I had a great second week here at SLAC. I’ve been learning more about accelerator physics, and now I’m at the point where I can actually help with the research being done here, which means now I understand enough that I’m not totally confused all the time.
Soon I’ll start running simulations with Juhao on a new technique for improving the coherence of the X-ray laser called improved Self-Amplified Spontaneous Emission (iSASE). The idea is to improve the coherence of the X-rays produced in the undulator by using the X-ray wavelength photons emitted from the back of the electron bunch to stimulate electrons further forward to oscillate in the same phase and emit light that is coherent with the original photons. This does already happen in the accelerator right now, but the distance that light actually travels forward relative to the electrons while in the undulator is very small. This means that only a small percentage of the X-rays are coherent.
To improve this, the beam is put through a chicane, which forces electrons onto a slight detour away from the straight beam so that they take a longer path than the photons that they emitted, allowing the photons to move forward and stimulate electrons further ahead in the bunch. Tor gave me some problems to practice calculating the extra distance the electrons had to cover when they get put through a chicane and how far the light would slip ahead. I had to use some really hard math to solve it, but I did eventually figure it out.
Calculating the delay from a chicane
Now I can run a simulation on the computer instead that does all the complex math for me. The IT department just got the linux computer at my desk working and connected to SLAC’s big computer core that the simulation actually runs on. So next week I can start using it to model different arrangements of chicanes in the beam.
Also, I’ve been hanging out with other interns here at SLAC that are here with a program called SULI (Science Undergraduate Laboratory Internships). I work with a few of them on the iSASE project with Juhao. They’re super fun.
One night we all went out to dinner then went back to their dorm house and had a bike race around the Stanford campus that we called the Tour de Stanford. This weekend I went with a big group of them to the beach in Big Sur. It’s about a 3-hour drive so we left Stanford at 6 AM and got back at around midnight. We hung out on the beach and went swimming and bodysurfing, even though the water was freezing. Then we went for a hike to see a waterfall, which was barely trickling because of the drought in California. I had a lot of fun though and I’m excited to continue my internship.
The waterfall we hiked to in Big Sur
An arch in the ocean. I had to take this picture quickly and climb back up to get out of the way of the wave.
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