The 8th, 9th, and 10th strings of the season were successfully deployed this week. The string for the 8th hole was secured on December 31st followed by a holiday break; the 9th string was secured on January 3rd and the 10th string was secured on January 5th. The drilling of the hole for the 11th string of the season has commenced on January 5. The table below provides the hole location and string installation completion dates for the holes planned for this season. The IceCube baseline plan is 14 strings with a stretch goal of 18. Three strings have been installed since December 30, 2007. Strings 75, 69, and 60 have been a great success and have allowed the project to meet its scheduled goal of ten strings by January 5, 2008. The safe production of deep ice holes continues to be the most critical activity.
| IceCube Drilling and String Installation Plans | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| String (2007/08) | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| Hole Location | 63 | 64 | 55 | 71 | 70 | 76 | 77 | 75 | 69 |
| String Installed | 12/08 | 12/1 | 12/16 | 12/19 | 12/22 | 12/24 | 12/29 | 12/31 | 1/3 |
| 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | |
| Hole Location | 60 | 68 | 61 | 62 | 52 | 44 | 53 | 54 | 45 |
| String Installed | 1/5 |
The IceCube population at the end of the week is 47, one below plan. We had a big day at the Pole on January 3rd when we had 7 arrivals and 6 departures. The meet and greet at the flight line was a happy occasion with a lot of hugs and smiles.
The IceCube team at the Pole did enjoy a Happy New Year's though it was a day delayed from the station. Flights started up again and as a result we have caught up on DOMs and Surface to DOM cables. We are now on schedule. We have 15 Surface to DOM cables on the ice as well as enough DOMs to support 18 strings. Additional DOMs coming in will go to next year's startup.
Drilling commenced on Tuesday Jan 1 this week, after the New Year's Day off. We began hole 9 at around 09:00 that day and had it completed by around 22:00 on Wednesday. We commenced hole 10 at around midday on Thursday and completed it by late Thursday evening. Hole 11 is currently being drilled and we expect that to be completed sometime late Sunday night. At the moment we are achieving a hole turnaround time of approximately 50 hours. We are currently on schedule and assuming no major problems with the drill we expect to get somewhere above 16 holes for the season.
Drilling is going reasonably smoothly, despite continued problems with air in the fuel. We have now installed a fuel pump in the system so air is being pushed into the building rather than being pulled into them. The setup incorporates a pressure limiting system to limit the fuel pressure to the building to less than 3psi.
Firn drilling of all holes for this season has been completed and we expect to begin drilling some of next year's holes when they have been marked out. Work is expected to start on compaction of the pad for next year's Seasonal Equipment Site (SES) location sometime within the next few days.
The 28 IceTop tanks deployed this season continue to freeze-in nicely. The process takes about 40 days, and we have hit the 30-day mark for the first sets installed. Freeze monitoring data is being collected in the ICL by the IT-freeze computer. Automatic transmission of the data to the north continues to be a bit troublesome, but there have been no negative impacts on the freeze process.
All 64 DOMs from South Pole Acceptance Tests, (SPATs) 15 and 16 passed. And were taken to holes 60 and 68, respectively. This SPAT featured all Swedish DOMs, and we encountered a few bizarre problems. Four DOMs did not run DOMcal, and there was a local coincidence failure for the first time this season. We swapped cables and the problem went away, however we will retest the two DOMs that failed the lC-chain test just to be sure.
This week wrapped up the SPATS Pole season. String D has frozen in and all sensor and transmitter channels are working. It was noisy with many frequent transient events during freeze-in but is quieter now. The acoustic pinger was run in hole 69 and could be heard on all 4 SPATS strings, including all sensor channels of String D except for one which had too low a gain. On behalf of the Acoustic Neutrino Detection group, thanks to everyone from IceCube on and off ice who has made this season successful.
Failing hardware issues were addressed on various hosts across the South Pole data system (SPS). Eight hard drives and ten memory modules were replaced with spares and decommissioned. Decommissioned equipment, shipping containers, and cases have begun to make their way into the South Pole cargo manifests for transport by vessel to the north. Network secure webcams and environmental monitoring devices were reconfigured both inside and outside the ICL.
To date, six strings have been powered up. Of the 360 DOMs, 359 communicate, the exception being 71-39 "Beaver". The high current wire pair mentioned in a previous weekly report is now normal after freeze-in.
Integrated IceCube/AMANDA runs were restarted this week after several cables in the ICL were switched in order for the AMANDA readout to look right
There were two reportable safety incidents this week. In the first, a fitting disconnected while a driller was holding on to a metal tube in one of the Main Heating Plants and the cable-driven CO2 fire suppression system was consequently activated (see photograph). This was a potentially dangerous situation, but the drillers involved handled the situation well and no one was ever in any real danger. Steps have been taken to prevent a similar accident in the future.
In the second incident, one of the drillers shut the door of a loader and it pinched his thumb, which caused a fracture at the tip. Shutting a door on your hand is the type of thing which could happen to just about anyone. Unfortunately, it was a heavy door. The driller will be fine.
On January 3, the South Pole Station was visited by the Baird Congressional Delegation, with members of the House Science and Technology Committee including Rep. Brian Baird (D-3rd-WA). The 12 members of the House of Representatives delegation were escorted by Kathy Olsen, Deputy Director of the NSF. The visit was part of a 4-day tour to Antarctica. The visitors were escorted in three groups to the various sites at the Pole, including, the ICL, the drill tower and the tower where a string had just been deployed a few hours prior to the arrival of the delegation.
The tour to the drill towers required the use of a snowmobile with sled, which was an interesting change from just riding in the van. The group was very interested in IceCube construction and science. The visitors appeared satisfied if not impressed with IceCube on ice operations and the progress that was made to date.
On January 5 we had another visit of a delegation of staff members of Congress, that visit also went very well.
Finally a Chilean traverse team of about a dozen people and several tractors came through on their way to the Pole of maximum inaccessibility, the place farthest from any coast, which is located about 850 km from the Pole. One of the senior people of that team was quite knowledgeable about neutrinos. He asked if IceCube was able to do flavor identification of neutrinos. He was quite happy to meet his fellow Australian Alan Elcheikh, while he was inspecting the outer jacket on the drill cable.
