Lattice dynamics of materials under high strain is a field of great interest in material physics. Scientists at KEK, along with a team at TITECH and JST have managed to observe time-series of shock-induced lattice deformation processes of cadmium sulfide (CdS) single crystal by 100-ps time-resolved single-shot Laue diffraction method.
 
The Photon Factory-Advanced Ring at KEK is a 6.5 GeV storage ring which is operated for dedicated single-bunch mode, and suitable for 100-ps time-resolved x-ray studies. A beam line NW14A was constructed for the time-resolved x-ray studies, and this work was done by utilizing this capability. This new technique, which produces a single-shot Laue diffraction image only by a single-bunch x-ray pulse with duration of 100 ps, enabled to fully explore irreversible process like lattice deformation and explosion of single crystals after intense laser excitation.
 
The scientists successfully observed the irreversible shock-induced processes in detail; the shock wave propagates in the crystal at 4.20.5 kms, and the maximum pressure by the shock compression reaches up to 3.92 GPa with 4.4 of volume compression. Although the maximum pressure is above the threshold pressure of phase transition from wurtzite to a rocksalt structure, the incubation time at the maximum pressure (10 ns) was not long enough to promote the phase transition, and the compression remained uniaxial and elastic. In other words, a transient state of CdS crystal above Hugoniot elastic limit was successfully observed by this shock compression experiment.
 
K. Ichiyanagi, S. Adachi, S. Nozawa, Y. Hironaka, K. G. Nakamura, T. Sato, A. Tomita and S. Koshihara, "Shock-induced lattice deformation of CdS single crystal by nanosecond time-resolved Laue diffraction", Appl. Phys. Lett. 91, 231918 (2007)
 
 

Figure 1  :  Time-series of Laue diffraction images of shock-induced lattice deformation processes of cadmium sulfide (CdS) single crystal. Each diffraction image was obtained only by a single-bunch X-ray pulse with duration of 100ps.