• A. Bocci, A. Drago, A. Marcelli
  INFN/LNF, Frascati (Roma)
• C. Li, Z. Qi, B. Sun, B.Y. Wang, J.G. Wang, Z.Y. Wu
  USTC/NSRL, Hefei, Anhui
• J.P. Piotrowski
  VIGO System S.A., Ozarow Maz.

Real time diagnostics is a fundamental tool for accelerator physics, particularly important to improve performances of existing synchrotron radiation sources, colliders and a key issue for 4th generation sources and FELs. We report the first measurements in the time and frequency domain performed at Hefei Light Source (HLS), the SR facility of the National Synchrotron Radiation Laboratory (NSRL), of the longitudinal bunch lengths. A fast uncooled HgCdTe photodiode optimized in the mid-IR range has been used to record at the IR port the length of the e^- bunches. IR devices are compact and low cost detectors suitable for a bunch-by-bunch longitudinal diagnostics. The data are useful to investigate longitudinal oscillations and characterize the bunch length. The IR signal has been used to measure the synchrotron oscillation frequency, its harmonics in the multi-bunch mode and the bunch lengths in multi-bunch mode at different beam currents. For the first time, simultaneously, data have been collected at visible wavelengths using a fast photodiode at the diagnostics beamline of HLS. A comparison between IR data and diagnostics realized in the visible will be presented and discussed.