The ARC petawatt laser system is designed to achieve extreme laser intensities through chirped-pulse amplification: an ultrashort laser pulse, only picoseconds or femtoseconds (10^–12 to 10^–15 seconds) long, is first stretched in time to reduce its intensity. The pulse’s frequency content is distributed in time to create a nanosecond-long (10^–9 second), frequency-swept (chirped) pulse that can be safely amplified without generating intensities above the damage limit of laser glass and optics. After amplification, the chirped pulse is passed through an arrangement of diffraction gratings (pulse compressor) to undo the frequency sweep and re-create the initial short pulse, producing a high-energy, high-power laser pulse which will be used to take x-ray images of NIF implosions and other high-energy density physics processes with tens-of-picosecond temporal resolution.