| Popis: |
The erosion of the channel wall in Hall effect thru sters (HETs) limits the maximum HET operating life time. HET channel wall materials are often binary composites of boron nitride and silica. The heterogeneity of the material drive s the development of complex surface features and roughness during the erosion process. To aid the understanding of the erosion processes, a three dimensional model of the atomic sputtering of a heterogeneous material is developed. The model investigates, through a ray-tracing technique and empirical models for the erosion rate of each phase, the interaction between ion beams and the underlying grain-level microstructure. Simulated erosion histo ries and surface profiles are compared with empirical data collected from the eroded channel wall of the AFRL/UM P5 HET. Simulated surface features and expected surface roughnesses for moderate ion incidence angles of 30˚ and 45˚ resemble those found through scanning electron microscopy and optical profilometry of the P5 channel wall. Predic ted rms roughnesses for 30˚ incidence are on the order of 7 µm, and rms roughnesses measured on the channel wall are 6±2.5 µm. The composition of the channel wall surface is investig ated via X-ray photoelectron spectroscopy and is comparable to prior work, but the reduction in the presence of BN with erosion is not adequately captured by this model. |
