DOE OSTI · 2537932
Measurement of post-disruption runaway electron kinetic energy and pitch angle during final loss instability in DIII-D
Abstract
Post-disruption runaway electron (RE) kinetic energy K and pitch angle sin$\vartheta$ are critical parameters for determining resulting first wall material damage during wall strikes, but are very challenging to measure experimentally. During the final loss instability, confined RE K and sin$\vartheta$ are reconstructed during center-post wall strikes for both high impurity (high-Z) and low impurity (low-Z) plasmas by combining soft x-ray, hard x-ray, synchrotron emission, and total radiated power measurements. Deconfined (wall impacting) RE sin$\vartheta$ is then reconstructed for these shots by using time-decay analysis of infra-red imaging. Additionally, deconfined RE K and sin$\vartheta$ are reconstructed for a low-Z downward loss shot by analyzing resulting damage to a sacrificial graphite dome limiter. The damage analysis uses multi-step modeling simulating plasma instability, RE loss orbits, energy deposition, and finally material expansion (MARS-F, KORC, GEANT-4, and finally COMSOL). Overall, mean kinetic energies are found to be in the range $\langle$$K$$\rangle$ $≈ 3-4$ MeV for confined REs. KORC simulations indicate that the final loss instability process does not change individual RE kinetic energy K. In conclusion, confined RE pitch angles are found to be fairly low initially pre-instability, $\langle$sin$\vartheta$$\rangle$ $≈ 0.1 – 0.2$, but appear to increase roughly 2x, to $\langle$sin$\vartheta$$\rangle$ $≈ 0.3 – 0.4$ for both confined and deconfined REs during instability onset in the low-Z case; this increase is not observed in the high-Z case.
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Hollmann, E. M. [University of California, San Diego, La Jolla, CA (United States)] (ORCID:0000000262676589), Marini, Claudio [University of California, San Diego, La Jolla, CA (United States)] (ORCID:0000000348197765), Rudakov, D. L. [University of California, San Diego, La Jolla, CA (United States)] (ORCID:0000000252664269), Martinez-Loran, E. [University of California, San Diego, La Jolla, CA (United States)] (ORCID:0000000338414981), Beidler, Matthew [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:0000000273853886), Herfindal, Jeffrey L. [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)] (ORCID:000000032846597X), Shiraki, Daisuke [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)], Liu, Yueqiang Q. [General Atomics, San Diego, CA (United States)] (ORCID:0000000281928411), Bykov, I. [General Atomics, San Diego, CA (United States)], Lvovskiy, Andreas [General Atomics, San Diego, CA (United States)] (ORCID:0000000236491169), Lasnier, C. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000271092278), Ren, Jun [University of Tennessee, Knoxville, TN (United States)] (ORCID:0000000222561007), Ratynskaia, Svetlana [KTH Royal Institute of Technology, Stockholm (Sweden)] (ORCID:0000000267123625), Rizzi, Tommaso [KTH Royal Institute of Technology, Stockholm (Sweden)] (ORCID:0009000521957260), Paschalidis, Konstantinos [KTH Royal Institute of Technology, Stockholm (Sweden)] (ORCID:0009000173335544), Tolias, Panagiotis [KTH Royal Institute of Technology, Stockholm (Sweden)] (ORCID:0000000196328104), Kulachenko, Artem [KTH Royal Institute of Technology, Stockholm (Sweden)], Pitts, R. A. [ITER Organization, Saint-Paul-lez-Durance (France)] (ORCID:0000000194552698). 2025-02-21. Measurement of post-disruption runaway electron kinetic energy and pitch angle during final loss instability in DIII-D. https://doi.org/10.1088/1361-6587%2Fadb5b6
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