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 740 nm. The H7421-50 is sensitive over a wide spectral range from 380 nm to 920 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.


Photocathode Area Shape Round
Photocathode Area Size Dia.5 mm
Wavelength (Short) 380 nm
Wavelength (Long) 920 nm
Wavelength (Peak) 730 nm
Dimension (W x H x D) 56 x 36 x 104 mm
Input Voltage +4.5 to +5.5 V
Max. Input Voltage 6 V
Max. Input Current 50 mA
Count Senstitivity at 800 nm Typ. 5.1 x 105 s-1・pW-1
Count Linearity 1.5 x 106 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 395 g

Contact us for more information.

  • Literature
  • Price
  • Delivery
  • Custom order
  • Support
  • Other

Contact us