Investigation of Changes in Electron Density of a Hydrogen Plasma Over Time

The Caltech plasma jet experiment is a versatile experimental platform which generates plasma jets of various species, which can all undergo an instability cascade that ultimately leads to the emission of hard x-rays measuring 6-7keV in energy, exceeding the average plasma 2eV temperature by a factor of roughly 3000. An optical diagnostic tool was used to simultaneously image a hydrogen plasma jet generated in the Caltech plasma jet experiment at two different frequencies near the H_β line. The near and far wings of the H_β line were captured using ultra-narrowband filters centered on 485.4nm and 484.7nm, with pass-bands of 0.4nm and 0.6nm respectively. Preliminary data has demonstrated observable differences in image intensity in these frequency ranges, and previous spectroscopic measurements of Stark broadened H_β profiles indicate the FWHM routinely measures as wide as 1.1nm in the Caltech jet. Images of the H_β profile will be generated and processed to extract the FWHM of the Stark broadening profile of the jet, thereby estimating the local electron density over the lifetime of the jet. These images will also be compared to existing maps of neutral temperature, and a discussion placing the temperature and density changes in the context of the jet energization over time will be offered.