Transient bubble domain configuration in garnet materials observed using high speed photography

Abstract

The dynamic domain configurations of bubbles in garnet materials have been studied using a sampling optical microscope capable of single exposure photographs with a 10 nsec exposure time. The microscope is an integral part of a sampling system so that the transient shape of the bubble is recorded at various times after a field pulse or, for bubbles in field access devices, during a clock cycle. A triggerable flowing nitrogen gas laser pumping a low Q Rodamine 6G Dye laser is used as an illumination source giving light pulses of ∼1.5 KW for 10 nsec. This light is sufficient to expose Kodak 4 × 16 mm movie film. Standard pulse generators (HP 214A) are used to make free bubble radial velocity measurements. A modified generator allows free bubble collapse measurement to be made. For bubbles propagating at operating frequency within field access devices, a standard bubble exerciser is used, synchronized to the sampling system. In this case, special samples with an internal mirror and epi-mode illumination are used. Illustrative results of bubble domain shapes in a chevron propagating structure and a 90° chevron expander detector are included.