Development of a Superconducting RF 500 MHz Quarter Wave Resonator for Synchrotron Light Sources

In the last ten to fifteen years, superconducting radio frequency cavities have begun to be utilized in accelerators for light sources, first as passive cavities for stabilizing the beam and later in the accelerating sections. In this SBIR proposal, Niowave will build and test the quarter-wave cavity design developed in Phase I of the SBIR. This new cavity system is simpler and less expensive to build and maintain than contemporary cavities used at large light sources. This novel design will allow new compact systems to meet the demand from the user community for high-energy light at high brightness and high duty factor currently only available at large light sources located at national laboratories. The interaction between the electron beam and higher-order modes in the accelerating cavities can lead to beam breakup instabilities that limit the maximum current that the cavities can maintain. Quarter wave structures have a higher-order mode spectrum which differs greatly from conventional elliptically-shaped cavities. The Phase I project resulted in a cavity design that is more compact and simplified compared to the industry-leading CESR-B cryomodule. The proposed design will reduce the initial and operating costs to incorporate superconducting RF in a compact light source project, with MeV energy gain at reasonable cavity surface fields. For smaller projects which do not require the voltages available with the large elliptical cavity designs, the simpler and less expensive cavity and module presented here will be immediately attractive. Furthermore, making this quarter wave SRF cavity design available to the designers of small machines in Phase III of this SBIR can be an important path toward demonstrating the technology and eventually making it relevant for even large machines at national labs. Commercial Applications and Other Benefits:The successful conclusion of this project puts Niowave in position to market quarter-wave accelerating systems to light source projects around the world in Phase III, and by reducing the capital and operating costs of the system, to expand the availability of superconducting RF to university-scale groups.