CRYOGENIC TEST OF HELIUM TRANSFER LINE MODULES FOR HERA

We report on the cryogenic test of a string of two 23.5 m long prototype helium transfer line modules. These modules are part of a helium distribution system which is being installed in a 6.3 km long underground tunnel of the HERA superconducting proton storage ring. With the test we could confirm the low heat load of the four shielded inner tubes which was specified to be 0.17 W/m ± 10% for the 4.5 K supply and return lines and 1.56 W/m ± 10% for the 40 K supply/80 K return shield cooling lines. These values include all components like elbows, branchpoints, fix points, vacuum barriers and interconnections between the modules. Heat loads for most of the components are measured. After a total of 24 cryogenic cycles and after pressure tests up to 21.5 x 10 5 Pa the heat loads had not changed although after dismounting of the inner tubes minor changes of the mechanics turned out to be necessary.