Avalanche photodiode detector for high dynamic range point counting and timing experiments

• Many experiments still use NaI-phototube detectors for point-counting situations. These have a count-rate limit of around 100KHz.
• It is therefore frequently necessary to attenuate beams in order to bring the count rate into the linear range of such a detector.
• Integrating detectors have significant disadvantages and a serious noise penalty at low rates.
• Avalanche photodiodes have become quite reliable, and have capabilities above 107 Hz, with similar energy discrimination to NaI.
• Fast rise time ~700 pSec., timing resolution of better than 100 pSec. is achievable.

• This data was collected without any attenuators.
• Maximum rate is limited by NSLS 54MHz bunch rate.

• VUV ring bunch structure

• Auto correlation of APD signal using CFD and TAC.
• Timing resolution of 70 pSec. FWHM is shown.