A photoemission plate-type photon beam monitor has been fabricated and tested using a HeI (21 eV) lamp light source. The sensitivity ΔI IΔs, obtained by using a picoammeter (Keithley Model 617), is 3.38/mm for both OFHC copper plate and tungsten plate which agrees with the theoretical value. Current-voltage converting and voltage-amplifying electronics have also been devised to measure the sensitivity directly. The degradation introduced by the offset voltage of the electronic components has been analyzed. The sensitivity of this monitor has been verified to depend on both the integral part of the spatial distribution of the light on the plate and the background current generated by the picoammeter.
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