IceCube

Spencer Klein in the IEEE Spectrum reflects on the deployment of IceCube's last string. (February 2011).

"On Saturday, December 18, the IceCube Neutrino Observatory sank the last of 86 strings of sensitive photodetectors to a depth of almost two and a half kilometers in the ice at the South Pole, marking completion of the huge neutrino telescope.
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Icecube completes drilling and construction of the detector with the deployment of the 86th string on December 18th (New Zealand time).

"The highlight of the week was the successful completion of major IceCube construction. The drilling of the 7th borehole of the season, the final hole of the IceCube array, was completed in the morning hours of December 18. The 86th and final IceCube string was tied off on Saturday, December 18, around 1800h New Zealand time."

The final configuration of the IceCube neutrino observatory after the coming 2010-2011 season deployment is shown below.

A record total of 20 strings were deployed this season, bring the number of IceCube strings to 79. The deployment was finished ten days ahead of schedule.

Spencer Klein and Thorsten Stezelberger camped out at Moore's Bay on the Ross Iceshelf to test a protoype station for ARIANNA (Antarctic Ross Iceshelf ANtenna Neutrino Array) a prospective neutrino telescope that uses radio frequencies instead of optical light.

Read Spencer's blog for an account of their adventure.
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The ice sheet in which the IceCube sensors are deployed is a dynamic medium. The sheet moves about 10 meters per year at the surface, but how, and how much, it moves at depths approaching bedrock is unknown. Since precise knowledge of the locations of the DOM modules is a prerequisite for tracking neutrino-induced muons, studies of the movement of the ice using the deployed modules are both of interest and essential. There are various methods for determining the locations of the modules, and previous investigations with AMANDA indicate that the direction of strain is perpendicular to the direction of flow, a remarkable result. Buford Price's group and, in particular, Ryan Bay, have been conducting these and other studies of ice properties.

About two years ago, Jerry Przybylski noticed a new MEMS (Micro-Electro-Mechanical-System) chip that can measure inclination to 0.025 degree and determined that the chip could be mounted in some vacant real estate on the DOM mainboard. Working with Thorsten Stezelberger and Ryan Bay, he designed a daughterboard to hold the inclinometer chip. About 50 were produced, and 32 of them were deployed in DOMs this season (09-10). Next year another 16 "iDOMs" will be deployed. When combined with flasher measurements, it will be possible to determine not only the amount of the tilt of a module, but the direction of tilt as well.

Here's the briefest of descriptions of how an inclinometer is fabricated on a silicon chip (courtesy of Ryan Bay): The tilt sensor is based on a dual axis accelerometer. The accelerometer is a "surface-micromachined polysilicon structure built on top of the silicon wafer. Polysilicon springs suspend the structure over the surface of the wafer and provide a resistance against acceleration forces. Deflection of the structure is measured using a differential capacitor that consists of independent fixed plates and plates attached to the moving mass. The fixed plates are driven by 180° out-of-phase square waves. Acceleration deflects the beam and unbalances the differential capacitor, resulting in an output square wave whose amplitude is proportional to acceleration. Phase-sensitive demodulation techniques are then used to rectify the signal and determine the direction of the acceleration."

Their work is described in the following article "IceCube DOM Embedded MEMS Inclinometer/Accelerometer (iDOM) by Ryan Bay, Gerald Przybylski, and Thorsten Stezelberger. Download pdf.
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AMANDA, the neutrino detector that made IceCube possible was turned off and decomissioned this month after two years of combined operation with IceCube strings. AMANDA deployed 19 strings over the period 1996-2000, one of which - String 18 - used the prototype digital optical module technology that was selected for IceCube.
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In March 2008 Berkeley Lab scientists and engineers met to celebrate the completion of 5,693 “mainboards” that are key components of the unique IceCube observatory. PDF

IceCube has very successful third season (2006-2007) at the South Pole with the deployment of thirteen additional strings.

During a highly productive season, IceCube scientists and engineers successfully positioned 13 strings of optical sensors deep in the polar ice. Each string carries 60 of the digital optical modules (DOMs), which capture the light emitted in the ice by the products of neutrino collisions. This year's efforts more than doubled the number of installed DOMs to a total of 1,320, roughly one-fourth of the 4,800 sensors that will ultimately make up the IceCube Neutrino Observatory when it is completed in 2011.

The lowest DOM on a string

resides 2500 m below the surface of the ice (and about 300 m above bedrock). A special purpose five-megawatt hot-water drill is used to melt ice and form a column of water 60 cm in diameter to a depth 2500 m. The DOMs are attached to the electrical cable one by one until all 60 are in place. Then the entire string is lowered to the final depth and the water column refreezes. Once the water freezes, neither the string nor any modules can ever be retrieved. Located at the top of each string are two tanks of ice, each containing two DOMs. These form the surface air-shower array, IceTop. During the first season (2004-2005) one string was deployed, which was followed by eight strings the next season. The 13 strings put in place this season show that IceCube is on track to reach its deployment goal of 16 strings per season.

Another major accomplishment of the season was the construction of the new IceCube Lab, which houses the surface electronics and computers that form the data acquisition system. This system collects the information from the DOMs, sorts and analyzes it to determine the detection of cosmic rays and neutrinos. A small percentage of the data will be transmitted via satellite to North America, while the rest is written on magnetic tape at the Pole and brought north when regular flights to the South Pole resume the following October.

Even though the last of the deployed strings was still "freezing in" at the end of February, by March, 2007 cosmic ray events involving 20 of the 22 strings have been observed. This is one example:________________________________________________________

In the Nov. 2005 to Feb. 2006 season, IceCube successfully deployed 8 strings of InIce detectors, containing 540 DOMs. In addition, another 24 IceTop ice tanks, containing another 48 DOMs were deployed on the surface. About 99% of the DOMs are operating as designed, an outstanding record.

LBNL played a major role in this years construction season. Nine LBNL researchers traveled south to the Pole to participate in the deployment
and testing: Keith Beattie (Computational Research) Bill Edwards (Engineering), David Hayes (Nuclear Science Division), Arthur Jones (Engineering), Spencer Klein (NSD), Chuck McParland (Computational Research), Jerry Przybylski (Physics) and Mike Solarz (NSD guest), and consultant John Jacobsen (Physics).

Following is an event triggered by our 'Standard Candle' laser, roughly simulating a
10^15 electron volt electron neutrino:

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