A Few Dollars Worth of Cross-Linked Foam

LAWRENCE, MA (October 3, 1997) – Astronomers at Princeton University are using Volara, a fine-celled, cross-linked, polyethylene foam, to protect a $5.5 million digital camera from condensation and ice. The camera uses CCDs (charged couple devices) to sense light sources in the sky over a wide area. These sensitive devices are operated in a vacuum and continuously cooled to -80C with liquid nitrogen.

The 1/4″ stainless steel lines which deliver the liquid nitrogen must be kept free of ice and condensation because water would damage other sensitive components in the 30″ round camera. This is easier said than done since conventional insulating materials become inflexible and brittle, and disintegrate under cryogenic conditions. This can lead to expensive and time-consuming repairs and cleanups.

The CCD camera, built over a 4-year period at Princeton, will be installed at the Apache Point Observatory in New Mexico in the Fall of 1997 for use in the Sloan Digital Sky Survey. Data gathered in the survey will enable astronomers to construct a 3-D map of the universe, a thousand times larger than existing surveys.

Michael Carr, mechanical engineer and a senior professional staff member at Princeton University, explained that the CCD cooling system behaves like a high efficiency dehumidifier. “Normally, while running liquid nitrogen through a stainless steel tube, ice appears immediately. When the liquid nitrogen is turned off (which happens frequently with this type of cooling system), melting ice gets into areas where metal components can corrode and sensitive electronics can foul causing damage to expensive instrumentation.”