August 1, 2018.
The Pacific Northwest National Laboratory (PNNL) prototype bubble chamber is intended to address issues encountered with the current PICO dark matter search detectors and improve the functionality of future experimental designs. The PNNL bubble chamber accomplishes this with a simplified interface between the hydraulic pressure controls and the target vessel and altering the standard chamber design such that it can be easily exchanged and replaced with vessels of various sizes and materials for testing purposes. The chamber itself is a glass vessel which houses perfluorobutane and holds the target fluid above room temperature and atmospheric pressure. The target fluid becomes a metastable superheated liquid that undergoes a localized phase change in areas where particles with sufficient energy interact with the fluid’s nuclei and nucleate bubbles. The temperature of the chamber is controlled by submersing the target vessel in a heated water bath to ensure the target fluid remains in a metastable superheated state. The hydraulic pressure can be adjusted to maintain energy thresholds above which gamma rays or electron (significant backgrounds to most dark matter searches) energy deposition is insufficient to cause the target fluid to undergo a phase change. The chamber itself is monitored by 200 fps cameras adapted with nucleation threshold trigger algorithms and a series of piezo-electric sensors to capture visual and acoustic information of bubble nucleation events. Once triggered, nucleated bubbles are collapsed by the opening of automatic solenoid valves contained in the hydraulic cart which causes a compression of the cold system and increases the pressure within the bubble chamber. The pressure in the hydraulic cart is then reduced, allowing for the system to expand, releasing pressure within the cold zone and the bubble chamber, and prepares the chamber for the next event. The presented work towards the commissioning of the PNNL bubble chamber includes the design and construction of the hydraulic cart, system mounting framework, compressed air and water testing, laboratory setup and organization, and solid works structure design.
Engineering Mechanics | Nuclear Engineering | Physical Chemistry
Pacific Northwest National Laboratory (PNNL)
The 2018 STEM Teacher and Researcher Program and this project have been made possible through support from Chevron (www.chevron.com), the National Marine Sanctuary Foundation (www.marinesanctuary.org), the National Science Foundation through the Robert Noyce Program under Grant #1836335 and 1340110, the California State University Office of the Chancellor, and California Polytechnic State University in partnership with Pacific Northwest National Laboratory and Cal Poly San Luis Obispo. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funders.