SPATIAL UNIFORMITY AND UV SENSITIVITY OF MICROSPHERE PLATES (MSPS)

We have recently reported on a detailed study of basic microsphere pla te (MSP) operation [A.S. Tremsin et al., Nucl. Instr. Meth. A 368 (199 6) 719]. In this paper, we describe, with specific regard to imaging a pplications, the spatial uniformity of MSP quantum efficiency and gain . Measurements were made using 0.7 and 1.4 mm thick MSPs, both ''bare' ' (nichrome-electroded) and coated with an Al layer for enhanced UV de tection efficiency. As might be expected from the granular structure o f the MSP, the relative variation in pulse gain dG/G was found to decr ease with scale size, falling from similar to 12% when averaged over 0 .18 mm areas to similar to 7% for 1 mm square cells. The efficiency of the Al-coated MSP to 2540 Angstrom radiation was one order of magnitu de higher than that of the bare plate. The details of image transfer f rom the input to the output face of the MSP were measured by scanning a fine slit across the working diameter of the detector.