Battelle Memorial Institute

Battelle Development Corporation

Philip J Mallozzi

Harold M Epstein

David C Applebaum

William J Gallagher

Bernerd E Campbell

Barry P Fairand

Richard G Jung

Myron C Muckerheide

Robert E Schwerzel

Ronald L Uecker

Apparatus for providing X-rays (11) to an object (12) in air. A lens (13) directs energy (14) from a laser (27) onto a target (15) to produce X-rays (11) of a selected spectrum and intensity. A substantially fluid-tight first enclosure (16) around the target (15) has a pressure therein substantially below atmospheric pressure. An adjacent substantially fluid-tight second enclosure (18) contains helium (24) at about atmospheric pressure. A wall (19) has an opening (20) large enough to permit X-rays (11) to pass through and yet small enough that gas (21) can be evacuated from the first enclosure (16) at least as fast as it enters through the opening (20) at the desired pressure. Intermediate enclosures (34, 34') at logarithmically increasing air pressures have similar openings (20', 20') in line with the opening (20) and a transparent portion (36) in the near wall (35) of the second enclosure (18). The target (15) is located close to the opening (20) and emits a substantial portion of the X-rays (11) through the opening (20) and (via 20',20',36) on toward the far wall (22) of the second enclosure (18) having a portion (25) that is highly transparent to them, so that the object (12) to which the X-rays (11) are to be provided may be located outside the second enclosure (18) and adjacent thereto and thus receive the X-rays (11) substantially unimpeded by air or other undesired intervening matter.

Providing X-rays

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

Method and apparatus for applying radiation by producing X-rays of a selected spectrum and intensity and directing them to a desired location. Radiant energy is directed from a laser onto a target to produce such X-rays at the target, which is so positioned adjacent to the desired location as to emit the X-rays toward the desired location; or such X-rays are produced in a region away from the desired location, and are channeled to the desired location. The radiant energy directing means may be shaped (as with bends; adjustable, if desired) to circumvent any obstruction between the laser and the target. Similarly, the X-ray channeling means may be shaped (as with fixed or adjustable bends) to circumvent any obstruction between the region where the X-rays are produced and the desired location. For producing a radiograph in a living organism the X-rays are provided in a short pulse to avoid any blurring of the radiograph from movement of or in the organism. For altering tissue in a living organism the selected spectrum and intensity are such as to affect substantially the tissue in a preselected volume without injuring nearby tissue. Typically, the selected spectrum comprises the range of about 0.1 to 100 keV, and the intensity is selected to provide about 100 to 1000 rads at the desired location. The X-rays may be produced by stimulated emission thereof, typically in a single direction.

Applying radiation

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

A method of producing X-rays by directing radiant energy from a laser onto a target. Conversion efficiency of at least about 3 percent is obtained by providing the radiant energy in a low-power precursor pulse of approximately uniform effective intensity focused onto the surface of the target for about 1 to 30 nanoseconds so as to generate an expanding unconfined coronal plasma having less than normal solid density throughout and comprising a low-density (underdense) region wherein the plasma frequency is less than the laser radiation frequency and a higher-density (overdense) region wherein the plasma frequency is greater than the laser radiation frequency and, about 1 to 30 nanoseconds after the precursor pulse strikes the target, a higher-power main pulse focused onto the plasma for about 10.sup.-3 to 30 nanoseconds and having such power density and total energy that the radiant energy is absorbed in the underdense region and conducted into the overdense region to heat it and thus to produce X-rays therefrom with the plasma remaining substantially below normal solid density and thus facilitating the substantial emission of X-rays in the form of spectral lines arising from nonequilibrium ionization states. The X-rays may be produced essentially as from a point source (i.e., they are spatially coherent) and thus are suitable for many applications that would otherwise require an X-ray laser. In some embodiments phase coherence is achieved, thus providing a true X-ray laser. In a similar method, providing a controlled nuclear fusion reaction, the target comprises alternate layers of high-Z and lower-Z material.

Producing X-rays

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.

Growing community of inventors

Columbus, OH, United States of America

Philip J Mallozzi