Some characteristics of Co2‐laser‐induced multiple spark breakdown at pressures up to 11 atm
| Autor: | C. Swail, R. W. Morrison |
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| Rok vydání: | 1975 |
| Předmět: | |
| Zdroj: | Journal of Applied Physics. 46:3817-3827 |
| ISSN: | 1089-7550 0021-8979 |
| DOI: | 10.1063/1.322178 |
| Popis: | A study has been made of the visible breakdown plasma produced by focusing single TEA CO2 laser pulses 200 nsec wide with salt lenses of 16‐ and 22‐cm focal lengths in argon, helium, neon‐helium, and nitrogen at pressures up to 11 atm. Pulse energies ranged from 0.9 to 11 J, with a maximum intensity at the 1‐mm focal diameter of 6.6×109 W/cm2. At this incident intensity, well above the breakdown threshold, the main breakdown plasma in argon occurred well upstream of the focus and its multiple structure extended over 5–9 cm. In the focal region only a few isolated sparks were seen. At incident powers closer to threshold, the breakdown occurred closer to, or at, the focus, and migrated upstream toward the laser as the pressure was increased. The spatial structure of the breakdown plasma as seen by time‐integrated photography, and the temporal development, monitored by photon drag observations of the transmitted power pulse, were studied with various gases, pressures, and incident pulse energies. A description of the breakdown process is offered which accounts for many of its features, especially the absence of breakdown in the focal region. |
| Databáze: | OpenAIRE |
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