Science Magazine recently ran an article on their website detailing the upcoming expansion of the Telescope Array.
Japan will spend $3.7 million to nearly quadruple the size of the Telescope Array (TA), which currently consists of 507 particle detectors spread across 700 square kilometers of Utah desert. The detectors sense the avalanche of particles, or what physicists call an "extensive air shower," triggered when a ray hits the atmosphere. Physicists will deploy 400 more loosely spaced detectors to stretch TA's area to about 2500 square kilometers—twice the area of New York City—says Yoshiki Tsunesada, a physicist and TA team member at the Tokyo Institute of Technology. From the size and direction of an air shower, physicists can deduce the energy and direction of the original ray. Researchers hope to complete the expansion in 2017. Japan paid two-thirds of the current array's $25 million cost.
The expansion, known simply as TAx4 or "TA times four," could help researchers pin down the origins of the highest energy rays, in which a single subatomic particle can carry as much energy as a golf ball plunging to the green. Physicists have yet to find the sources of the rays. However, last July TA researchers reported an excess of rays with an energy above 60 exa–electron volts (EeV) coming from the general direction of the constellation Ursa Major, which includes the Big Dipper. "We've got about 20 events in a cluster with a width of about 20 degrees," says Hiroyuki Sagawa, a physicist at the University of Tokyo and co-spokesperson for the TA team. If the rays come equally from everywhere, then such a circle ought to contain about five rays, Sagawa says. "If we obtain more data we may observe structure within the hotspot," he says.
The article also notes that in addition to the construction of new surface detectors, the Telescope Array Project is also seeking funding from the National Science Foundation to build additional batteries of fluorescence detection telescopes.