CLASSE NEWS | 10 Jul 2010
Cornell is a critical contributor to the international ERL cryomodule collaboration (Daresbury/Cornell/DESY/Rossendorf/LBNL/TRIUMF) which develops an optimized cavity/cryomodule solution for ERL facilities. This week, Cornell’s SRF group completed fabrication and testing of both seven-cell superconducting RF cavities for this cryomodule. This is an important milestone for this collaboration as well as for Cornell’s ERL which will have similar 7-cell cavities.
The cavity sections from the first to the last equator were cut from two seven-cell superstructure cavities provided by DESY. The outer half-cells and associated beam pipes (end groups) are of a new design developed by LBNL, Daresbury and Cornell. Their geometries were optimized to facilitate the propagation of higher order mode power to ferrite-lined beam-pipe loads, identical to those used in the Cornell ERL injector cryomodule. One of the two end groups is fitted with an input power coupler port that will accommodate a slightly modified version of the Cornell ERL injector coupler.
Upon completion of the mechanical design, the end cells were fabricated and electron-beam welded to the center sections. Subsequently, the cavities have been tuned to achieve desired resonant frequency and field flatness of the π-mode. As the cavities will operate in CW mode with moderate gradients, only BCP and HPR treatments were used for the cavity preparation. After series of vertical tests, both cavities achieved accelerating gradients in excess of 18 MV/m. Following the successful vertical testing, titanium helium jackets were welded to the cavities; the structures went through the final cleaning cycle and are ready to be shipped to Daresbury to be assembled in the cryomodule.
Fabrication of seven-cell cavities for the international ERL cryomodule collaboration
Cornell's 7-cell superconducting RF cavity.
The cavity sections from the first to the last equator were cut from two seven-cell superstructure cavities provided by DESY. The outer half-cells and associated beam pipes (end groups) are of a new design developed by LBNL, Daresbury and Cornell. Their geometries were optimized to facilitate the propagation of higher order mode power to ferrite-lined beam-pipe loads, identical to those used in the Cornell ERL injector cryomodule. One of the two end groups is fitted with an input power coupler port that will accommodate a slightly modified version of the Cornell ERL injector coupler.
Upon completion of the mechanical design, the end cells were fabricated and electron-beam welded to the center sections. Subsequently, the cavities have been tuned to achieve desired resonant frequency and field flatness of the π-mode. As the cavities will operate in CW mode with moderate gradients, only BCP and HPR treatments were used for the cavity preparation. After series of vertical tests, both cavities achieved accelerating gradients in excess of 18 MV/m. Following the successful vertical testing, titanium helium jackets were welded to the cavities; the structures went through the final cleaning cycle and are ready to be shipped to Daresbury to be assembled in the cryomodule.