Proton Accelerator
Posted: Wed Jan 14, 2015 10:11 pm
Upon achieving high vacuum reliably with my diff pump I've turned toward getting a nicely collimated beam for shooting protons at my boron target. What you here see is the Van De Graaff generator with the accelerator column penetrating the shell. The test is being performed at about .5 torr and 350 kV. The gas in the tube is ionized air. The high pressure was chosen to make the shape of the beam visible. I was looking for poor beam behavior before I go on to lower pressure with hydrogen gas. The "target" for lack of a better word was just a grounded copper wire located in the center of the accelerator tube. (not visible in this picture.)
No increase in background radiation is observed with this test. No nuclear phenomenon were expected with this test.
This is what it looks like with the lights on.
This is what it looks like with the lights off. I don't have anything better than my smart phone to take pictures. This picture isn't quite as exciting as the purple glow given off in my darkened garage. The beam was very bright, straight, with no streamers running off to the side of the tube wall. I was very excited to see this result. Previous attempts resulted in all manner of bad behavior from the beam line.
Another curious phenomenon occured. When I grounded the VDG terminal with my magic wand, the beam turned orangish and appeared to be tighter and more focused. I think the planar geometry of the end cap of the accelerator column is a factor. I plan to try a couple different configurations of the gas nozzle/end cap to see if I can get a tighter beam yet.
I have a neat video of this test run. The server won't let me post it because it's too big. I doubt I could make it small enough and still provide any useful visuals. If you really want to see it, I can send it to you off the boards.
Air was introduced via a vinyl tube running inside the Van De Graaff drive column. Some people cautioned me about loosing terminal voltage but the leakage doesn't seem to prevent a nice beam. I did take the advice to ground my gas supply tube very near to the VDG. Well... actually... I had to learn the hard way. I got bit (not too bad) by voltage on my brass needle valve even as far away from the VDG as 36 inches of tube length.
The plywood box serves as an environmental chamber. I have a dehumidifier routed to the box.
No increase in background radiation is observed with this test. No nuclear phenomenon were expected with this test.
This is what it looks like with the lights on.
This is what it looks like with the lights off. I don't have anything better than my smart phone to take pictures. This picture isn't quite as exciting as the purple glow given off in my darkened garage. The beam was very bright, straight, with no streamers running off to the side of the tube wall. I was very excited to see this result. Previous attempts resulted in all manner of bad behavior from the beam line.
Another curious phenomenon occured. When I grounded the VDG terminal with my magic wand, the beam turned orangish and appeared to be tighter and more focused. I think the planar geometry of the end cap of the accelerator column is a factor. I plan to try a couple different configurations of the gas nozzle/end cap to see if I can get a tighter beam yet.
I have a neat video of this test run. The server won't let me post it because it's too big. I doubt I could make it small enough and still provide any useful visuals. If you really want to see it, I can send it to you off the boards.
Air was introduced via a vinyl tube running inside the Van De Graaff drive column. Some people cautioned me about loosing terminal voltage but the leakage doesn't seem to prevent a nice beam. I did take the advice to ground my gas supply tube very near to the VDG. Well... actually... I had to learn the hard way. I got bit (not too bad) by voltage on my brass needle valve even as far away from the VDG as 36 inches of tube length.
The plywood box serves as an environmental chamber. I have a dehumidifier routed to the box.