Greetings to my hoard of internet friends!  My work at Columbia University’s Plasma Physics Laboratory this week mostly consisted of building my circuit on an actual board, testing it, and putting it in its own box.  A picture of the finished prototype is attached to this post,  and I’m very happy with the circuit so far.

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The phase shifter, after being properly tuned by those knobs you can see on the front of the box labeled “Cosine Amplitude” and “Sine Amplitude” does give a wide range of phase shifts, which means the concept itself that I have been working with is sound.  The problem is that this device needs to cover a wide range of frequencies (0.1 – 20 KHz), and the way the box is set up now, you have to specify the frequency it works at before you use it on the actual plasma machine (CTX or Collisionless Terrella Experiment).  This isn’t ideal, but the good news is that the only reason the box doesn’t work for all frequencies can be fixed by implementing the digital solution that I’ve spoken of in previous posts.

The Cosine and Sine amplitude knobs that are shown in the picture I’ve attached above are actually called potentiometers, which is a fancy way of saying that they are resistors that you can control by turning the knobs.  The idea that I’m going to be working on this week is to replace the “Cosine Amplitude” knob with a digital potentiometer, which will be able to adjust itself to the proper resistance based on the frequency of the incoming signal from the plasma within the machine.  It’s not going to be easy, mostly because I’m relatively unfamiliar with programming these digital components, but I’ve given myself enough time so that I believe that I can get it working before the summer is over.  On the plus side, after I get this digital business working, I should be very close to completing the project, which is very exciting and keeping me motivated!

I’m not sure what I expected when Professor Volpe gave me the job in April, but it certainly wasn’t a huge desk with huge measuring tools on it in a lab populated with a solid mixture of undergraduate and graduate students.  I’m attaching a picture of my desk so that you, my readers, can see where I work everyday.

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Those three big boxes, from left to right are a power supply, which I use to power various electrical components that I use during the day.  The second box is a function generator.  This one is important because it lets me feed signals of different frequencies to my circuit, which is important because this circuit is supposed to work for a pretty wide range of frequencies.  The last box is an oscilloscope, which I use to measure the signal that my circuit is outputting against the signal that the function generator is inputting.  Everyone at the lab has been very accommodating and, while I’ve never worked in a lab to compare this one to, I can say that I always feel like the myriad instruments, tools, and materials are well organized and readily available for anyone who wants to use them, which can’t be easy because there is a lot to keep track of!

So off I go, into the hinterlands of programming microcontrollers.  This should be a relatively low stress week, as my twenty-first birthday is on Wednesday, which means I probably wont be working the last half of the week.  However, I’m looking forward to trying out the digital solution, and am hopeful that it can produce the desired effects.

That’s all for now internet!

Scooby Doo!

Lucas

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