Observation of lower-hybrid-current drive in the JIPP T-II torus

Ohkubo, Κ.; Takamura, S.; Kawahata, K.; Tetsuka, T.; Matsuura, K.; Noda, N.; Sakurai, Keiichi; Tanahashi, S.; Fujita, J.

doi:10.1088/0029-5515/22/2/002

Cited by 58 publications

(32 citation statements)

References 24 publications

(24 reference statements)

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“…Upon injection of the 130 MHz power into a plasma driven only by LHCD with V, = 0, an increase in ECE is observed, indicating direct coupling of the wave power to electrons. However, later during the 130 MHz pulse the density increases beyond the LHCD density limit, He s 1 x 10 l9 m' 3 [22], and the superthermal electrons produced by LHCD as well as the LH driven current disappear.…”

Section: Current Drive Resultsmentioning

confidence: 99%

Perpendicular Ferromagnetic-Resonance Equations Derived by Effective Demagnetizing Factors

Kohmoto¹

2003

Jpn. J. Appl. Phys.

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Fast wave absorption and heating at a relatively high ion cyclotron harmonic (u> = 6ft D ) were studied on JIPP T-IIU. In spite of the low absorption efficiency predicted by a simple theory for present experimental parameters, appreciable electron and ion heating was observed. Heating is most effective at relatively low densities (n e = 1 x 10 19 m" 3 ). An ion tail on the majority deuterium energy spectrum was observed, but not an ion tail on the minority hydrogen spectrum, which suggests the possibility of direct absorption of mode converted ion Bernstein wave power by deuterium ions. * Permanent address:

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Section: Current Drive Resultsmentioning

confidence: 99%

Perpendicular Ferromagnetic-Resonance Equations Derived by Effective Demagnetizing Factors

Kohmoto¹

2003

Jpn. J. Appl. Phys.

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“…There is a variety of applications of lower hybrid (LH) waves for plasma control. The most successful application is non-inductive current drive (CD) in tokamaks [1][2][3][4][5][6][7][8], which emphasizes the importance of steady state operation of a tokamak reactor. The second application is lower hybrid electron heating (LHEH) [9,10].…”

Section: Introductionmentioning

confidence: 99%

Enhancement of energy confinement by acceleration of fast ions in combined lower hybrid and neutral beam heating on JT-60

Imai¹,

Ushigusa²,

Ikeda³

et al. 1990

Nucl. Fusion

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A strong ion tail with a temperature of ~ 60 keV was produced in JT-60 by lower hybrid wave acceleration of neutral beam injected fast ions. The incremental energy confinement time due to neutral beam heating of a lower hybrid heated plasma was improved by more than a factor of two and reached approximately 110 ms. The confinement of the tail ions is classical and the improvement of confinement can be fully explained by the contribution of the fast ions. The heating process of the beam ions is consistent with the predictions of the quasi-linear theory.

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“…Next, the LHW is injected into the ECR plasma via the launcher of a pair of C-shaped waveguides. 4 The calculated spectrum of the power emitted from the waveguides has a wide spread of parallel refractive index (n\\) from 4 to 1.4, which corresponds to a critical value of the accessibility condition for n e = 2x 10 12 cm -3 . In the current startup by rf alone, it is particularly essential to control the vertical field carefully.…”

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confidence: 99%

Startup and Quasistationary Drive of Plasma Current by Lower Hybrid Waves in a Tokamak

et al. 1984

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A plasma current is initiated and raised to a quasistationary level of about 20 kA by injection of the lower hybrid wave into a cold and low-density plasma produced by electron cyclotron resonance. The plasma current rises more slowly than the experimentally obtained L p /Rp magnetic diffusion time of the bulk plasma. The current rise time is inversely proportional to the bulk electron density, and agrees well with the collision time of the currentcarrying high-energy electrons with the bulk plasma.PACS numbers: 52.40.Db, 52.55.Gb A plasma current generated by an Ohmic heating electric field is maintained by injecting lower hybrid waves (LHW) in many tokamaks. 1 "" 6 These experimental results demonstrate the possibility of a steady-state operation in a future large tokamak.The startup of plasma current by a noninductive method is attractive for the further saving of the volt-seconds of the Ohmic heating transformer.Recently, experiments on current-startup by LHW have been tried in a target plasma produced by LHW alone 7 or by electron cyclotron resonance (ECR). 8 In the WT-2 tokamak, the plasma current increases linearly in time. However, the quasisteady state is not attained since the pulse duration of LHW is relatively short. The realization of the quasisteady state in the plasma current initiated by rf is necessary to clarify the mechanisms of the startup and quasistationary drive and to establish the startup scenario in a future large tokamak.In this Letter, we report on the startup and quasistationary drive of the plasma current by LHW in which the pulse width (=170 ms) is much longer than the experimentally obtained L p /R p time, where L p and R p are the total inductance and resistance of the bulk plasma. The experiments are carried out on the Japanese Institute of Plasma Physics T-IIU tokamak (major radius R 0 = 0.93 m and minor radius a L = 0.25 m). First, a cold and lowdensity target plasma is produced by the electron cyclotron wave of an ordinary mode (/=35.5 GHz) which is injected from the low-field side. 9 The electron cyclotron-resonance layer (ECR layer) is located at R =0.91 m where the toroidal field B t is L27 T. The initial filling-gas pressure P is 5x 10" 5 Torr for hydrogen. The electron temperature and density of the ECR plasma are about 20 eV and 2x 10 12 cm" 3 , which are measured by a movable floating double probe. Next, the LHW is injected into the ECR plasma via the launcher of a pair of C-shaped waveguides. 4 The calculated spectrum of the power emitted from the waveguides has a wide spread of parallel refractive index (n\\) from 4 to 1.4, which corresponds to a critical value of the accessibility condition for n e = 2x 10 12 cm -3 . In the current startup by rf alone, it is particularly essential to control the vertical field carefully. A quasistationary vertical field of about 10 G is always applied at the beginning of the LHW pulse to bring the Larmor radius of a high-energy electron beam inside the vacuum vessel, 10 where the stray field is estimated at below 2 G under this exper...

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Observation of lower-hybrid-current drive in the JIPP T-II torus

Cited by 58 publications

References 24 publications

Perpendicular Ferromagnetic-Resonance Equations Derived by Effective Demagnetizing Factors

Perpendicular Ferromagnetic-Resonance Equations Derived by Effective Demagnetizing Factors

Enhancement of energy confinement by acceleration of fast ions in combined lower hybrid and neutral beam heating on JT-60

Startup and Quasistationary Drive of Plasma Current by Lower Hybrid Waves in a Tokamak

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