The 6th and 7th strings of the season were successfully deployed this week. The string for the 6th hole was secured on December 24th and the 7th string at 3am on December 29th, following a two-day holiday break. The drilling of the hole for the 8th string will be completed late on Sunday, December 30th, and deployment preparations will begin before December 31st. Assuming that deployment proceeds as planned there will be 8 strings installed between the actual start of drilling on December 5th and the end of the month. 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.
| 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 | ||
| 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | |
| Hole Location | 60 | 68 | 61 | 62 | 52 | 44 | 53 | 54 | 45 |
| String Installed |
A tradition has been started that IceCube personnel on ice during the Station's holiday break sign a DOM that will be installed on one of the next strings deployed.
The commissioning of the installed instrumentation is now well underway following the arrival of Mark Krasberg. So far there are no surprises with respect to the DOMs deployed with the new strings and IceTop stations. One of the IceTop DOMs installed in the first season (hydrogen) has failed due to a failed photomultiplier tube. There is an ongoing effort to investigate possible factors contributing to this latent failure.
The safe production of deep ice holes continues to be the most critical activity.
The IceCube population at the end of the week is 48. This last week had very little turnover. On January 3rd there will be a big turnover day for IceCube. We will have 7 arrivals and 6 departures. It will make for a good group picture at the meeting area near the LC-130 parking location. Flights to the Pole have been infrequent in the last two weeks. As a result, we are behind our plan for surface to DOM cable deliveries. We will end the week 3 cables behind plan and we hope that flights will resume a more normal schedule next week so that we can catch up. There is currently no danger in cable delivery delaying drilling in any way as we will start next week with 2 surface to DOM cables on the ice. The vertical turbine pump shipment which we have been looking for is now in McMurdo and should arrive soon at Pole.
Drilling continues to proceed very close to the original schedule and is paced by efforts to maintain drilling equipment. Three sections of hose were replaced due to damage to localized parts of the hose, one section during each of the three holes drilled. Replacement of each section requires about a two-hour delay.
The drill cable used from the start of this season was replaced with a spare cable stored at pole. The old cable had developed problems with communications due to water in the connector joining the cable to the drill head. The spare drill cable was spooled onto the cable reel winch over the holiday break and was performing well until it was noticed that the jacket was cracking as it spooled off the reel. We elected to use the cable for the 8th hole, paying close attention to the damaged sections. We may use the original cable for the 9th hole, by reversing the cable so the end with the potential for water intrusion is used on the surface and the good end is used for the connection with the drill head. There is an additional cable at the pole that was re-spooled for similar reasons in previous seasons.
The deployment night crew completed their second installation for the week with the cable drop and drag of String 77, the first string of the week. Hole 76, was installed and tied off safely on Monday, December 24th. Eight strings are projected for installation before the start of the new year on January 1st.
The 28 IceTop tanks deployed this season are freezing in nicely. Each insulated tank holds about 625 gallons of water that freezes from the top down into optically clear ice by means of an active Freeze Control Unit. The process takes about 40 days. Freeze monitoring data continues to be collected in the ICL by the IceTop freeze computer.
Transmission of the data to the north has been troublesome this past week, but there have been no negative impacts on the freeze process.
The new Freeze Control Unit (FCU) enclosure and heater design is keeping the FCUs nice and toasty on each tank. We continue patrols to monitor for snow drifting inside the tanks that would reduce the freeze rate.
The IceTop water filter is being prepared for vessel retro to Delaware for refurbishment. Many thanks to Dennis Duling for his help and advice.
The week started with the deployment of string #76. After the holiday break, string #76 was tied off and connected to the Surface Junction Box. All quads passed QCT (Quad Connectivity Test). Patch cables were pulled for string #76 and QCT and WCT (Wet Connectivity Test) were done in the ICL. Preparations were made for the deployment of string #77 and patch cables were pulled. One quad failed QCT in the ICL and that failure was found to be shorted pins on a connector in the SJB. The connector was removed and is scheduled to be replaced. Deployment of string #75 is scheduled to start on Dec 30 around 7pm.
DOM testing proceeded as scheduled with few problems. The Buffer size is now quite large at 150. Since we have so many extra DOMs in the buffer, the possibility of not doing a few test cycles at the end of the season and using DOMs from the buffer instead has been discussed. Finally, it seems the majority of the DOMs with names ending in "ish" and having a color theme have database problems, since the mainboards in these DOMs were replaced, and therefore have multiple entries in the database. Special thanks to Mark Krasberg for resolving these database issues.
Photo to the left shows Standard Candle after final alignment. There is a piece of paper inserted behind the sapphire window to fluoresce and trace a cross section of the emitted light cone. The three vanes supporting the reflective cone in the center are visible. The laser spot is centered on this reflective cone so that a cone of light is flashed in the ice at the Cherenkov angle, simulating a signal produced by a neutrino-induced cascade in order to calibrate the response of IceCube to cascades.
One additional type of special device will be deployed this season, an inclinometer. This small device will be used to measure shear in the ice.
The SPATS acoustic string-D was successfully deployed on Monday December 24th 2007 NZDT, after IceCube string 76 deployment and anchoring. It took about 4 hours and 6 people. String-D was hooked up to the AJB (Acoustic Junction Box) on December 25th 2007 NZDT and commissioning and early data-analysis have shown that all sensor channels and transmitter are operational. String-D is now included in regular SPATS data-taking and monitoring.
The South Pole Acoustic Test Setup now has 4 operational strings, each with 7 acoustic stages at depths going from 80 to 500 meters.
Furthermore there was successful pinging in holes 6 (string 76) and 7 (string 77), each run took about 2 hours to complete, going down to 500m depth with 5 minute stops on each SPATS breakout level. String-D was still freezing in during the last pinging and the data shows frequent and large transient events.
A new data archive system was brought on-line this week for testing. The system consists of a server host, attached storage, and a tape library unit, with four drives and a capacity for 66 tapes. The new hardware addresses expanding data recording requirements as the IceCube detector continues to grow.
Backup software and storage was installed in the ICL. The system is targeted at server configuration data and database dumps with 4.6 TB of near-line backup storage available.
Serial cable was run through the ICL for the eventual benefit of the IceCube Teleport System (Iridium SBD-based message passing). The cable stretches from the antenna box on the roof into one of the racks in the data center.
This week saw additional DOM hubs brought on-line and integrated into the existing SouthPole data System (SPS) compliment. To date, DOM hubs that will service new strings 63, 64, 55, 71, 64, 76, 77, 75, 69, 60, 68, 61, 62, 52, 44, 53, 54, 45, 41 and 35 have been installed at the ICL. Several of the strings have been powered up as freeze-in continues.
There are now 23 South Pole System DOMHubs that are not part of the first 22 Hubs and all installed software versions and appropriate GPS checks have been made.
IceCube's second deployed string of the season, string 64 (deployed on Dec 12), was briefly powered up on Dec 26. All 60 DOMs communicated, and all were either frozen-in or newly frozen-in, i.e, still high rates.
On December 27, string 55 (deployed on Dec 16) was briefly powered up. All 60 DOMs consequently powered up and communicated (one was still in water). Then, on Dec 28, string 71 (deployed on Dec 19) was briefly powered up. All DOMs had initially passed the DCM and also the WCT & QCT. 71-39 "Beaver" did not draw any current. This DOM now also fails the QCT and will probably never work.
We are very close to running the full set of commissioning tests on the first group of the newly deployed strings of the season. To date, 239 out of 240 In-Ice DOMs have powered up and communicated.
A busy week in safety began with station physician Patricia McGuire leading a group of seven IceCube participants through an AED overview course. Pat discussed how an AED works, what to do when an unconscious person is found, and things to think about during this process to increase the success rate of a revival. The course was very helpful and thanks go to Pat McGuire for her help.
Two incident reports were initiated for incidents occurring this week. No one was hurt and no equipment was damaged. The second incident involved a punctured deployment cable reel by the forks of a 953. The deployment cable was not damaged and was used successfully in the deployment. Both incidents have been communicated to all drillers to ensure they understand why they occurred. Advanced safety audits continued this week.