PMT preamp

[plesa]

I do not want  to start the flame, but what you suggested require high output current of PMT. With this it will be difficult to measure the dark counts  nor detection of sigle photons or some light pulses with e.g. neutral density filter.
Just try it ;-)

I assume you mean sending the output of the PMT into a 50 ohm scope input? Works fine on high gain PMTs, even for single pulses. Low gain devices (mostly not intended for photon counting anyway) may struggle to produce pulses high enough for some scopes scope to trigger on, but a high gain PMT can produce pulses of several millivolts.

http://www.triumf.ca/sites/default/files/lecture_SignalRecovery_PMT_SRS.pdf

It is nice theory :-) We are talking about the old PMT (FEU68/31) these Russian PMT has a gain 2x10^4 (at 1.4 kV) when new. Base on their lifetime (1000h) I expect they are beyond.
So it is imposible to make the test you described.
With new PMT and gain about >10^7 it can be possible but you need to spend several hundred EUR on PMT.

[Wim_L]

Indeed, that won't work then. But a device with such characteristics isn't likely to be suitable for counting scintillations anyway. Such low performance photomultipliers do have their purposes, but most of what they do, a modern photodiode (perhaps of the avalanche type) will do better.

[Dajgoro]

I do have a cheap APD, the AD500, but I haven't tried it yet. Also, the die is kinda tiny and the surface of the PMT tube is way bigger.

[plesa]

Your mentioned APD is for photon counting useless. As alternative are popular MPPC nowadays.

[Dajgoro]

Your mentioned APD is for photon counting useless. As alternative are popular MPPC nowadays.

I am guessing those must be expensive, since I couldn't find a price.

[plesa]

Price is almost on the same level like PMT.
Lot of useful information you can find in
http://www.edm.ethz.ch/teaching/vp/mppc

[penfold]

The PMT lifespan issue isn't necessarily a problem, we have a 1970's scintillation counter that's been turned on for nearly its entire life and its just as good as it once was.  The PMT really needs to be properly shielded from interference, they'll be the ambient static magnetic fields that'll affect the gain, but more importantly there's a lot of high impedance nodes they'll have as much of a problem, so in short you really need to keep it inside something like a paint tin with coax feed-throughs for your terminations. (as per the diyphysics link posted earlier)

The PMT will probably need to 'relax' for a while before any dark counts die down to their ideal values.  As a rough guide a scintillation probe with a 2mm x 1 inch diameter sodium iodide crystal that i'm familiar with starts up counting about 10k counts before settling down to about 10 counts/second after a minute or so, and those are only the counts that come into the discriminator window.

If you need a sanity check on whether that noise is related to your dark counts, store the PMT in the fridge or freezer for a little while, and see if the noise changes characteristics at all.

A good trick for eliminating the dark counts is to use a coincidence counter.  In its simplest form its basically an AND gate with fast monostables on the inputs, but that all depends whether you can couple two PMTs onto the scintillator.

Coupling to the scintillator is also a problem in its own right, you need very clean and polished surfaces and some optical coupling grease,