Study of thermal radiation shields for the ILC cryomodule

The main linacs of the International Linear Collider are composed of 1824 cryomodules. As part of the R&D on the cryomodule, simplifications of the design were considered to reduce the construction and installation costs, including the possibility of removing a portion of the 5 K thermal shield. For this investigation the heat load measurements of a 6 meter cryomodule with and without the 5 K shield were performed, and used to determine emissivity coefficients. A thermal model of a full cryomodule was then created, and the heat loads of the cryomodule with the full set of the 5 K shield and without the lower 5 K shield were calculated with these parameters. By using a modified cooling scheme for the high temperature thermal shielding, we showed that the heat loads at 2 K between two models are substantially equivalent, and indeed, the thermal model without the 5 K lower shield requires 2% less work from the refrigerator.