Performance characteristics of a chevron expander

Domain motion and stretching in bubble device chevron expander stacks is characterized over the frequency range 100 kHz to 500 kHz. Lateral motion through the stacks shows stable resting positions at the two ends and at the center of the chevrons with the strip transferring quickly between these. The transfer requires a progressively longer phase angle as the frequency is increased, and this reduces the resting phases correspondingly, e.g., at the apex from 45° at 100 kHz to 10° at 500 kHz. Transverse expansion takes place principally during the pauses at the ends of the chevrons. The form of the stretching is largely linear with phase, but slows to a limiting value before a lateral transition occurs. However, the linear region reduces in phase-width at increased frequencies to allow only minimal expansion, combined with a small contraction when crossing the gap between stacks, at frequencies above 400 kHz. Some asymmetry in the stretching is noted, related to different velocity variations with bias in the two directions.