Trouble Making a Penning Ion Source

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SUMMARY

The forum discussion centers on troubleshooting a Penning ion source that operates correctly at lower vacuum levels but experiences plasma ignition in the supply tube at high vacuum levels (1x10-4 or more). The user has attempted to isolate the gas supply using a ceramic inlet and has experimented with grounding techniques, yet the issue persists. Key parameters of the ion source include an anode voltage of 5kV, cathode voltage of 4.3kV, and an extraction voltage of -300V with a hydrogen gas flow rate of 0.5 sccm.

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sam2212
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Hi
I built penning ions source , works fine on lower vacuum, my issue is in high vacuum 1x10-4 or more, the plasma ignites in the supplied tube to the penning source not inside the chamber. Tried to isolate the gas supply with ceramic inlet, ( feedthrough metal metal => teflon tube=>ceramic =>chamber). Didn't work still plasma in the teflon, tried to ground the inlet and remove the ground still the same. My setup for the ion source:
Anode 5kv
Cathode 4.3kv
Extraction -300v
Gas H 0.5 sccm
Diameter of the feedthrough and teflon 2mm ID.
Any ideas?
Thanks for the help
 
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sam2212 said:
the plasma ignites
The hydrogen gas is igniting (as in combustion) or arcing? If the former, it would seem one has an air (oxygen) leak, or free F through decomposition of teflon. H + F = HF is a fairly energetic reaction.

Is the Penning source a negative H- ion supply?
 
Not igniting as explosion. Like plasma. This happens in the tube. It's high vacuum no gases there. The plasma should happen inside the chamber not in the tube
 

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