Single Photon Detection With Photomultipliers

Unless you are an audiophile, you likely think of tubes as mostly relegated to people who work on old technology. However, photomultiplier tubes are still useful compared to more modern sensors, and [Jaynes Network] has a look into how they work, especially with scintillating detectors.

The RCA photomultiplier he examines has ten stages and can detect even a single photon. Combined with a scintillating detector, they make good radiation detectors.

We can’t help but smile when we hear someone obviously in love with the engineering behind a tube like this. We get it. The inside of the tube is crowded, so it is hard to identify the dynodes and other portions, but some diagrams make it readily apparent how the tube does its job.

We were impressed with how good the documentation that came with the tube looked, considering its age. We mean the condition it was in. The document itself was obviously a reproduction of a typewritten document with hand-drawn figures and graphs.

We were hoping for some footage of the tube in action, but we’ll have to wait for a future video. We are betting that is coming, though. Although there are some solid-state detectors, they are not suitable for all applications. There was a time, though, when the tubes were in many applications, including X-ray scanners and photography equipment.

25 thoughts on “Single Photon Detection With Photomultipliers

  1. Ibought a EMI 9558QA from a ditch auction site and it arrived in shatters. A lot of people still think postal services carry parcels with velvet gloves and put them on a cushion in a slow driving truck…

  2. When I worked for Xerox Research (UK) the image quality group used a photomultiplier in a micro-densitometer for measuring the MTF of imaging systems. A friend of mine who worked in the group bought a Sinclair digital watch. Wherever he went near the test system his watch would malfunction because of the high voltages!

  3. There is a big tank of dry cleaning solution out west somewhere. Same stuff as your local dry cleaner, except a whole dam lot of it. PMT’s are loaded all around inside the tank. The experiment is looking for the photon given off by a collision of a neutrino and the solution. Of the billions that pass through the earth everyday nothing stops them. Except a random collision and a photon given off. Yes they caught a photon event. Took a long time.

    The experiment did not go unnoticed. A close-hanger salesman came knocking with an enquirer.

      1. According to your link, that’s in Japan, not “out west,” and it also uses ultrapure water, not drycleaning chemicals.

        Otherwise yeah, thousands of these photomultipliers all around. Cool.

          1. Ray Davis’s neutrino detector experiment proved that neutrinos can changed from 1 of the 3 kinds in another, which basically means that neutrinos have mass. This is one of the most important phyisics findings of the last century and Ray got the Nobel price for it.
            I worked in the same Nuclear Chemistry departments at Brookhaven National Lab where Ray spent his whole carreer. He was very, very nice guy. Unfortunately his brain was not was it used to be anymore when he finally got the Nobel price. He passed away 4 years later.
            If you go into the Chemistry department basement you might still find containers with Ray’s ‘cleaning fluid’ with a sign on it that says “Do not throw out! Ray Davis”.

  4. In the 1980s Liquid Scintillation (radiation) counters used to be quite common in hospitals and research centers . A sample was dissolved in a scintillator that would emit a photon following radioactive decay. This was picked up by photo multiplier tubes.

  5. I worked with PMTs used in laboratory instruments. If they were accidently exposed to room light they would literally melt down which I unfortunately have first hand experience.

    1. From what I understand if they are not powered up, they calm down after a while but they do go blind for a bit after being exposed to light. I am not sure how or why being powered up would make much difference except they would pull a lot more current. That may be why they called for 2 watt resistors in the divider. I saw the paint bucket scintillator and they used little resistors in the divider. I can think of two reasons to use larger ones. One is obviously if it gets hit with light the current it may pull and the other is they are physically larger parts so you have less of a chance of arcing. I saw a couple 1 megohm resistors from some kind of a high voltage toy the other day and they were about 3 feet long.

  6. “Unless you are an audiophile, you likely think of tubes as mostly relegated to people who work on old technology”. Dont forget the magnetron in your microwave oven, the traveling wave tubes on satellites, the X-ray tubes in medical equipment and the vacuum fluorescent display in your HiFi

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.