Fig. 11.

The $\alpha$ survival probability of three possible $\alpha$ event cuts, applied at each scanning position. The efficiency of the 99% (99.9%) bulk event acceptance DCR cut is given by the red (blue) points. The black points indicate the efficiency of an $\alpha$ event rejection cut using both the DCR and A/E parameters, each applied at the 99.9% bulk event acceptance level. Downward-pointing arrows indicate that the uncertainty given is an upper limit