A detector for use with an EUV photon source emitting around 11-15 nm includes
at least one multilayer mirror for reflecting the beam along an optical path include
a detector element, a filter for reducing the bandwidth of the beam, and the detector
element. The detector element preferably comprises a Si pn diodes with doped dead
region and zero surface recombination or PtSi-nSi barrier for increasing the long
term stability of the detector.