Accession Number:

ADA179201

Title:

CO2 Pulsed Laser Damage Mechanism and Plasma Effects (Focused Beam)

Descriptive Note:

Master's thesis

Corporate Author:

NAVAL POSTGRADUATE SCHOOL MONTEREY CA

Personal Author(s):

Report Date:

1986-12-01

Pagination or Media Count:

93.0

Abstract:

An experiment was conducted at NPS with AISI SS 304 stainless steel targets in a 0.000001 Torr vacuum using a CO2 TEA high energy, pulsed laser with a beam focused to 1 sq cm. An investigation of the laser damage mechanism was conducted. The power density required for onset of plasma formation and the start of surface damage were determined. Targets were polished to 0.25 micro finish. Target specimens were examined using a scanning electron microscope to determine damage features of micron size dimensions. Experimental results confirmed that the surface damage was confined solely to unipolar arcing and thermal effects resulting from the arcing process. Several targets were cross- sectioned and chemically etched to determine changes in the microstructure of the stainless steel. At high power densities, the surface was heated sufficiently to cause a change in the stainless steel from austenite to austenite and ferrite. The localized change in the microstructure confirmed that the energy deposition from the plasma was confined to the arcing craters. The power density for onset of plasma was confined to the arcing craters. The power density for onset of plasma formation and unipolar arcing was determined to be 0.41 MWsq cm. A Sequential Unipolar Arcing Model which incorporated the details of the confirmed by the experimental results. Keywords Carbon Dioxide lasers TEA lasers Pulsed laser Damage thresholds Laser damage Laser beams Unipolar arcing.

Subject Categories:

  • Lasers and Masers
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE