Last String!

The last string of IceCube for the Season has been deployed! In all, we deployed 20 strings this season and we are 10 days ahead of schedule. We started drilling on December 10, 2009, and finished on January 20, 2010. There are 60 DOMs (digital optical modules, the globe in the middle) on each string separated by 17 m (see photo). Each string is 2500 m long (1.5 miles) and weighs several tons, and the DOMs are attached in the depth between 1500 to 2500 m. Each DOM weighs about 40 pounds, and the cable is spooled on an 8 ft reel before installation. For deployment, we attach the DOM to the cable as the cable is being lowered into a hole in the ice.

It takes about 24 hours for the hot water drill to drill the hole, a couple of hours to switch from drilling to string deployment, then three to five hours to deploy the string depending on the team and whether there are special devices being deployed as well. The hole is drilled by a whole different set of crew of 30 working on three 8-hour shifts per day, drilling at the rate of two to three holes per week. The deployment works on two shifts since it usually takes maximum of five hours per hole.

During string deployment, there is one person operating the two motorized winches (one for the main cable and another to help keep the DOM in place while it gets installed) (the woman in the yellow helmet), two people standing next to the string to prep the string and install upper connection to the DOM (two guys in sunglasses), one person hooking up the lower connector (the guy behind me with black neck warmer), one person prepping the DOM (fourth from left), one person with a clip board and a check list making sure all connections are made, measuring the distance between each DOM, and writing down the cable markings (the guy in blue fleece), and one person feeding the signal cables and taking a photo of each DOM as a record of how they were connected and which one was deployed (this was my job). You see two more people in the photo: the woman in the green helmet in the back helped prep the DOMs, and the blue helmet to the right of the DOM oversaw the whole thing, making sure that the main cable was spooling out correctly and helping out with whichever job may be falling behind.

Once it starts flowing, it's like playing in a string quartet: everyone knows their job and everything flows very smoothly. It was extremely satisfying to be working in a team of very competent, hard-working (and fun of course) people, and at the end, there is a very tangible result.

Since this was the last string, we had many visitors during deployment, from IceCube drillers and scientists to past members of the collaboration who now works on other projects at the Pole, and DV's (distinguished visitors) from the NSF and DOE who just happened to be visiting the South Pole for the day. We all got to sign the last DOM, and it was lowered into the hole by 6 PM. From there, the cable had to be lowered another 1500 m, put on an R&D device at -50 m, the cable tied off, and were really done by 9 PM. This morning, we turned on the DOMs for a quick look, and everything seem connected. In all, I helped deploy three strings this season.

Now it's time to clean up, and my job is to start the initial calibration of the DOMs, make some configuration files for the data acquisition system, and hand them off to the collaboration.

The drillers will be packing everything up for the winter and start leaving the Pole in the next one to two weeks. I will be leaving with the first of the crew. After that, we wait for the DOMs to freeze in and it's up to us scientists to turn on the detector and discover something.