Absolutely Calibrated Vacuum Ultraviolet Spectra in the 150 nm to 250 nm Range from Plasmas Generated by the NIKE KrF Laser
NAVAL RESEARCH LAB WASHINGTON DC SPACE SCIENCE DIV
Pagination or Media Count:
High resolution vacuum ultraviolet VUV spectra were recorded from plasmas generated by the NIKE KrF laser for the purpose of observing emission from the two-plasmon decay instability TPDI at 23 the NIKE wavelength 165 nm. The targets were irradiated by up to 43 overlapping beams with intensity up to approximately equal to 10exp 14 Wsq cm and with beam smoothing by induced spatial incoherence ISI. The targets consisted of planar foils of CH, BN, Al, Si, S, Ti, Pd, and Au. Titanium-doped silica aerogels in pyrex cylinders were also irradiated. Spectra of the target elements were observed from charge states ranging from the neutral atoms to 5 times ionized. The spectrometer was absolutely calibrated using synchrotron radiation, and absolute VUV plasma emission intensities were determined. Emission from the TPDI at 165 nm wavelength was not observed from any of the irradiated targets. An upper bound on the possible TPDI emission was less than 4x10exp -8 the incident NIKE laser energy. The NIKE laser radiation backscattered from the silica aerogel targets at 248 nm was typically 6x10exp -6 the incident NIKE laser energy, and the spectral broadening corresponded to the 1 THz bandwidth of the ISI smoothing. The spectra from the moderately charged plasma ions up to 5 times ionized, spectral line widths, absolute continuum emission level, and slope of the continuum were consistent with plasma temperatures in the 100 eV to 300 eV range.
- Inorganic Chemistry
- Atomic and Molecular Physics and Spectroscopy