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The AEgis Technologies Group and RTI International are developing microsensors for High Energy Laser (HEL)
diagnostic applications. The conformal sensor array will measure the irradiance profile of an incident laser beam, and
concomitant rise in surface temperature of the target. The open mesh architecture allows 90% of the beam to impact the
surface. A critical part of this program is developing a protective coating that ensures sensor survivability at high
irradiance levels for operational lifetimes on the order of 10 seconds. The protective coating must transmit a measurable
amount of light to the irradiance sensor. We have conducted experiments to evaluate candidate heat shield materials.
In the first round of experiments, a 10kW CO2 laser was used to irradiate pure materials, including metals and carbon
foils. Although many of the metal foils were perforated by the laser, no significant amount of material was ablated
away. In fact, most of the test samples gained mass, presumably due to oxidation. Analysis of high speed video shows
that once the metal melted, surface tension caused the molten metal to coalesce into droplets around the rim of the hole.
The second and third rounds of testing, conducted with a 3kW, 1.07μm fiber laser, included samples of highly reflective
metals and ceramics, standard plasma-sprayed coatings, and multilayer stacks. We have also measured the performance
of temperature sensors and irradiance sensors fabricated from nanoparticle solutions deposited by advanced printing
technology and have completed a preliminary investigation of high temperature adhesives.
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