Table-top picosecond sources

A paper by C. Rose-Petruck et al., Nature 398, 310-312 (1999) brings together X-ray diffraction and picosecond ultrasonics. X-ray pulses with tens of picoseconds to nanosecond duration were used to study shocked and annealed crystals and photo-initiated reactions within proteins. The picosecond X-ray barrier was broken following rapid developments in high-power laser technology.

Rose-Petruck et al. describe the generation of picosecond bursts of copper Kα radiation by irradiating a thin copper wire with a shortpulse high-power laser. This ultrashort radiation is used to measure the response of a gallium arsenide (GaAs) crystal to sudden heating. This did not require a large facility and uses equipment of a cost and scale commensurate with the ambitions of a well-equipped university department. It may ultimately allow changes in electron density to be monitored during biological and chemical reactions, with femtosecond resolution.