Plume Expansion and Ionization in a Micro Laser Plasma Thruster (Postprint)
Abstract
Ion density measurements have been performed on the plasma generated by an ablative diode laser thruster using a negatively biased flatplate probe. The biased probe data was coupled with measurement of the ablation crater through use of a scanning electron microscope (SEM). The SEM was used to analyze the post-pulse ablation spots to determine the volume of fuel ablated. Themicro-laser plasma thruster (uLPT) discussed here ablates a target material through the back surface by focusing the laser through a transparent substrate in a process typically referred to as Transmissive mode (T-mode) ablation. The target materials investigated were polyvinyl chloride (PVC) and glycidyl azide polymer (GAP), while the substrates used were cellulose acetate and Kapton(R). Peak ion densities for a GAP (target)/acetate (substrate) were found to be 1.6x107cm-3, while for GAP/kapton and PVC/acetate the peak ion densities were 4.5x107cm-3 and7.9x109cm-3 respectively. Although these corresponded to low ionization fractions calculated from the observed mass loss, the results indicate there are ways to improve the ionization fraction and in turn increase the specific impulse.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 10, 2005
- Accession Number
- ADA460867
Entities
People
- George H. Miley
- Michael P. Reilly
- William A. Hargus
Organizations
- Air Force Research Laboratory