Imaging properties of a delay line readout using large microchannel plates

Measurements made on the readout of large microchannel plates (MCPs) with crossed delay line anodes are reported. Two chevron pairs of MCPs were used: a 127-mm-diameter circular pair and a 100-mm×100-mm square pair. The modal gain varied over the surface of the MCPs by as much as a factor of three, both before and after extensive UV scrubbing. Attempts to decrease the variations in gain by further full flood scrubbing and by spot scrubbing the high-gain areas were unsuccessful. The full width at half maximum (FWHM) of the charge distributions was 100% before the scrubbing and improved to 45% afterwards. Characteristic deviations from spatial linearity for the delay line anode are presented. For positions within a diameter of 120 mm, the deviations from linearity were less than ±150 μm. For MCP gains greater than 3×10⁶, the FWHM spatial resolution was measured. The resolution at the center at the MCPs was 54 μm, while at the edge (57 mm from the center) it was 64 μm