Radiation Detection
One of my other hobbies that started my interest in fusion is radiation detection and repairing old detectors. The picture above only shows a couple of my detectors from a range of decades. I found interest in many safety systems such as radiation detection, shielding, and High Voltage safety.
My Radiation Detection Evolution
I started out with a cheap Geiger-Muller (GM) counter that I got for one of my birthdays when I was a teenager. We took road trips to many significant destinations like the Experimental Breeder Reactor 1 (EBR-1). My interest in detection grew from seeing the many types of detectors they had in their labs. I upgraded to a better GM counter that had a Mica window to detect alpha particles as well as beta and gamma. I brought this across the country to antique shops and the like. It wasn’t until 2021 that I started looking at professional-grade detectors. The most widely used was the industry-standard Ludlum and pancake probe. I found a used model 3 that was not working, but when I took it apart, I found significant corrosion on one of the boards. One of the major benefits to owning an older detector is that they almost always contained a circuit diagram inside the case making repairs very easy, compared to the modernized IC electronics with no user-repairable parts. I cleaned this up and repaired one of the traces with copper wire and it immediately started working.
I enjoyed repairing the Ludlum enough that I sought out other detectors that were originally out of my price range when sold as working. I bought the ubiquitous trio of bright yellow Civil Defense Victoreen detectors from the 1960’s and 70’s. Only one of them worked when I received it which was thankfully the more complex GM counter. I made minor repairs on the two ion chamber detectors and got them back up and working.
After these repairs, I started to fall down the inevitable rabbit hole of chasing detector sensitivity. This is what lead me to the realm of scintillation detectors. These have unparalleled sensitivity for their size, and come in many different types for a range of applications. I purchased a Ludlum scintillation probe that could be used by my Ludlum detector and I was amazed by the sensitivity. I could detect the natural Uranium content of a granite table with this. I started finding more and more interesting scintillation detectors for sale, including a very cheap option from a decommissioned medical gamma camera. These were very narrow detectors that only sold for $60 because there were so many and used a proprietary coaxial connector. I purchased one to try replacing the connector with a standard BNC. This was a very successful operation and I now keep a couple on hand if I need a spare detector.
Neutron Detectors
When I started building my fusor, the first neutron detector I purchased is also my oldest detector, an Eberline PNC-1 Neutron Counter. It has the beautiful hammer-tone silver paint and chrome handle standard for the era as well as a dual logarithmic meter face. It uses a small N. Woods BF3 tube in an included HDPE moderator block. It was sold as not working, but the corrosion was worse that what I originally saw. The meter face works when checking the battery and HV is produced, but no detections are registered. There is significant corrosion on one of the daughter boards that handles the pulse counting. I believe I can repair it, but it was too big of a task for me to take on at the time, so I explored other options. I briefly tried piecing together my own detector system using a Ludlum 2221 Scaler/Ratemeter and the BF3 tube from the PNC-1, as these tubes rarely go bad. I had too many issues with not knowing if the tube or the detector was working, which is when I found the neutron detection system I use today. I go into detail about it on my Neutron Detection page, but it uses a SI-19N Russian He3 Corona tube. This system has worked extremely well for me.