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Conceptual design of a Doppler spectrometer for 102 m/s cross-field flows in tokamak divertors

Publication Type
Conference Paper
Journal Name
Review of Scientific Instruments
Publication Date
Volume
95
Issue
7
Conference Name
25th Topical Conference on High Temperature Plasma Diagnostics (HTPD)
Conference Location
Asheville, North Carolina, United States of America
Conference Sponsor
Oak Ridge National Laboratory
Conference Date
-

The cross-field transport in the scrape-off-layers (SOLs) and divertors in tokamaks is of a similar size to the poloidal component of the parallel flow, thereby significantly impacting the plasma transport there. However, its direct observation has been challenging because the drift velocity (102–103 m/s) is significantly below the detection limit of conventional diagnostics. To realize cross-field ion flow measurement, a variety of systematic uncertainties in the system must be narrowed down. Here, we develop a conceptual design of the Doppler spectrometry that enables us to measure the impurity flows with 102-m/s accuracy based on an in situ wavelength-calibration technique developed in the astrophysics field, the iodine-cell method. We discuss its properties and applicability. In particular, the scaling relation between wavelength accuracy and various spectroscopic parameters is newly presented, which suggests the high importance of the wavelength resolution of the system. Based on transport simulations for the JT-60SA divertor, the feasibility of the system is assessed.