The String Shutdown Report: December 97 - March 98

The main reason for the shutdown was the installation of a tube containing a prototype auxiliary bus-bars cable. This tube runs in one of the beam tube apertures of the String from the front of MB1 to the rear of MB3 and is hydraulically connected to the cold mass of MB3. A ceramic leak tight feed-through was installed, for the first time in operational conditions, to route the signal wires for the temperature sensors and the voltage taps out of the 1.9 K helium bath. Leaks in the beam-screen capillary had prevented the connection of the beam screens to the cooling circuit. The opportunity of t his shutdown was taken to install a cryogenically cooled beam-screen in the other aperture of MB3. In addition, the calibration of temperature and positioning sensors took place. The SRB had to be re moved to install the long tube and the lines carrying cryogens had to be cut, therefore a pressure test and a leak test had to be carried-out.