Sputter Calculator (alpha version)

Sputtering is surface erosion by impacting energetic particles. Sputtering is used in material processing to create a “molecular cloud” which then deposits on the substrate as a thin surface layer finish. But not all sputtering is desirable. Sputtering is the main life-limiting process for electric propulsion devices. Ion thruster grids will eventually fail due to sputtering by backflowing CEX ions [1]. Sputtering is also encountered on cathode keepers. In the case of Hall thrusters, sputtering may erode the discharge channel to the magnetic circuit, however this is configuration specific[3]. Degradation of spacecraft blankets is also similarly related to both bombardment and chemical reaction with the impacting atomic oxygen. For this reason, many spacecraft-environment interactions codes pay attention to modeling the sputter process.

The difficulty in modeling sputtering is in computing the sputter yields. Sputter yield will be in general a function of the incoming ion energy and the incident angle. Large number of experimental data has been amassed, however, collecting data for all material pairs of interest may be difficult. For this reason, the analytical model of Yamamura and Matsunami are often used. This model computes the yield as a function of material properties such as mass, sublimation energy, and so on. The interactive calculator below implements this model, based on the following reference noted below.

References

[1] Yamamura, Y., Itikawa, Y., and Itoh, N., "Angular dependence of sputtering yields of monatomic solids", Institute of Plasma Physics Report, IPPJ-AM-26, 1983
[2] George C. Soulas, Hani Kamhawi, Michael J. Patterson, Melissa A. Britton, and Michael M. Frandina, "NEXT Ion Engine 2000 HourWear Test Results," 40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 11 - 14 July 2004, Fort Lauderdale, Florida, AIAA 2004-3791
[3] Ioannis G. Mikellides, Ira Katz, Richard Hofer, Dan Goebel, Kristi de Grys, and Alex Mathers, Magnetic Shielding of the Acceleration Channel Walls in a Long-Life Hall Thruster
Ioannis G. Mikellides, 46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 25 - 28 July 2010, Nashville, TN, AIAA 2010-6942

Future Work

This page is still a work in progress. Here is the list of features I plan to implement in the near future. Please leave a comment if you have suggestions for other items. The repository for this code is located on Github.

1. Add section summarizing the equations being plotted
2. Expand material database to include additional materials
3. Add input boxes to allow overrides of the database values
4. Plot angular data on a polar plot