After taking a hiatus to focus on my studies, I have finally put together the vacuum chamber that Ross Moffett gave to me last year. Currently, the vacuum pump is not connected to the chamber, however I have the connecting hose and only need to attach it. Since epoxy didn't work (the epoxy didn't stick to the hose) , I'm going to attempt to attach it with a lot of tape. I had tried to get space and resources from the local science center and my school but I had issues convincing the principle/head researcher that the demo fusor does not produce any significant radiation that needs to be contained outside of the chamber. Apparently the forum is not a legitimate source of information to them. I'm currently doing some last steps to reduce any leaks before starting it at home.
Pictures:
Chamber pic 1:
http://imgur.com/blDplPq
Chamber pic 2:
http://imgur.com/TXYx71O
Inner Grid (Close up)
http://imgur.com/byNbhFF
Update on demo fusor.
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Julian Kang
- Posts: 48
- Joined: Mon Jun 03, 2013 6:41 am
- Real name: Julian Kang
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Adam Szendrey
- Posts: 1333
- Joined: Fri Mar 29, 2002 5:36 pm
- Real name: Adam Szendrey
- Location: Budapest, Hungary
Re: Update on demo fusor.
Hi!
Make sure you put some sort of protection around the glass jar, at least I definitely would (metal wire mesh, or a "can" or something). Also the grid might be too close to the metal endplate there, a longer, insulated, "mast" would probably be a good thing. Actually an "inverted" spark plug worked very well for me. By inverted I mean that the long glazed insulator part of the plug is inside the chamber and the smaller end (which is normally in the engine cylinder) is outside. Using a file and/or a small saw you can probably remove the ground electrode of the plug, and shorten the threaded part to improve insulation. Keep the voltage and current down (you could use a flyback from an old TV for example) to avoid producing too much x-ray radiation.
About the vac. connection, I'm not sure but it looks like it's some sort of KF connector on there? If it was just a straight pipe section you could simply push the hose onto it and then tighten using a hose clamp. Tape will *probably* work for a while in this vacuum range, but you might get biggish leaks there. If your pump has a high flow rate it's not really an issue tho. We are talking about low/mid vacuum here. As one of my teachers said it during a vacuum tech. course, "When it comes to a few tens of mTorrs you can easily manage that with your finger (on a hole) as a sealant". These levels of vacuum are quite forgiving.
Adam
Make sure you put some sort of protection around the glass jar, at least I definitely would (metal wire mesh, or a "can" or something). Also the grid might be too close to the metal endplate there, a longer, insulated, "mast" would probably be a good thing. Actually an "inverted" spark plug worked very well for me. By inverted I mean that the long glazed insulator part of the plug is inside the chamber and the smaller end (which is normally in the engine cylinder) is outside. Using a file and/or a small saw you can probably remove the ground electrode of the plug, and shorten the threaded part to improve insulation. Keep the voltage and current down (you could use a flyback from an old TV for example) to avoid producing too much x-ray radiation.
About the vac. connection, I'm not sure but it looks like it's some sort of KF connector on there? If it was just a straight pipe section you could simply push the hose onto it and then tighten using a hose clamp. Tape will *probably* work for a while in this vacuum range, but you might get biggish leaks there. If your pump has a high flow rate it's not really an issue tho. We are talking about low/mid vacuum here. As one of my teachers said it during a vacuum tech. course, "When it comes to a few tens of mTorrs you can easily manage that with your finger (on a hole) as a sealant". These levels of vacuum are quite forgiving.
Adam
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Julian Kang
- Posts: 48
- Joined: Mon Jun 03, 2013 6:41 am
- Real name: Julian Kang
Re: Update on demo fusor.
Thanks for the advice!
Sorry if I'm asking needless questions but what would the protection be needed for? It wouldn't be to protect the glass and a mesh wouldn't be the best choice to shield against neutrons. The grid does indeed seem to be too close to the endplate now that you mentioned it. Would epoxying it be advisable as i might need to redo the inner grid in the future and thus might have to cut part of the feed through off? It is a KF-25 connection that I was given by Ross Moffett, although the vacuum pump does not share the same size as the connector pipe. Which is why I've switched to using a washing machine hose that fitted. The flow rate is about 3m/s if I recall correctly, which may or may not be enough to keep up with the leaks.
Julian
Sorry if I'm asking needless questions but what would the protection be needed for? It wouldn't be to protect the glass and a mesh wouldn't be the best choice to shield against neutrons. The grid does indeed seem to be too close to the endplate now that you mentioned it. Would epoxying it be advisable as i might need to redo the inner grid in the future and thus might have to cut part of the feed through off? It is a KF-25 connection that I was given by Ross Moffett, although the vacuum pump does not share the same size as the connector pipe. Which is why I've switched to using a washing machine hose that fitted. The flow rate is about 3m/s if I recall correctly, which may or may not be enough to keep up with the leaks.
Julian
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Adam Szendrey
- Posts: 1333
- Joined: Fri Mar 29, 2002 5:36 pm
- Real name: Adam Szendrey
- Location: Budapest, Hungary
Re: Update on demo fusor.
Hey!
I'd add the protection to shield myself against glass shrapnel, in case the jar breaks under vacuum due to an accidental impact, or heat stress (uneven heating by a stray electron beam maybe), that sort of thing. In case of a demo fusor you don't need to worry about neutrons anyway, and even if you are running a neutron producer, usually the flux is quite low. Typically I really don't like epoxy and such in a vacuum environment, not sure what sort you use, but they can outgas like crazy, although, again, this is not a high vacuum scenario. What I did was simple. Spark plugs sometimes (or always? not sure) have a screw on thing on their "long end". It's the copper cap that you push the ignition cable onto. So I simply wound the wire of the grid around the threaded stem a few times and screwed the cap on, that holds the grid in place very nicely. You should avoid "permanent" fixing the grid in there, as you'll probably want to do experiments with different geometries. If you could put a thread, into that baseplate, and screw a plug in there (use an o-ring to seal it), that would work nicely. You'd avoid all that epoxy snot. Maybe you could epoxy the plug in place? See attached photo. Not the best, but I couldn't find my closeups. Next to the chamber's upper part you can see the spark plug with the grid on it's "long end", and in the foreground you can see the baseplate (facing down) with the two vacuum connections and in the middle a threaded hole for the plug.
Not sure about the washing machine hose, it might collapse under vacuum, but I never tried it. What connection do you have on your pump?
I'd add the protection to shield myself against glass shrapnel, in case the jar breaks under vacuum due to an accidental impact, or heat stress (uneven heating by a stray electron beam maybe), that sort of thing. In case of a demo fusor you don't need to worry about neutrons anyway, and even if you are running a neutron producer, usually the flux is quite low. Typically I really don't like epoxy and such in a vacuum environment, not sure what sort you use, but they can outgas like crazy, although, again, this is not a high vacuum scenario. What I did was simple. Spark plugs sometimes (or always? not sure) have a screw on thing on their "long end". It's the copper cap that you push the ignition cable onto. So I simply wound the wire of the grid around the threaded stem a few times and screwed the cap on, that holds the grid in place very nicely. You should avoid "permanent" fixing the grid in there, as you'll probably want to do experiments with different geometries. If you could put a thread, into that baseplate, and screw a plug in there (use an o-ring to seal it), that would work nicely. You'd avoid all that epoxy snot. Maybe you could epoxy the plug in place? See attached photo. Not the best, but I couldn't find my closeups. Next to the chamber's upper part you can see the spark plug with the grid on it's "long end", and in the foreground you can see the baseplate (facing down) with the two vacuum connections and in the middle a threaded hole for the plug.