Kristen Hacker & Florian Loehl created a "femtosecond resolution bunch arrival time monitor." This device uses the signal of a beam pick-up to modulate the intensity of a femtosecond laser pulse train. By detecting the energies of the laser pulses, the bunch arrival time can be deduced.
Read more about Kristen Hacker and Florian Loehl's device. Read about the 2010 conference here.