Production of Large Warm Plasmas by Staged Laser Heating of Solid Targets.
Abstract
A 1000 Joule CO2 laser pulse, focussed on a slowly expanding (dr/dt = 200,000 cm/sec) gas cloud in a vacuum chamber, ionizes the gas by laser spark breakdown, and then heats it by inverse bremstrahlung absorption. The resulting plasma contains about 10 to the 19th power ions at a temperature of approximately 50 eV. The gas cloud is created by irradiating a solid plastic target with a 10 J prepulse and a 100 J main pulse from a Nd/glass laser. Two advantages of these two laser plasma production systems over irradiating a solid target directly with the CO2 laser are (1) the density of the target gas cloud in an adjustable parameter that can be used to vary the plasma temperature and total number of particles, and (2) since the temperature of an expanding plasma decreases as T(r) = (T sub o)((r sub o)/r) squared, and since r sub o is a factor of ten larger for a gas than a solid, the temperature at large r of a plasma that originated as a cloud is a factor of 100 higher than one that was heated at the radius of a solid, provided of course, that the initial temperature and particle number are the same in both cases. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1977
- Accession Number
- ADA038533
Entities
People
- Joseph R. Greig
- R. E. Pechacek
Organizations
- United States Naval Research Laboratory