Very high resolution RF cavity BPM

Linear collider (LC) interaction region beam sizes and component position stability requirements are expected to be a few nanometers. It is important to show that the related tolerances can be achieved, with an electron beam if possible. Using recently developed component stabilization technology, very high-resolution beam position monitors (BPM´s), and the ultra-low emittance beam at the KEK ATF, we plan to demonstrate the required stabilization. Our first step is to develop high-resolution RF cavity beam position monitors, using either C or X band frequencies. A C-band cavity BPM with a resolution of 25 nm has been reported in tests at FFTB. By correcting for the effects of nonaxial trajectories and using both position and angle BPM movers, we expect to be able to demonstrate a resolution of 2 to 3 nm over a dynamic range of ± 20 um. We report on the progress of the tests here.