- 64 views
- 76 downloads
Studies on Radioactive Background Mitigation for the PICO-500 Dark Matter Search Experiment
-
- Author / Creator
- Miller-Chikowski, Shawn P
-
The PICO-500 dark matter search experiment features the next-generation bubble chamber detector designed by the PICO collaboration. The sensitivity and live-time of ultra-low background detectors, such as PICO-500, are crucially dependent on the radio-pure materials used in the construction. The PICO-500 detector is anticipated to achieve world-leading sensitivity in the spin-dependent dark matter regime, necessitating radioactive background control during the construction and assembly.
This thesis focuses on strategies and measurements related to mitigating radioactive backgrounds, specifically focusing on Radon-222, a gaseous and radioactive product of the Uranium-238 decay chain, and its progeny. The diffusive nature of radon prompts investigation into radon emanation from detector materials and radon permeation through a Parker PTFE Prädifa series NAE, FlexiSeal®, which is to be used in the PICO-500 inner vessel. The Parker PTFE seal permeation coefficient was determined using a noble gas extrapolation method and direct measurement using a radon emanation chamber detector, yielding 5.10 (+0.92, -1.10) x 10^-10 cm^3(STP)·cm / (s·cm^2·cm-Hg) and 5.37 ± 0.49 x 10^-10 cm^3(STP)·cm / (s·cm^2·cm-Hg), respectively. The radon activity contribution from the PTFE seals in the PICO-500 detection volume was estimated to be 30.5 Radons/Day.
To prepare for the deployment of PICO-500, studies establishing cleaning strategies for the synthetic quartz vessels were developed. Full-sized PICO-500 natural quartz vessels were subjected to tests using ultra-pure water soap solutions to remove dust and particulates, which can also act as carriers for radon progeny. Using a 0.05-micron filtration and a customized cleaning system built at the UofA, surfaces of the vessels were documented to be cleaned to the IEST-STD-CC1246D-25 standard. Techniques to reach this standard consistently were developed for the synthetic quartz cleaning of PICO-500, which will be implemented at the SNOLAB facility.
-
- Graduation date
- Fall 2024
-
- Type of Item
- Thesis
-
- Degree
- Master of Science
-
- License
- This thesis is made available by the University of Alberta Library with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.