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Photon counting head



The H7421 series is a photon counting head device containing a metal package photomultiplier tube having a GaAsP/GaAs photocathode and a thermoelectric cooler. The thermoelectric cooler reduces thermal noise generated from the photocathode which also offers a high quantum efficiency, allowing measurement to be made with a good S/N ratio even at very low light levels. The H7421-40 has high sensitivity on wavelength from 300 nm to 720 nm. The H7421-50 is sensitive over a wide spectral range from 380 nm to 890 nm. The photomultiplier tube is maintained at a constant temperature by monitoring the output from a thermistor installed near the photomultiplier tube and regulating the current to the thermoelectric cooler.

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Photocathode Area Shape Round
Photocathode Area Size Dia.5 mm
Wavelength (Short) 380 nm
Wavelength (Long) 890 nm
Wavelength (Peak) 800 nm
Dimension (W x H x D) 56.0 x 36.0 x 104.0 mm
Input Voltage +4.5 to +5.5 V
Max. Input Voltage 6 V
Max. Input Current 50 mA
Count Senstitivity at 400 nm Typ. 3.3 x 104 s-1・pW-1
Count Senstitivity at 500 nm Typ. 1.6 x 105 s-1・pW-1
Count Senstitivity at 600 nm Typ. 2.7 x 105 s-1・pW-1
Count Senstitivity at 700 nm Typ. 3.4 x 105 s-1・pW-1
Count Senstitivity at 800 nm Typ. 3.9 x 105 s-1・pW-1
Count Senstitivity at 900 nm Typ. 2.8 x 103 s-1・pW-1
Count Linearity 3.9 x 105 s-1
Dark Count Typ. 125 s-1
Dark Count Max. 375 s-1
Pulse-pair Resolution 70 ns
Output Pulse Width 30 ns
Output Pulse Height Min. 3 V
Output Pulse Height Typ. 3.6 V
Recommended Load Resistance 50 Ω
Signal Output Logic Positive logic
Operating Ambient Temperature +5 to +35 ℃
Storage Temperature -20 to +50 ℃
Weight 340 g

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