With the deployment of strings 12 and 13, this week completes the drilling and deployment operations at the South Pole for this season. We now have 22 strings, 1320 in-ice DOMs including those from the last two seasons. The 48 members of the IceCube team who remain will secure the equipment for the long dark winter ahead and begin returning north. All of the water needs to be drained from all of the surface hoses at the end of the season, for example. The picture below shows one of the drillers removing all of the water from the main hose.
New this season is the independent firn drill and system. The firn is the uncompressed snow that occurs on the top 40 meters of the ice. Previously, the firn drilling took place using the main drilling tower and heating supply. The smaller firn drill and system was able to drill for holes 12, 13, and 14. Only holes through number 13 were drilled and deployed this season so the firn hole for number 14 will be covered, marked and finished next year. Next season, we expect that each firn hole will take about 10 hours using this new system. The use of this new independent firn drill will therefore shave about 10 hours from each hole and enable a faster turnaround of the TOSs and result in more holes drilled each season.
The DOM testing season ended January 28. The test facility was cleaned up: the cables, computers and other equipment were moved for winter storage in the ICL, and the domtest hub is now offline. The new cables used for testing this year did well in the cold and they will be ready for next year's early season testing. The new sleds were very effective in loading and unloading test cycles and in supplying DOMs for the deployment crew. We have tested this year 860 DOMs in 16 testing cycles, out of which 820 were deployed. The remaining DOMs were moved for storage in the new station together with the DOMs from previous years. We now hold some 200 DOMs at the Pole, out of which 23 are IceTops'.
The IceCube Lab (ICL) is operating after computers and cable from the Temporary ICL and new computers and cables were installed. The current version of the South Pole System (SPS) in the ICL is supporting IceCube string commissioning and various other experiments. Among other equipment, currently the system has the following:
In addition to IceCube-dedicated computing, the hardware listed below has been integrated into the SPS computer facilities at the ICL:
Since all of the cables from the 9 strings from past seasons were moved to the ICL and 13 new cables from this season were added, the team is spending the rest of the season verifying and commissioning the whole array and new software. So far, 17 strings and an IceTop hub have been checked. (The newer strings are still in water, so they will be checked after they have been frozen in.)
Seven out of ten new IceTop trenches have been backfilled. For those seven stations, the preparations for closing have been completed. All the inspected tanks have been freezing without incident. Snow drift has been minimal throughout this week. Tanks deployed early are about 60% frozen, while the latest tanks have about 30% ice thickness. The energy calibration of 2005/2006 tanks with muons is continuing.
There will be two or three more reports from the South Pole this season.