First cavity in Cryomodule 2 achieves goal gradient

Cavity 1 in Fermilab’s Cryomodule 2 achieved a gradient of 31.5 MV/m on Dec. 20. Image courtesy of Elvin Harms, AD

On Dec. 20, members of the Accelerator Division SRF Electron Linac Department and the Technical Division SRF Development Department successfully brought the first accelerating cavity in Cryomodule 2 to a gradient of 31.5 megavolts per meter, the gradient required for the proposed International Linear Collider. The achievement demonstrates the cavity’s successful integration into the cryomodule.

“Everyone involved should take satisfaction in this first step of bringing this cryomodule into operation,” said Elvin Harms of the SRF Electron Linac Department.

A cavity’s gradient is one measure of how efficiently beam is transmitted from one end of the cavity to the other. Although each of Cryomodule 2’s eight cavities had previously achieved 31.5 MV/m prior to installation, this is the first time a cavity inside the cryomodule has been measured at this value. The test validates that the high gradient can be maintained even after the cavity is installed in the cryomodule.

The SRF teams will proceed with tests of the other seven cavities in Cryomodule 2, bringing them up to no higher than 31.5 MV/m. Once they ensure stable operations at this level, they will investigate the possibility of increasing the gradient from there.

“It is important that we become world experts in operating these and similar cryomodules,” said Fermilab Director Nigel Lockyer. “This impressive achievement is the culmination of a long road.”