Simple, general, realistic, robust, analytic tokamak equilibria. Part 1. Limiter and divertor tokamaks

Guazzotto, L.; Freidberg, Jeffrey P.

doi:10.1017/s002237782100009x

Cited by 8 publications

(4 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To find how the MHD equilibrium of the negative triangularity plasma shape affects the n = 0 RWM mode instability, the relevant characteristics of the MHD equilibrium [32,33] such as Shafranov shift and elongation are investigated in sections 2.1 and 2.2, respectively. Through this section, we can conclude that the negative triangularity plasma has a bigger Shafranov shift and elongations of internal flux surfaces, which will be likely connected to the larger instability of the n = 0 RWM mode in section 3.…”

Section: Mhd Equilibrium Of Negative Triangularity Plasma Shapementioning

confidence: 99%

Impact of negative triangularity plasma shaping on the n = 0 resistive wall mode in a tokamak

Song¹,

Paz-Soldan²,

Lee³

2021

Nucl. Fusion

View full text Add to dashboard Cite

The axisymmetric (n = 0) resistive wall mode instability is numerically investigated for the negative triangularity plasma shape, which has shown several benefits in terms of improved confinement time and fusion engineering. To evaluate the shape effects, we modified a MHD instability code AVSTAB (Axisymmetric Vertical STABility), which calculates the marginally controllable elongation in a simplified feedback capability parameter. The plasma characteristics (poloidal beta and internal inductance) as well as the geometric effects (wall shape and plasma location) are important to determine the instability. In contrast to positive triangularity, the higher poloidal beta provides more instability drive for the negative triangularity because of the higher Shafranov shift and the higher elongation of the inner flux surface of the MHD equilibrium. Non-conformal wall shapes to the plasmas (positive triangularity wall and negative triangularity plasma) are found to be rather helpful to stabilize the n = 0 mode, unless the plasma is too close to the walls at the nulls for the opposite triangularity.

show abstract

Section: Mhd Equilibrium Of Negative Triangularity Plasma Shapementioning

confidence: 99%

Impact of negative triangularity plasma shaping on the n = 0 resistive wall mode in a tokamak

Song¹,

Paz-Soldan²,

Lee³

2021

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…The magnetic equilibrium is an analytic model based on the work described in (Guazzotto & Freidberg 2021). The major radius of the plasma, plasma current and toroidal magnetic field vary over typical ranges for the EAST tokamak in this database.…”

Section: Design and Methodsmentioning

confidence: 99%

Towards fast and accurate predictions of radio frequency power deposition and current profile via data-driven modelling: applications to lower hybrid current drive

et al. 2022

View full text Add to dashboard Cite

Three machine learning techniques (multilayer perceptron, random forest and Gaussian process) provide fast surrogate models for lower hybrid current drive (LHCD) simulations. A single GENRAY/CQL3D simulation without radial diffusion of fast electrons requires several minutes of wall-clock time to complete, which is acceptable for many purposes, but too slow for integrated modelling and real-time control applications. The machine learning models use a database of more than 16 000 GENRAY/CQL3D simulations for training, validation and testing. Latin hypercube sampling methods ensure that the database covers the range of nine input parameters ( $n_{e0}$ , $T_{e0}$ , $I_p$ , $B_t$ , $R_0$ , $n_{\|}$ , $Z_{{\rm eff}}$ , $V_{{\rm loop}}$ and $P_{{\rm LHCD}}$ ) with sufficient density in all regions of parameter space. The surrogate models reduce the inference time from minutes to $\sim$ ms with high accuracy across the input parameter space.

show abstract

“…In tokamaks, the plasma is typically taken to be axisymmetric, allowing the MHD equilibrium to be described by the Grad–Shafranov equation, for which there exist analytic solutions (Cerfon & Freidberg 2010; Guazzotto & Freidberg 2021) and efficient codes to numerically solve for equilibria (Lao et al. 1985).…”

Section: Introductionmentioning

confidence: 99%

The DESC stellarator code suite. Part 1. Quick and accurate equilibria computations

Panici,

Conlin,

Dudt

et al. 2023

J. Plasma Phys.

View full text Add to dashboard Cite

Three-dimensional equilibrium codes are vital for stellarator design and operation, and high-accuracy equilibria are also necessary for stability studies. This paper details comparisons of two three-dimensional equilibrium codes: VMEC, which uses a steepest-descent algorithm to reach a minimum-energy plasma state, and DESC, which minimizes the magnetohydrodynamic (MHD) force error in real space directly. Accuracy as measured by satisfaction of MHD force balance is presented for each code, along with the computation time. It is shown that DESC is able to achieve more accurate solutions, especially near axis. The importance of higher-accuracy equilibria is shown in DESC's better agreement of stability metrics with asymptotic formulae. DESC's global Fourier–Zernike basis also yields solutions with analytic derivatives explicitly everywhere in the plasma volume, provides improved accuracy in the radial direction versus conventional finite differences and allows for exponential convergence. Further, DESC can compute a solution with the same accuracy as VMEC in order-of-magnitude less time.

show abstract

Simple, general, realistic, robust, analytic tokamak equilibria. Part 1. Limiter and divertor tokamaks

Cited by 8 publications

References 19 publications

Impact of negative triangularity plasma shaping on the n = 0 resistive wall mode in a tokamak

Impact of negative triangularity plasma shaping on the n = 0 resistive wall mode in a tokamak

Towards fast and accurate predictions of radio frequency power deposition and current profile via data-driven modelling: applications to lower hybrid current drive

The DESC stellarator code suite. Part 1. Quick and accurate equilibria computations

Contact Info

Product

Resources

About