LEAD (AP) -- Scientists will begin the process to move the most sensitive dark matter detector in the world into the Davis Cavern of the Sanford Lab later this month.
After spending several years planning and building their ultra-sensitive detector in a surface laboratory on the Sanford Lab campus, scientists with the Large Underground Xenon (LUX) dark matter detector are slowly disassembling their work, packing it up and preparing to move it underground. At the end of March they plan to gain access to the Davis Cavern, and at the end of April they plan to start transporting the detector 4,850 feet underground.
Yards upon yards of bubble wrap line a back room of the LUX surface laboratory as scientists carefully take down the detector that they have so painstakingly constructed over the last year. From driving ultra-sensitive, light detecting tubes down from Rhode Island to ensure their protection, to making frequent trips to the local hardware store for parts and supplies, the process to build the dark matter detector in the surface lab has been a labor of love for more than 75 scientists from around the country.
Those scientists are just completing the second test run for the detector, having fully immersed a titanium can of ultra-sensitive photomultiplier (light detecting) tubes, which observe a target of more than 350 kilograms of liquid Xenon and related instruments into a massive 100-ton tank of water that measures about 10 feet in diameter, in order to simulate exactly how the experiment will work underground. Underground, that tank is even larger, at about 25 feet in diameter with 300 tons of water.
The test run also included cooling the detector down to negative 150 degrees Fahrenheit in order to accommodate the liquid Xenon, sending the Xenon through a complex purification system into the detector, and running the detector with all of the photomultiplier tubes in place to ensure that all 122 ultra-sensitive light detectors are working properly.
"We built the detector as it will be underground. The layout is exactly the same," said LUX Collaboration member James Verbus of Brown University in Rhode Island. "Essentially what we did with Run 2 is test out all of the systems exactly as they will be underground to make sure everything is working as it should, and we get experience deploying and dismantling systems."
Once scientists have the entire system disassembled, Verbus said it will be transported via the Yates Shaft to the Davis Cavern, where it will take a few months to re-assemble the detector and related instruments. Scientists expect to be taking data from the detector by Fall 2012.
"It's very exciting," Verbus said. "I have personally worked on this experiment for two years as an undergraduate, and three years as a graduate student. So, to finally see it go underground and actually achieve the goal that we all set out to do many years ago is exciting. Based on all the results we have had so far we are very optimistic because everything has been going very well and we are very confident that we are going to be able to do what we set out to do."
Scientists believe that dark matter particles, labeled as Weakly Interacting Massive Particles (WIMPS), are uniformly distributed throughout the galaxy and passing through us all the time. Using their Xenon detector that is strategically placed ones mile underground to avoid cosmic rays that are naturally present on the earth's surface, scientists expect dark matter particles to interact with the Xenon, emitting a small flash of light.
Upon impact, Verbus said electrons from the particles will drift to the surface of the detector, where a larger flash of light will occur. Photomultiplier tubes will detect both light flashes, and by comparing the sizes and shapes of the events scientists will be able to determine whether the lights are the result of dark matter detection.
The race to detect dark matter is one that has been ongoing for decades, in various parts of the world. Once it is assembled and operational, LUX will be the most sensitive dark matter experiment in the world. Verbus said LUX scientists expect to take data from its position in the Sanford Lab for at least one year.