The 3rd string of the season was successfully deployed in drill-hole #55 on Sunday morning, December 16, 2007. The last of the 14 surface cables were pulled into the ICL this week resulting in a total of 40 surface cables now installed into the ICL. The final IceTop tanks were filled with water this week, 14 for the season and 40 overall.
IceCube hosted an open house on Sunday from 2-4pm. There were about 40 visitors to the ICL, Seasonal Equipment Site, and the two drilling/deployment towers.
Population and logistics support remain on plan. The total IceCube population at the station is currently 50. There will not be much change in population between now and the Christmas/New Year holidays. Our next big turnover in population will be on January 3rd when we have seven people depart and six arrive. DOMs and Surface to DOM cables were delivered in line with plans. We are expecting a shipment from PSL next week which includes the vertical turbine pump.
This week the Tower Operations Structure 2 (TOS2) was made operational and two holes were drilled and strings successfully deployed. We were hoping for three holes during the week, but a few problems prevented that from happening. Most of these problems have been overcome and the fuel system seems to have settled down and is operating smoothly. We hope for a smooth week of drilling next week. The drilling equipment was relocated and set up at hole #71, ready for a start of drilling on Monday morning, after a Sunday break. The crew is well and looking forward to and hoping for a 3-hole stretch before the Christmas break
The firn drilling is proceeding smoothly despite problems with pump longevity. We are currently firn-drilling hole #12.
The final three cables were pulled into the ICL and connected to Surface Junction Boxes (SJBs), IT stations and patch panels. This completed IceTop cabling for 2007-08. In the ICL, the Electrical-Mechanical Workstations were assembled and moved into place. Construction and organization of the ICL work areas continues.
The DOM testing continues to be well advanced in respect to what is needed for deployment. During the week one sled with 64 DOMs was tested. The results of the tests are still preliminary, final results will come early next week. The preliminary results indicate that 3 DOMs should be re-tested. A new batch of 64 DOMs has been put on a sled and placed in the testing facility, the DOM Milking Parlour (DMP), and the test cycle is about to start.
Weather conditions during the week with winds up to about 10 m/s showed that improvements in the stability of the DMP are needed. These improvements will, weather permitting, be done during the coming week.
Alignment of Standard Candle 2 required more work than expected. Final alignment was shock tested and is more stable than it was before shipping from Berkeley. The final absolute intensity of the output per pulse was also measured and found to be stable. The Standard Candle was deployed on String 55 at 5:30 am on December 16, between DOM's 42 and 43. Deployment went smoothly with great work by the night shift. Leak testing will be done once the SJB connections are made. If it passes this test a first run of the Standard Candle will be taken in water.
Pinging of Hole 55 with the South Pole Acoustic Test Setup (SPATS) occurred from 11:45pm December 15 to 1:45am December 16 NZT, including set up and take down time. The retrievable pinger emits a click once per second aligned to absolute time using a GPS clock to trigger the pulses. The pinger run went smoothly and pulses were heard on all 3 deployed SPATS strings, determined by monitoring the SPATS sensor data in real time during pinging. The data should be valuable for both speed of sound and acoustic attenuation analysis by the IceCube Acoustic Neutrino Detection group. All sensors and transmitters to be deployed on SPATS String D in Hole 76 have passed on-ice testing.
IceTop had another incredibly successful week! We completed the filling of all 28 IceTop tanks on Saturday, December 15th. We filled 28 tanks in nine days, five days ahead of schedule. Not only is this the most tanks we have deployed in one season, but it also marks the half way point in the IceTop construction phase. A total of 80 of the 160 IceTop tanks are now deployed. Staff battled 26 Knot winds to install sunshades and open the tanks for freezing. Everyone pitched in to complete all the tasks. Raytheon was there to provide heavy equipment support for transporting our water tank for the fills. In most cases we filled two stations a day. This was a team effort and all that helped deserve credit and our thanks.
A total of 31 new Dom Hubs were shipped to the South Pole this season with 12-15 to be used to support new In-Ice strings and two to be used to support new IceTop stations. The remaining DOM hubs will be used for spares this season and then will be integrated into the IceCube DAQ system in future seasons. We will be integrating new in-ice DOM hubs into the system as strings freeze in. Low-level commissioning follows on the new hubs.
The IceCube South Pole Archive Data Exchange (SPADE) taping system was brought on-line in B2 science after relocation from the IceCube Lab. The system consists of eight Ultrium-2 tape drives. Six of the drives support raw data archiving. The two remaining drives are used for filtered data. A new LTO-3 based tape library was received this week. The library will also reside in B2 Science, and will address expanding data archiving requirements as the IceCube detector continues to grow.
Preparations were made this week for the South Pole data System (SPS) at the ICL to receive an operating system software upgrade. In addition, hardware is being added or upgraded to provide better processing margins at various system choke points.
This week the IceCube advanced safety audits continued with auditors looking at the IceTop fill process. The auditors did not find any major significant issues and the people performing the procedure did not express any concerns regarding safety.