{'fraction_non_alphanumeric': 0.023746701846965697, 'fraction_numerical': 0.012532981530343008, 'mean_word_length': 4.577205882352941, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 1, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Estimation of suppressed erosion by vapor shielding at Be and W walls under transient loads

In ITER and future fusion devices, wall erosion caused by transient heat loads, edge-localized modes (ELMs) and disruptions is a serious concern. Suppression of the erosion occurs when a significant vapor emission happens under the heat loads, which is known as vapor shielding. Estimation of the suppressed erosion amount is essential for life time analysis and reactor design. In this study, we developed a particle-in-cell simulation code for the vapor shielding, PIXY, and applied the code to the erosion estimation for Be and W walls under a pulsed heat flux of 1–20 GW m−2 within 0.2 ms, which simulates a short-duration ELM pulse. Heat fluxes reaching the wall are recorded separately for electrons and ions, and reveal effective physical processes during the vapor shielding at Be and W walls. Then, for these walls, the total erosion amounts with and without vapor shielding are evaluated and compared. Estimated total erosion is larger for the Be wall up to 10 GW m−2. The Be wall erosion becomes saturated for the heat flux  >10 GW m−2 due to its effective shielding, while the estimated W wall erosion eventually overcomes the Be wall erosion. In the short-time scale studied in this paper, effective radiation cooling by W vapor clouds is not observed. A simple wall life time analysis based on the estimated erosion rate shows 10 mm of W wall will survive 107 ELM loads with energy density less than 1 MJ m−2.