Study of the validity of LTE condition in Laser Induced Plasma Experiments
Abstract
Temperature and electron density evolution are measured in many plasmas by emission spectroscopy assuming Local Thermal Equilibrium (LTE). The validity of this condition is not always satisfied and there is a great dispersion in reported values. Here we proposed a new method to select the lines satisfying the LTE condition. To validate this method we spectroscopic analyzed the temporal evolution of several spectral lines belonging to the Ar II spectrum in a Laser Induced Plasma (LIP) experiment. Electric breakdown in Ar at controlled pressure, was obtained by focusing the emission of a pulsed Nd: YAG laser, operated at 1064 nm, delivered pulsed up to 350 mJ at a 10 Hz repetition rate, with 7 ns pulse width (FWHM) and 6 mm beam diameter. The light emitted by the plasma was sent to a 0.5m spectrograph and the spectrum was temporal analyzed by an ICCD camera and the signal was stored in a PC. This camera was synchronized with the pulsed laser using a delay generator. Results show that the intensity of a spectral line as a function of the intensity of another one must be a straight line, for each time during the validity of the LTE. Finally under LTE condition we determine the temporal evolution of the temperature and of the electron density.
- Publication:
-
APS Division of Plasma Physics Meeting Abstracts
- Pub Date:
- November 2002
- Bibcode:
- 2002APS..DPPBP1022S