Femtosecond X-ray Diffraction: Applications for Laser-Irradiated Materials

• Published in: AIP conference proceedings Vol. 1161; no. 1; p. 253
• Main Author: Wark, Justin S
• Format: Journal Article
• Language: English
• Published: United States 10.09.2009
• Subjects: COHERENT SCATTERING; COMPRESSION; CRYSTALS; DEPTH; DIFFRACTION; DIMENSIONS; ELECTROMAGNETIC RADIATION; ELEMENTS; FREE ELECTRON LASERS; GRAIN SIZE; GRANULAR MATERIALS; IRON; IRRADIATION; ISENTROPIC PROCESSES; LASER RADIATION; LASERS; MATERIALS; MATERIALS SCIENCE; METALS; MICROSTRUCTURE; MONOCHROMATIC RADIATION; PHONONS; POLYCRYSTALS; PULSED IRRADIATION; QUASI PARTICLES; RADIATIONS; SCATTERING; SHOCK WAVES; SIZE; TIME DEPENDENCE; TRANSITION ELEMENTS; X-RAY DIFFRACTION
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.3241197

Over the past few years short pulse x-ray diffraction at the nanosecond and picosecond level has become an established technique in many high-power laser laboratories for interrogating the lattice response of laser-perturbed and shocked matter, and is now finding applications in diagnosing the state of crystalline materials subject to quasi-isentropic compression. We review some of the previous results obtained in this area, for example the direct observation of coherent phonons, the first direct confirmation of the alpha-epsilon transition in shocked iron, and recent measurements indicating that the strength of matter can be measured at shock pressures exceeding a Mbar. The majority of sources used to date have been laser-plasma based, with some work being performed using 3rd generation synchrotron sources. However, the development of 4th generation x-ray free-electron lasers, such as LCLS, afford many new opportunities, with pulse lengths in the femtosecond regime. The extremely low divergence and monochromatic nature of the LCLS beam make it well suited to study compressed polycrystalline matter, especially samples with small grain sizes. At extremely short pulse lengths, such that the pulse is shorter than an x-ray extinction depth traversal time, the diffraction process itself becomes time-dependent, and in certain cases the full wave-field solution will be required, particularly if the matter itself is being rapidly perturbed, as will occur if the intense x-ray radiation is used to create warm dense matter, as in recent experiments on FLASH at DESY.