Investigation of linear gyrokinetic ion-scale modes ( k θ ρ s = 0.3) finds that a transition from ion temperature gradient to microtearing mode (MTM) dominance occurs as the density is increased near the pedestal region of a parameterized DIII-D sized tokamak. H-modes profile densities, temperatures, and equilibria are parameterized utilizing the OMFIT PRO_create module. With these profiles, linear gyrokinetic ion-scale instabilities are predicted with CGYRO. This transition (nMTM) has a weak dependence on radial location in the region near the top of the pedestal ( ρ = 0.7 − 0.9), which allows simulating single radii to examine the approximate scaling of nMTM with global parameters. The critical nMTM is found to scale with plasma current. Additionally, increasing the minor radius by decreasing the aspect ratio and increasing the major radius are found to reduce nMTM. However, any relationship between nMTM and density limit physics remains unclear as nMTM increases relative to the Greenwald density with larger minor radius and with larger magnetic field, suggesting that the transport due to MTM may be less important for a reactor. Additionally, nMTM is sensitive to the pedestal temperature, the local electron and ion gradients, the ratio of ion to electron temperature T i / T e, and the current profile. MTMs are predicted to be the dominant instability in the core at similar Greenwald fractions for DIII-D, NSTX, and NSTX-U H-mode experiments, supporting the results of the parameterized study. Additionally, MTMs continue to be the dominant linear instability in a DIII-D L-mode after an H–L transition as the plasma approaches a density limit disruption despite the large change in plasma profiles.
Skip Nav Destination
Transition from ITG to MTM linear instabilities near pedestals of high density plasmas
Article navigation
April 2023
Research Article|
April 13 2023
Transition from ITG to MTM linear instabilities near pedestals of high density plasmas
J. McClenaghan
;
J. McClenaghan
a)
(Conceptualization, Writing – original draft)
1
General Atomics
, PO Box 85608, San Diego, California 92186-5608, USA
a)Author to whom correspondence should be addressed: mcclenaghanj@fusion.gat.com
Search for other works by this author on:
T. Slendebroek
;
T. Slendebroek
(Investigation)
1
General Atomics
, PO Box 85608, San Diego, California 92186-5608, USA
Search for other works by this author on:
G. M. Staebler
;
G. M. Staebler
(Investigation)
1
General Atomics
, PO Box 85608, San Diego, California 92186-5608, USA
Search for other works by this author on:
S. P. Smith
;
S. P. Smith
(Investigation)
1
General Atomics
, PO Box 85608, San Diego, California 92186-5608, USA
Search for other works by this author on:
O. M. Meneghini
;
O. M. Meneghini
(Supervision)
1
General Atomics
, PO Box 85608, San Diego, California 92186-5608, USA
Search for other works by this author on:
B. A. Grierson
;
B. A. Grierson
(Investigation)
1
General Atomics
, PO Box 85608, San Diego, California 92186-5608, USA
Search for other works by this author on:
K. E. Thome
;
K. E. Thome
(Investigation, Writing – review & editing)
1
General Atomics
, PO Box 85608, San Diego, California 92186-5608, USA
Search for other works by this author on:
G. Avdeeva
;
G. Avdeeva
(Investigation)
2
Oak Ridge Associated Universities
, Oak Ridge, Tennessee 37831-0117, USA
Search for other works by this author on:
L. L. Lao
;
L. L. Lao
(Supervision)
1
General Atomics
, PO Box 85608, San Diego, California 92186-5608, USA
Search for other works by this author on:
J. Candy
;
J. Candy
(Investigation, Writing – review & editing)
1
General Atomics
, PO Box 85608, San Diego, California 92186-5608, USA
Search for other works by this author on:
W. Guttenfelder
W. Guttenfelder
(Investigation)
3
Princeton Plasma Physics Laboratory
, Princeton, New Jersey 08543-0430, USA
Search for other works by this author on:
a)Author to whom correspondence should be addressed: mcclenaghanj@fusion.gat.com
Phys. Plasmas 30, 042512 (2023)
Article history
Received:
January 03 2023
Accepted:
March 22 2023
Citation
J. McClenaghan, T. Slendebroek, G. M. Staebler, S. P. Smith, O. M. Meneghini, B. A. Grierson, K. E. Thome, G. Avdeeva, L. L. Lao, J. Candy, W. Guttenfelder; Transition from ITG to MTM linear instabilities near pedestals of high density plasmas. Phys. Plasmas 1 April 2023; 30 (4): 042512. https://doi.org/10.1063/5.0141179
Download citation file:
Sign in
Don't already have an account? Register
Sign In
You could not be signed in. Please check your credentials and make sure you have an active account and try again.
Sign in via your Institution
Sign in via your InstitutionPay-Per-View Access
$40.00