Spaceflight Now's Astronauts finish repairs to space station cosmic ray detector says:
Originally designed to operate for just three years, the AMS chalked up eight years of operation before being sidelined by the sequential failures of four carbon dioxide coolant pumps. The coolant system is what allows the AMS detectors to achieve the required levels of sensitivity.
To repair the system and extend the instrument’s life through the end of the station program, engineers developed a four-spacewalk plan to install a custom-built 350-pound module containing four pumps and a reservoir of fresh carbon dioxide coolant.
The AMS was not designed to be serviced in space, making the work particularly challenging. But during spacewalks last Nov. 15, 22 and Dec. 2, Morgan and Parmitano opened up the AMS, removed insulation, snipped eight coolant lines, installed the new pump module and spliced, or “swaged,” the coolant lines back into place.
- Is the carbon dioxide used to cool detectors, or the superconducting magnet, or both, or neither?
- Are these pumps gas compressors, or is there actual liquid CO2 flowing?
- Why carbon dioxide? This sounds a bit exotic to me. Freon or ammonia can be used for general cooling and refrigeration and liquid helium is usually used for superconducting magnets.