|Cargo Shipped (year)||970000 lbs.||740000 lbs.||535000 lbs.||528925 lbs.||572000 lbs.|
|Cargo Shipped (total)||970000 lbs.||1710000 lbs.||1975000 lbs.||2773925 lbs.||3345925 lbs.|
|Avg Drill Time for Deep hole||57 hrs.||48 hrs.||41 hrs.||41 hrs.||35 hrs.|
|Ave. Hole Depth||2500 m.||2452 m.||2452 m.||2452 m.||2452 m.|
|Avg. Drilling Rate||1 m/min||2 m/min||2 m/min||1 m/min||1 m/min|
|Avg. Fuel per Hole||7164 gal||4800 gal||7400 gal||5520 gal||4810 gal|
|Fuel per Season||33118 gal||60423 gal||97000 gal||129169 gal||112220 gal|
|Fuel Used to Date||33118 gal||93541 gal||190541 gal||319710 gal||431930 gal|
|Drill Thermal Power Output||4 MW||4 MW||4 MW||4 MW||4 MW|
|Time to Deploy String||18 hrs.||11 hrs.||10 hrs.||8 hrs.||10 hrs.|
|Total In-Ice DOMs||76||595||1320||2400||3540|
|Funding||US-MRE: $43 million||US-MRE: $48 million||NSF-MRE: $52 million||PY 6 NSF-MRE: $37 million||NSF-MRE: $22 million|
Neutrino Telescope Statistics
- has 86 Strings
- has 160 IceTop tanks
- has 5480 Digital Optical Modules
- has 1 km3 of instrumented volume
- was completed on December 18th, 2010
- took approximately 7 years to complete
|Number of Researchers||~300|
|Total constructin funding||$275.3 million USD|
|Travel time from L.A. to South Pole||48 hrs|
|Austral Summer Avg. Temp.||-35 °F (-37 °C)|
|Weight of hose||25,000 lbs.|
|Ice Melted per Hole||200,000 gal.|
|DOM Power Consumption||3 W|
2008 - 2009
Education and Outreach
The International Polar Year (IPY) featured IceCube as one of the projects in its Above the Poles day December 4, 2008. IceCube researchers participated in an IPY-related webcast from the South Pole Station as part of the San Francisco Exploratorium's Dispatches from Polar Scientists on December 18, 2008.
Mark Krasberg, one of IceCube’s scientists, posted his South Pole experiences on the Exploratorium's Dispatches from Polar Scientists web site. His January posting pictured a 15,000 lb. IceCube surface-to-DOM cable in the cargo bay of a LC-140.
Working with another NSF sponsored program, PolarTrec, and the Knowles Science Teaching Foundation, IceCube selected a high school teacher to be trained to take part in IceCube construction at the South Pole in 2009/10.
IceCube winterovers participated in the 100 Hours of Astronomy's Around the
World in 80 Telescopes with a live webcast from the South Pole, on April 4,
2009 as part of the Year of As tronomy activities. IceCube uploaded text,
images, and video to the 100 Hours website. The event was celebrated at
several collaboration sites.
19 Strings Deployed in 08-09
The IceCube MREFC project exceeded its 2008/09 seasonal goal by deploying 19 detector strings, instrumented with 60 digital optical modules (DOMs) each, at the U.S. Amundsen Scott South Pole Station. Fifty-nine strings laced with 3540 digital optical modules now comprise the IceCube Neutrino Telescope that will be completed in 2011. Drilling the 2500 meter deep-ice holes with the Enhanced Hot Water Drill began without delay this season and with a new, optimized drilling procedure the drilling season ended one week ahead of the planned 16-holes schedule.
The efficiencies also led to less fuel consumption for the planned 16 strings. Consequently, IceCube received permission to drill three more holes than scheduled. The IceTop detector array continues to keep pace with IceCube with 19 new stations installed.
In 2008, IceCube was running for 349 days with nearly 99% of the DOMs operational. The system triggered over 34 billion events, sending 13 TB of data by satellite and 50 TB of preprocessed data by magnetic tape north for further processing.
One of the strings installed this year is the first prototype of potential six deep core strings that may continue the detection of lower energy events (in GEV range) now provided by the AMANDA detector, IceCube’s predecessor. The cost of Deep Core instrumentation will be funded by Swedish, Belgian and German funding agencies and installation by some contingency funds of the IceCube project.
AMANDA, scheduled to be decommissioned this year, provided scientific data for over 10 years. The planned six deep core strings will be located near the center of the array, have higher efficiency photomultipliers, and have more closely spaced digital optical modules in the deepest, clearest ice than do the regular strings. Deep Core will probe the same physics with a statistics of atmospheric neutrino events of order 10,000 per year. In the next few years Deep Core will have a glimpse at physics that will only be accessible to the next generation of long-baseline experiments over a significantly lIocnegCeur tbimeescale.22 String Skymap
Results from data taken with 22 strings for less than one year, bettered the AMANDA detector with seven years of data taking. Both detectors have accumulated more than 5000 neutrinos, but the angular resolution of IceCube is superior. The final sample of 5114 neutrino events agrees well with the expected background of atmospheric neutrinos. No evidence of a cosmic source is found yet, with the most significant excess of events in the sky at 2.2 sigma after accounting for all trials. The IceCube team looks forward to the results from data collected in 2008 with 40 strings deployed by the end the previous season 2007/08.
Among many other analyses, one was performed to search for muon neutrinos from the annihilation of Dark Matter particles trapped in the Sun. No signal was observed. The limits obtained on the annihilation rate were converted to limits on the cross-section for Dark Matter particles interacting with ordinary matter. Especially in the case of Dark Matter particles with spin-dependent interactions with ordinary matter the results are noteworthy–they improve by two orders of magnitude on the sensitivity previously obtained by direct experiments.
The IceCube extensible event viewer, known as the glshovel, is an event visualization tool developed to give IceCube physicists new perspectives on IceCube events using some of the latest visualization tools available. The glshovel is available on Linux and Mac OSX platforms and uses the Qt and OpenGL graphical user interface libraries. It has a user-extensible plug-in architecture, enabling end-users to add new functionality to view events in new and different ways. Finding new ways to look at data is key to developing new and novel approaches to event reconstruction and background rejection.
IceCube data is divided into multiple parallel "streams" of data (i.e. raw waveforms exist next to feature-extracted hits, simulated particles and reconstructed particles) and the glshovel provides a framework in which each stream can be rendered by one or more separately configurable classes. The glshovel can load these renderers at runtime, allowing users to easily create their own visualizations of their own data. The glshovel insulates physicists from most of the intricacies of the GUI framework; for the most part, only a knowledge of OpenGL and the data to be rendered is required to extend the event viewer, and the application takes care of managing animation and the viewport.
Plug in renderers simply specify what types of objects they can render, what their configurable parameters (e.g. colors, sizes, scales) are, and provide a function that renders such an object within a given time window. By varying the time window and storing generated frames, the application can very flexibly generate animations of simulated or real data.
IceCube Is Half-way There
Piles of empty cartons indicate only slightly the scope of this year's success–1080 DOMs deployed on 18 strings as well as 56 DOMs in 28 IceTop tanks. Improvements in the drilling process and hardware enabled the drilling teams to exceed the season's goal of 14 strings, 5 days ahead of schedule, despite a late start due to bad weather. Strings were deployed at the rate of one every 50 hours. This season's efforts suggest that 18 string seasons are achievable and that plans to incorporate a central deep core of DOMs to replace the AMANDA array will not change the overall timeline to complete IceCube by the end of the 2011 season.
Furthermore, IceCube manufacturing is more than half-way complete toward the 75+ string goal. DOM production is winding down–all of the main boards are complete and all PMTs have been delivered. Cable production is on schedule as well and all of next season's cables are at Pole.
A new heating system has been installed to maintain a minimum temperature for the drill hose stored on the main hose reel. This system will decrease the number of hose segments that need to be replaced due to leaks during the drilling season. Enough spare hose sections are now on site to last through the 2011 season.
So far 99% of the deployed DOMs that have been powered on are working. Analysis of the data from the DOMs deployed in previous years began in May of 2007. The forty-string data period begins on April 1, 2008.
IceTop Freezes In Early
The photo shows an IceTop tank at station 63 being filled on December 8, 2007. The supply tank carries water drawn from the drill system to fill two tanks at each station. The tanks are managed by a freeze control unit (FCU) that removes dissolved gas from the water as it freezes to form clear ice with few bubbles. It takes about 50 days to freeze 650 gallons in each tank. For the first time, this season's schedule permitted us to freeze all 28 new tanks before the end of the season and remove their FCUs. IceTop, like the rest of IceCube, is now half finished, with 80 tanks at 40 stations spread over half a square kilometer.
Two DOMs frozen into each tank record flashes of light from particles that enter the tank. Such particles are produced by interactions of primary cosmic rays high in the atmosphere. IceTop DOMs are fully integrated into the IceCube data acquisition system. By finding events in which several widely separated tanks fire within a few microseconds, we identify cascades of secondary particles produced by individual cosmic-ray nuclei that enter the atmosphere with energies equivalent to millions of times the rest mass of a hydrogen atom. The pattern of times gives the direction of the primary cosmic ray and the sizes of the signals give its energy.
Events on trajectories that pass near the deep detectors as well as IceTop light up both components of IceCube. Such coincident events are of particular interest because they carry novel information about the relative abundances of protons, helium and heavier nuclei in the primary cosmic radiation. Knowing the composition and how it changes with energy will allow us to distinguish among different models for the high-energy end of the spectrum of galactic cosmic rays and perhaps to see the onset of particles from extra-galactic sources, such as active galaxies or massive stellar collapses called hypernovae. IceTop can also detect bursts of lower energy particles, such as those produced in large solar flares, by continuously monitoring the counting rates of hits in each tank.
Analysis Groups Hard At Work
The IceCube working groups have been in existence for about two years and are now analyzing data from the 2007, 22-string configuration. Since their inception, groups have worked to prepare for analysis, developing reconstruction, simulation and high-level analysis tools. Much of this work was based on ideas developed during the operation of AMANDA. Many of these ideas were tested on the 2006, 9-string data set, leading to publication in journals and conference proceedings.
The 22 string analyses cover all the planned physics topics, but of course with the hope that something completely unexpected will surprise us–in a good way!
One of the most advanced analysis types is the search for point sources of neutrinos from cosmic objects. The hope is that the first identified source of extra-terrestrial high energy neutrinos will be revealed as a hot spot in the skymap of neutrino arrival directions. This could be a steady source of neutrinos or, perhaps, a shortlived burst from one of the enigmatic gamma-ray bursts, which output enormous fluxes of gamma-rays over time scales of seconds to minutes.
There may also be a diffuse glow of neutrinos from the sum of all sources in the universe. Each source may be individually unresolvable, but the sum might be detectable as an excess of high energy events above the expected rate of atmospheric neutrinos.
We are looking for evidence of dark matter, by looking for WIMPs from the earth and sun. Other exotic particles are also sought after–signatures of particles predicted "beyond the standard model" which may yield clues on the nature of supersymmetric theories of our universe.
IceCube Lab Inaugurated
After two years in the temporary IceCube Counting House, the IceCube Team moved cables and computers into the new IceCube lab (ICL). This move required that the surface cables from the nine strings from the past two seasons be disconnected and then relocated through new trenches to a tower of the ICL. Similarly, the surface cables from the 13 new strings were drawn into the ICL. The ICL (formerly used as a dormitory) sits at the center of the whole IceCube array. In addition, 34 DOM Hub computers that communicate with the DOMs and 44 server class computers for DAQ, processing and filtering, data handling and network services were installed. The servers each have 2 dual core Opteron 64 bit CPUs and with the DOM Hub computers have 420GB of RAM. The 184 hard drives have a raw storage capacity of about 20 TB. Altogether, the system requires about 25 kW of power and is backed up by enough UPSs to keep all systems going for at least 30 minutes if station power is lost. This completes the computer hardware required for all of the IceCube strings.
13 Strings Deployed in 06-07
The IceCube team deployed thirteen strings in the 2006-07 season–exceeding the 12-string goal. Without the weather related one-week delay at the beginning of the season, a 14 string season was clearly possible. This year the time to deep drill each hole averaged 41 hours, and more importantly, the average time between holes was reduced to 75 hours. In the end, the drillers could drill a hole less than every 3.5 days. An independent firn drill was new this season and drilled firn for holes 12, 13, and 14. Hole 14 will be first hole for next season. The use of this independent firn drill should reduce the time between holes by a half-day. Deploying time for each string averaged 10 hours. There are 1,424 deployed DOMs (InIce and IceTop). Only one DOM does not communicate from this season. Of the total, 1,417 DOMs or 99.5% are working.At the end of the season, the drill camp was placed in a ready location for next season, instead of being towed back to the winter storage site, saving about one week next year. Ready for next season are about 500 DOMs at the South Pole and McMurdo.
Data Acquisition System
In November 2006 the project adopted a plan to streamline the DAQ software. Principally the new DAQ merged the hub and string processor and changed the distributed control framework. An XML based deployment simplified the DAQ configuration and the server architecture system auto discovers and configures itself based on minimal input and few rules. Coinciding with the computer and server upgrades in the ICL, the new DAQ software integration began in late January 2007. By the close of the South Pole season on February 21, 2007, the 22 in-ice strings, 26 IceTop stations and the AMANDA detector were integrated into the DAQ. The new software has fewer lines of code and requires fewer computing hosts. The configuration server system is simple and flexible allowing uniform deployment across several platforms. Each developer can bring up real instance of DAQ (simulated DOMs) on a system as simple as single laptop for development work. Turn-around time is very fast: 30 seconds for complete deploy and start-up to running state compared to the previous system which took 10 minutes. This enables quick edit-compile-debug looping.
Until one year ago the priority for simulation was the implementation of all of the ingredients for the generation of physics events, their propagation through the Earth and ice, the simulation of Cherenkov photon propagation in the ice, the photomultiplier tubes response to photons, the DOM functionalities, and the data acquisition trigger decisions. The comparison of simulated physics events with the real data taken during 2006 with the first nine strings provided precious information for the refinement of simulation software. Then the software underwent a major structural change last year requiring adaptation to a new data structure. This transition led to the implementation of an efficient and well scoped series of unit software tests to ensure stability and reliability. Consequently, simulation quality improved substantially in terms of how the physics is described and how the detector functions. We are now able to simulate coincident events between IceTop surface arrays and IceCube in-ice strings. We can simulate events with IceCube and AMANDA responses and merge them in a single event, as the real detector does. The quality of simulation continues to improve.
Improved Drilling in 2005-06
Using a second drill tower and and improved firn drill, the IceCube drill team was able to drill eight holes this year. By coordinating their efforts they increased their rate from one hole every six days at the beginning of the season to one hole every three and one-half days at the end of the season. If drilling can begin by December 1, then it will be possible to drill an average of 14 holes each season. Contributing to the efficiency of drilling was the increase of drill speed from 1.3 m/min at the beginning of the season to 2.2 m/min at the end. The second season also led to better performance in drill camp set-up and shutdown. Plans for next season include three nine-hour driller shifts instead of two twelve-hour shifts and dedicated heavy equipment for IceCube operations. Other improvements included a new hose, improved heater reliability, and elimination of fuel system air problems.
8 Strings Deployed in 05-06
The yield of fully functional DOM from this year's deployment of 480 in-ice and 48 IceTop DOMs was excellent. Approximately 99% of the DOMs that were deployed continue to operate as of April 2006. Four DOMs failed and three of the failures appear to be related to in-ice connector, cable or penetrator failures and not a failure of the DOM internal electronics. One in-ice DOM suffered a high voltage failure soon after turn-on. Cold-temperature communications problems with a number of DOMs were encountered this season and changes were made in the software and there is no longer an effect on data taking. Data can now be taken continuously with all DOMs using the testing and commissioning data acquisition system. Locations where DOMs have taken a long time to freeze in are correlated with higher drill dwell time at that depth. Within hours of the turn-on of the 9th string, it was possible to obtain clear multi-string events (many of the DOMs were in water at the time). Locations where DOMs have taken a long time to freeze in are correlated with higher drill dwell times at those depths.
South Pole Test System
The South Pole Test System (SPTS), a mirror site for the South Pole System, operates in Chamberlin Hall, UW-Madison Physics Department. The SPTS is the final test bed for the data acquisition and data handling software and is used to test patches and upgrades to the software operating on the South Pole System (SPS). An additional test facility is located at the UW-Madison Physical Sciences Laboratory that includes a fulllength surface to DOM cable and DOMs in portable freezers to simulate actual DOM operating conditions. This additional test facility will eventually be moved to Chamberlin Hall. All the electronic and computer equipment required for the 2006-07 season is received and assembly of the actual system will be completed in Madison to confirm performance prior to disassembly and shipment to the South Pole. Ordering has been completed for the cluster that is being built to support simulation analysis. The cluster is currently scheduled to be online sometime in June 2006.
Data Acquisition Progresses
Data continues to flow from the detector, with about 25GB/day of raw data being archived to tape at pole and 5GB/day being transmitted over satellite to the data warehouse at UW. The event count for the IceCube 9 string array, with 595 DOMs currently reading out into the data stream, surpassed 250 million events on 4/4/06 and is upwards of 360 million events two weeks later. Detector uptime peaked at 99% on 4/4/06 and holds at approximately 80% averaged over week intervals–a 122% increase over the same period in mid-March. This increase in uptime is due to improvements to both DOMHub hardware components and DAQ software. In the Northern Hemisphere, the DAQ application level software (not resident in the DOM itself) will migrate to 64-bit computing platforms in order to increase computing density and decrease power consumption. Preliminary testing has run smoothly and there are predictions for an easy transition. (Above as of April 4, 2006)
Enhanced Hot Water Drill (EHWD)
IceCube staff shipped the hose reel and some of the components of the EHWD from Wisconsin to the South Pole in the 2003-2004 Austral season (∼Nov. 1-Feb.15). The hose reel had to be disassembled to fit into the cargo bay of a LC-130 aircraft for the final leg of the journey from McMurdo to the Pole. A team of seven reassembled the hose reel in January 2004. The following Austral summer the rest of the EHWD, 900,000 lbs., arrived in 30 separate flights. In addition to the hose and heating plant, a drilling/deployment tower was shipped and assembled. Twenty-four IceCube and Raytheon staff members spent two months putting the system together and field testing the heating plant and control system. The working temperature at the pole averages -35°F during the summer. Drilling for the first hole began on January 15, 2005.
2004-2005 Austral Season
Drilling on the first hole stalled at about 1200 meters. The team determined that damage to the drill head prevented further progress so they relocated the tower and started a second hole. After 38 hours they reached a depth of 2450 meters. Reaming the hole on the way up took another 19 hours before they turned the tower over to the deployment team. Within 20 hours the first string of 60 Digital Optical Modules (DOMs) was deployed. In addition, 16 DOMs were installed in eight IceTop tanks. These DOMs will be part of an array that will identify IceCube events that are coincident with cosmic ray air showers and examine cosmic rays with energies up to 1018 eV. Only three weeks of the usual 12-week Austral summer were available for drilling and deployment during this first season. Early analysis indicates that all DOMs are working and that the DOM clocks are calibrated to within 2 ns.
2005-2006 Austral Season
Ten strings are planned for the 2005-2006 season and over 800 DOMs are under construction in Wisconsin, Germany, and Sweden. One hundred and eighty DOMs are stored at the South Pole. Over 1800 components comprise each DOM, including 10 inch Hamamatsu photomultiplier tubes. The DOMs undergo extensive final acceptance testing (FAT) at their respective assembly sites. This testing includes three weeks in a dark freezer to establish the lowest noise levels for each DOM. In the 2005-2006 season the average IceCube population at the South Pole will be 45 people. Each will have completed medical and dental exams to be physically qualified (PQ'd) to work at the 10,000 ft. equivalent altitude of the South Pole. While installation of instrumentation proceeds at the South Pole, scientists and engineers in the northern hemisphere are developing the software to analyze the 54.7 terra bytes of data that will be produced annually once the telescope is finished. This data is stored on magnetic tape at the South Pole and shipped to the University of Wisconsin for archiving and retrieval by IceCube scientists. Researchers are developing tools that will enable scientists around the world to access and analyze the data for evidence of gamma-ray bursts, WIMPS, and dark matter.
IceCube is Already Working
The first new optical sensors of the IceCube neutrino observatory, 60 on one string and 16 in four IceTop stations, were deployed during the austral summer of 2004-05. Analysis of the first few months of data collected by this configuration is underway demonstrating that hit times can be determined across the whole array to a precision of a few nanoseconds. Coincident IceTop and deep-ice events are recorded and the capability to reconstruct muons with a single string has been verified. Muon events are compared to a simulation. The performance of the sensors meets or exceeds the design requirements. Fig. 1 shows an event involving all 76 DOMs. The circle size is proportional to the signal amplitude, while the color (from blue to red) indicates relative times of the hits recorded in the DOMs. All hits are consistent with an air shower on the surface coincident with a deepice muon, traveling down at a zenith angle of 3 +/- 2°. From the ice scattering-length profile shown next to the detector string, one sees that most of the detector is located in very clear ice. In fact, the lower 25 DOMs are in ice that is up to 2 times clearer than that available to the AMANDA  sensors located at depths of 1500-2000 meters. (from the introduction of Dima Chirkin's paper for the 29th International Cosmic Ray Conference in Pune, India, August 2005)