Speaker
Petra Bilkova
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1027.pdf
Relative shift in pedestal position during power and gas scans at the
COMPASS tokamak
P. Bílková1, L. Frassinetti2, M. G. Dunne3, J. Havlíček1, M. Komm1, M. Peterka1,4,
T. Markovič 1, P. Böhm1, E. Štefániková2, M. Šos1,5, J. Seidl1, O. Grover1,5,
K. Mitošinková1,4, J. Varju1, P. Vondráček1,4, J. Urban1, V. Weinzettl1, M. Hron, R. Pánek1
and the EUROfusion MST1 team6
1
Institute of Plasma Physics of the CAS, Za Slovankou 3, 182 00 Prague 8, Czech Republic
2
KTH, Div Fus Plasma Phys, SE-10044 Stockholm, Sweden
3
Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748, Garching, Germany
4
Fac. Math & Phys., Charles Univ., V Holešovičkách 2, 180 00 Prague 8, Czech Republic
5
FNSPE, Czech Technical University in Prague, Břehová 7, Czech Republic
6
See the author list (H. Meyer et al 2017 Nucl. Fusion 57 102014
Recent analysis performed on ASDEX Upgrade, NSTX and DIII-D suggest that the density
profile position plays an important role in pedestal stability [1,2,3]. On JET and on ASDEX
Upgrade, it has been observed that the electron temperature and electron density profiles can
have a different relative pedestal positions (so-called relative shift). As shown in [4], the
increase of the relative shift is correlated with the reduction in the normalized pressure
gradient, leading to a weakening of the pedestal stability. Systematic measurements of
pedestal structure were performed during Ohmic and NBI-assisted H-modes at the
COMPASS tokamak [5]. For PNBI exceeding 200 kW the electron pedestal temperature
∗
reached 300 eV, allowing to achieve pedestal collisionality 𝜈𝑝𝑒𝑑 < 1 at q95 ~3. Measurements
during the last 30% of the ELM cycle were considered for analysis and were processed as
described in [6]. First results on analyses of pedestal shift on COMPASS were published in
[7]. A linear trend between the shift and Psep was observed similarly as on JET [8].
Dependence of αcrit on pedestal shift was more complex - it followed the trend observed
previously on JET only for low collisionalities. The pedestal stability was analysed with the
peeling-ballooning model [9].
In this contribution, analyses on an extended dataset was performed. Particularly, data from
power and gas scans are included. The experimental data are compared to EPED.
[1] T.H. Osborne et al., Nucl. Fus. 55,063018 (2015) [6] L. Frassinetti et al., Rev. Sci. In. 83, 013206 (2012)
[2] R. Maingi et al., Nucl. Fus. 52 083001 (2012) [7] P. Bilkova et al., 44th EPS C. on Pl. Phys., P2.120
[3] M. Dunne et al., Plas. Phys. Contr. Fus.59 (2017) [8] E. Stefanikova et al., 43rd EPS C. Pl. Phys., O4.117
[4] E. Stefanikova et al, 2018 Nucl. Fus. in press [9] P. Wilson et al., Phys. Plasmas 9, 1277 (2002)
[5] M. Komm et al., Nucl. Fus. 57, 5 (2017), 056041
