Quantifying electron cyclotron power deposition broadening in DIII-D and the potential consequences for the ITER EC system

J.H. Slief (Corresponding author), R.J.R. van Kampen, M.W. Brookman, J. van Dijk, E. Westerhof, M. van Berkel

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Abstract

The injection of electron cyclotron (EC) waves fulfills a number of important tasks in nuclear fusion devices for which detailed knowledge of the spatial power deposition profile is critical. This deposition profile is commonly determined using forward models such as beam or ray tracing. Recent numerical and experimental studies have shown that small-angle scattering of the EC beam as it passes through the turbulent plasma edge can cause significant broadening of the effective deposition profile, leading to considerable underestimation of the deposition width by forward methods. However, traditional inverse methods to determine the deposition profile from measurements overestimate the deposition profile width due to transport broadening. In this work, we implement three novel methods to resolve the EC power deposition profile from measurements that counteract transport broadening by simultaneously resolving transport and power deposition. We validate their assumptions and compare the results from these methods to the traditional break-in-slope method as well as to the TORAY ray-tracing code in a set of DIII-D discharges spanning five different confinement modes. We show that the four different inverse methods, novel and established, paint a consistent picture of deposition broadening. Specifically, we show that the measured power deposition profile is between 1.6 and 3.6 times wider than the TORAY profiles. Moreover, we show the considerable consequences that this level of broadening can have for ITER.
Original languageEnglish
Article number026029
Number of pages16
JournalNuclear Fusion
Volume63
Issue number2
DOIs
Publication statusPublished - Feb 2023

Funding

Data used in this publication was generated in experiments funded by the US Department of Energy under DE-FC02-04ER54698. This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200—EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them.

FundersFunder number
U.S. Department of EnergyDE-FC02-04ER54698
European Commission101052200—EUROfusion

    Keywords

    • DIII-D
    • ECRH
    • ITER
    • deposition broadening
    • power deposition

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