Tuners/Lorentz Force detuning       Matthias Liepe (8/25/2005)

Overview

Main objectives for the frequency tuner are to provide means to tune the cavity on resonance, detune a cavity to by-pass operation if needed, and to compensate Lorentz-force detuning. The tuner further needs to allow for a high linac fill factor (compact design), should be hysteresis free, and should not cause cross-tuning of neighboring cavities. Long life time of the tuner is essential; see discussion below. All this needs to be achieved with lowest cryogenic losses, and at low cost.

ILC requirements:

Coarse tuning range: 500 kHz (1.6 mm at 315 Hz/mm)

Coarse resolution: <5 Hz

Fast tuning range (static at 2K): Df=2*K*E^2 (factor 2 for dynamic operation overhead)

        2.5 kHz (for K=1 Hz/(MV/m)^2 cavity at 35 MV/m)

3.2 kHz (for K=1 Hz/(MV/m)^2 cavity at 40 MV/m)

                        4.0 kHz (for K=1 Hz/(MV/m)^2 cavity at 45 MV/m)

The requirement on fast running range is not well known at this point. Significant spread in the dynamic Lorentz-force detuning constant has been seen (factor 2 at TTF). Unless K can be controlled well in the ILC cavity/LHe vessel production, more fast tuning range is required. Also, significant difference can exist between the static range and the dynamic range (maximal frequen