Isotopic scaling of confinement in deuterium–tritium plasmas

Scott, S.D.; Zarnstorff, M. C.; Barnes, Cris W.; Bell, R. E.; Bretz, N.; Bush, C. E.; Chang, Z.; Ernst, D. R.; Fonck, R.J.; Johnson, L. C.; Mazzucato, E.; Nazikian, R.; Paul, S. F.; Schivell, J.; Synakowski, E. J.; Adler, H.; Bell, M.G.; Budny, R.; Fredrickson, E. D.; Grek, B.; Janos, A.; Johnson, D. W.; McCune, D.; Park, H.; Ramsey, A. T.; Redi, M. H.; Taylor, G.; Thompson, Mark E.; Wieland, R.

doi:10.1063/1.871253

Cited by 62 publications

(61 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Second, an apparent dependence of the energy confinement on the mixture of hydrogenic isotopes was observed in TFTR [111][112][113][114], and this contributed to the rise in T e (0) in going from D to DT. Finally, inherent performance variations due to magnetohydrodynamic (MHD) instabilities and limiter conditioning resulted in T e (0) changes which competed with the rise in T e (0) due to alpha particle heating.…”

Section: Alpha Particle Heatingmentioning

confidence: 99%

Alpha particle physics experiments in the Tokamak Fusion Test Reactor

Zweben¹,

Budny²,

Darrow³

et al. 2000

Nucl. Fusion

104

View full text Add to dashboard Cite

Alpha particle physics experiments were done on the Tokamak Fusion Test Reactor (TFTR) during its deuterium-tritium (DT) run from 1993-1997. These experiments utilized several new alpha particle diagnostics and hundreds of DT discharges to characterize the alpha particle confinement and wave-particle interactions. In general, the results from the alpha particle diagnostics agreed with the classical singleparticle confinement model in magnetohydrodynamic (MHD) quiescent discharges. Also, the observed alpha particle interactions with sawteeth, toroidal Alfvén eigenmodes (TAE), and ion cyclotron resonant frequency (ICRF) waves were roughly consistent with theoretical modeling. This paper reviews what was learned and identifies what remains to be understood.2

show abstract

Section: Alpha Particle Heatingmentioning

confidence: 99%

Alpha particle physics experiments in the Tokamak Fusion Test Reactor

Zweben¹,

Budny²,

Darrow³

et al. 2000

Nucl. Fusion

104

View full text Add to dashboard Cite

show abstract

“…Diagnostic inconsistencies on the T i measurements could then be ruled out. Following earlier results from the Tokamak Fusion Test Reactor (TFTR) [17], an isotopic effect on the energy confinement, heat transport and electron temperature was also considered [18][19][20][21][22][23]. However, since the T i and T e increase was measured to be similar and not significant at the two extremes of the DT mixture ratio scan (n T /(n D + n T ) = 0, as in the comparison discharges with ICRF heating, and n T /(n D + n T ) = 0.92), possible isotopic effects in the energy confinement and electron-ion equipartition had to also be excluded as the dominant reason for the observed T i0 increase.…”

Section: The Anomalous Ion Heating Observed In the Jet Dte1 Experimentsmentioning

confidence: 99%

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

Testa¹,

Albergante²

2012

Nucl. Fusion

View full text Add to dashboard Cite

In the so-called 'alpha-heating' experiment performed on the JET tokamak during the deuterium-tritium campaign of 1997, the ion temperature was found to be far exceeding (both in absolute value and in its rise time) the level that could have been expected from direct collisional heating by the fusion-born alpha particles themselves and energy equipartition with the electrons. To date, no explanation has been put forward for this long standing puzzle, despite much work having been performed on this subject in the early 2000s.Two analysis methods that have recently become available have been employed to re-analyse these observations of an anomalous ion heating. First, an algorithm based on the sparse representation of signals has been used to analyse magnetic, reflectometry and electron-cyclotron emission measurements of the turbulence spectra in the drift-wave range of frequencies. This analysis has then been complemented with turbulence simulations performed with the GENE code.We find, both experimentally and in the simulations, that the presence of a minority, but sufficiently large, population of fusion-born alpha particles that have not yet fully thermalized stabilizes the turbulence in the ion-drift direction, but practically does not affect the turbulence in the electron-drift direction. We link such stabilization of the ion-drift-wave turbulence to the increase in the ion temperature above the level achieved in similar discharges that did not have (at all or enough) alpha particles. When the fusion-born alpha particles have fully thermalized, the turbulence spectrum in the ion-drift direction reappears at somewhat larger amplitudes, which we link to the ensuing reduction in the ion temperature. This phenomenological dynamics fully corresponds to the actual experimental observations. By taking into account an effect of the alpha particles that had not been previously considered, our new analysis finally presents a phenomenological explanation for the so-far-unexplained anomalous ion heating observed in the JET alpha-heating experiment of 1997.Through the formulation of an empirical criterion for ion-drift-wave turbulence stabilization by fusion-born alpha particles, we also show why similar observations were not made in the other deuterium-tritium experiments run so far in JET and TFTR. This allows assessing the operational domain for this stabilization mechanism for ion-drift-wave turbulence in future burning plasma experiments such as ITER, which may open a new path towards the sustainment of a high energy gain in such forthcoming devices.

show abstract

“…2. We note that in previous isotope scaling experiments in beam-heated discharges, the enhanced energy content of the plasma was observed primarily in the ion channel [7,8] as opposed to the electron channel. The enhanced energy confinement is maintained throughout the ICRF heating pulse, which extended over more than 4 energy confinement times.…”

Section: Disclaimermentioning

confidence: 99%

“…Previous experiments comparing global energy confinement in hydrogen and deuterium plasmas, heated either ohmically or with auxiliary heating such as neutral beam injection (NBI) or electromagnetic wave -particle interactions] in general display an increase in the global energy confinement with increasing isotopic mass, though the magnitude depends on operating regime and device [6]. However, isotope scaling experiments utilizing NBI are subject to uncertainties arising from differences in the beam stored energy content and related power deposition profiles, both of which depend on the beam and background ion species [7,8]. In a similar vein, the analysis of previous isotope scaling experiments i n hydrogen and deuterium plasmas heated with electromagnetic waves is subject to large uncertainties because the chosen heating scenario] and, therefore, the power deposition characteristics, differ significantly depending on the majority isotope under consideration [6].…”

Section: Disclaimermentioning

confidence: 99%

“…In a similar vein, the analysis of previous isotope scaling experiments i n hydrogen and deuterium plasmas heated with electromagnetic waves is subject to large uncertainties because the chosen heating scenario] and, therefore, the power deposition characteristics, differ significantly depending on the majority isotope under consideration [6]. More recently, experiments comparing global and local energy confinement in D and mixed D-T plasmas in the hot ion NBI-driven supershot regime i n the Tokamak Fusion Test Reactor (TFTR) [7] have also shown a strong enhancement of confinement with increasing isotopic mass.…”

Section: Disclaimermentioning

confidence: 99%

See 1 more Smart Citation

Scaling of confinement with isotopic content in deuterium and tritium plasmas

Phillips¹,

Scott²,

Bell³

1997

Self Cite

View full text Add to dashboard Cite

The scaling of the electron thermal diffusivity, Xe, with relative gyro radius, p, has been measured on TFTR by comparing nearly identical ICRF-heated discharges which differ only in hydrogenic isotopic content. Contrary to the gyro-Bohm scaling (xe -X B~, where XB is the Bohm diffusivity) observed on DIII-D when p* was varied through a scan of magnetic field strength, Xe is found to scale inversely with p*. Hence, global energy confinement is 8-11% higher in deuterium-tritium plasmas than in deuterium only plasmas, with the higher stored energy attributed almost entirely to the electrons. PACS 52.55.Fa, 52.50 Gj DISCLAIMERThis report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracj, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

show abstract

Isotopic scaling of confinement in deuterium–tritium plasmas

Cited by 62 publications

References 20 publications

Alpha particle physics experiments in the Tokamak Fusion Test Reactor

Alpha particle physics experiments in the Tokamak Fusion Test Reactor

A phenomenological explanation for the anomalous ion heating observed in the JET alpha-heating experiment of 1997

Scaling of confinement with isotopic content in deuterium and tritium plasmas

Contact Info

Product

Resources

About