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About Me
My name is Travis Nichols and I am an undergraduate physics major and math minor from California Polytechnic State University - San Luis Obispo, interested in lasers, plasmas, and accelerator physics. I am an experimentalist to my core, and I love being in the lab, pressing buttons, flipping switches, and turning knobs. There is something I find uniquely satisfying about the troubleshooting process of experimental physics, and being at SLAC was a wonderful opportunity for me to gain valuable experience and confirm my passion for this field. I was fortunate enough to be an intern at SLAC in the summer of 2023 where I worked primarily with Robert Ariniello and Spencer Gessner on alignment diagnostics and characterizations for the lithium Ionizing Bessel laser used in sector 20 of the linac for PWFA experiments.
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Phase and the Deformable Mirror
Since the axicon is flat on the upstream side, it imparts no phase on the emerging beam, thus we can look at the images after the axicon to clearly observe phase issues of the beam. Ideally the laser would reach the axicon as a perfectly flat plane like shown on the left below. But in reality, all kinds of phase aberrations can occur as shown on the right, most commonly we get these saddle or bowl shaped pulses that wont produce clean Bessel beams.
There is a camera installed in the beam path that views the laser as it emerges from the axicon. If the wavefront is nice and flat we will see the clean bullseye pattern below on the left. But if the incoming beam looks like a saddle or trefoil when the beam reaches the axicon, we get patterns that look like these on the right. We can solve these phase issue with a deformable mirror. Essentially the deformable mirror is made of a somewhat flexible glass and has a bunch of tiny pistons allowing us to change the shape of the mirror surface to impart a corrected phase on an aberrated wavefront .
Rail Camera
Downstream Holed Mirrors (Near and Far)
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