Breakdown experiment on a Tokamak

Sometani, Taro; Fujisawa, N.

doi:10.1088/0032-1028/20/11/002

Cited by 14 publications

(4 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Wall conditions and stray magnetic fields also play a significant, even if slightly less decisive, role. Early theoretical and experimental investigations on initial discharge in a toroidal plasma can be found in Dimock et al (1973), Sand, Waelbroeck & Waidmann (1973), Papoular (1976), Strachan (1976), Sometani & Fujisawa (1978). Later, in order to reduce the toroidal electric field, electron cyclotron resonance heating (ECRH) (Erckmann & Gasparino 1994), ion cyclotron resonance heating (ICRH) (Steinmetz et al 1987) and low hybrid wave heating (LHWH) (Yoshino & Seki 1997;Shinya et al 2017) started being employed to help initiate the discharge.…”

Section: Introductionmentioning

confidence: 99%

“…Early theoretical and experimental investigations on initial discharge in a toroidal plasma can be found in Dimock et al. (1973), Sand, Waelbroeck & Waidmann (1973), Papoular (1976), Strachan (1976), Sometani & Fujisawa (1978). Later, in order to reduce the toroidal electric field, electron cyclotron resonance heating (ECRH) (Erckmann & Gasparino 1994), ion cyclotron resonance heating (ICRH) (Steinmetz et al.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

On the breakdown modes and parameter space of ohmic tokamak start-up

et al. 2018

View full text Add to dashboard Cite

Tokamak start-up is strongly dependent on the state of the initial plasma formed during plasma breakdown. We have investigated through numerical simulations the effects that the pre-filling pressure and induced electric field have on pure ohmic heating during the breakdown process. Three breakdown modes during the discharge are found, as a function of different initial parameters: no breakdown mode, successful breakdown mode and runaway mode. No breakdown mode often occurs with low electric field or high pre-filling pressure, while runaway electrons are usually easy to generate at high electric field or low pre-filling pressure (${<}1.33\times 10^{-4}$ Pa). The plasma behaviours and the physical mechanisms under the three breakdown modes are discussed. We have identified the electric field and pressure values at which the different modes occur. In particular, when the electric field is $0.3~\text{V}~\text{m}^{-1}$ (the value at which ITER operates), the pressure range for possible breakdown becomes narrow, which is consistent with Lloyd’s theoretical prediction. In addition, for $0.3~\text{V}~\text{m}^{-1}$, the optimal pre-filling pressure range obtained from our simulations is $1.33\times 10^{-3}\sim 2.66\times 10^{-3}$ Pa, in good agreement with ITER’s design. Besides, we also find that the Townsend discharge model does not appropriately describe the plasma behaviour during tokamak breakdown due to the presence of a toroidal field. Furthermore, we suggest three possible operation mechanisms for general start-up scenarios which could better control the breakdown phase.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the breakdown modes and parameter space of ohmic tokamak start-up

et al. 2018

View full text Add to dashboard Cite

show abstract

“…The difference in the values of B , in these cases is attributed to the toroidal drift which increases with increasing E. Figure 5 shows two B, versus b relations in the cases where B, and E are unchanged in magnitude but are either the same or opposite in direction. AS is explained in the introduction, the difference in the values of B , is attributed to the fact that the direction of the error field drift depends on that of E , while the direction of toroidal drift does not (Sometani and Fujisawa 1978).…”

Section: Luminescence Growth and Electron Lossmentioning

confidence: 99%

Luminescence growth measurement and toroidal drift study in tokamak ionization phase

Sometani¹,

Suganuma²,

Mizuno³

1993

Plasma Phys. Control. Fusion

Self Cite

View full text Add to dashboard Cite

The luminescence from excited helium atoms is measured on a small tokamak Hamana-T. The exponential growth rate of the luminescence is maximized when the resultant effect of the toroidal and the error field drifts of electrons is compensated by the optimum value B , of external vertical magnetic field. The error vertical magnetic field E,, and the equivalent vertical magnetic field B,,, which yields the same displacement as the toroidal drift and is proportioional to toroidal magnetic field B,, are experimentally determined by the values of B,, obtained with different values of B . and electric field E. The field B,, is approximately proportional to E".

show abstract

“…Other new methods include coaxial helicity injection [24,25], alternating current ohmic coil [26], center solenoid-free [27][28][29][30][31], electrode assistance [32] and point source dc helicity injection [33]. The effect of impurities [34], vertical field or horizontal field [35,36], pre-fill gas pressure [37], wall [38] and size [3] on pre-ionization or start-up has also been investigated. Different simulation codes or model, such as the tokamak simulation code [39], typical zero-dimensional model [34], toroidally symmetric plasma simulation [40], TRANSMAK [41], two-dimensional breakdown model [42], DINA [43], dynamic zero-dimensional (0D) model of non-fully ionized plasma (DYON) [2,44], electromagnetic models [45,46], onedimensional burn-through model [47] and particle in cell/-Monte Carlo collision [48], have also been developed to support start-up research.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical modeling of plasma start-up assisted by electron drift injection on J-TEXT

et al. 2023

View full text Add to dashboard Cite

Start-up is one of the critical phases for tokamak discharge. The electron drift injection (EDI) system has been developed on J-TEXT for start-up studies. The experiment of breakdown with EDI assisted has been conducted, which verified the effect of pre-ionization by EDI to achieve start-up at a lower Ohmic field voltage. A 0-dimensional model has been developed to explain the effect of EDI quantitatively. The comparison between the experiment and simulation verified the credibility of this model. Based on this model, the comparison between pure Ohmic heating start-up and EDI assisted start-up was presented, showing that EDI improved ionization, causing lower delay to the peak of hydrogen ionization and radiation losses and the electron and ion energy to rise more smoothly. This result verified the pre-ionization effect of the EDI to start-up quantitatively. The effects of injecting different currents and electron energy were investigated. The better pre-ionization effect can be realized by improving injected current, which can be a reference to the upgrading of EDI system.

show abstract

Breakdown experiment on a Tokamak

Cited by 14 publications

References 6 publications

On the breakdown modes and parameter space of ohmic tokamak start-up

On the breakdown modes and parameter space of ohmic tokamak start-up

Luminescence growth measurement and toroidal drift study in tokamak ionization phase

Experimental and numerical modeling of plasma start-up assisted by electron drift injection on J-TEXT

Contact Info

Product

Resources

About