Digital Optical Detectors in IceTop (IMAGE) University of Delaware Caption This is a close-up of the two digital optical detectors in each IceTop tank as a tank is filled with water. The ice must be frozen perfectly with no bubbles or cracks. Such imperfections could obstruct the tiny flash that occurs when neutrino particles pass through the ice. Credit University of Delaware Usage Restrictions Image must include credit to University of Delaware. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.