Abstract
The increased low to high confinement mode (L to H-mode) power threshold P L H in DIII-D low collisionality hydrogen plasmas (compared to deuterium) is shown to result from lower impurity (carbon) content, consistent with reduced (mass-dependent) physical and chemical sputtering of graphite. Trapped gyro-Landau fluid (TGLF) quasilinear calculations and local non-linear gyrokinetic CGYRO simulations confirm stabilization of ion temperature gradient (ITG) driven turbulence by increased carbon ion dilution as the most important isotope effect. In the plasma edge, electron non-adiabaticity is also predicted to contribute to the isotope dependence of thermal transport and P L H , however its effect is subdominant compared to changes from impurity isotopic behavior. This L-H power threshold reduction with increasing carbon content at low collisionality is in stark contrast to high collisionality results, where additional impurity content appears to increase the power necessary for H-mode access.
| Original language | English |
|---|---|
| Article number | 126009 |
| Journal | Nuclear Fusion |
| Volume | 63 |
| Issue number | 12 |
| DOIs | |
| State | Published - Dec 2023 |
Funding
This work was supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award Nos. DE-FC02-04ER54698, DE-SC0020287, DE-SC0019352, DE-FG02-95ER54309, DE-SC0018287, DE-AC02-09CH11466, DE-FG02-08ER54999, and DE-AC05-00OR22725. Computing resources were provided by the National Energy Research Scientific Computing Center under Contract No. DE-AC02-05CH11231. Part of the data analysis was performed using the OMFIT integrated modeling framework [, ]. This Letter was prepared as an account of work sponsored by an agency of the U.S. Government. Neither the U.S. 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 accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof. This work was supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award Nos. DE-FC02-04ER54698, DE-SC0020287, DE-SC0019352, DE-FG02-95ER54309, DE-SC0018287, DE-AC02-09CH11466, DE-FG02-08ER54999, and DE-AC05-00OR22725. Computing resources were provided by the National Energy Research Scientific Computing Center under Contract No. DE-AC02-05CH11231. Part of the data analysis was performed using the OMFIT integrated modeling framework [48, 49]. This Letter was prepared as an account of work sponsored by an agency of the U.S. Government. Neither the U.S. 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 accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. The views and opinions of authors expressed herein do not necessarily state or reflect those of the U.S. Government or any agency thereof.
Keywords
- L-H transition
- isotope
- turbulence