Edge Current Profile Analysis with Lithium Beam Polarimetry on DIII-D
Abstract
The development of analysis techniques for measurements from the DIII-D lithium beam Zeeman polarimetry edge current profile diagnostic will be presented. The initial analysis examines the edge current during ELM-free H-mode and QH-mode where the pedestal gradients are expected to drive a strong bootstrap and Pfirsch-Schluter current. The magnetic field line pitch angles measured at the outboard midplane are used both to determine the edge current profile and constrain the magnetic equilibrium used for stability analysis. The pitch angle is determined by measuring all polarization states of the lithium beam emission. A description of the entire system and measurement technique will be given. Uncertainties in the measurement arise from a number of factors, including background signal subtraction, plasma density fluctuations at the polarization modulation frequency and photon statistics. In addition a calibration using a plasma discharge with very low edge current is required for determining important spectroscopic characteristics of the detection system. A discussion of how these factors contribute to the total measurement uncertainty will be presented.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- October 2003
- Bibcode:
- 2003APS..DPPKP1021L