Undergraduate Research for Intercollegiate Search for the Neutron Electric Dipole-Moment
Undergraduate researcher for NC State and Duke University Physics Departments
Individual Project — Status: Complete
Sept 2017 - Aug 2018 — Raleigh/Durham, North Carolina
Overview:
The neutron electric dipole moment (nEDM) is essentially measuring the distance between the up / down quarks within an individual neutron in order to determine its electric moment. The existence of the nEDM implies violation of time reversal invariance, which is why it is very important to look for. Oak Ridge National Laboratory has been setting up experiments in an attempt to search for the nEDM.
Details can be found in the reports below in the Literature section.
The project I was assigned entailed measuring the spatial resolution of a highly sensitive sensor called a silicon photomultiplier (SiPM). In searching for the nEDM, ultracold neutrons (UCN's) are produced and their ionizing radiation is scintillated using superfluid helium. This scintillation is ultraviolet and is carried by wavelength shifting (WLS) fibres to be measured using said SiPMs. My task was finding the spatial resolution of the SiPMs in order to know the tolerance of the fibre-to-SiPM coupling when setting up the experiemnt through a variety of factors, such as SiPM size, peak absorbtion wavelength, configutation (operating voltage, temperature), fibre optic cable properties (diameter, length, polishing, SNR, etc), distance between coupling, intensity of scintillation, and relative position between center of fibre and center of SiPM.
To simulate the scintillation, a UV LED with WLS fibre coupling was purchases, a small multi-axis translation-stage with micrometer accuracy was used for positioning the fibre over the SiPM. The fibre was held inside an acryllic cast with a precision machined aluminum housing for optimal position. The use of a dark room would have been ideal for this experiment, to prevent overheating (increased thermal noise, cross talk, etc. of the SiPM), however none was provided. This made each individual datapoint on the light intensity based off the relative position of the fibre-SiPM air coupling be manually moved and measured.
Personal Statement:
After my project on Muon Scattering Tomography, I had become somewhat specialized in using silicon-photomultipliers (SiPMs). I wanted to continue working with them and potentially pursue a double degree in physics (as my original plan was to become an experimental physicist). Being at a young age (freshman in college), I immediately sought out research in the beginning of the semester with the physics department to see if I could get any undergraduate research. Our department at NC State University actually had a project going where they needed to test the spatial resolution of a SiPM used in a project with Oak Ridge National Lab. With my experience, I picked up this research for well over a year. I had my own office in the physics building, worked closely with other ORNL researchers and NCSU professors / graduate students, and worked at Duke University over the summer. I shortly left in my sophomore year, since my part of the project came to a close and I decided against fully pursuing physics, and wanted to focus my full attention into theoretical aspects of electrical engineering (analog / digital signal processing, communications, information theory, machine learning, etc.)
Literature:
NOTE: I had already left by the time of this publication. However, note pages 7, 33, and 37 to see what I partially worked with.
