The LZ Xenon project consists of transparent acrylic tanks created by Reynolds Polymer, which surround a central detector for a nearly mile-deep experiment called LUX-ZEPLIN (LZ) in South Dakota. The tanks are filled with liquid that produces tiny flashes of light in some particle interactions. The tanks will help scientists to track these flashes and determine their likely source. The tanks will also serve as a shield for some unwanted particle “noise” that could interfere with other sought-after signals, and as a veto system – a sort of lie detector that can help scientists to sort out false detections of dark matter from a real discovery.
Dark matter, which makes up an estimated 85 percent of all matter in the universe, has never been seen directly though scientists detect its presence through gravitational effects.
LZ was designed to be at least 100 times more sensitive to possible dark matter particle signals than LUX. The veto system formed by the acrylic tanks and a related sequence of light-sensing detectors represents a new addition since the LUX design that will improve LZ’s ability to rule out non-dark-matter signals.
The four largest tanks, which are custom-designed and contoured, measure 12.3 feet tall, 7.5 feet wide and 3.4 feet thick and weigh 1,500 pounds apiece. There are also six smaller tanks – three that sit atop the main detector and three that reside below it.
Like layers of an onion, the acrylic tanks will fit snugly around the central LZ detector and will themselves be surrounded by a large tank holding about 60,000 gallons (230 tons) of ultrapure water. “Everything must fit together within a quarter-inch tolerance,” said Sally Shaw, a UC Santa Barbara postdoctoral researcher who has been working to ensure the tanks meet the rigorous requirements of the LZ experiment.