A Multiple Radiation Effects Facility for the Study of Structural and Flexible Materials Exposed to the Space Environment
A radiation effects facility is described which utilizes multiple radiation sources, vacuum chambers and thermal control to simulate the space environment. Use of the facility for eight months' continuous testing of thin film flexible materials is discussed and summary results, primarily from in-situ testing, are presented.
Effect of Neutron and Proton Irradiation on Some Properties of Kapton
Photoacoustic, dielectric and surface-morphological properties of Kapton* were studied after exposing sheets (25 μm thick) separately to fast reactor neutrons (E>0.1 MeV) and to 250 keV protons up to doses 1.2×1018 (maximum)and 7.0×1015 cm−2, respectively. The photoacoustic spectrum (PAS) of the maximum neutron dose irradiated sample shows the red-shift of the absorption peak from 450 nm to 470 nm, whereas in the proton irradiated (7×1015 cm−2) sample, a new flattened absorption peak appears at λ ≃ 515 nm. There is a net enhancement in the D.C. dielectric constant of about 13% after the maximum neutron dose. It is attributed to the enhanced water absorptivity of the material due to neutron induced radiation damage.
Modeling Coherent Backscattering Errors in Fiber Optic Gyroscopes for Sources of Arbitrary Line Width
We present a new model of the noise and drift induced by coherent backscattering in a fiber optic gyroscope (FOG) interrogated with a light source of arbitrary temporal coherence. This study is critical to understand whether a FOG driven with a laser instead of a broadband source can attain high sensitivity and stability, which would have the overwhelming benefit of improving the FOG scale factor stability by at least ten-fold and would enable the use of FOGs for inertial navigation of aircrafts. Analytical and numerical solutions bring to light two significant new predictions. First, coherent-backscattering noise can be made negligibly small by utilizing a laser with a very narrow linewidth (less than ~ 20 kHz), although in this regime the drift is high. Second, by using a laser with a broad linewidth (greater than ~ 10 MHz), both the noise and the drift are low enough for aircraft inertial navigation. The dependencies of the noise and drift on fiber loss, loop coupling coefficient, and backscattering coefficient are also presented to define the optimum mode of operation of this new class of FOGs.