The Accelerator for the European X-Ray Free Electron Laser delivers femtosecond electron bunches at an energy of currently 14GeV at a repetition rate of up to 4.5MHz in bursts of up to 2700 pulses every 100ms to distribute them between different undulator beamlines. The emitted femtosecond x-ray laser pulses at wavelengths between 0.05nm and 6nm can serve up to three experiments in parallel.
To measure the longitudinal bunch profile of the electron bunches, three detection systems based on electro-optical spectral decoding have been installed and are currently being commissioned. The systems are capable of recording individual longitudinal bunch profiles of all bunches in a burst with sub-ps resolution at a bunch repetition rate of 1.1 MHz, sampling the electron Coulomb field with laser pulses at 1030nm. A short detector latency of about 10µs also gives the prerequisites to establish a fast intra-burst feedback to stabilize the bunch profile. Bunch lengths and arrival times of entire bunch trains with single-bunch resolution have been measured as well as jitter and drifts for consecutive bunch trains.
For comparison of detection techniques at one position, the laser signal is split and measured with a time-stretch setup in parallel.
KALYPSO is a novel detector operating at line rates above 10 Mfps. The detector board holds a silicon or InGaAs linear array sensor with spectral sensitivity ranging from 400 nm to 2600 nm. The sensor is connected to a cutting-edge, custom designed, ASIC readout chip, which is responsible for the remarkable frame rate. The FPGA readout architecture enables continuous data acquisition and processing in real time. This detector is currently employed in many synchrotron facilities for beam diagnostics and for the characterization of self-built Ytterbium-doped fiber laser emitting around 1050 nm with a bandwidth of 40 nm.