Reduced Physics Model of the Tokamak Scrape-off-Layer for Pulse Design

Contact: Xin Zhang at Laura.Zhang@tokamakenergy.co.uk

The dynamic interplay between the core and the edge plasma has important consequences in the confinement and heating of fusion plasma. The transport of the Scrape-Off-Layer (SOL) plasma imposes boundary conditions on the core plasma, and neutral transport through the SOL influences the core plasma sourcing. In order to better study these effects in a self-consistent, time-dependent fashion with reasonable turn-around time, a reduced model is needed. In this paper we introduce the SOL Box Model, a reduced SOL model that calculates the plasma temperature and density in the SOL given the core-to-edge particle and power fluxes and recycling coefficients. The analytic nature of the Box Model allows one to readily incorporate SOL physics in time-dependent transport solvers for pulse design applications in the control room. Here we demonstrate such a coupling with the core transport solver TRANSP and compare the results with density and temperature measurements, obtained through Thomson scattering and Langmuir probes, of an NSTX discharge. Implications for future interpretive and predictive simulations are discussed.

============= Contents of Data Repository ======================

Power and particle fluxes used in Fig.3 are in txt files:
EHEAT.txt / IHEAT.txt: electron / ion power
EFLUX.txt / IFLUX.txt: electron / ion particle fluxes

=======================

Thomson and CHERS data used in Figs.4-7 are in the .sav files
139396cx.sav - CHERS data
139396mpts.sav - Thomson data

To open, use IDL, or the following python commands:

from scipy.io import readsav

fcx = dirin + shot + 'cx.sav'
wcx = readsav(fcx)
data = wcx['w']  # a dictionary containing CX data

Dictionary keys are:
times, radius, 
ti: ion temperature
dti: error for ion temperature

Similarly, for TS data:

fts = dirin + shot + 'mpts.sav'
wts = readsav(fts)
data = wts['w']

Dictionary keys are:
times, radius
tef: electron temperature
dtef: error for electron temperature
nef: electron density
dnef: error for electron density

===================

SOLPS data files in Fig.4 are saved as dictionaries in the .pkl files:
SOLPS139396_R97_new.pkl  recycling = 0.97
SOLPS139396_R98_new.pkl  recycling = 0.98
SOLPS139396_R99_new.pkl  recycling = 0.99

To load and view, use python:

import pickle
f = open('/path/to/pkl' + 'SOLPS139396_R*.pkl', 'br')
D = pickle.load(f)

The entries to the dictionary are:

(from OMP to target, in the SOL)
cnL: connection length
ne: electron density 
te: electron temperature
ti: ion temperature
u: plasma flow speed
M: mach number 
S: particle source
R: midplane major radius

(in the radial direction only, at OMP)
fullR: major radius
TeR: electron temperature
NeR: electron density

==================

Langmuir probe data used in Figs.5,6 are in LP_139396.pkl
To load in python, do:

import pickle
f = open('/path/to/pkl' + 'LP_139396.pkl', 'br')
[tt, LPT_e, LPT_err, LPne, LPne_err] = pickle.load(filein)

Dictionary keys are:
tt: time
LPT_e: electron temperatures
LPT_err: error for electron temperature
LPne: electron density
LPne_err: error for electron density

==================

Recycling coefficients plotted in Fig.8 are:
ERCY.txt / IRCY.txt: electron / ion recycling coefficients