Precision Measurements of Ion-Engine Grids for Erosion Studies
Abstract
Two methods of measuring grid erosion in ion engines and ion-beam sources are described. The first method uses a microscope and mechanical stages to measure four edges on each of two grid holes on a front-back grid pair for a small subset of grid holes. From these measurements, the diameters and roundness of the holes and the intergrid separation and concentricity are derived to a precision of +- 10 micrometer. The second method uses a digital imaging system and image processing to measure diameter, shape, and area of a large number of holes of a front-back pair of a grid set simultaneously. Square pixels with 21.5 micrometer sides are recorded using a Kodak 1.6 Megapixel camera and a lens system that images a 20 mm x 30 mm area. Sampling more than 100 holes allows statistical information to be obtained quickly. Standard deviations of hole diameters can be less than the pixel size, but when image processing is required to enhance hole edges due to uneven lighting across the image, a systematic error as large as 10 micrometer can be introduced.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 2000
- Accession Number
- ADA387410
Entities
People
- E. J. Beiting
Organizations
- The Aerospace Corporation