Lower hybrid current drive efficiency in the JT-60 tokamak

Ushigusa, K.; Imai, T.; Ikeda, Yoshitaka; Naito, O.; Uehara, K.; Yoshida, H.; Kubo, H.; Team, Jt

doi:10.1088/0029-5515/29/6/015

Cited by 48 publications

(34 citation statements)

References 8 publications

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“…Effects on η * CD from some of the variables considered here have been found for other tokamaks also, but the contemporary variation of the other quantities implied in equation 4is almost never taken into account when comparing different plasmas. The efficiency improvement with T e was first noticed by Porkolab [15], further evidenced in JT-60 [16] and JT-60U [17], and confirmed in JET [18]. The increment of η CD with I p has been observed both in Tore Supra [19] and JT-60U [20], even though it is not considered as the effect of decreasing q a , a view which we favour instead.…”

Section: Regression Analysis Resultsmentioning

confidence: 63%

Study of lower hybrid current drive efficiency over a wide range of FTU plasma parameters

et al. 2005

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The key quantities affecting the efficiency of Lower Hybrid (LH) radiofrequency waves in driving non-inductively the toroidal current in a tokamak have been recognized by means of a linear regression analysis over all the data available for the Frascati Tokamak Upgrade. The parameter space is bounded within the following ranges: line averaged plasma density 0.29 × 10 20 n e 1.29 × 10 20 m −3 , central electron temperatures 1.1 T e0 7.4 keV, corresponding to volume averaged temperatures 0.27 T e 1.2 keV, plasma current 0.3 I p 0.7 MA, magnetic field 4 B T0 7.2 T, with a safety factor between 4.7 q a 10.7, LH power 0.4 P LH 2.1 MW and LH parallel refraction index 1.32 N 0 2.42. The experimental current drive (CD) efficiency, reduced to the effective ion charge state Z eff = 1, varies for this data set within 0.12 η * CD 0.34 A W −1 × 10 20 m −2. A linear regression analysis gives a reliable scaling law for η * CD with a correlation coefficient close to 0.9 that points out the importance of the various quantities. The CD efficiency is a significantly increasing function of T e and B T , and a decreasing one of q a and P LH , while N andn e have limited influence. The physical reasons for the observed trend related to the variation of each parameter are recognized and discussed. The main causes are identified in the modification suffered by the N spectrum along the ray trajectory before the power can be absorbed by the electrons and in the interaction with the edge plasma density fluctuations. The analysis also allows putting into evidence the synergy between the LH and electron cyclotron waves, when the latter are absorbed directly on the LH generated suprathermal electron tails and produce the highest values of η * CD .

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Section: Regression Analysis Resultsmentioning

confidence: 63%

Study of lower hybrid current drive efficiency over a wide range of FTU plasma parameters

et al. 2005

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“…In JT-60, perpendicular charge exchange measurements indicate that injected 70 keV protons are accelerated up to 200 keV, with a tail temperature of ~6 0 keV [177]. Both passive channels and an analyser with a crossed beam geometry observe beam acceleration [176], which implies that a.t least some of the energetic ions are located near the plasma centre. The long decay time of the accelerated ions (-200 ms) supports this conclusion as well [177].…”

Section: Lower Hybrid Bandmentioning

confidence: 99%

The behaviour of fast ions in tokamak experiments

Heidbrink¹,

Sadler²

1995

Nucl. Fusion

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Fast ions with energies significantly larger than the bulk ion temperature are used to heat most tokamak plasmas. Fast ion populations created by fusion reactions, by neutral beam injection and by radiofrequency (RF) heating are usually concentrated in the centre of the plasma. The velocity distribution of these fast ion populations is determined primarily by Coulomb scattering; during wave heating, perpendicular acceleration by the RF waves is also important. Transport of fast ions is typically much slower than thermal transport, except during MHD events. Intense fast ion populations drive collective instabilities. Implications for the behaviour of alpha particles in future devices are discussed.

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“…According to the CD theory [10], LHCD efficiency increases with the square of the parallel resonant velocity, which is about 3.5 times of the thermal velocity  th = √𝑘𝑇 𝑒 /𝑚 𝑒 . The experimental results also demonstrated that the LHCD efficiency is a significantly increasing function of <Te> [11,12]. Fig.…”

Section: Lhcd Efficiency Improved By Ecrhmentioning

confidence: 76%

Plasma heating and improvement of lower hybrid current drive efficiency by electron cyclotron waves on EAST

Xu²,

Wang³

et al. 2023

EPJ Web Conf.

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The electron cyclotron (EC) system on EAST consists of four gyrotrons with a frequency of 140 GHz (second harmonic of the extraordinary mode), each of which is expected to deliver a maximum power of 1.0 MW and be operated at 100-1000 s pulse length. Significant progress in long-pulse operation has been achieved recently, including the pulse duration up to 1056 s with EC power injected into plasma of 0.55 MW and the pulse duration of 310 s with EC power of 1.6 MW (output by 3 gyrotrons). High electron temperature (Te >12 keV) plasma measured by Thomson scattering was produced with the combination of EC and lower hybrid (LH) waves. It is found that the plasma heating effect depends on the EC power location greatly. By adjusting the EC power location, the plasma current profile can be modified. As a consequence of the increment of electron temperature by electron cyclotron resonance heating (ECRH), the lower hybrid current drive (LHCD) efficiency is improved, benefiting for the long-pulse operation. In addition, a synergy effect between EC and LH current drive was observed in steady-state operation on EAST.

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Lower hybrid current drive efficiency in the JT-60 tokamak

Cited by 48 publications

References 8 publications

Study of lower hybrid current drive efficiency over a wide range of FTU plasma parameters

Study of lower hybrid current drive efficiency over a wide range of FTU plasma parameters

The behaviour of fast ions in tokamak experiments

Plasma heating and improvement of lower hybrid current drive efficiency by electron cyclotron waves on EAST

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