Thursday, November 29, 2007

Happy Birthday, Jesus!

When I was home for Thanksgiving, I drove out to CCC Vineyard, run by our friend, with my longtime friends Maura and Sarah. On our way out Hwy 519 near Morehead, we were treated to some lovely Jesus paraphernalia.

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Tuesday, November 13, 2007

Ultra High Vacuum

I've written very little about what I actually do in the lab, so I'm going to try to put up a few posts that explain some of what I do. This serves 2 purposes:

1) To give some relevant information about some topics that may not have clear explanations easily found elsewhere.

2) (more importantly) So that my father can reference it multiple times when he tries to remember the acronyms related to my work.

Today's acronym: Ultra-high Vacuum (UHV). Since there's a lot that goes into UHV technology, this post will focus specifically on copper gaskets.

While the UHV part of what I do takes up a lot of my time, it's not directly related to my actual research, but we cannot do the research without the vacuum. Ultra-high vacuum is usually defined as pressures that are lower than 10-10 torr. One atmosphere of pressure is 760 torr and this is anything below 0.0000000001 torr. In simple terms, there is very little air inside the chambers in which we work and even the tiniest leak ruins our ability to be at UHV. So the question arises, how do you seal all of the separate pieces so that there are no leaks? The answer is conflat flanges and copper gaskets. The first picture shows a 2 3/4" conflat flange setup. On the right is the STM (scanning tunneling microscope...the part that is related to our research) chamber and the left is a small window built into a flange. The inner ring of the flange is what is known as a "knife edge." The knife edge is an angled part of the stainless steel with a sharp edge that will cut into the copper gasket.
The second image shows a copper gasket that fits perfectly into the knife edges on both flanges. It's just a flat copper disk that comes clean and sealed inside its own plastic pouch that we open just before we install it between the flanges. Since copper is relatively soft, the steel knife edges will bite into the copper gasket as the flanges are tightened towards each other, leaving an impermeable metal-metal seal, which prevents even single gas molecules from entering the high vacuum side.
This picture shows a larger conflat flange with the copper gasket stuck to the knife edge after being removed from the system. In this picture, you can see the ring where the knife edge on the other side bit into the copper gasket to make the seal. The consequence of this sealing mechanism is that gaskets can only be used once, so everytime a flange is opened (hopefully, you never have to open them, but that's wishful thinking), you have to put in a new copper gasket and discard the old one. This gasket doesn't show it, but often the edge outside the knife edge will be greenish where the copper oxidized on the atmospheric side of the seal, but the inside part of the knife edge will still have a pristine copper shine because it was on the UHV side and was not exposed to oxygen.
The last step is to actually tighten the flanges together, which we do by evenly tightening down a set of bolts to pull the flanges toward each other until the vacuum seal is achieved. It doesn't always work the first time and can fail if there is a tiny scratch in the knife edge or a piece of grit gets in the knife edge, leaving a small passageway for gas molecules to enter. The only way we know that has happened is by leak testing, but that's another post!
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Saturday, November 03, 2007


A few weeks ago, I started mentoring through Champaign-Urbana One to One. It's a school-based mentoring program (unlike a community based mentoring program; eg Big Brothers and Sisters), where I spend an hour a week with my student at school. So every Monday morning, I ride my bike to Urbana Middle School and meet with my 6th grade student. I'll stay with the same student year after year as well so that we can develop a long-term relationship.

I've only been to mentor for two weeks now and I absolutely love it and am so excited to go every week. With how much I miss the classroom, I knew that I was going to love it. It's a completely different experience than being a classroom teacher for a lot of reasons, primarily because I have just one student and the focus is not academic. Although we've already started reading together some, the focus is not academic; it's on having a fun, positive relationship, so we spend time outside kicking the soccer ball or playing games like foosball in the "splash room" at the middle school.

If you're in the Champaign-Urbana area, you should definitely look into CU1to1, but no matter where you are, you should consider mentoring. A commitment like an hour a week means nothing to your schedule and can meet a lot to a kid (and to you too!). My experience with Teach For America helped me realize how badly students need advocates and this is one way to play a positive role for students and for society.

Thursday, November 01, 2007

Trick or Treaters

In 2006, I had 159 trick or treaters come to my house. This year, we totally dominated that with 230! My favorite trick or treater was the one who repeatedly said, "My momma said don't give me gum. I can't have gum. Don't give me gum. I'll swallow it. My momma says don't give me gum." I also enjoyed the really little ones who tried to wander into the house and the kid who walked up to the screen door and yelled "Open the door!"