Improvement of the blade tuner design for superconducting RF cavities

As of today, no complete technological solution exists for a cold tuning system fulfilling the requirements envisaged for the International Linear Collider, based on the superconducting RF technology. We present here the design improvements for the blade tuner, a coaxial device, which can provide both the slow structure tuning and the fast tuning capabilities needed for Lorentz Force Detuning (LFD) compensation and microphonics stabilization (by means of the integration with a piezoelectric system). The system has been originally built by INFN and installed and tested at DESY on the superstructures, since it is located around the cavity helium vessel and does not require longitudinal clearance. Its design here is parametrically reviewed in terms of the requirements for higher accelerating fields and of the mechanical integration with a piezoelectric based system for the LFD and microphonics compensation