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Submitted on 30 Jul 2020
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Investigation of the dependency of midplane separatrix density as a function of engineering parameters for
H-mode pulses in JET with the ITER Like Wall Julio Balbin, Jérôme Bucalossi, Hugo Bufferand, Guido Ciraolo
To cite this version:
Julio Balbin, Jérôme Bucalossi, Hugo Bufferand, Guido Ciraolo. Investigation of the dependency of midplane separatrix density as a function of engineering parameters for H-mode pulses in JET with the ITER Like Wall. 17th international workshop on plasma edge theory in fusion devices, Aug 2019, La Jolla, United States. �hal-02909430�
Investigation of the dependency of midplane separatrix density as a
function of engineering parameters for H-mode pulses in JET with the
ITER Like Wall
Contact:
Julio.Balbin@cea.fr
Motivation
REFERENCES
[1] A. Leonard et al, Compatibility of separatrix density scaling for divertor detachment with H-mode pedestal operation in DIII-D, Nucl. Fusion 57, 2017. [2] P.C. Stangeby et al, Identifying the location of the OMP separatrix in DIII-D using power accounting, Nucl. Fusion 55, 2015.
POWER BALANCE DESCRIPTION
RESULTS
ABSTRACT
CONCLUSIONS
DATA PROCESSING
J. Balbin
1
*, J. Bucalossi
1
, H. Bufferand
1
, G. Ciraolo
1
1
CEA, IRFM, F-13108 Saint-Paul-lez-Durance, France.
*J. Balbin email: Julio.Balbin@cea.fr
Midplane separatrix density is a crucial parameter in tokamaks since it strongly impacts the divertor downstream conditions. Therefore, predicting the midplane separatrix density (MSD) as a function of main engineering parameters such as auxiliary heating Pinj, toroidal magnetic field Bt, plasma current Ip and electron pedestal density [1] is of interest for ITER operation and next step device design. In this perspective, a dataset of JET H-mode pulses performed with the ITER Like Wall (ILW) has been analyzed. The midplane density is collected from a high resolution Thomson scattering diagnostic and the MSD is determined by power balance analysis. The parameters are averaged over several ELM cycles. A clear positive dependency is found with pedestal density and auxiliary heating while a negative one is observed with Ip and Bt. The ratio between MSD and pedestal density ranges from 0.3 to 0.7 in the dataset. A tentative scaling law will be presented.
Params. Psol (MW) Bt (T) Ip (MA)
Deuterium pulse
6.0 2.5 2.5
S2D map for Temperature
S2D map for density
Midplane separatrix electron density range in function of electron pedestal density.
Midplane separatrix Electron temperature values show a scattered tendency with a high median value of 142 eV
An increase of Psol is followed by an increase of separatrix density
Fig 11,
Values used in the simulation (equilibrium from JET pulse 89088)
Magnetic configuration of the pulses in the dataset
The power balance method uses Spitzer and Flux-limited model with the Kin-Corr-Spitzer model and matches the Psep given by Psep = Pinjected – Prad to obtain the radial separatrix position.
The midplane separatrix density ranges between the 30% and 70% of electron pedestal density while the temperature data shows scattered values around a median value of 142 eV
Electron temperature and density profiles. The pedestal zone is determined by gradient profile analyze. The separatrix is determined
by the KCS method
Comparison of heat flux models with S2D separatrix on electron density profile
Separatrix postion given by the different heat flux models on electron temperature profile
Separatrix density variation in function of Psol Separatrix density variation in function of Ip Separatrix density variation in function of Bt
An increase of Ip corresponds to a decrease of separatrix density An increase of Bt corresponds to a decrease of separatrix density JET datas et. Ne_ped (1019 ) Psol (MW) Bt (T) Ip (MA) Ne_se p (1019 ) Te_s ep (eV) Min 2.97 9.14 1.77 1.47 1.68 107 Max 8.80 23.75 3,07 3.47 4.25 200
71 discharges have been analyzed
Thomson Scattering diagnostic used to collect data of electron density and temperature
Tentative scaling law on the dataset
70%
30% 42%
• It is shown that the ratio between separatrix density and pedestal density is a good
reference to analyze dependencies with respect to engineering parameters and provide a scaling law.
• From the analyzed JET data we find that increasing Psol the separatrix density at OMP
increases too. However the large scatter in the dataset produces a weak dependence of MSP from Psol requiring further analyses to a more precise determination of such exponent.
• Concerning the dependence on Bt and Ip we find negative exponents i.e. an inverse
dependency on Ip and Bt of separatrix density at OMP. A relation or entanglement between Bt and Ip can be suggested because their exponents have a similar sign;
• This analysis will be improved considering larger dataset and other tokamak devices.
This picture shows a good correspondence between separatrix density obtained from Data and Scaling Law. This linear fitting is constrained with the point (0,0). The 97% value showed in the picture represent between the correspondence of the obtained values with respect to the expected values.
Spitzer model: Flux-limited model:
Kin-Corr Spitzer model:
