Laser ablation plume thermalization dynamics in background gases studied by time-resolved imaging, spectroscopic, and ion probe diagnostics
A combination of fast plasma diagnostics are utilized to probe the propagation of laser ablation plumes in vacuum and low-pressure background gases in order to understand key gas dynamic processes relevant to film growth by pulsed laser deposition. During expansion into low-pressure background gases, the ion flux in the plasma plume splits into fast and slow components over a limited range of distances and times. This general effect is presented here for the case of yttrium ablation into argon, a single-element target into an inert gas. Time-resolved optical absorption spectroscopy and optical emission spectroscopy are employed to simultaneously view the populations of both excited and ground states of Y and Y{sup +} for comparison with intensified-CCD photography of the visible plume luminescence and ion flux measurements made with fast ion probes during this phenomenon. These measurements indicate that plume-splitting in background gases is consistent with momentum transfer from an initial, vacuum velocity distribution into a second, slowed velocity distribution initiated by scattering collisions between plume and background gas atoms. The fast distribution is exponentially attenuated in accordance with Beer`s law, and the second, slowed distribution coalesces into a stable, propagating shock structure.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 67256
- Report Number(s):
- CONF-950226--37; ON: DE95010277
- Country of Publication:
- United States
- Language:
- English
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