Energy confinement and plasma heating during lower hybrid experiments

Alladio, F.; Barbato, Emanuele; Bardotti, G.; Bartiromo, R.; Bracco, G.; Bombarda, F.; Buceti, G.; Buratti, P.; Cardinali, A.; Cesario, R.; Crisanti, F.; Angelis, R. De; Marco, F. De; Pretis, M. de; Frigione, D.; Giannella, R.; Grolli, M.; Mancuso, Salvatore; Marinucci, M.; Mazzitelli, G.; Orsitto, F.; Pericoli‐Ridolfini, V.; Pieroni, L.; Podda, S.; Righetti, Giulia; Romanelli, M.; Santi, D.; Santini, F.; Tonini, Gian Paolo; Tuccillo, A. A.; Tudisco, O.; Vlad, G.; Zanza, V.

doi:10.1088/0741-3335/28/1a/016

Cited by 19 publications

(23 citation statements)

References 5 publications

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“…23 (a, c)). The almost linear scaling of r E with n e q 1/2 is also consistent with the results previously referenced [30,[66][67][68][69][70][71][72][73][74][75]. Degradation of the total confinement time is seen for n e q 1/2 > 5 X 10 13 cm" 3 ; as previously mentioned, this is due to increased electron thermal conduction losses.…”

Section: Fig24supporting

confidence: 91%

“…The high values of n e q 1/2 for the last two cases are due to higher densities (n e % 3.5 X 10 13 cm~3 for these cases). The linear portion of the scaling, due either to increasing n e or q, or both, is consistent with Ohmic scalings reported previously [66][67][68][69][70][71][72][73][74][75]. The degradation in confinement at high values of n e has been documented on D-III [66], and has been modelled quantitatively [30].…”

Section: Electron Heating and Confinementsupporting

confidence: 88%

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Thermal energy confinement scaling in PDX limiter discharges

et al. 1984

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Experiments were performed on the PDX tokamak to study plasma heating and beta scaling with high-power, near-perpendicular neutral-beam injection. The data taken during these experiments were analysed, using a time-dependent data interpretation code (TRANSP), to study the transport and thermal confinement scaling over a wide range of plasma parameters. This study focuses on results from experiments with D° injection into H* plasmas using graphite rail limiters, a = 40-44 cm, R = 143 cm, I p = 200-480 kA, B T = 0.7-2.2 T, and, typically, n e = (2.5-4.2) X 10 13 cm" 3 . The results of this study indicate that for both Ohmic and neutral-beam-heated discharges the energy flow out of the plasma is dominated by anomalous electron losses which are attributed to electron thermal conduction. The ion conduction losses are not inconsistent with neoclassical theory; however, the total ion loss influences the power balance significantly only at high toroidal fields and high plasma currents. Therefore, except for these cases, the total thermal energy confinement time for the neutral-beam-heated discharges follows the scaling of electron energy confinement. While the confinement is found to have little dependence on toroidal field, it is a strong function of plasma current, increasing with increasing I p . In contrast, Ohmic confinement times are found to scale as n e q 1/2 . Because of the dominant effect of the electrons, the total confinement is found to depend heavily on the variation of the electron thermal diffusivity, Xe, in t n e outer region of the plasma (a/2 < r < 7a/8). The values of Xe m this region of the plasma show an approximately inverse dependence on the local value of the poloidal magnetic field.

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Section: Fig24supporting

confidence: 91%

Section: Electron Heating and Confinementsupporting

confidence: 88%

Thermal energy confinement scaling in PDX limiter discharges

et al. 1984

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“…L is the Coulomb logarithm, Zj characterizes the charge of the ions. The second term in expression (11) describes the frictional force -due to collisions between runaway electrons and thermal particles of the plasma -obtained from Landau's collision integral [5].…”

Section: Results Of Numerical Calculationsmentioning

confidence: 99%

“…The formation of an electron distribution function not in equilibrium with respect to transverse momenta as a result of the knocking out of thermal electrons in the runaway region takes place in tokamaks with satisfactory confinement of fast electrons. The formation of this distribution function may be responsible for the cyclotron radiation at integral and half-integral harmonics of the cyclotron frequency of the beam electrons in the FT tokamak [11].…”

Section: Pi Dp ±mentioning

confidence: 99%

Stability of a runaway electron beam

Besedin

Pankratov

1986

Nucl. Fusion

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The paper studies the distribution function of a runaway electron beam with allowance for close collisions of fast tail electrons with thermal ones, as a result of which momentum is imparted to the latter sufficient for escape into a continuous acceleration regime. It is shown that a beam is formed which is not in equilibrium with respect to transverse momenta; it may excite electromagnetic plasma instabilities under the conditions of linear and non-linear electron cyclotron resonance.

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“…Generally, the value for x e as derived from heat pulse analysis, x" P » is found to exceed the value x°L 0 as derived from a global power balance analysis. This discrepancy ranges from a factor of 1 to 4 (T-10, FT, ISX-B, JET, Refs [3][4][5][6][7]) to up to a factor of 20 (TFTR, Ref. [8]).…”

Section: Introductionmentioning

confidence: 99%

Tokamak heat transport – a study of heat pulse propagation in JET

1987

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The propagation of heat pulses originating from sawtooth activity in JET has been investigated in a series of limiter discharges with the following parameters: plasma current, Ip ≃ 3 MA, toroidal magnetic field, BT ≃ 3 T and elongation, κ = 1.45. The auxiliary power was varied such that the total power ranged from 2 to 13.5 MW. Electron temperature perturbations in a 20 cm region around a minor radius of r = (2/3)a were recorded with high time resolution, using a 12 channel electron cyclotron emission polychromator. From these measurements the electron heat diffusivity was derived. Over the whole range of powers considered, was found to be independent of power and to lie in the range of 2.5 ± 0.5 m2·s−1. The quantity is compared to as derived from global power balance analysis. For Ohmic heating, the latter is lower than by a factor of 2.5. For increasing auxiliary power, approaches . A model for the dependence of the local χe n the temperature gradient is presented; it permits a unified description of the heat pulse behaviour, the deterioration of confinement and a certain degree of profile consistency. The model does not invoke non-local parameters such as the total power input. It is shown that the present heat pulse data, subject to this interpretation, contradict the τE scaling laws of the typical form τE ∝ P−0.5.

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Energy confinement and plasma heating during lower hybrid experiments

Cited by 19 publications

References 5 publications

Thermal energy confinement scaling in PDX limiter discharges

Thermal energy confinement scaling in PDX limiter discharges

Stability of a runaway electron beam

Tokamak heat transport – a study of heat pulse propagation in JET

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