New methods of beam position monitors for measurement of quadrupole component

Stripline beam position monitors(BPM) can be used as a nonintercepting emittance monitor and it is independent of the beam distribution. Usually, difference over sum method is used to pick up the quadrupole component. This paper puts forward two new methods’ log-ratio method and combination method. The analysis and comparison of these methods are introduced. Combination method is the best, and log-ratio method is better than difference over sum method. Changing the current of quadrupole magnets m times (more than six times) upstream from BPM to change the transfer matrix and measuring the quadrupole component for each change, the emittance can be calculated.