Metal package PMT with Cooler
Photon Counting Head H7421 Series

The H7421 series are photon counting head devices 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 monitor
ing the output from a thermistor installed near the photomultiplier tube and regulating the current to the thermoelectric cooler.