I’ve bought a couple of FEU84-5 PMT’s from an eBay seller. I’ve bought because of an occasional low price and because I heard that this tube is very good for gamma spectrometry.
I’ve extensivelly tested it with a 30 dia. 40 lengh (mm) CsI(Tl) crystal. Result? This tube is useless. It’s resulting FWHM at 662keV vary from 11 to 13% uppon voltage setting. The same crystal coupled with a FEU85 that’s a bialkali tube not a multialkali like FEU84-5 gived me 7-7.5%. I’ve expected a better result from FEU84-5 because it’s multialkali photokatode is designed to couple with 550nm-light emitting crystals like CsI(Tl) but obtained better results from FEU85 that’s made for 420nm light. Ha ha ha! FEU84-5 –> trash bin.
GENERAL SPECIFICATIONS Photocathode - antimony-potassium-sodium-cesium Optical input - front The diameter of the working area of the cathode - 25mm The number of amplification stages - 12 Wavelengths of maximum sensitivity - 420-550 nm green light Dark current - < 50 nA Sensitivity of the photocathode - 80 uA/lm Anode sensitivity - 80 A/lm Life time - more than 1000 hours Maximum Ratings : Max Voltage - 1900 V Max anode current - 5 micro A
It comes into a cardboard envelope with some sponge that starts to disintegrate after 30 years of storage. Nothing to complain… some paper and alcool and I’ve cleaned the tube.
This version of the tube doesn’t have a socket, it have just some teflon insulated wires. This is not bad…there is no need to buy a proper ceramic socket.