Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
The Seebeck effect plays a crucial role during the cooldown procedure in SRF based accelerators, like LCLS-II at SLAC. The temperature-dependent Seebeck coefficient quantitatively measures the strength of electric potential induced by thermal gradients in metals. This effect is present in cryomodules and drives thermoelectric currents generating magnetic fields. These fields can get trapped in cavities and cause additional dissipation in RF fields. We have therefore designed and commissioned an experimental setup that does continuous measurements of the Seebeck coefficient for cryogenic temperatures ranging from 200K down to below 10K. We present results of the measurements of this coefficient for materials commonly used in cryomodules, such as niobium, titanium, niobium-titanium, silicon bronze, and stainless steel.
