| 摘要 |
PROBLEM TO BE SOLVED: To provide a photo-detecting tube which selectively detects only the light of wavelength near 125 nm. SOLUTION: The detecting tube 1 is provided with an incidence window 3 and a photocathode 5, the incidence window 3 is made of MgF2 , and the photocathode 5 is made of KBr. The MgF2 selectively transmits the light of wavelength >= about 90 nm, and the KBr selectively and photoelectrically converts the light of wavelength <= about 160 nm. Thus, in the photo-detecting tube, the peak of detecting sensitivity lies in wavelength 125 nm, and only the light of wavelength 125 nm±about 35 nm can be selectively detected without an optical band-pass filter.
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