Experimentally inferred ion thermal diffusivity profiles in the Doublet III tokamak: Comparison with neoclassical theory

Groebner, R. J.; Pfeiffer, Wayne; Blau, F.P.; Burrell, K.H.; Fairbanks, E.S.; Seraydarian, R.; John, H. St.; Stockdale, R. E.

doi:10.1088/0029-5515/26/5/001

Cited by 110 publications

(62 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The inferred ion thermal diffusivity is in general agreement with Chang-Hinton neoclassical values for these ohmically heated PLT plasmas and is consistent with earlier PLT results for Ohmic heating [2]. In neutral beam-heated Doublet III discharges [6] the diffusivity was about a factor of three larger relative to the neoclassical value than in our experiments, but the shapes of the PLT and Doublet III profiles are similar. The large errors in both experiments preclude a definite conclusion, but it seems likely that the difference in Xj is due to enhanced ion transport during neutral beam injection.…”

Section: Resultssupporting

confidence: 91%

“…In DITE, charge exchange measurements by Gill et al [5] indicated ion heat fluxes about five times greater than predicted by neoclassical theory in both Ohmic and beam-heated discharges. Recent measurements using charge exchange recombination spectroscopy in heavily beam-heated Doublet III discharges [6] found that the ion heat conduction was comparable to Chang-Hinton [7] neoclassical conduction at r/a = 0.1 but exceeded the value from neoclassical theory by a factor of 3-13 at r/a = 0.5. One source of uncertainty in these measurements is uncertainty in the local gradient of the ion temperature, which was inferred from measurements of the ion temperature at a few points.…”

Section: Introductionmentioning

confidence: 95%

See 1 more Smart Citation

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

et al. 1987

View full text Add to dashboard Cite

show abstract

Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 95%

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

et al. 1987

View full text Add to dashboard Cite

show abstract

“…6 numerical results from comprehensive fully toroidal linear calculations (including complete trapped-particle dynamics, wave-particle resonant interactions, and collisions) support the conclusion that these modes are easily destabilized in tojcamaks for t^-> 2. 17 An appropriate expression for the anomalous thermal diffusivity associated with iij-modes is, of course, much more difficult to justify from "first principles.'…”

Section: Introductionmentioning

confidence: 65%

“…14 with regard to plasmas heated by neutral beam injection (NB1), data analysis again indicates that the ion thermal losses generally exceed standard neoclassical estimates. 15 Moreover, recent experimental studies 6 involving direct measurement of the ion temperature profile in the D-lll tokamak have indicated that the thermal diffusivity is not only much larger in magnitude but also exhibits a radial dependence in strong disagreement with the usual neoclassical model (Xj NE0 ).…”

Section: Introductionmentioning

confidence: 99%

Gyrokinetic particle simulation of ion temperature gradient drift instabilities

Lee

Tang

1988

The Physics of Fluids

View full text Add to dashboard Cite

Ion temperature gradient drift instabilities have been investigated using gyrokinetic particle simulation techniques for the purpose of identifying the mechanisms responsible for their nonlinear saturation as well as the associated anomalous transport. For simplicity, the simulation has been carried out in a shear-free slab geometry, where the background pressure gradient is held fixed in time to represent quasistatic profiles typical of tokamak discharges. It is found that the nonlinearly generated zero-frequency responses for the ion parallel momentum and pressure are the dominant mechanisms giving riseto saturation. This is supported by the excellent agreement between the simulation results and those obtained from mode coupling calculations, which give t.ie saturation amplitude as |e*/T e | = (|u 8 + iir^|/si|)/(k x p s ) 2 . and the quasilinear thermal diffusivity as Xj = y i/ k j. z -where Wj and t^ are the linear frequency and growth rate, respectively, for the most unstable mode of the system. In the simulation, the time evolution of Xj after saturation Is characterized by its slow relaxation to a much lower level of thermal conduction. On the other hand, a small amount of electron-ion collisions, which has negligible effect on the linear staDNIty, can cause significant enhancement of Xj in the steady state.

show abstract

“…Stix's asymptotic expansion of Sivukhin's formula [19] yields similar results for r n . The expression given by Strachan et al [8] 1 - ri (1) T^ is the slowing-down time on electrons and E n is the energy at which the fusion reactivity has fallen to e" 1 of its value at E b .) The ~27% contribution of half-energy ions to the neutron emission was included in the calculation.…”

Section: Comparison Of Experimental and Theoretical Fast Ion Slowing-mentioning

confidence: 99%

Comparison of experimental and theoretical fast ion slowing-down times in DIII-D

1988

Self Cite

View full text Add to dashboard Cite

ABSTRACT. Short deuterium beam pulses are injected into the D III-D tokamak to study the variation of beam slowingdown time with temperature and density. The slowing-down time is inferred from the rate of decay of the d (d,n) 3 He neutron emission. To within ~30%, the results are consistent with Sivukhin's classical theory. The short beam pulses,are also useful for measurements of the central deuterium density.Analysis of tokamak plasmas routinely assumes classical Coulomb coupling between different plasma species. For example, the conclusion that ion thermal conduction is anomalous in beam heated tokamaks [1] hinges on the assumption that the beam power is deposited in the ion channel classically. Only a few experiments have tested the assumption of classical coupling between species. Beam ion spectra measured by charge exchange agreed with spectra computed from classical theory [2,3], although discrepancies of a factor of two were observed in the fits. A higher impurity temperature than hydrogen temperature in low density, * Permanent address: University of California, Irvine, CA 92717, USA.beam heated PLT plasmas was explained by using classical coupling arguments [4]. Measurements of the time evolution of the 15 MeV proton emission indicated that 0.8 MeV 3 He ions [5] and fast wave heated 3 He minority ions [6] slowed down at roughly the expected rate. On T-10, the time evolution and magnitude of the drop in ion temperature during electron cyclotron heating was consistent with the expected reduction in power flow from the electrons [7]. Although each of these experiments was consistent with classical theory, their accuracy was such that deviations as large as 50%, or more, from theory may have escaped detection.Perhaps the best quantitative check of beam energy loss is from studies of the rate of decay of the neutron emission following deuterium beam injection [8,9]. This emission comes from the d (d,n) 3 He reaction between the fast ions and the plasma deuterons. Since the neutron measurement is volume averaged, ±10% uncertainties in the profiles of electron temperature and density have a relatively small effect on the expected rate of decay; hence, the interpretation of the measurements is straightforward. The major weakness of the previous studies [8,9] is that the decay in neutron emission was measured immediately after beam injection, when the classical slowing-down time T S [10] was rapidly changing due to changes in T e and n e . In a preliminary study, Kim et al. attempted to improve the accuracy of the neutron technique by injecting short beam pulses into the D-III tokamak [11].In our experiment, we have studied the deceleration of beam ions by measuring the decay in neutron 1897LETTERS emission following the injection of ~2 ms pulses of deuterium beams into steady state deuterium plasmas in the D III-D tokamak. The total energy injected during the beam pulse was only ~3 % of the plasma stored energy, and, hence, density and temperature of the discharge were not perturbed (T e changed by <5%), ...

show abstract

Experimentally inferred ion thermal diffusivity profiles in the Doublet III tokamak: Comparison with neoclassical theory

Cited by 110 publications

References 42 publications

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

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

Gyrokinetic particle simulation of ion temperature gradient drift instabilities

Comparison of experimental and theoretical fast ion slowing-down times in DIII-D

Contact Info

Product

Resources

About