Showing papers on "Flattop published in 1994"

Gaussian-beam profile shaping by acousto-optic Bragg diffraction.

Abstract: We study how Gaussian laser-beam profiles can be modified into a desired form using acousto-optic Bragg diffraction By exploiting the angular dependence of Bragg diffraction of plane waves by acoustic gratings, we demonstrate that the conversion from a Gaussian-profile beam into either a near-field or a far-field flattop profile is possible

Detailed measurements and shaping of gate profiles for microchannel-plate-based x-ray framing cameras

Abstract: Gated, microchannel-plate-based (MCP) framing cameras are increasingly used worldwide for x-ray imaging of subnanosecond laser-plasma phenomena. Large dynamic range (> 1,000) measurements of gain profiles for gated microchannel plates (MCP) are presented. Temporal profiles are reconstructed for any point on the microstrip transmission line from data acquired over many shots with variable delay. No evidence for significant pulse distortion by voltage reflections at the ends of the microstrip is observed. The measured profiles compare well to predictions by a time-dependent discrete dynode model down to the 1% level. The calculations do overestimate the contrast further into the temporal wings. The role of electron transit time dispersion in limiting the minimum achievable gate duration is then investigated by using variable duration flattop gating pulses. A minimum gate duration of 50 ps is achieved with flattop gating, consistent with a fractional transit time spread of {approx} 15%.