Pushing the Limits: RF Field Control at High Loaded Q

Design of the ILC Crab Cavity System

“…For bunches arriving within 0.33 deg (at 1.3 GHz) of their correct timing, the effect of beamloading on cavity phase is almost a factor of five smaller than the effect of microphonics at the level seen in prototype CKM cavities. It is anticipated therefore that the level of cavity phase stability that can be achieved against a local reference will be comparable with the 0.02 deg at 1.5 GHz (equal to a timing stability of 20 fs) achieved in ERLs 13 . The peak power requirement for the simulation of figure 9 was 250 W per cell or 2.25 kW for a nine cell cavity.…”

“…Intelligent control allows prediction of necessary control action in advance of a measurable error. Stabilisation of cavities using intelligent control to the level of 20 milli-degrees at 1.3 GHz has been demonstrated elsewhere 13 . Optimisation of intelligent control for the ILC crab cavities cannot be completed until fully developed cavities and horizontal cryostats are available.…”

Fast Ferroelectric L-Band Tuner for ILC Cavities

“…The optimal loaded quality factor in this case is 10 7 , a very modest value [22]. Of course, proper cavity detuning is necessary to compensate the reactance introduced by the beam and minimize the required power.…”

“…Of course, proper cavity detuning is necessary to compensate the reactance introduced by the beam and minimize the required power. Note that for Q l significantly higher than10 8 , there may be problems with field startup, because the cavity bandwidth will be very small compared to the Lorentz-force detuning [22]. Another problem for higher Q l may be with low level RF control that should provide accurate compensation of any perturbation of the small-bandwidth cavity resonant frequency [22,23].…”

“…Note that for Q l significantly higher than10 8 , there may be problems with field startup, because the cavity bandwidth will be very small compared to the Lorentz-force detuning [22]. Another problem for higher Q l may be with low level RF control that should provide accurate compensation of any perturbation of the small-bandwidth cavity resonant frequency [22,23]. Thus, the cavity resonant frequency control and control of the coupling of the cavity with the feeding line reduces the power demands and provides stable operation of the SRF linac.…”