FGS Detectors
The FGS PMTs (four per FGS) are end-illuminated, 13 stage venetian blind dynode S-20 photon-counting detectors with an effective photocathode area of about 4 mm. The A and B channels for each FGS interferometric axis operate independently. The PMTs are sensitive over a bandpass of 4000-7000A, with an efficiency of ~ 18% at the blue and diminishing linearly to about 2% at the red end.
The FGS1r dark counts for each channel are given in Table 2.1.
Table 2.1: FGS1r Dark Counts
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1 Values based on an average of 40Hz PMT counts and associated standard deviations.
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