photocathode types

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Photocathode materials used in Electron Tubes photomultipliers are :

solar blind (KBr, CsI, RbTe, CsTe)
these photocathodes are sensitive to vuv and uv light only - hence the name. The long wavelength response can be extended between 170 nm to 370 nm dependent on which photocathode material you choose.

high temperature bialkali (Na-K-Sb)
recommended for operation at high temperature because of its very low dark current. This photocathode is also suitable for applications in low level light detection.

S11 (SbCs)
one of the earliest photocathodes with a spectral response covering the ultraviolet and visible range.

bialkali (Sb-K-Cs)
this photocathode has mostly superseded the S11, offering better blue response and lower dark current.

rubidium bialkali (RbCs -Sb)
offers high blue and enhanced green response    but with twice the dark current of the bialkali.

S20, trialkali or multialkali (Na-K-Sb-Cs)
the multialkali photocathode response extends from uv to the near infra-red.  It has high light level capability but may require cooling to reduce dark current.

The photocathode is deposited as a semitransparent layer directly on the inside of the window.

The choice of photocathode together with the window type will determine the wavelength detection range.

For more detailed information, request our brochure "Understanding photomultipliers" via this form.