Background: Measurement of the fill pattern of synchrotron storage rings is important for several reasons

including checking the quality of the injection system and the generation of special fill patterns for time-resolved experiments. User experiments on these synchrotron radiation sources typically require the pattern to be as exact as possible

with ideally no electrons in unwanted bucket/bunch positions: a typical ratio of 10?5:1 between unwanted/wanted populations is desired. This ratio is often referred as the bunch purity. Purpose: In order to establish a bunch cleaning system

a bunch purity of storage ring has to be set up. Methods: For the time-resolved facility based on the electron storage ring

it is planned to measure the beam quality in a short time of several minutes by using a time-correlated single photon counting method. Results: The purity measurement results show that a purity of 10?5 for BEPCII declines to 10?4 in dozens of hours after injection. Conclusion: A bunch purity measurement system has been set up in BEPCII storage ring using synchrotron light

which can give the bunch purity in tens of seconds. The bunch purity measurement results show the purity of BEPCII is better than 10?4. Abstract