjacent columns of waveguides were phased 180° relative to each other. The power spectrum of the launched waves extended from N u =ck n / co-±2 to Nn = ±4, and had maxima at N u -±3.1. 6 Figure 1 shows the time evolution of plasma parameters during a typical high-rf-power shot in deuterium plasma with silicon-carbide-coated graphite limiters. The ion temperature measurements were carried out by neutron yield analysis (corrected for impurity influx) and by a massresolving charge-exchange fast-neutral analyzer looking perpendicular to the magnetic field. The fast-neutral energy spectrum was measured every FIG. 1. Time history of a typical rf shot. 5 = 9T,D + ions, and n e \4 is in units of 10 14 cm -3 .

show abstract

“…The increase in HQ, and visible radiation from 25 ms (see observations on ASDEX [14] and FT [15]), as well as the decrease in off-axis soft X-ray intensity and in r s , are the first indications that m = 2 growth will occur. However, the start of the growth phase of the m = 2 is not at all closely linked with the start of the Ha increase, especially at the higher ('type B') puff rate (Figs 6(c) and (e)).…”

Section: Predisruptive Phase: External Modesmentioning

confidence: 99%

Major disruptions of low aspect ratio tokamak plasmas caused by thermal instability

et al. 1986

View full text Add to dashboard Cite

Reproducible major disruptions of low aspect ratio plasmas (R/a = 2.17) obtained in the Tokoloshe tokamak, have been studied. These disruptions are triggered by contact of a large m = 2 island with the inside of the limiter. The m = 2 growth is precipitated by a thermal collapse of the plasma periphery during the current decay phase. The time-scale of this island growth is strongly dependent on relatively small changes in the gas puff rate affecting the shear at the q = 2 surface. As a result, the start of the m = 2 growth before the disruption is not necessarily at all closely linked to the start of the thermal collapse. Clear evidence is found that the m = 1 mode plays no direct role in these major disruptions, nor does any other mode except the m = 2 appear to be important.

show abstract

Heating experiments on the FT Tokamak in the lower hybrid frequency range

Cited by 19 publications

References 2 publications

High magnetic field tokamaks

High magnetic field tokamaks

High-Power Electron Landau-Heating Experiments in the Lower Hybrid Frequency Range in a Tokamak Plasma

Major disruptions of low aspect ratio tokamak plasmas caused by thermal instability

Contact Info

Product

Resources

About