Battelle Memorial Institute

Bernerd E Campbell

Harold M Epstein

Philip J Mallozzi

David C Applebaum

William J Gallagher

Allan H Clauer

Craig Thompson Walters

Jeffrey L Dulaney

Robert E Schwerzel

Boyd A Mueller

Methods and apparatus for improving properties of a solid material in a target (11) by providing shock waves therein. There are directed to the surface of the material (11) pulses of coherent radiation (12) having average energy fluence of at least about 10 Joules per square centimeter and rise time of not longer than about 5 nanoseconds within a fluorescence envelope lasting about 0.5 to 5 milliseconds, at a rate of about 1 radiation pulse per 100 to 200 microseconds. The leading edge of each pulse (12) is sharpened by providing in its path an aluminum film (18) about 150 to 5000 angstroms thick that is vaporized by the pulse and then is moved across the path so that a later pulse (12) strikes an area of the film (18) not already vaporized by an earlier pulse (12). The radiation (12) is amplified by an amplifier (23) comprising a rod of phosphate laser glass that was strengthened by an ion exchange process.

Material properties

Apparatus (10) for obtaining EXAFS data of a material (11). A lens (12) directs a pulse of radiant energy (13) from a laser (14) onto a metal target (15) to produce X-rays (16) of a selected spectrum and intensity at the target (15). A baffle (17) directs X-rays (16) from the target (15) onto a spectral dispersive monochromator (18) which directs the spectrally resolved X-rays (16R) therefrom onto a photographic film 20. A film of material (11) is located in the path (22) of only a portion (16L) of the X-rays (16) throughout a selected spectral band, and the resolved X-rays (16R) directed onto the photographic film (20) form two separate images thereon comprising a reference spectrum (26R) representative of a portion of the X-rays (16U) throughout the selected band that was not affected by the film of material (11) and an absorption spectrum (26A) representative of a portion of the X-rays (16L) throughout the selected band that was modified by transmission through the film of material (11). The laser pulse (13) typically has a width of less than about 10 nanoseconds, and the material (11) may be in a highly transient state.

Laser EXAFS

Methods and apparatus for directing radiation pulses to a region wherein either a pulse or a substance in the region is adversely affected by the presence of more than a given power density therein. A laser pulse is split into a plurality of portions and each portion is directed along a path of different length to provide in rapid succession a plurality of pulses each having less than the given power density. Each pulse is caused to arrive at the region at an angle differing by at least its divergence angle from the arrival angle of every other pulse (or, if at a smaller angle from another pulse, with opposite polarization therefrom) and at a time enough later than the arrival time of the preceding pulse that the total power density in the region at any instant is less than the given power density. Thus, the effective total power density of the radiation directed through the region may exceed the given power density without adversely affecting any pulse or substance in the region. Typically, the region comprises an amplifier from which each pulse emerges at an angle differing by at least its divergence angle from the emergence angle of every other pulse (or, if at a smaller angle from another pulse, with opposite polarization therefrom). Each emerging pulse is separated from the others and is directed along a path of such length as to cause it to arrive at the selected location substantially simultaneously with the other pulses (or, alternatively, at such time relative to the other pulses as to provide a predetermined effective combined pulse shape at the location).

Directing radiation

Methods and apparatus for directing a radiation pulse from a laser to a target or other selected location and preventing undesired earlier radiation from the laser having less than a selected intensity from reaching the selected location. A beam splitter directs a major portion of the radiation pulse energy along a longer main path to a predetermined region and continuing on toward the selected location, and directs a minor portion along a shorter secondary path to the predetermined region. A reflective surface on a transparent support in the predetermined region prevents energy having less than the selected intensity from continuing on toward the selected location. The surface comprises a thin layer, as of aluminum, that remains substantially unimpaired until it is subjected to radiation having at least the selected itensity, and then is substantially removed in the area impinged by such radiation, so that when the minor portion of the radiation pulse energy along the shorter secondary path has at least the selected intensity, and thus substantially removes the impinged area of the reflective layer, the major portion of the radiation pulse reaching the predetermined region thereafter can continue on through the area of removal toward the selected location. Alternatively, the minor energy portion actuates an electrical discharge to vaporize the reflective layer at least substantially.

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Upper Arlington, OH, United States of America

Bernerd E Campbell