[devaiops9001]

I have seen some examples of Farnsworth Fusor on the web but they are admittedly (stated by those posting the videos) amateur. Can you show me strong examples of something that could be called "industrial class" that is in the category of Farnsworh Fusor?

As far as I am presently aware, a Farnsworth Fusor has not produced multiple plasma layers.

>> but not useful for a sustained fusion reaction.

The plasma in Safire meets the definition of "sustained fusion reaction", but whether this particular sustained fusion reaction is useful or not is a legitimate bigger question.