Theoretical Study of Laser-Induced Breakdown in Particle-Contaminated Air
Abstract
Of the physical effects that limit the propagation of a high intensity laser beam through the atmosphere, air breakdown has the most catastrophic influence. Completely ionized air attenuates 10.6 micron radiation within a few centimeters. It is therefore imperative that the threshold for air breakdown under realistic circumstances be determined. In this report the physics of long pulse laser-induced breakdown process in particle-contaminated air is studied in four stages. The first stage is particulate heating and vaporization. Simple models are used to predict the time to vaporization at the particle surface, the time to vaporize a given fraction of the particle, and the pressure of the vapor immediately above the particle surface. The second stage is the heating of the vapor cloud. The heating rate is calculated under two approximations. The third stage of the breakdown process is the creation of air plasma. An estimate is made of the temperature the surrounding air must reach in order to readily absorb the laser energy. Then, from crude estimates of the energy flux into the air, the rate of expansion of the plasma into the air is determined. The final stage is the growth of the air plasma. The growth is followed as a function of time for various values of the initial air plasma size and the laser intensity.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1977
- Accession Number
- ADA044073
Entities
People
- A. N. Pirri
- P. K. S. Wu
- R. G. Root
Organizations
- Physical Sciences (United States)