Electronics > Projects, Designs, and Technical Stuff
A decent photomultiplier / scintillation preamp
ChristofferB:
It's in the upper end of the scale of preamp gain. Maybe a lower gain would be nice in that it could allow for higher pmt voltages.
Right now the scintillation probe runs at 600-700v which is quite low.
Muon interactions are usually so energetic that the signal just saturates completely. I see a few per minute, but they dont make it to the multichannel analyzer, so I assume the pulse pileup rejection recognizes the messed up peak shape and vetoes the count.
jmelson:
--- Quote from: ChristofferB on July 20, 2020, 10:50:31 pm ---Hi all!
I've been searching far and wide for a PMT preamplifier for scintillation spectroscopy - that is: a charge sensitive preamp for PMT's coupled to scintillation crystals.
--- End quote ---
TL072? Yikes, how 1980's. That will only work for very slow scintillators. There are much better and faster op-amps now available.
Of course, if the TL072 is good enough for your application, then fine. For general-puepose op-amps, I've used the OP275 in a lot
of stuff.
Jon
ChristofferB:
Well this is specifically made for NaI(Tl) scintillators which are some of the slowest in use. I'd previously used EL2006 op amps but had some stability issues.
The OP275 looks nice, though, and is pin compatible. Maybe I should upgrade.
Kleinstein:
The op275 is more like an odd one - kind of hybrid between BJT and JFET. It is not really suited for high impedance. For direct upgrade of the tl072 I would more consider OPA2172, OPA1642 or OPA2134. The speed and noise is comparable to the op275, but without the high bias.
calzap:
quote from Andy3055:
Some 30+ years back I worked for a company that supplied Gamma counters among other laboratory instruments to universities, research institutes and hospitals. One brand we dealt with was LKB based out of Sweden, if I remember correctly. Those machines always had 2 PMTs and the noise in one of them (not visible to the sample) was used to cancel out the noise signals from the "counting" PMT, leaving the "required" signals usable. The 2 PMTs had to be factory matched and replaced together if required, for obvious reasons. Does your design take this sort of thing into consideration?
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LKB still makes radiation counters. They were based in Sweden, but are now in Australia. The concept you were referring to is called coincidence counting. AFAIK, it has always been used in liquid scintillation counting. In crystal scintillation counting, it is used in high-end counters, but not low-end. The most massive example of coincidence counting is the LIGO system of gravitational wave detection.
Mike in California
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