Sunday, July 11, 2004

Lab Work

I keep meaning to take pictures of the vacuum chamber while it's wrapped in tinfoil... Right now it's "baking." The idea is to evaporate any crud which may have condensed on the walls, and then pump it out, so that you get a better vacuum when you turn the heat down again. The tinfoil is wrapped around a layer of "heat tape" which just consists of wires that get hot when you run a current through them, inside a layer of fiberglass. The foil does the same thing it would do on your baked potato -- keeps the heat inside. Apparently it works better than whatever expensive material they were specially purchasing before. But it looks like a giant ball of foil. Like something you'd expect to see at a third-grade science fair, or in an extremely low-budget movie, or like a joke...

In the meantime, we also had a leaky pipe in the ceiling (fixed rapidly) and a melted power-strip thing -- in the event of a power loss, it prevents stuff from turning back on when the power comes back, because really that's not something you want happening when you're not there to make adjustments. No one seems to know exactly what melted it. But you know, my dad's office in Kansas City had a whole room of uninterruptable power supplies, and I think two back-up generators, and when for some reason the supply of "clean" (ie, filtered, no spikes, no outages, no variations) power was temporarily cut off, there were dire warnings about the dangers of plugging your computer into an ordinary outlet... I guess that's the difference between the corporate world and academia, eh?

We are also facing a shortage of capacitors, which is bad because I have just discovered, to my delight, that I am making a radio. I mentioned the solenoid, right? Well, we're going to put an oscillating current through it, which means we'll produce an oscillating magnetic field at the center. I want to detect the strength of that field. To do that, I have to use another loop of wire as a sort of antenna. But there's a catch -- if the antenna has a different resonant frequency than the field is oscillating at, it will only pick up a fraction of the field. So I have to tune it to the right channel. On your radio, you do this with a knob that changes the capacitance of a variable capacitor by sliding plates back and forth so that the area of their overlap changes (at least, I think this is how it works in principle.) I only want my loop to pick up one channel, so I don't need a variable capacitor -- but I do need a different capacitor than any of the ones we've got.

The experiment actually has nothing to do with transmitting a signal. This is just an intermediate step, to figure out our field strength. But if I hooked up a microphone to my solenoid and a speaker to my loop, I could actually use them for a (pathetic) little transmitter and reciever set. How cool is that?

Now I'm gonna go re-read A Connecticut Yankee in King Arthur's Court and imagine myself introducing radio to the dark ages.

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