Speaker
Description
See the full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P1.1077.pdf
An efficient fuelling capability is mandatory for large fusion devices; this being of primary importance for helical devices [1]. The injection of cryogenic pellets is the best candidate to refuel the plasma core in large devices. During the past decades pellet injection (PI) technologies have become well developed while advancement in the understanding of pellet ablation, and subsequent particle deposition, has been substantial. Moreover, PI simulation codes, such as HPI2 [2-4], have been developed in order to aid experimental analysis and to design PI systems for new large devices, e.g., W7-X. Despite such advances, further effort in pellet physics studies is needed since a complete comprehension of experimental observations, e.g., related to pellet particle deposition, remains outstanding, in particular for stellarators. In parallel, it is necessary to incorporate new insights into the underlying physics of pellet ablation, drift, and diffusion into simulation codes in order to improve predictions.
Cryogenic PI is used for low-field side fuelling of the TJ-II heliac, a medium-sized stellarator, characterized by high flexibility [5,6]. Its PI database has been used to benchmark a new stellarator version of the HPI2 code [7] that would allow predictions for the new stellarator W7-X. In general, good agreement with experiment has been found for TJ-II injections, thus providing confidence for W7-X simulations. However, under certain experimental conditions in TJ-II, deposition profiles deviate significantly from predictions. For instance, when suprathermal electrons are present in the plasma core, particle deposition is significantly deeper than predicted and fuelling efficiency is improved [7,8]. In order to understand this, an upgraded fast imaging camera follows plasmoid drift during dedicated experiments. This has provided input for developing new algorithms for the stellarator versions of HPI2.
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[4] F. Köchl et al., Prepr. EFDA-JET-PR(12)57 (2012) 82.
[5] J.L. Velasco et al., Plasma Phys. Control. Fusion 58 (2016) 084004.
[6] K.J. McCarthy et al., Nucl. Fusion 57 (2017) 056039.
[7] N. Panadero et al., Nucl. Fusion 58 (2018) 026025.
[8] K.J. McCarthy et al., Plasma Phys. Control. Fusion 61 (2019) 014013.
