University of Wisconsin-Madison Physical Sciences Lab

Digital Optical Modules

IceCube Digital Optical Module

PSL has built more than 3,500 optical modules for the IceCube project over the past several years. Each 330mm diameter optical module contains a large diameter photomultiplier tube and a printed circuit board base potted in a clear glass hemisphere using an optically clear silicone gel. The upper hemisphere contains a connection to the outside world through which the power source and electronic controls on the surface interact with the module. The sealed modules are frozen in the ice, up to 2,400 meters deep, with tubes pointing toward the center of the Earth. Due to their deployment in such harsh conditions, each module is extensively tested for quality, including being frozen in a specially designed dark freezer for six weeks at -55° C.