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Adams, David P.; Murphy, Ryan D.; Saiz, David J.; Yalisove, Steven M.; Bahr, David F.; Lawrence, Samantha K.; Moody, Neville R.; Neiser, Geneva; Sobczak, Catherine

Pulsed laser irradiation has been used to create complex, intrinsic markings that can be used as unique identifiers for authentication and asset protection. Markings have been made on the surface of various materials by rapidly scanning a focused laser beam across a designated area as large as several square inches. Markings include macro-scale patterns, such as barcodes, that contain encrypted information. More complex markings are comprised of macro-scale patterns and embedded, unique micro-scale features. Micro-scale features form spontaneously during scanned laser irradiation and have different shapes, spacings, color and other characteristics that are virtually impossible to recreate. The macro-scale patterns can be interrogated rapidly in the field using a digital camera, while the embedded micro-scale features are best evaluated in the laboratory using microscopy or related optical techniques. Interrogated markings are compared with archived maps of the original patterns (obtained at the time of their manufacture) to determine component authenticity. The majority of experiments have involved marking planar solids. A new instrument that marks non-planar substrates is described for future work.

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TYPE Other Report YEAR 2016

DOI OSTI

The dynamics of Al/Pt reactive multilayer ignition via pulsed-laser irradiation

Applied Physics Letters

Murphy, Ryan D.; Reeves, Robert V.; Yarrington, Cole Y.; Adams, David P.

Reactive multilayers consisting of alternating layers of Al and Pt were irradiated by single laser pulses ranging from 100 μs to 100 ms in duration, resulting in the initiation of rapid, self-propagating reactions. The threshold intensities for ignition vary with the focused laser beam diameter, bilayer thickness, and pulse length and are affected by solid state reactions and conduction of heat away from the irradiated regions. High-speed photography was used to observe ignition dynamics during irradiation and elucidate the effects of heat transfer into a multilayer foil. For an increasing laser pulse length, the ignition process transitioned from a more uniform to a less uniform temperature profile within the laser-heated zone. A more uniform temperature profile is attributed to rapid heating rates and heat localization for shorter laser pulses, and a less uniform temperature profile is due to slower heating of reactants and conduction during irradiation by longer laser pulses. Finite element simulations of laser heating using measured threshold intensities indicate that micron-scale ignition of Al/Pt occurs at low temperatures, below the melting point of both reactants.

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TYPE Journal Article YEAR 2015

DOI OSTI Scopus

Direct Nanoparticle Printing of CL-20 Using Ultrafast Laser Irradiation

Kohl, Ian T.; Murphy, Ryan D.; Farrow, Darcie F.

Abstract not provided.

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TYPE Conference Poster YEAR 2015

OSTI

Laser Marking and Composition Analysis of 13-8 Steel and Nitronics 60 Surfaces

Murphy, Ryan D.; Saiz, David J.; Cruz-Cabrera, A.A.; Aragon, Phil R.; Rodriguez, Mark A.; Adams, David P.

Pulsed laser irradiation is used to irradiate and mark 13-8 steel and Nitronics 60 parts in order to create observable markings on the surfaces. The best optical contrast ratio between marked regions and unmarked regions is desired for digital image correlation. The contrast is optimized by using pulsed-laser irradiation and varying the laser power, pulse length, and scan speed. X-ray diffraction was used to characterize the laser-irradiated surface, and it was found that oxide formation and surface roughness are responsible for the observed contrast.

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TYPE SAND Report YEAR 2015

DOI OSTI