A
photo-emissive detector inside an evacuated envelope with a transparent window, the photocathode, and the
anode. The photocathode can be opaque or semitransparent.
Source:
PAC, 1995, 67, 1745
(Nomenclature, symbols, units and their usage in spectrochemical analysis-XI. Detection
of radiation (IUPAC Recommendations 1995))
on page 1752