Upgrade and Status of Standard Diagnostic-Systems at FLASH and FLASHForward

Electron beam diagnostics plays a crucial role in the precise and reliable generation of ultra-short high brilliance XUV and soft X-ray beams at the Free Electron Laser in Hamburg (FLASH). Most diagnostic systems monitor each of up to typically 600 bunches per beam, with a frequency of up to 1 MHz, a typical charge between 0.1 and 1 nC and an energy of 350 to 1250 MeV. The diagnostic monitors have recently undergone a major upgrade. This process started several years ago with the development of monitors fulfilling the requirements of the European XFEL and of the FLASH2 undulator beamline and it continued with their installation and commissioning. Later they have been further improved and an upgrade was made in the old part of the linac. Also the FLASHForward plasma-wakefield acceleration experiment has been installed in the third beamline. This paper will give an overview of the upgrade of the BPM, Toroid and BLM systems, pointing out to their improved performance. Other systems underwent a partial upgrade, mainly by having their VME-based ADCs replaced with MTCA type. The overall status of the diagnostic will be reviewed. INTRODUCTION FLASH [1] is self-amplified spontaneous-emission free electron laser (SASE-FEL) user facility. It generates high brilliance ultra-short XUV and soft X-ray pulses. It is also a test facility for various studies. Figure 1 shows a schematic drawing of the facility. Seven TESLA accelerating modules accelerate the beam to an energy of 350 to 1250 MeV. Within each bunch train with a length of typically 400-600 s different lasers generate the sub-trains destined to the various beamlines. These can have different bunch frequency, up to 1 MHz, and bunch charge, typically between 0.1 and 1 nC. The train repetition rate is 10 Hz. During machine setup or special bunches may have a reduced rate of 1 Hz. While the first 2 beamlines, FLASH1 and FLASH2, generate intense photon pulses for users, a plasma experiment, FLASHForward, was recently installed in the third beamline [2]. The FEL requires a precise control of the beam. The diagnostics system is essential for this, and therefore has to follow the increasing requirements over time. Figure 1: Schematic view of the FLASH facility [1]. This paper describes the recent upgrades that the various diagnostics systems underwent. After an overview of the diagnostics, the monitor types which underwent main upgrades are described, followed by the smaller work. The paper ends with a summary. Standard Diagnostics at FLASH Many different kinds of diagnostics have been installed along the years in FLASH: toroids to monitor the individual bunch charge, beam position monitors (BPM) of various kinds, beam loss monitors (BLM), beam size monitors, mainly OTR stations and wire scanners, dark current monitor etc. So-called special diagnostics has been developed mainly for longitudinal diagnostics, and is not the topic of this paper. Many of the systems deliver bunchby-bunch information, and have to deal with the different bunch charge and pulse structure of the sub-trains for the various beamlines. In recent years, many diagnostics systems have been developed for and installed in the European XFEL [3] and FLASH2 [4], which fulfil new requirements. The MTCA.4 standard [5] has been introduced for several systems. Besides the diagnostics, also LLRF and the timing system are based on this standard. Different systems ___________________________________________ * nicoleta.baboi@desy.de. Proceedings of IBIC2018, Shanghai, China Pre-Release Snapshot 25-Sep-2018 14:00 (UTC+8)