I'm pretty sure I got my system from the same person. There are a lot of good points about that system, but needs some work and adjustment to make it work properly. It seems in my experience to detect neutrons properly with a sufficient amount of moderator. In my case that's 4 inches of HDPE and 12 quarts of mineral oil (motor oil) all surrounding the corona tube.
In my case I use a copper tube 1" diameter (from Home Depot, plumbing section) in which I inserted the neutron tube wrapped in a few layers of plastic wrap to make a tight fit. The copper tube has one end closed with a copper cap soldered on, and the other end has the SHV connector threaded through a hole in another similar cap. The copper cylinder is electrically connected to ground. I haven't run extensive tests yet but I think it should provide enough screening. Will post in the relevant section of the forum when I have more data.The Faraday cage is an excellent point too. Do you think maybe a cylinder of paraffin wax wrapped in a grounded tin foil shell would work?
That was a superfluous question of my part. As you're not using the helium during the actual fusion attempts the purity shouldn't matter. Much.Yes bottle under the table is helium, and according to the supplier it is at least above 80% purity. I don't exactly have access to a mass spectrometer, so I don't know the exact purity, but its a whole lot cheaper then the laboratory grade stuff, and it seems to be working just fine.
BTW, I don't know which version of the application program (pulsecounter.exe) you are using. If yours has in the setup section parameters for the sampling frequency, delay at starting of the counting and minimum pulse size then you have the latest version I know of. If not, you can request the latest version from the vendor, or I can send it to you. There is presumably another version in the pipeline that will add more features (though those would be targeted more at gamma spectroscopy and not really useful for neutron counting).