Re: An interesting thermionic device.
If a source gets hot enough it will emit electrons but these will just form a space charge and there will not be a flow of current until a positively charged source is introduced. I perhaps should not have said thermionic without being able to confirm that the wire gets sufficiently hot. However both tubes are evacuated, or at least were.
The tube with the 1mm wire definitely had a getter. Apart from the deposit on the glass due to the loss of vacuum the structure can still be seen inside.
Chris
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