Stanford Linear Accelerator Center
My first research position was with the Medium Energy Physics group (MEnP) at U. Mass. Amherst. My time was split between working in an on-campus lab during the semester and then working at SLAC during the winter and summer breaks. My advisor, Professor Krishna Kumar, was the spokesman for Experiment 158, a large experiment being performed at SLAC that aimed to measure the weak mixing angle.
Basic Motivation
The purpose of the experiment is to determine the electron's weak charge at low energy, and you can find a more complete explanation of what that means here. The measurement was made by observing the interaction of electrons with hydrogen atoms, the simplest atom that we understand. To increase the number of electron-hydrogen interactions we used the most dense form of hydrogen that we had access to, liquid hydrogen.
The electron beam would be directed towards End Station A, seen in the photo above, where the measurements of particle interactions would be made. At the very front of End Station A was a large tank of liquid hydrogen, followed by a series of powerful magnets that would collimate the particles scattered from the hydrogen-electron collissions. Towards the very rear of the End Station is our diagnostic detector.
Diagnostic Detector
The front (left) and back (right) of the UMass primary diagnostic detector.
Our group was tasked with the design, construction, and installation of a large device that would serve as E-158's primary diagnostic detector. The detector's job is to observe the number, position, and types of particles being scattered from the hydrogen target, located upstream. Basically, the detector was relied upon to calibrate the entire experiment. Our device would tell the electron-beam operators if the beam was aimed too high, low, or whatever.
Cerenkov Radiation Detectors
As electrons travel through air they leave behind a sort of wake, similar to any object traveling through a medium. However, for electrons, this wake is observed as a form of radiation, or Cerenkov Radiation. My task was to design, build, test, and eventually install these radiation detectors. Four of them were installed on the primary detector, as you can see in the diagram here. Using linear drivers (the blue bars), and a computer system, we had independet control of the position of each detector (the four cylinders), which helped us obtain a clear picture of the beam's position (the large clinder in the center).
