The 4th and 5th strings of the season were successfully deployed this week. The hole for the 6th string was completed late on December 23rd and the string deployment is expected to be completed on December 24th. The table below provides the location and dates for the first nine holes planned for this season. The baseline plan for this season is 14 strings with a stretch goal of 18.
| IceCube Drilling and String Installation Plans (Holes 1-9) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| 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 | ||||
Commissioning of the newly deployed strings is now underway. The first hole is still not completely frozen. Commissioning activities are limited to checking communications, current, and temperatures for each of the DOMs. Only one of the 300 DOMs installed on the first 5 strings does not communicate. Population and logistics support remain on plan. The total IceCube population at the station is right on target with 50 Cubers set to enjoy Christmas at the Pole. The total station population is 251 so we make up quite a portion of Pole pop. There are no pending population changes. DOMs and Surface to DOM cables remain on the delivery schedule. As of two days ago, the vertical turbine pump shipment was in Chicago waiting for shipment to Christchurch.
Despite a range of drill problems, this week saw 3 holes drilled, with hole 4 starting at 11:00am on Monday morning and hole 6 expected to be completed around 10:30pm on Sunday night. We are still dealing with air in the fuel issues, although we are slowly making progress in that area and the fuel system is more stable than it has been for the past 3 weeks.
We have also experienced our first hose failure for the season. The hose section was replaced immediately, which caused a 2 hour delay to drilling. We have identified another section of suspect hose which will be replaced during the next hole.
The transition point from the firn to the ice on hole 6 had a significant constriction. The constriction was removed using a 40 meter hose with a nozzle and about 20 gpm of bypass water.
We expect to commence drilling again on Wednesday, after the two day Christmas break, and expect to complete two more holes before the new year. Firn drilling is proceeding smoothly. We are currently on hole 15 and expecting to complete the 18th firn hole within the next week and a half. The plan is to then drill a couple of next year's holes.
The drill crews are in good spirits, although tired and looking forward to the two day break.
The deployment team completed the installation of two strings during the past week. Strings 71 and 70 were installed using the DOM Connection Monitor (DCM) which provides information on the accuracy of the DOM connection. The night crew completed the last two deployments while the day crew helped with setup, hole moves, and preparations for the deployments. The installation of String 76 is due to began in the early morning of December 24, 2007 and should be completed soon after this weekly report is issued. The deployment team is also looking forward to the coming holiday break but will spend some of that time working on special devices equipment, archiving photographs and preparing for future deployments.
During the past week three DOM test cycles were finished and 180 DOMs delivered to deployment in strings 70, 77, 76. A fourth test cycle has just been started, to be finished in a few days. Due to the hot weather (up to about -22 C) several DOMs had higher temperatures than foreseen in the test-criteria, but showed reasonable temperature curves and were thus passed. Two DOMs had to be retested due to a bad connection in the test system. 11 other DOMs had formal fails that were waived as the DOMs are considered fully functional. The Instant Garage used to shelter the DOMs during the tests was repaired and stabilized during the week, such that it will now have much improved capability to withstand strong winds as discussed in last weeks report. The DOM-testing activity continues to be in good shape with respect to the holes drilled and plans for the next holes.
The Standard Candle survived deployment to large pressure at 2150 m depth. After deployment, impedance measurements across the power input pins in the ICL matched pre-deployment measurements directly on the device, indicating there was no water leakage. We routed the ICL patch cables and did a successful power up test followed by a successful communications test (without laser pulsing). This was followed by the first laser pulsing run of Standard Candle 2, taken while still in water Friday December 21 NZT. A 22-string pDAQ run was taken. Both Standard Candle operation and IceCube data taking were successful. Elevated charge per event per DOM was seen as expected in the monitoring stream and the data are being analyzed in the North.
This week brought continued acoustic pinger runs following the first successful run last week. The purpose of the pinger is to measure acoustic signal amplitude after traveling multiple different distances from the same transmitter to the same sensor. This should overcome the systematic effects due to module-to-module variations that have prevented a successful attenuation length measurement with the first three deployed strings. During each pinger run we have watched SPATS waveforms in real time and confirmed that the pinger running in each hole has been heard by all three SPATS strings. The only SPATS string to be installed this year, String D, will be deployed in Hole 76 on Monday December 24th NZT following DOM deployment.
The SouthPole data System (SPS) at the IceCube Lab received an operating system software upgrade this past week. The process was handled incrementally, to minimize detector downtime. In all, 27 DOM hubs + 35 server-class operational computers were covered by the upgrade.
New DOM hubs have begun the integration process into the existing data system compliment. To date, DOM hubs to service strings, 63, 64, 55, 71, 64, 76, and 77 have been brought on-line to be commissioned as freeze-in continues.
Work has begun on improving the Gamma Ray Notificaton interface to the SPS. This work will include a software upgrade and re-cabling of the Iridium antenna on the roof of the IceCube Lab.
Elements of the South Pole Outdoor Test System (SPOTS) were relocated to make room for this season's new strings. The system consists of a DOM hub, several DOMs located outside of the ICL, and non-operational in-ice DOMs. The relocation will allow for future expansion as needed.
New DOMHubs are being kickstarted and added to the "paw" DOMHub configuration as they come online. The software on each new hub required by TestDAQ and pDAQ commissioning is then verified to be correct, and the GPS/DOR card functionality is also tested. All DOMHubs (IC22 plus 9 new hubs) have passed so far.
IceCube's first string deployed this year, string 63, was turned on by Jim Yeck on the evening of Dec 22 (the string was deployed on Dec 4, so it was expected that not all DOMs would be frozen-in). All 60 DOMs communicated. However, one wire pair was found to be high current (81 mAmps instead of the expected 60 mAmps), and the corresponding quad (#14) was unplugged as a precaution. The following morning, additional tests were run. The 56 remaining DOMs were powered up and put into iceboot, where their temperatures and scalar rates were quickly measured.
Three of the DOMs were still in water, including 63-48 "Pagophobia" (means "fear of ice"). An additional five DOMs appeared to be newly frozen-in but were seeing significant amounts of triboluminescence. We will wait a while before further tests are performed on this string.
This week a Mass Casualty Incident (MCI) drill occurred at the Pole. The MCI drill is an opportunity for the station to practice responding to potential emergency situations. IceCube staff participated in the response by quickly supplying available personnel, equipment, and transportation to the hypothetical accident site. IceCube staff helped transport victims to the station, establish the perimeter of the accident, and transport victims to the medical room. IceCube's quick and calm response to the drill was commendable and Perry Sandstrom deserves special mention for his role as a paralyzed victim in the scenario.
Advanced safety audits continued this week in the drill camp. Audits this week looked at third shift drilling operations, second shift firn drilling with the Independent Firn Drill (IFD), and first shift moving of the Tower Operations Structure (TOS). No major safety concerns were identified but action items of adding safety razors to the TOS, repairing a power switch to the IFD and adding inside outlets to the IFD were found.
Two incident reports were generated during deployment of the string at hole #70. The first incident involved the breaking of the yellow safety rope which struck a deployer in the hand (hand is fine). The second involved a five to six feet free-fall drop of the deployment cable during deployment due to loose spooling of the cable. While neither incident caused serious injury or damage to equipment there will be follow-up investigation and incident reporting according to procedure.