Closure of pinholes under intense laser radiation

The closure of pinholes due to plasma created by intense laser radiation interacting with the pinhole perimeter is studied. Pinholes with 100-300-microm initial diam close in 3-14 nsec, respectively, for a 10-nsec FWHA, 10-J incident laser pulse. For a constant focal spot size and pulse duration, the closure time and rate are found to be a function of laser energy; however, the energy transmitted through the pinhole is independent of the incident energy for the pulse duration, pinhole diameters, and focal spot size used in these experiments.