BEAM PICKUP DESIGNS SUITED FOR AN OPTICAL SAMPLING TECHNIQUE

The beam arrival-time monitor and large horizontal aperture chicane BPM at FLASH are important tools to stabilize the arrival-time of the beam at the end of the linac. The pickups for these monitors will be paired with a front-end that samples the zero-crossing of the transient through the use of electro-optical modulators (EOMs) and sub-picosecond-long laser pulses delivered by the master- laser oscillator (MLO). The design of pickups for this front-end requires the consideration of the transient shape as well as the amplitude. Simulations and oscilloscope traces for pickups that use or will use the EOM based phase measurement and the expected limitations of each pickup are presented. In particular, a method to reduce the beam position sensitivity of the beam arrival-time pickup, the potential resolution of a button pickup arrival-time measurement, and the design for a 5 μm resolution BPM with a 10 cm horizontal aperture are described.