Electro-optical detection has proven to be a valuable technique to study temporal profiles of THz pulses with pulse durations down to femtoseconds. As the Coulomb field around a relativistic electron bunch resembles the current profile, electro-optical detection can be exploited for non-invasive bunch length measurements at accelerators. We have developed a very compact and robust electro-optical detection system based on spectral decoding for single-shot longitudinal bunch profile monitoring at the European X-ray Free Electron Laser (XFEL) for electron bunch lengths down to 200 fs (rms). Apart from the GaP crystal and the corresponding laser optics at the electron beamline, all components are housed in 19 in. chassis for rack mount and remote operation inside the accelerator tunnel. An advanced laser synchronization scheme based on radio-frequency down-conversion has been developed for locking a custom-made Yb-fiber laser to the radio-frequency of the European XFEL accelerator. In order to cope with the high bunch repetition rate of the superconducting accelerator, a novel linear array detector has been employed for spectral measurements of the Yb-fiber laser pulses at frame rates of up to 2.26 MHz. In this paper, we describe all sub-systems of the electro-optical detection system as well as the measurement procedure in detail and discuss the first measurement results of longitudinal bunch profiles of around 400 fs (rms) with an arrival-time jitter of 35 fs (rms).

Fast evolution of high-performance cameras in recent years has made them promising tools for observing transient and fast events in large-scale scientific experiments. Complex experiments, such as ITER, take advantage of high-performance imaging system consisting of several fast cameras working in the range of visible and infrared light. However, the application of such devices requires a usage of high-performance data acquisition systems able to read and transfer large amount of data, reaching even 10 Gbit/s for a single camera. The MTCA.4 form factor fulfils the requirements of demanding imaging systems. The paper presents a first implementation of a complete image acquisition system built on the basis of MTCA.4 architecture, which is dedicated for the operation with high-resolution fast cameras equipped with Camera Link interface. Image data from the camera are received by the frame grabber card and transmitted to the host via the PCIe interface. The modular structure of MTCA.4 architecture allows connecting several cameras to a single MTCA chassis. The system can operate in two modes: with internal CPU installed in the MTCA chassis or with external CPU connected to the chassis with PCIe link. The usage of the external CPU opens a possibility to aggregate data from different subsystems. The system supports precise synchronization with the time reference using Precise Timing Protocol (IEEE 1588). The timing modules ensure clock distribution and triggers generation on backplane lines. These allow synchronization of image acquisition from different cameras with high precision. The software support for the system includes low-level drivers and API libraries for all components and a high-level EPICS-based environment for system control and monitoring.

Plasma diagnostics systems are becoming progressively more advanced. Contemporarily, researchers strive to achieve longer plasma pulses, and therefore, appropriate hardware is required. Analogue-to-Digital Converters are applied for data acquisition in many plasma diagnostic systems. Some diagnostic systems need data acquisition with gigahertz sampling frequency. However, gigasample digitizers working in continuous mode generate an enormous stream of data that requires suitable, high-performance processing systems. This becomes even more complicated and expensive for complex multi-channel systems. Nonetheless, numerous plasma diagnostic systems operate in a pulse mode. Thomson scattering (TS) diagnostics is a good example of a multi-channel system that does not require continuous data acquisition. Taking this into consideration, the authors decided to evaluate the CAEN DT5742 gigasample digitizer as a more cost-effective solution that would utilize the pulsed nature of the TS diagnostic system. The paper presents a complete data acquisition and processing system dedicated for plasma diagnostics based on the ITER real-time framework (RTF). Integration of RTF with real hardware is discussed. The authors of the paper have developed software including RTF function block for the CAEN DT5742 digitizer, example data processing algorithms, data archiving and publishing for plasma control system.