Decay rate plot of stored beam current and Touschek limit of current-lifetime product

It is demonstrated that the decay rate of the stored beam current I is a good means for indicating the gas-pressure conditions of a storage ring and the stored beam loss due to the Touschek effect. A new analytical method for evaluating the Touschek lifetime of the stored electron beam is also presented. The observed Touschek limit of the current-lifetime product I0τT is 5 Ah at 500 MeV for TERAS. This value is fifty times as large as the theoretical value. I0τT is proportional to the fourth power of the electron energy E and becomes of the order 0.12 Ah at 205 MeV. A computer-made decay-rate plot against I is very useful for indicating the decay modes and the 1/e lifetime of the stored beam current. (author)