The teams installing the IceCube experiment at the South Pole have completed a highly successful austral summer season, during which they installed 18 detector strings – 4 more than in the baseline plan. This marks the halfway point in the construction of the neutrino telescope, which will detect extraterrestrial neutrinos with energies of above 1 TeV.
Not only has the team exceeded the 2007/08 baseline plan, they also finished the deployment ahead of schedule. This means that there is plenty of time to prepare the site for next year’s season, and suggests that construction of the detector will be complete in three more seasons, as currently planned. Meanwhile, the detector will reach an exposure of a km2-year within two years – a long-anticipated milestone of neutrino astronomy.
IceCube now consists of 40 strings, each instrumented with 60 digital optical modules (DOMs). The drilling and deployment teams were able to make holes 2500 km deep in the Antarctic ice and lower the detector strings at the rate of about one every 50 hours. IceCube now has a volume of half a cubic kilometre.
The last members of the IceCube construction team were due to leave on 15 February, after which the IceCube winter team would take over the job of incorporating the new DOMs into the data acquisition system. The researchers are evaluating each DOM to determine that it survived the deployment and “freeze-in” process. There are now 2400 DOMs in the ice at the South Pole, and in February, 99% of the DOMs that had been powered were working.
In addition to deploying the strings, this season the teams also installed a further 28 tanks for the IceTop array, a surface array to detect high-energy cosmic rays and to provide a veto for air showers that interfere with neutrino detection within IceCube.
• IceCube is an international effort involving 28 institutions and is funded by the US National Science Foundation, with significant contributions from Germany, Sweden, Belgium, Japan, New Zealand, the Netherlands and Switzerland.
