Dear Photomultiplier Doctor,
What is the meaning of A/lm and how does it relate to the applied high voltage?
Mr. Derek Tam Sing
Rapiscan
Anode sensitivity in A/lm is a measure of the gain of a photomultiplier, but it is expressed in a way that
is of little use to scintillator users (sorry about that). It is an historic, white light, unit that tells you that
at the stated HV you will get 50 Amps if you shine a beam of light of 1 lumen onto the photomultiplier.
As previously stated not at all useful to scintillator users, however, we calibrate the photocathode in
terms of microamps per lumen. If you divide the anode sensitivity by the cathode sensitivity you will get
a dimensionless quantity - the gain. For the 9390B we quote a typical cathode sensitivity of 75 µA/lm,
and 1000V to get 50 A/lm at the anode.
Gain = 50A/lm / 75 µA/lm = 0.7 x 106 as stated in our brochure and in the 9390B data sheet.
Download a copy of the 9390B data sheet, in PDF format, from here.
Regards,
Photomultiplier Doctor.
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