December 9, 2008, South Pole Station -- James Roth
Building IceTop
I was the first of the UDEL IceTop team to arrive At South Pole this season. It is my job to handle the deployment of the 160 IceTop tanks that make up the surface array of the IceCube project. 80 IceTop detector tanks have been deployed during the previous four seasons. This year is by far our most aggressive season with the planned addition of 38 new tanks to the detector array. It has been a whirlwind of activity since my arrival. I’d like to share with you the preparation that goes into constructing this large array of clear ice detectors.
Much of the ground work for a season on the ice happens way before we arrive at Pole. Meetings were held throughout the spring and summer. We reviewed our successes and challenges of the 07 season and developed a detailed and coordinated plan for 2008. With a construction season that is only 3 months long, there is not much time in the schedule for delays.
I was scheduled to arrive on Nov. 6th, but due to weather delays, I spent a few extra days in McMurdo. I did get to go bowling at McMurdo’s two lane bowling alley. It is one of the only alleys in the world (possibly the only) to be operating a Brunswick manual pinsetter. Watch for brightly colored socks before you bowl!
Brunswick Manual pinsetter at McMurdo
I finally arrived at Pole on Nov. 11th. My first job was to inspect and refurbish the 28 Freeze Control Units (FCUs) that were used during the 2007 season. The work was started in the IceCube Lab because we did not yet have heat and power at our IceTop weather port in the drill camp.
Hermann and James begin FCU refurbishment in the IceCube Lab- Photo Hermann Kolanoski
Within a few days the drill camp generators were online and we were able to move all of our equipment to our IceTop weather port. I finished the refurbishment of the FCUs and began to calibrate them for another season freezing a new batch of IceTop tanks. Ten new FCUs arrived from Delaware and were added to the list to prep for use.
While I worked on FCUs, Hermann and Tom began preparing the tanks for use. Sunshade frames had to be installed. Cloth gaskets had to be applied to enclosure doors and additional insulation work to protect the FCU from the -35 temperatures.
The Digital Optical Modules (DOMs) began arriving from the DOM testers. These DOMs are the same detectors used in the deep ice array. When they come to us they need to be mounted on a holder that will suspend them in our tanks until they are frozen into the ice. There are two DOMs per tank so 76 need to be mounted.
Tom at IceTop weather port with boxes of DOMs Photo Jim Haugen
Tom and Olle mount a DOM for IceTop installation Photo Hermann Kolanoski
The IceTop tanks are placed on level pads in pits at each station. Once the tanks are in place, Tom, Herman and others lending a hand, mount two DOMs in each tank.
An IceTop tank is placed in the pit. Photo James Roth
With the tanks and DOMs now in place, it’s time to connect them to a Surface Junction Box (SJB). The SJB connects the DOMs and FCUs to the IceCube lab by means of a surface cable. Without the power provided by the surface cable, I would not be able to deploy a single IceTop tank.
Hermann and James connect a Surface Junction Box Photo Jim Haugen
The surface cables are laid in trenches to protect them from damage by vehicles. Our cables this season will be distributed into four trunks. The first trunk provided cables to five IceTop stations. All 19 cables this season will be pulled into one tower of the IceCube Lab.
Once the cables are connected in the ICL, We are ready to install FCUs into the tank enclosures in the pits. The FCUs will control the enclosure temperature for safe operation.
Hermann works to install an FCU Photo James Roth
With the FCUs operating, there is one more step before filling a tank. I have to climb into the tank, sweep it out and install a membrane contactor to remove the dissolved gasses from the water. By removing the gasses the ice will freeze perfectly clear. The contactor assembly is eventually frozen permanently into the ice.
James inside an IceTop tank after installing the contactor. Photo Tom Gaisser
Perfect ice requires perfect water. Hermann operates a Reverse Osmosis water filter to remove any contaminants, especially glycol from water provided by the drill camp. Testing is done to assure the glycol content is below minimum thresholds. The purified water is filled into a transport tank for delivery to each IceTop station.
After the tanks are filled the lids are closed to allow some of the dissolved gasses to be removed before freezing starts. After three days, Sunshades are installed on the frames to keep direct sunlight off of the sensitive DOMs. The tank lids are then opened and the freezing process begins.
DOMs in Station 6 at the start of Freezing. Photo James Roth
Station 6 with the sunshades on and the new elevated station in the background. Photo James Roth
It will take 50 days to freeze the 600+ gallon tanks. A computer in the IceCube Lab monitors the freezing process. Once a day, data is sent to the northern hemisphere, analyzed and can be monitored on a website. An alarm program sends an alert to technicians if a problem occurs.
As of today, 10 tanks are filled and 6 have started freezing.
