University of Wisconsin-Madison

The start of the IC86-2014 physics run

IceCube has been called the strangest detector in the world. People of all ages are surprised to learn that thousands of sensors are buried deep in Antarctic ice to help us learn about the most extreme and remote places in our Universe. What if a sensor breaks? Is there something you can do to improve IceCube now? These are questions that IceCubers are asked again and again.

It’s true that we cannot physically get at the sensors, the so-called DOMs (digital optical modules), but we can interact with them electronically. Moreover, improving how a detector works also means tailoring data to the needs of the IceCube Collaboration, or even to the needs of wider research communities.

This happens every year for IceCube around mid-May, when new detector configurations are applied to keep up its performance and to improve scientific results. When this happens, it signals the start of a new physics run. Last week, on May 6, the IC86-2014 physics run was launched.

“Having our detector buried in the ice provides very stable conditions, so we don’t need to tune the IceCube DOMs very often,” explains John Kelley, manager of IceCube detector operations and a researcher at the Wisconsin IceCube Particle Astrophysics Center (WIPAC, UW–Madison). “We’ve found that changing settings once per year provides a good balance between keeping the detector in peak operating condition and keeping the data stable for analysis.”

What’s new for the IC86-2014 physics run?

Every year, the detector is recalibrated to tune its response to the light emitted by very high energy neutrinos and muons interacting with the ice. To do that, enhanced knowledge about the ice properties and possible changes in the DOM operations are taken into account. Dedicated electronics and software built into the DOMs provide a means for calibration by flashing onboard LEDs in the ice. This calibration allows researchers to tune the DOMs’ operating settings, an important step since understanding the detector’s light response is key to measuring neutrino and muon energies.

But operating the IceCube detector requires more than taking care of the DOMs, explains Erik Blaufuss, an IceCube researcher at the University of Maryland who is responsible for the real-time neutrino filters that run at the South Pole. "We are constantly improving our software that reconstructs neutrinos, and this yearly run change is our opportunity to bring the best tools into service." The 2014 configuration includes improved neutrino reconstruction techniques with the hope of localizing the elusive sources of the recently observed extraterrestrial neutrinos.

The new physics run in IceCube also benefits other members of the astrophysics community. IceCube has an exceptional and somewhat peculiar view of our Universe, as it can detect neutrino bursts from potentially anywhere in the galaxy and beyond. Very high energy particle bursts, as neutrinos or gamma rays, are immediately shared within a growing number of experiments and collaborations looking at the extreme Universe, because they may point to interesting places or set up time frames to search for new information about the Universe.

But IceCube alerts have to deal with an extra challenge as relevant data must first be selected and then sent by satellite to the alert community network. With the new run and new neutrino reconstruction tools, IceCube has put in place the tools needed to quickly identify neutrino events and has made an important step toward more real-time neutrino alerts.