A density rise experiment on PLT

Strachan, J.D.; Bretz, N.; Mazzucato, E.; Barnes, Cris W.; Boyd, D. A.; Cohen, Samuel A.; Hovey, J.; Kaita, R.; Medley, S. S.; Schmidt, G. L.; Tait, G. D.; Voss, D. E.

doi:10.1088/0029-5515/22/9/002

Cited by 71 publications

(55 citation statements)

References 20 publications

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“…For example, in tokamaks, the flux-tube volume is proportional to the safety factor, dV / q, and density peaking scales as 1=q. [15][16][17] Similar density peaking has been observed in stellarators. 18 By comparison, a significantly larger inward pinch occurs when the plasma torus is confined by a strong levitated current ring.…”

Section: Introductionsupporting

confidence: 76%

Turbulent fluctuations during pellet injection into a dipole confined plasma torus

et al. 2017

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We report measurements of the turbulent evolution of the plasma density profile following the fast injection of lithium pellets into the Levitated Dipole Experiment (LDX) [Boxer et al., Nat. Phys. 6, 207 (2010)]. As the pellet passes through the plasma, it provides a significant internal particle source and allows investigation of density profile evolution, turbulent relaxation, and turbulent fluctuations. The total electron number within the dipole plasma torus increases by more than a factor of three, and the central density increases by more than a factor of five. During these large changes in density, the shape of the density profile is nearly “stationary” such that the gradient of the particle number within tubes of equal magnetic flux vanishes. In comparison to the usual case, when the particle source is neutral gas at the plasma edge, the internal source from the pellet causes the toroidal phase velocity of the fluctuations to reverse and changes the average particle flux at the plasma edge. An edge particle source creates an inward turbulent pinch, but an internal particle source increases the outward turbulent particle flux. Statistical properties of the turbulence are measured by multiple microwave interferometers and by an array of probes at the edge. The spatial structures of the largest amplitude modes have long radial and toroidal wavelengths. Estimates of the local and toroidally averaged turbulent particle flux show intermittency and a non-Gaussian probability distribution function. The measured fluctuations, both before and during pellet injection, have frequency and wavenumber dispersion consistent with theoretical expectations for interchange and entropy modes excited within a dipole plasma torus having warm electrons and cool ions.

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Section: Introductionsupporting

confidence: 76%

Turbulent fluctuations during pellet injection into a dipole confined plasma torus

et al. 2017

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“…No distortion should be seen when the energetic ion transport time r p is significantly longer than the ion-ion equilibration T hi , where r hi is the time for the hot ions (E ^ 3Tj) producing most of the fusion emission to equilibrate with the bulk distribution. For PLT, the criterion for negligible distortion is r p ^ 10 ms, which is probably satisfied since typical gross confinement times are 30-100 ms [12]. While it is possible that local transport is energy dependent and considerably faster than implied by gross confinement [12], the total effect on Xi of the outward energetic motion predicted by Ware is less than 1% for our PLT Ohmic plasma.…”

Section: Fig 3 Ion Thermal Diffusivity (Eq (4)) Versus Minor Radiusmentioning

confidence: 77%

“…In the absence of sufficient information for a full inversion, we calculated the ion temperature profile (Fig. l(c)) with a timeindependent radial-profile analysis code (SNAP) [11] by matching the neutron emission and assuming Chang-Hinton neoclassical conductivity for the ions with a 'neoclassical multiplier' of 1.5 and a particle con- finement time of 30 ms [12]. Using this profile, the radii <r> of the proton temperature measurements were found by calculating the average birth position <r> of the detected protons with an orbit code [8].…”

Section: Local Ion Temperature Gradientmentioning

confidence: 99%

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Fusion product measurements of the local ion temperature gradient in the PLT tokamak

et al. 1987

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“…On the PLT 4 and T-10 5 tokamaks the information gained from the H B has been aug mented by gas puffing. On PLT the evolution of the density profile after a gas puff is used to estimate the diffusion coefficient and convective velocities.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the local particle diffusion coefficient in a magnetized plasma

Levinton

Meyerhofer

1987

Review of Scientific Instruments

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Local impurity particle diffusion coefficients have been measured in a low temperature plasma by the injection of test particles at the center of the plasma. The injection is accomplished by a high-voltage discharge between two small graphite electrodes on a probe. The probe can be located anywhere in the plasma. The diffusion is observed spectroscopically. An analysis of the spatial and temporal evolution of the C ii radiation from the carbon discharge can determine the parallel and perpendicular diffusion of the impurity ions. Results with the diagnostic have been obtained in the Proto S-1/C spheromak. The measured value of the diffusion coefficient in the afterglow plasma is in good agreement with classical predictions.

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A density rise experiment on PLT

Cited by 71 publications

References 20 publications

Turbulent fluctuations during pellet injection into a dipole confined plasma torus

Turbulent fluctuations during pellet injection into a dipole confined plasma torus

Fusion product measurements of the local ion temperature gradient in the PLT tokamak

Measurement of the local particle diffusion coefficient in a magnetized plasma

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