KEK, Ibaraki
Button-type beam position monitors for SuperKEKB rings have been designed. The RF characteristics such as beam response, trapped modes or wake functions have been simulated using 3-D E-M codes such as GdfidL and HFSS. The estimated instability threshold from the trapped modes was much higher than the radiation damping time. The prototype units have been tested in the prototype-antechambers installed in KEKB and KEK-PF BT line. The mechanical reliability and the beam responses are also reported.
LBNL, Berkeley, California
CLASSE, Ithaca, New York
The experimental study of the electron cloud dynamics and mitigation techniques is one of the main objectives of the CESR Damping Ring Test Accelerator (Cesr-TA) program. Shielded pick-up buttons are a relatively simple diagnostic device for obtaining time-resolved information on the electron cloud density. They have been already successfully employed on the SPS at CERN, although with different resolution parameters due to the different type of beams. We present the initial results obtained using such a detector in the Cesr-TA electron/positron ring. By carefully designing the read-out electronics we were able to resolve the individual bunch contribution to the electron cloud formation process along a bunch train and gain useful information on its decay time. Alternatively, by increasing the electronics integration time, we could use our device as a sensitive detector of the average electron cloud density level generated by the passage of a bunch train.