In the framework of CARE/SRF, the task of CEA Saclay DAPNIA is the design, the fabrication, and the full test in CRYHOLAB of the new piezo tuner for Lorentz force detuning compensation on a TTF cavity.
The present tuner is working inside the TTF cryomodules without any piezo actuator. Thus the Lorentz force detuning in the pulsed mode of the accelerator is limiting the maximum accelerating field of the cavities at about 25MV/m.
Piezo actuators have been integrated in this tuner by the DESY team for tests, and this system demonstrated the compensation of the Lorentz force detuning at field higher than 35 MV/m.
Nevertheless this system is an adaptation of a piezo actuator on a mechanical part which was not initially developed for that. As a consequence this tuner has several defects: its stiffness is too low, it is difficult to adjust the preload applied at cold on the piezo actuator in the good range with a good reproducibility, and only part of the maximum piezo actuator stroke is transmitted to the cavity flange.
Our goal is now to develop a new tuner which should allow obtaining a better preload adjustment and a better efficiency of the stroke transmission. The mechanical studies are now finished, and fabrication is in progress. This report presents the principle of this new system with associated mechanical calculations.
|
