faq 7

Dear Photomultiplier Doctor,

I have some questions about Photomultiplier 9111B80.

1. What is the available operating range of the input light power? We have two laser sources: one of them is Helium-Neon laser which has 4 mW maximum output power and operates at 594 nm; another one is Argon Ion laser which has 500 mW maximum output power and operates at 457~514 nm. Can I use these lasers directly as input light?
2. If the input light power exceeds the available operating range, which causes count overflow, will this result in physical damage to the module?

Wei Wei Wang.

Dear Ms Wang,

Please study the photocathode spectral responses given in our brochure. You will note that the bialkali cathode has a response of 6 mA/W at 594 nm and about 60 mA/W for Argon Ion. Note 4 mW of laser power will give a photocurrent of 6 x 10^-3 x 4 x 10^-3 = 2.4 x 10^-5 amps but for the argon ion the cathode current is 30 mA.

The answer to your question is: no you can't use these to view the lasers. Note that pmts are designed to measure nA or pA of cathode current. You are in danger of doing damage to the photomultipliers.

If these lasers are pulsed then the answers may be quite different based on the pulse duration.

Regards,

Photomultiplier Doctor.

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