The default IceCube configuration is optimized for the TeV-PeV neutrino energy region. In the scenario where a potential signal is seen at PeV energies or above, but the IceCube array has not yet been fully deployed, the IceCube design permits considerable flexibility. String deployments can be modified to increase subsequent interstring spacings, expanding the geometrical area at little added financial expense. Since muons at these energies are brighter, one crossing the array would experience no "blind" corridors. Of course, performance at lower energies would suffer with increasing interstring spacing. Conversely, if a signal is detected at the lower end of the TeV-PeV energy scale, the detector can be "backfilled" using as-yet-undeployed DOMs to increase the overall pixel density. This would enhance sensitivity to lower energy neutrinos.
