Speaker
Description
See full abstract here
http://ocs.ciemat.es/EPS2019ABS/pdf/P4.1013.pdf
A detailed characterization of flows, density and temperature profiles is necessary to shed light on transport in magnetically confined fusion devices. The most common technique to measure these profiles is Charge Exchange Recombination Spectroscopy (CXRS). The CXRS systems are usually located at the low field side but several studies [1, 2, 3] have shown that impurity density and flows are poloidally asymmetric in the pedestal region. At ASDEX Upgrade, the inboard-outboard impurity density asymmetry can reach a factor of 3, while the temperature and the electrostatic potential are found to be flux functions [4]. However, at Alcator C-Mod, inboard-outboard variations were also found in plasma potential or ion temperature, indicating that both might not be constant on flux surfaces [5]. The maximum observed inboard-outboard impurity density asymmetry on Alcator C-Mod reached a value of 10. These differences may be related to different methods of aligning the profiles [5]. The high field side CXRS system at the plasma edge of ASDEX Upgrade has been upgraded with a new gas valve and a new poloidal optical head in order to understand these differences. The fast opening and closing of the new piezoelectric valve allow for a better characterization of the background emission. Dedicated calibrations for different gases have been performed in order to determine the flowrate accurately. Moreover, the number of lines of sight has been increased to improve the radial resolution. First studies of poloidal asymmetries using the measurements of the new diagnostic will be presented.
[1] K.D Marr et al. Plasma Physics and Controlled Fusion, 52:055010, 2010. [2] T. Pütterich et al. Nuclear Fusion, 52:083013, 2012. [3] R.M. Churchill et al. Nuclear Fusion, 53:122002, 2013. [4] E. Viezzer et al. Nuclear Fusion, 55:123002, 2015. [5] C. Theiler et al. Nuclear Fusion, 54:083017, 2014.
