Observation of a Laser-Driven-Shock Induced Phase Transition in KTP
Abstract
The time-scale for laser-driven shock experiments is 2-3 orders of magnitude faster than gas-gun shock experiments offering great potential to study the dynamics of fast Martinsitic transitions. However, there have been very few studies of laser induced phase transitions since i) phase transitions are more difficult to observe at the very high pressures probed by laser shocks, and ii) phase transition dynamics are generally many nanoseconds and are difficult to observe on a laser-shock time scale. Potassium titanyl phosphate (KTP) undergoes a phase transition with a large volume discontinuity ( 4pressure (5.8 GPa). In static experiments the transition is iso-symmetric (no change in space group), very nearly uniaxial, and the crystal does not fracture. We used a line VISAR (Velocity Interferometer System for Any Reflector) diagnostic to measure the release-wave structure of KTP on the JANUS laser at LLNL. The observed two-wave structure is distinct and the transition stress is very close to the observed DAC transition pressure, so we believe that the phase transition dynamics are very fast. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARA28007E