Evaluation of characteristic impedance of the electrode and its fabrication method in stripline-type BPMs

A relationship between characteristic impedance and its fabrication method of the electrode edge in stripline-type beam potion monitors (SBPMs) was investigated on the basis of experiments and theoretical calculations. The upgrade of the SBPMs with higher accuracy and resolution in the beam-position measurement is strongly required in the Super KEK B-factory (SKEKB), which has been started in 2010 while the main development of the SBPMs is for the signal-detection system. Such SBPMs are widely used in order to precisely measure the transverse beam positions in linear accelerators. Although conventional SBPMs were first developed at the KEKB injector linac in 1995, the author has reconsidered the fabrication method with having higher mechanical accuracy. As a result it was found that the modification of the fabrication method clearly affected the characteristic impedance of the electrode. In this report, the modification of the fabrication method and its quantitative effect to the characteristic impedance are discussed in detail. (author)