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

Abstract

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.

Simulation and design of a fast neutron radiography detector based on MCP

“…Another factor that affects the detector's spatial resolution is the diffusion of the electron stream emitted from the MCP. Because the energy of the electrons from the MCP is too low to excite luminescence efficiently [21,22], an electric field (E) is usually added to the MCP-PS gap (d). This electric field can not only accelerate the electrons but also suppress the electron stream's diffusion.…”

“…When d is set as 2 mm, the diameter of the electron stream is about 100 µm, which is comparable with the HDPE's spatial resolution. Moreover, the PS's luminous efficiency is almost saturated when d = 2 mm and −2 kV/mm [21]. To ensure the PS's luminous efficiency and spatial resolution, the gap between MCP and PS is selected as 2 mm.…”