Plasma heating in the TM-3 Tokamak at electron-cyclotron resonance with magnetic fields up to 25 ke

Alikaev, V. V.; Bobrovskii, G. A.; Poznyak, V. I.; Razumova, K. A.; Sannikov, V. V.; Sokolov, Yu. A.; Shmarin, A. A.

doi:10.2172/4957388

Cited by 14 publications

(27 citation statements)

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“…Numerical evaluation of formula (1) shows that any reasonable reactor-grade plasma will be optically thick to the ordinary mode, ensuring good absorption. The ordinary wave will propagate to the central resonance providing the plasma frequency does not exceed the wave frequency, i.e.…”

Section: Wave Propagation and Absorptionmentioning

confidence: 99%

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Ta/Mo Stack Dual Metal Gate Technology Applicable to Gate-First Processes

Matsukawa

Liu

Endo

et al. 2007

jjap

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A set of constraints is derived for the operating characteristics of tokamak power reactors which are bulk-heated by electron cyclotron resonance heating (ECRH). Four heating modes are considered: ordinarywave heating at the electron cyclotron frequency, £2, and at the second-harmonic frequency, 2£2, and extraordinary-wave heating at J2 and at 2£2. For ordinary-wave heating at J2, which appears to be the most promising method, the wave frequency w « J2 must exceed the plasma frequency, co p , for wave penetration into the plasma. The authors' main conclusion is that the need for high-density operation (n o >4 X 10 2O m" 3 ) in moderate-size tokamak reactors, coupled with the wave accessibility condition S2>GJ P , leads to the requirement of frequencies in the 200-GHz range for ECRH of reactor plasmas. A further condition on the heating frequency may be derived by consideration of the ignition condition using empirical scaling laws for the energy confinement time. This latter condition does not increase the heating frequency requirement unless impurities are present or the energy confinement degrades with increasing temperature. It is also found that, for ordinary-wave heating at J2, the average plasma B is limited to less than 0.039 for a central temperature below 15 keV, assuming parabolic density and temperature profiles. The use of extraordinary heating at £2 might lower the frequency requirement for ECRH of a reactor. However, it appears to be unattractive for reactor operation because, in order for the wave to penetrate to the centre of the plasma, the heating ports must be located on the inside of the torus. High-beta, lowerfield reactors can be heated from the outboard side of the torus with second-harmonic radiation. However, these devices will have to be heated at frequencies which are as high as or higher than those needed for devices which are heated with the ordinary wave at the fundamental frequency. Extrapolation of cyclotron resonance maser (gyrotron) technology to provide modular heating systems in the 200-GHz range is discussed.

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Section: Wave Propagation and Absorptionmentioning

confidence: 99%

“…The support for this technique is largely based on the results of ECRH experiments on TM-3 and other devices [ 1 ] and on the development of efficient cyclotron resonance masers (gyrotrons) in the USSR [2,3].…”

Section: Introductionmentioning

confidence: 99%

Ta/Mo Stack Dual Metal Gate Technology Applicable to Gate-First Processes

Matsukawa

Liu

Endo

et al. 2007

jjap

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“…Apart from basic plasma formation, heating and current drive, profile control and spatially localized heating (with beneficial consequences, for example, suppression of NTM instabilities) [5][6][7][8][9][10][11][12][13][14][15][16][17], ECR-produced discharge has also evolved as a promising and effective method to improve the wall conditions of the fusion devices. Earlier in 1980s, ECR discharge cleaning has been performed on many small and medium size fusion devices (like JFT-2M [18], JIPP-II [19] and CHS [20]) and have produced encouraging results.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of electron cyclotron resonance plasma formed by lower hybrid current drive grill antenna

et al. 2008

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A 3.7 GHz system, which is meant for LHCD experiments on ADITYA tokamak, is used for producing ECR discharge. The ECR discharge is produced by setting the appropriate resonance magnetic field of 0.13 T, with hydrogen at a fill pressure of about 5 × 10 −5 Torr. The RF power, up to 10 kW (of which ∼50% is reflected back), with a typical pulse length of 50 ms, is injected into the vacuum chamber of the ADITYA tokamak by a LHCD grill antenna and is used for plasma formation. The average coupled RF power density (the RF power/a typical volume of the plasma) is estimated to be ∼5 kW/m 3 . When the ECR appears inside the tokamak chamber for the given pumping frequency (f = 3.7 GHz) a plasma with a density (n e) ∼ 4 × 10 16 m −3 and electron temperature ∼8 eV is produced. The density and temperature during the RF pulse are measured by sets of Langmuir probes, located toroidally, on either side of the antenna. Hα signals are also monitored to detect ionization. An estimate of density and temperature based on simple theoretical calculation agrees well with our experimental measurements. The plasma produced by the above mechanism is further used to characterize the ECR-assisted low voltage Ohmic start-up discharges. During this part of the experiments, Ohmic plasma is formed using capacitor banks. The plasma loop voltage is gradually decreased, till the discharge ceases to form. The same is repeated in the presence of ECR-formed plasma (RF pre-ionization), formed 10 ms prior to the loop voltage. We have observed that (with LHCD-induced) ECR-assisted Ohmic start-up discharges is reliably and repeatedly obtained with reduced loop voltage requirement and breakdown time decreases substantially. The current ramp-up rates also decrease with reduced loop voltage operation. These studies established that ECR plasma formed with LHCD system exhibits similar characteristics as reported earlier by dedicated ECR systems. This experiment also addresses the issue of whether ECR plasma formed with grill antenna exhibits similar behavior as that formed by single waveguide ECR antenna. Our experimental observations suggest that the characteristics of (LHCD system-induced) ECR-assisted Ohmic start-up discharges show similar properties, reported earlier with normal ECR-assisted Ohmic start-up discharges and hence LHCD system may be used as ECR system at reduced toroidal magnetic field for other applications like wall conditioning.

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“…2 In the case of the runaway discharges, the VS are one of the characteristic features of the relaxation instability observed in many experiments in the first tokamaks. [3][4][5][6] This phenomenon is usually explained by a kinetic instability in a plasma-runaway beam system. 4 There exist other reasons for the fast current decrease in runaway discharges as well as in normal ones, such as magnetohydrodynamic ͑MHD͒ instabilities.…”

Section: Introductionmentioning

confidence: 99%

Positive voltage spikes in runaway tokamak discharges

et al. 2000

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Positive voltage spikes caused by a fast decrease of the plasma current are observed in runaway dominated discharges in the small Brazilian Tokamak TBR-1͓Kuznetsov et al., Phys. Plasmas 6, 4002 ͑1999͔͒. Comparison of the measured voltage spike with the value given by the solution of the one-dimensional diffusion equation for the toroidal electric field permits one to infer the plasma conductivity and initial electric field distribution. An additional runaway generation due to voltage spikes can be important. In this case, both the decay time of the voltage spike and the total toroidal current perturbation can decrease substantially.

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Plasma heating in the TM-3 Tokamak at electron-cyclotron resonance with magnetic fields up to 25 ke

Cited by 14 publications

References 0 publications

Ta/Mo Stack Dual Metal Gate Technology Applicable to Gate-First Processes

Ta/Mo Stack Dual Metal Gate Technology Applicable to Gate-First Processes

Characteristics of electron cyclotron resonance plasma formed by lower hybrid current drive grill antenna

Positive voltage spikes in runaway tokamak discharges

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