Fuzz growth in the gaps of castellated W in PISCES-A: Experiment and modeling

0477432 - ÚFP 2018 RIV GB eng J - Journal Article
Baldwin, M.J. - Dejarnac, Renaud - Komm, Michael - Doerner, R.P.
Fuzz growth in the gaps of castellated W in PISCES-A: Experiment and modeling.
Plasma Physics and Controlled Fusion. Roč. 59, č. 6 (2017), č. článku 064006. ISSN 0741-3335. E-ISSN 1361-6587
Institutional support: RVO:61389021
Keywords : tungsten fuzz * castellation * SPICE2 * PISCES
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 3.032, year: 2017
http://iopscience.iop.org/article/10.1088/1361-6587/aa6b32/meta

A castellated W target with gaps of width 0.5, 1.0, and 1.5 mm is exposed at 1120 K to He ions in the PISCES-A linear plasma device. The average ion impact energy was 70 eV and the accumulated ion fluence 3.6 × 1026 m-2 over the top surface, which is exposed normal to the plasma flow. A layer of W fuzz of 3.4 0.4 .mu.m thick developed on the top surface. In addition, fuzz morphology is found to develop on the side walls of the gaps. Particle in cell modeling of the plasma-target sheath using the SPICE2 code predicts the plasma penetration into the gaps. The He ion flux to gap side walls falls off quasi-exponentially with depth with a decay rate dependent on the gap width. When the variation in He ion wall fluence is used in conjunction with the fluence dependent growth expression of Petty et al (2015 Nucl. Fusion 55 093033), modeling correctly predicts the observed maximum depth of formation, and measured variation of layer thickness, for fuzz found on the gap walls.
Permanent Link: http://hdl.handle.net/11104/0273805