Saturday, February 21, 2015

Plausibly Plasma

For the past few weeks, I've been taking the Introduction to Neon class at the Crucible. It's been really fun! As a teacher, it's instructive to be a n00b at something because it's easy to forget how challenging things can be when you first approach them.

And neon is a little challenging: most of the class has been spent learning how to bend and weld the standard 10mm glass tubes. The neon shop at the Crucible has a variety of specialized burners for various glass bends and seals. They are remarkably hot, and soften a thin-walled tube in seconds. The trick is to bend the semi-molten glass, now the consistency of taffy, without kinking, collapsing, or perforating the tube. A rubber tube you can blow into is attached to the glass tube which helps blow out any kinks as you bend it (but blowing too hard pops it like bubblegum!). The instructors, well-practiced, make it look easy: it's not! I'm sure it's one of those things you become good at with time, and I'm feeling more confident after just a few hours of practice but still far from mastery. It's certainly one of those things that if you overthink it you tend to ruin it, so you just have to go by feel -- good practice for me!

Here's an experiment I did in the first week, with a neon tube supplied by the instructor. I didn't make it but I put some scavenged hard disk platters around the loop which had a neat mirror effect as you can see:

Neon experiments
This came out so well I was inspired to use disks in my final project, which will have to wait for another post when I've finished it.

The first neon tube that I actually fabricated was a straight length of glass with a bubble about 3cm in diameter. I was interested in seeing how the plasma inside would react to a magnetic field. The answer: rather subtly! Here's a video ov the results: when I say "current on," the current through the coils generates a magnetic field directed into the plane of the picture, and you can see the plasma move very slightly in response.

Here's a link to some neon inverter suppliers, I've searched for these on occasion and they turn out to be surprisingly hard to find.

I'm especially interested in the beadmaker (PDF link) inverter designed to produce and control the "beading effect" that's sometimes an unwanted side-effect of solid-state inverters. My hunch is that beads are solitons due to nonlinear effects in the neon plasma and I look forward to investigating those more. (One of the instructors gave me a spare iron-core transformer. It's fun to use that to make a Jacob's Ladder in case you need more toxic and corrosive ozone in your life. More later!)

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