Possible upgrade for the SRS RF system

The world´s first dedicated source for synchrotron radiation, the Synchrotron Radiation Source (SRS) at Daresbury, UK is now 20 years old. During its operational lifetime, the control and stability of the electron and photon beams have been significantly improved, to ensure continued reliable operation, in order to necessitate various lattice and insertion device (ID) upgrades. The SRS currently utilises four 500 MHz accelerating cavities, which can provide a maximum of 2.1 MV accelerating voltage, equating to ~300 mA of stored beam current at 2GeV. To operate the SRS at this beam current level routinely for users, would undoubtedly be very difficult due to cavity induced beam instabilities. As a possible way of upgrading the SRS to operate at these beam current levels and beyond, it is proposed to replace the existing SRS RF cavities with two new higher order mode (HOM) damped cavities. This would enable beam currents up to 1 Ampere to be stored both reliably and with a higher degree of stability. The availability of two additional straight sections would then offer the possibility of introducing two high field MPW devices. This paper details the new cavity design, highlighting the associated RF system modifications that would become necessary