What is up Gettysburg College summer researchers of 2016! I am Alex Grun and I have the privilege of working for Dr. Stephenson and Dr. Crawford in Gettysburg’s very own Proton Accelerator. The research I am conducting this summer is a continuation of past work done started in 2012 which has continued all the way up until today. The research is quite fascinating and I am going to tell you all about it right now.
The first step in understanding my research is simply understanding how the proton accelerator works.
It may look confusing, but it’s actually really confusing. A Proton Accelerator works by ionizing hydrogen atoms and shooting the positively charged protons down the beam line; this is where P-shooter comes from, or Pee-Shooter for short. The energy of the protons is determined by how much voltage we put into ionizing the hydrogen. Energy of the protons relates to how fast the protons move down the beam, so at higher energy levels the protons are moving relatively faster. However, at higher energies the protons are significantly more unstable and harder to control. Controlling the beam is the primarily objective of the majority of the devices along the beam line and inside the lead casket. Two prominent ways that we affect the beam is through our ability to control its focus and the concentration of protons sent down the pipe. Detectors located on the left and right side of the beam pipe tell us were the protons are located and the use of magnets help guide them into the center of the beam. Although this seams easy enough it is actually excruciatingly annoying because the energy is constantly fluctuating which moves the beam around. Our goal is to have an unfocused stable beam that hits targets uniformly and have the energy measured accurately to get conclusive results.
The protons are shot at PDMS samples in the target chamber down at the end of the beam line. The silicon based samples are irradiated with a specific number of protons at different energy levels and the damage done varies. The difference in the damage ranges from discoloration and cracking to odd unexplained uniform patterns. Primarily we are focusing on getting a variety of damaged samples, while also testing different techniques to measure accurately the energy of the protons. So far, the most interesting thing that has occurred is concerning the gold foil we used to measure the energy of the beam. The gold foil is microns’ thick and is laid across the protons path to measure their energy through a current conversion. But because protons are so easily deflected the width of the gold foil ended up scattering the protons too much. However, these protons were still able to hit the samples and damaged them in weird ways along the edges of the sample.
This pattern was uniform for the vast majority of the sample and are unexplained and cannot be found in literature.
This is the gold foil and the new metal mesh we made to compensate for the diffraction.
We ran 3 experiments after the gold foil with the new metal mesh to see how measuring the energy differently would effect the protons. The samples showed normal cracking and discoloration which is what we expect.
The reason why we are testing how silicon cracks is because of its ample use in satellites. Previous work by physicist with a lot of money test for high energy proton damage which is extremely important, but low energy and high energy protons both cause damage. When in space these satellites are bombarded with a variety of different energy level particles and damaged is caused on all different scales. Here we are trying to determine the lower threshold of where cracking begins and in the future we will try to minimize this damage.