background

home • the photomultiplier

Output from a photomultplier is obtained even in the absence of light input; this is referred to as dark current in dc application and dark count in pulsed applications also referred to as background.

The dark current or dark count varies considerabley even for photomultipliers of the same type. However, the following points are important when choosing a photomultiplier.

• dark current and dark count rate increase with photomultiplier diameter
• dark current and dark count increase with temperature
• dark current increases approximately linearly with gain
• dark count rate is essentially independent of gain

Electron Tubes can provide photomultipliers selected for low dark current or dark count, to special order.

Further reading; download a copy of our technical reprints, in PDF format:

RP/063 - Basic physics and statistics of photomultipliers.

RP/067 - Test parameters and general operating rules for photomultipliers.

RP/075 - An investigation of photomultiplier background.

RP/076 - Determination of the multiplier gain of a photomultiplier.

RP/092 - Photomultipliers for low background applications.

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