Simulation study of LINAC4 movable tuners using CST Microwave Studio

LINAC4 is employing four types of movable tuners. This study was made to verify whether there are electromagnetic fields in the tuners, which resonate at a frequency close to the one of the accelerating mode. If exited these fields could yield local heating and potentially lead to damage of the tuner components. For this purpose the tuners are simulated with different penetrations of the pistons into the cavities. Furthermore they are simulated with and without RF joints (and their supporting rings), which were originally introduced to avoid resonant heating of the tuner bellows.