Development and Performances of Spoke Cavity Tuner for MYRRHA Linac Project

In the framework of the Multi-purpose hYbrid Research Reactor for High-tech Applications (MYRRHA) 100 MeV linac construction, a fully equipped prototype cryomodule is being developed. In order to control the resonance frequency of the cavities during operation, a tuner has been studied with the specific requirements: high degree of reliability and high tuning speed. This paper reports the design consideration and the first performances measurement in vertical cryostat test at an early stage of the prototyping phase. INTRODUCTION Main purpose of the tuner is to bring the cavity at the nominal resonant frequency of 352.2 MHz, and to maintain it during beam operation. As a project requirement, an additional purpose is to be able to detune the cavity of 100 times bandwidth quickly [1,2] (within a second), but also to retune it quickly. Finally, another challenge is to enhance the reliability of the tuner. In order to meet this point, the selected tuner design is essentially coming from the ESS double spoke tuner design which is shown in Fig.1 and has already been extensively tested [3-5] and improved during the ESS prototype phase. Figure 1: ESS Prototype tuner. As shown in Fig. 2, an ESS prototype tuner has been adapted in order to fit on a MYRRHA single spoke prototype cavity for a vertical cryostat test to get preliminary results on the motor and piezo actuators performances during a cold test (cavity at 2K). During this test, cavity mechanical resonant modes were observed by both piezo and will be used to build a numerical model for control system loop simulation [6]. Figure 2: Adapted prototype tuner for MYRRHA single spoke cavity. MECHANICAL DESIGN The tuner applies a pulling action on the cavity beam flange in order to control the resonant frequency. This action results in a concentration of the stress around the iris side of the cavity end cup as shown in Fig. 3. Figure 3: Mechanical stress analysis. 19th Int. Conf. on RF Superconductivity SRF2019, Dresden, Germany JACoW Publishing ISBN: 978-3-95450-211-0 doi:10.18429/JACoW-SRF2019-TUP087 SRF Technology Ancillaries