Thursday, July 22, 2010

So far, so good...

We finished connecting the wires from the rings and the charge collectors in the experiment, and without any visible problems. After connecting the wires, we checked the resistances of all surfaces and they appeared to work exactly as we planned them, in a minor sort of miracle. Now all we can do is wait for the system to pump down to the vacuum pressures we need, then run the experiment to see if we are getting good levels of ions. We'll see what happens from there.

Tuesday, July 20, 2010

Additional Info

I thought a picture might be helpful to understand what we did a little better. Here is the central ring assembly:

I took this one from the beryllium7 website at BYU. On the far right side of the assembly is a silvery metallic colored piece, which is the aluminum support we think was giving us the problem. Another is on the left side side, and I've pointed out both.

Dr. Peterson said that he hopes we never have to take the assembly out is a pain in the neck to remove it, clean it, and make changes to it. We were lucky to start working on it at around 2:00 and make it out of there by 6:00.

Problems and solutions

For some two or three weeks, we've been running into a problem with the hasn't been giving us good data. We looked all over the place for answers...could it be a problem with the programming? No. The assembly itself? Maybe. After some time and bashing of ideas (mostly done by Drs Hart and Peterson) we came up with the idea that the support rings on either side of the potential assembly, made of an aluminum oxide, were charging up like a capacitor during the firing phase of our experiment. Since the aluminum has a decay constant of about three minutes, we waited for about that much time and found much better data for the dump of the plasma. The conclusion was to replace those rings with copper, a substance much less likely to charge up and ruin our plasma.

So we had new rings created. They were finished today and delivered to the plasma lab  at about two in the afternoon by Wes, the resident engineer at the physics department. Afterword, Dr Peterson, Chad and I worked on removing the central ring assembly, replacing the rings, then re-installing the assembly. We had to disconnect the wires leading to the potential assembly and haven't yet been able to reconnect them (that will be an adventure for tomorrow), but theoretically our data should be looking much better after we connect those lead wires and pump the system back down to the pressures we need (something like 10^-9 torr)

Wednesday, April 21, 2010

Another note on plasmas

One final thing I want to mention about plasmas: A plasma is generally defined by its "Debye Length", the length which the plasma "Screens out" electric fields. A wikipedia link on this is HERE.

To be considered a plasma, the plasma must be dense enough that one ion will affect many nearby ions, which creates a collective effect in the movement of the plasmas.

Recent Events

Welcome to the Plasma Physics page by yours truly. To begin, I'll link to a couple of posts on plasma physics I wrote on my other blog a couple of months ago:

Non-Neutral Plasma Physics I
Non-Neutral Plasma Physics II

So this blog will be a record of mainly what I'm doing in the lab at the Y, and a little on what the other students are doing.