Making Wakes in Lincoln, NE

So I’ve been in Lincoln at the University of Nebraska for about a month now doing research with their Summer Research Program, and I’ve been seriously slacking in the department of documenting my time here…oops. Hope you can forgive me.

Anyway, I guess the place to start would be the program. There are about 60 students from all over the country here with me working with professors on research projects in various disciplines, from Virology to Biomed Engineering to Laser and Optical Physics (me!) and several others. There are 8 of us in the Physics program, and probably about 30 total working on physics-related things (materials research, engineering, etc).

They’re housing all of us on a couple floors of one of the residence halls on campus and feeding us in the dining hall downstairs. All in all, the housing and food isn’t bad, considering it’s free. In fact, I’d say the cafeteria is a bit better than Sodexo back at Truman most of the time. The other people in the program are generally enjoyable too. It’s great to get to meet a lot of people from all over the place–my roommate is from Puerto Rico, the guys across the hall are from Minnesota and Texas, there are a couple people from California, and one or two from New York. There’s also a pretty big range of academic backgrounds: guys from Cornell and Princeton, and several from smaller schools like Truman; we have a girl who just finished her freshman year and, I think, more than one person who will be a 5th year.

As for my project, I’m working on some theoretical stuff–modeling the evolution of a plasma after a very short (femtosecond) laser burst is shot into it. Basically what happens is that the laser pulse pushes the electrons out of the way, and then they rush back in and create oscillations a bit like a wake behind a boat in a lake. Since the electrons are either pushed out of the way, or squished together, they create net electric fields which also oscillate in the wake of the laser. Since this wake is moving at almost the speed of the laser (very near the speed of light), the electric fields can be used to accelerate other particles, such as electrons or positrons that have been injected into the wake, to GeV levels with only a few cm of plasma! Specifically, I’m working with a computer program written in C++ that does 2D simulations of the EM fields along with the density and momentum in each direction. In the previous version, the code set up the plasma with no initial internal energy, a “Cold Fluid Model.” My job is to add in the requisite equations and functions to make the code a “Warm Fluid Model.” So far, I’ve pretty much gotten all the changes made; now it’s just a matter of testing to make sure the numbers it’s giving us are correct. I’ve added in a few diagnostics and so far everything’s looking good.

Aside from the research, we have a lot of fun here. The program has sponsored several fun events: canoe trips, picnics, a sailing trip; and we have a lot of fun individually too. Our evenings are pretty free, so we play sand volleyball usually 2 or 3 times a week, watch movies, find things to do in downtown Lincoln, and just hang out in general. With so many people in a program like this, you’re pretty much guaranteed to find some people you like and there’s almost always something going on if you’re willing to jump in on it. For the record…several people I know of (including myself) do also spend some time studying for the GRE this fall, and we’ve all had our nights of working until midnight–it’s not all fun and games.

Anyway, I think I’ve written enough for now. Thanks if you’ve stuck with me this far. Check back soon for another installment. Ciao!

Success?

I wish I had more time with this project.  It’s all coming together now.  I optimistically think I can have a “final product” probe early next week.  I’ll make many of them, and then the grad student I’m working with and I will do some measurements to see if they’re as good as the simulations would have us believe.  Basically, we just need to compare the performance of a stock probe to the modified probe in action and see what happens!

I’m kind of jumping the gun with this blog post, as you can see.  This week, I’ve been experimenting with techniques.  My laptop’s background is currently an SEM image of a nearly-finished probe, an image I have drawn so many times and wondered if I could ever build.

We have a final fabrication process down for the coatings, and a batch will finish this weekend.  I won’t be there for the final coating over the weekend because I’m visiting a friend from my REU last summer at Yale.  I plan to hit the ground running on Monday.  Hope for high yields!

Science is happening!

Well, it’s been a month, and things have developed quite a bit here at Harvard!  I can’t believe it’s already been five weeks.  At this point, I really only have three more weeks to get all the results I can before I need to make a paper, presentation, and poster–and get ready to fly to Minnesota for the “NNIN Convocation” (for the exceptionally curious:  http://www.nano.umn.edu/nninreuconvocation2010/) on August 11.

There were several hoops to jump through to get all the training I needed, but I’ve finished that part now.  I was trained on and can work independently on:

• Wet benches in the clean room
• Chemical vapor deposition
• Reactive ion etch
• Spectroscopic ellipsometer
• Thermal evaporator
• Scanning electron microscope
• Focused ion beam
• Atomic force microscope

As I was going through all the necessary training, my mentor (a grad student at Harvard) walked me through the details of the fabrication process.  For the last roughly 2.5 weeks, he was out of the country on vacation, so I worked independently.

The focused ion beam is awesome.  What I’m dealing with is an SEM that has another column poking down at the sample, 54 degrees from the vertical.  Instead of shooting accelerated electrons like the SEM, it shoots accelerated Gallium ions.  It can be used for imaging like an SEM (though the ions are much more abrasive to the sample).

Rest assured that this is singularly awesome.