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

Avalanche

  • 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.

 

Avalanche

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

 

Avalanche

  • VUV ring bunch structure

 

Avalanche

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