Vacuum chamber question
Posted: 13 February 2010 01:25 PM   [ Ignore ]
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How is the current passed from the capacitor bank to the cathode/anode through the vacuum chamber? It looks like the whole core is attached to a CF flange, does the flange have pass-through terminals machined into it?

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Posted: 13 February 2010 04:23 PM   [ Ignore ]   [ # 1 ]
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JesterX - 13 February 2010 06:25 PM

How is the current passed from the capacitor bank to the cathode/anode through the vacuum chamber? It looks like the whole core is attached to a CF flange, does the flange have pass-through terminals machined into it?

The vacuum chamber is not actually part of the circuit as I understand it. The actual plasma paths are from each of the cathodes to the anode, which conducts all of the plasma’s current during the axial phase rundown. The anode itself is actually shaped more like a circular Tee flange. I know it looks misleading in the gallery :)

The base plate and everything that bolt onto it are at the cap bank’s negative (frame ground) potential. The anode is insulated by a pyrex insulator in this case, but that could just as easily be ceramic or a composite.

The pix showing the tops of the caps show the high voltage plates on top with the anode flange as the bolt circle at the center.

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Posted: 13 February 2010 06:48 PM   [ Ignore ]   [ # 2 ]
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The vacuum chamber is not actually part of the circuit as I understand it. The actual plasma paths are from each of the cathodes to the anode, which conducts all of the plasma’s current during the axial phase rundown. The anode itself is actually shaped more like a circular Tee flange. I know it looks misleading in the gallery smile

Aeronaut, thanks for the response, but what I was asking was more about how the tee flange anode (as you described) manages to stay insulated from the rest of the chamber. Does the pyrex pass completely through the flange, if so how is it sealed to maintain vacuum?

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Posted: 13 February 2010 07:50 PM   [ Ignore ]   [ # 3 ]
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JesterX - 13 February 2010 11:48 PM

The vacuum chamber is not actually part of the circuit as I understand it. The actual plasma paths are from each of the cathodes to the anode, which conducts all of the plasma’s current during the axial phase rundown. The anode itself is actually shaped more like a circular Tee flange. I know it looks misleading in the gallery :)

Aeronaut, thanks for the response, but what I was asking was more about how the tee flange anode (as you described) manages to stay insulated from the rest of the chamber. Does the pyrex pass completely through the flange, if so how is it sealed to maintain vacuum?

The insulator would have to be roughly the same shape as the anode, JesterX. It probably extends beyond the anode to prevent arcing and minimize inductive losses. My guess is a neoprene or similar gasket. If all else fails, maybe an RTV bead or few ;-P

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Posted: 02 March 2010 10:29 PM   [ Ignore ]   [ # 4 ]
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The insulator at FF-1 is ceramic and is shaped like a hat, without the top.  You can see it in the photo gallery. A rubber o-ring goes between the insulator and the anode to seal the vacuum.

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