Scientific and Technical Aerospace Reports Volume 39 April 6, 2001

20010026201 Sandia National Labs., Albuquerque, NM USA
Laser Injection Optics for High-Intensity Transmission in Multimode Fibers
Setchell, R. E.; Aug. 29, 2000; 13p; In English
Report No.(s): DE00-761895; SAND2000-0251C; No Copyright; Avail: Department of Energy Information Bridge, Microfiche
An increasing number of applications are requiring fiber transmission of high-intensity laser pulses. The authors particular
interests have led them to examine carefully the fiber transmission of Q-switched pulses from multimode Nd:YAG lasers at their
fundamental wavelength. The maximum pulse energy that can be transmitted through a particular fiber is limited by the onset of
laser-induced breakdown and damage mechanisms. Laser breakdown at the fiber entrance face is often the first limiting process
to be encountered, but other mechanisms can result in catastrophic damage at either fiber face, within the initial entry segment
of the fiber, and at other internal sites along the fiber path. In the course of their studies they have examined a number of factors
that govern the relative importance of different mechanisms, including laser characteristics, the design and alignment of injection
optics, fiber end-face preparation, and fiber routing. The present study emphasizes the important criteria for injection optics in
high-intensity fiber transmission, and illustrates the opportunities that now exist for innovative designs of optics to meet these
criteria. The consideration of diffractive optics to achieve desired injection criteria began in 1993, and they have evaluated a progression
of designs since that time. In the present study, two recent designs for injection optics are compared by testing a sufficient
number of fibers with each design to establish statistics for the onset of laser-induced breakdown and damage. In this testing they
attempted to hold constant other factors that can influence damage statistics. Both designs performed well, although one was less
successful in meeting all injection criteria and consequently showed a susceptibility to a particular damage process.
NTIS
Laser Beams; Injection; Optical Fibers; Diffractive Optics
20010026222 California Univ., Dept. of Electrical and Computer Engineering, Irvine, CA USA
Illumination and Temperature Invariant Recognition in Multispectral Infrared Imagery Final Report, 15 Jun. 1997 - 20
Sep. 2000
Healey, Glenn; Sep. 2000; 6p; In English
Contract(s)/Grant(s): F49620-97-1-0492
Report No.(s): AD-A386225; AFRL-SR-BL-TR-01-0048; No Copyright; Avail: CASI; A01, Microfiche; A02, Hardcopy
Significant progress has been made towards achieving the research objectives in the areas of physical modeling, algorithm
development, and experimental evaluation. We have carefully analyzed the physics underlying the information of airborne hyperspectral
imagery over the 0.4 microns-2.5 microns spectral range which corresponds to the HYDICE and AVIRIS sensors. The
new spectral radiance model includes reflected solar and scattered radiation as well as the effects of atmospheric gases and aerosols.
We have shown using a statistical analysis of the radiance model that the variation in an object’s spectral signature lies in
a low-dimensional space. This result is the basis of a new maximum likelihood ATR algorithm that is invariant to illumination
and atmospheric conditions. We have demonstrated that the new recognition algorithm significantly outperforms existing algorithms
over a range of HYDICE and AVIRIS imagery over a range of conditions. We have also evaluated the use of linear models
for representing mid-wave and long-wave infrared spectral reflectance functions.
DTIC
Infrared Imagery; Image Processing; Target Recognition
75
PLASMA PHYSICS
�������� �������������������� ��� ������ ������� ��� ����������� ������� ��� �� ����������� ��� ����� ������� ��� �� ������
��������
20010022240 NASA Langley Research Center, Hampton, VA USA
Integrated Pulse Detonation Propulsion and Magnetohydrodynamic Power
Litchford, Ron J., NASA Langley Research Center, USA; January 2001; 58p; In English
Report No.(s): NASA/TP-2001-210801; NAS 1.60:210801; M-1002; No Copyright; Avail: CASI; A04, Hardcopy; A01, Microfiche
The prospects for realizing an integrated pulse detonation propulsion and magnetohydrodynamic (MHD) power system are
examined. First, energy requirements for direct detonation initiation of various fuel-oxygen and fuel-air mixtures are deduced
from available experimental data and theoretical models. Second, the pumping power requirements for effective chamber scavenging
are examined through the introduction of a scavenging ratio parameter and a scavenging efficiency parameter. A series
265