IMAGING BAND-PASS ANALYZER USING DOUBLE 90-DEGREES SPHERICAL ANALYZERS

The design and testing of an imaging band-pass analyzer (BPA) consisti ng of two 90-degrees spherical sectors operating in a magnetic-field-f ree region is described. Image electrons injected nearly parallel to o ne another and perpendicular to the first 90-degrees sector are focuse d into an energy plane where electrons of desired energy are band-pass filtered. A second 90-degrees sector is used to recover the energy-fi ltered image. With a 1-mm aperture, energy resolution of 1% and spatia l resolution of 0.01% of the main path radius are calculated and agree well with the test results over an image size of 12 X 12 mm2. The add ition of this analyzer to our magnetic projection photoelectron micros cope poses an additional technological problem in that the electrons a re required to pass from a relatively high-field area to a field-free region without disruption of the image. Design considerations for a st ructure that abruptly terminates a magnetic field yet is transparent t o image electrons are described.