Subnanosecond optical gating and irising properties of different types of microchannel plate image intensifiers (MCPII)

摘要

Proximity focused microchannel plate image intensifiers (MCPIIs) with a mesh underlay photocathode are analyzed for their irising time. It is found to be of the order of 650 ps for early prototypes. This is much longer than previously reported but is finally explained by the mesh thickness. Increased metal layer thickness provides highly nonlinear increase of mesh conductivity. Modified tubes show irising below 100 ps. It is expected to be only limited by its theoretical 40 ps minimum time caused by the propagation speed of the electrical field strength's change. A newly introduced impedance match has real broadband characteristics, and the irising is fully caused by other effects. The minimum gate time observable was clearly below 1 ns. The earlier investigated prototype mesh underlay MCPIIs did not open to its full diameter at the shortest applied times. Ni underlay photocathodes were analyzed for comparison. They also provide irising times down to 200 ps. The long laser diode pulse and a too flat voltage slope of the driving generator prevented exact results for subnanosecond gate timing. Continued development of the system is underway.