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Registered Member #2318
Joined: Fri Aug 28 2009, 01:22AM
Location:
Posts: 33
I have an acrylic tube that is about 18 inches long. My plan is to seal it off and add a valve, with an internal electrode on either end. My NST will create an arc around 3 to 4 inches in air, will the arc length increase inside the argon chamber? In other words, how short should I cut the tube before sealing it so that I can still get a good arc between the electrodes using the NST as a power source?
Registered Member #61569
Joined: Sat Apr 15 2017, 05:12PM
Location: Germany
Posts: 28
If you can seal the tube properly, so that you can hold a good vacuum, then you can leave the tube 18 Inches long. For the best arc length look at the Paschen curve and you will find, that you need approximately 1-10mbar for the paschen minimum. For the best looking arc you should watch the videos of Carl Willis on youtube like this one:
Registered Member #2318
Joined: Fri Aug 28 2009, 01:22AM
Location:
Posts: 33
That is a great video!
If I wanted to add a pressure gage to my chamber but keep it isolated from the arc how would be best to do that? Have it attached at the end of a line coming out from the chamber?
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
If you're thinking of argon at atmospheric pressure, just flow the argon through your tube (without any tight seal) and experiment with the electrode spacing.
Sounds like you are starting arcs with a small gap and then stretching them by moving an electrode. Can you make a Jacob's Ladder in an enclosure that you can fill with argon (which is heavier than air) ?
How soon do you thing the acrylic tube will melt, with a NST arc running inside it?
Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615
I give it about a minute before the tube melts. I doubt acrylic will hold a vacuum for long - most plastics are gas permeable to some degree. And if you are running at or near atmospheric pressure the arc will be very hot.
Registered Member #61612
Joined: Mon May 15 2017, 01:20PM
Location:
Posts: 3
I think that *experiment with the electrode spacing will be the good idea. What about the diameter of your tube? In any case you need to keep your arc far from tube walls - acryl will melt in seconds, not in minutes. also it will make much organic vapours in case of contact with arc, so your gas mix will change.
I think if you have 4 inches arc in air then you need minimum tube diameter of 4-5 inches to start such experiments. Also you need to place your tube and arc in vertical position.
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NST arc length in an argon vacuum chamber?
