Ohms LOAD Adjustable Shorted STUB Loop Coupler

When the total current in CESR was raised to about 300 ma a longitudinal instability threshold occurred which prevents a signi cant increase in the current. Experiments on CESR indicate that the main cause for the longitudinal instability is the H.O.M. in the cavities [1]. It has also been shown that by changing the cavities temperature the longitudinal instability threshold can be slightly raised [2]. In this paper an alternative method to shift the H.O.M. frequencies in a controlled way, without a ecting the fundamental frequency, is proposed.