Measurement of cathode luminescence efficiency of phosphors for micro-channel plate based x-ray framing cameras

From a point of a signal-to-background ratio, phosphors are a key component of micro channel plate (MCP) based x-ray framing cameras. In an MCP based framing camera, x-ray signal is converted to electrons, gated, amplified, and converted back to optical signal on the phosphor. To operate x-ray framing cameras in a harsh neutron induced radiation background of the National Ignition Facility, cathodeluminescence efficiency of the phosphor is very important. To avoid MCP damage due to high voltage breakdown, we have been operating phosphors below 3kV (acceleration field < 6 kV/mm). The signal-to-background ratio the camera can be significantly improved by increasing the phosphor potential to 10kV. We measured conversion efficiencies of standard phosphors at electron energies of 0.5 ~10 keV and assessed achievable performance of them with using a numerical model.