The main driving part of the X-ray free electron laser facility (SwissFEL) at Paul Scherrer Institute (PSI) is a compact electron linear accelerator (linac). The machine is highly optimized to generate a superior FEL radiation with the lowest suitable electron beam energy. In order to meet extremely stringent SwissFEL require-ments for electron beam quality and stability, a variety of advanced beam diagnostics tools were developed and implemented at PSI. All these tools are integrated into the SwissFEL control system. The paper describes basic control elements of advanced electron beam diagnostics tools and their operational performance.

The Athos line will cover the photon energy range from 250 to 1900 eV and will operate in parallel to the hard X-ray line Aramis of SwissFEL. The paper will describe the current layout of the Athos FEL line starting from the fast kicker magnet followed by the dogleg transfer line, the small linac and the 16 APPLE undulators. From there the photon beam passes through the photonics front end and the beamline optics before reaching the experimental stations AMO and FURKA. The focus of this contribution will be on the two bunch operation commissioning (two bunches in the same RF macropulse), which started in 2018, and the characterization of the major components like the APPLE X undulator UE38, the CHIC chicane and the dechirper. The Athos installation inside the tunnel is alternating with Aramis FEL user operation and the first lasing is planned for winter 2019 / 2020.

SwissFEL is a free electron laser user facility at the Paul Scherrer Institute in Villigen, Switzerland designed to provide FEL radiation at photon energies ranging from 0.2 to 12 keV. Beam commissioning of the hard x-ray line ARAMIS has started in October 2016 and lasing at 300 eV was achieved in May 2017. First pilot user experiments at photon energies ≥ 2 keV are foreseen for the end of 2017. This contribution comprehends commissioning results and first operational experience of various diagnostics systems, such as beam position monitors, charge and loss monitors as well as transverse profile measurements with screens, wire scanners and synchrotron radiation monitors. It also provides information about sliced beam parameters using a transverse deflector and shows first results from the BC-1 compression monitor and measurements with the electron bunch arrival time monitors.

Based on a Mach-Zehnder intensity modulator, Bunch Arrival time Monitor (BAM) is a single-shot nondestructive multi-bunch diagnostic instrument, which measures the arrival time with <10 fs precision in the range of 10-200 pC at 100 Hz repetition rate. Being directly coupled to a length stabilized fiber optical link, it has intrinsically low drift (<10 fs/day) and is thus a useful instrument for the machine feedback. The overall monitor complexity demands the development of an extremely reliable control system that handles basic BAM operations. Two BAM prototypes were successfully used in the SwissFEL Injector Test Facility and further two are being presently commissioned at the SwissFEL. The system is very flexible. It provides a set of tools allowing one to implement a number of advanced control features such as tagging experimental data with a SwissFEL machine pulse number or embedding high level control applications into the process controllers (IOC). The paper presents the structure of the BAM control setup. The operational experience with this setup is also discussed.

The SwissFEL Injector Test Facility operated at the Paul Scherrer Institute between 2010 and 2014, serving as a pilot plant and testbed for the development and realization of SwissFEL, the X-ray Free-Electron Laser facility under construction at the same institute. The test facility consisted of a laser-driven rf electron gun followed by an S-band booster linac, a magnetic bunch compression chicane and a diagnostic section including a transverse deflecting rf cavity. It delivered electron bunches of up to 200 pC charge and up to 250 MeV beam energy at a repetition rate of 10 Hz. The measurements performed at the test facility not only demonstrated the beam parameters required to drive the first stage of an FEL facility, but also led to significant advances in instrumentation technologies, beam characterization methods and the generation, transport and compression of ultra-low-emittance beams. We give a comprehensive overview of the commissioning experience of the principal subsystems and the beam physics measurements performed during the operation of the test facility, including the results of the test of an in-vacuum undulator prototype generating radiation in the vacuum ultraviolet and optical range.

SwissFEL will provide users with brilliant X-ray pulses in 2017. A comprehensive suite of diagnostics is needed for the initial commissioning, for changes to the operating point, and for feedbacks. The development of instrumentation for SwissFEL is well underway, and solutions have been identified for most diagnostics systems. I will present here an overview of the instrumentation for SwissFEL, and give details on some recent developments.

A high bandwidth Bunch Arrival-Time Monitor (BAM) has been commissioned downstream the bunch compressor at the SwissFEL Injector Test Facility (SITF). A new acquisition front end allowing utilization of the ADC full dynamic range was implemented. The resolution was measured as a function of the bunch charge for two different electro-optical intensity modulators (EOM). BAM measurements of machine relevant parameters were made. A comparison with the results from other diagnostics shows good agreement.

The development of the SwissFEL [1] reference distribution and synchronization system is driven by demanding stability specs of LLRF-, beam arrival time monitors (BAM) and laser systems on one and cost issues, high reliability/availability and flexibility on the other hand. Key requirements for the reference signals are <10fsrms jitter well as down to 10fspp temporal drift stability (goal) for the most critical clients (BAM, pulsed lasers). The system essentially consists of a phase locked optical master oscillator (OMO) with an optical power amplifier/splitter, from which mutually phase locked optical reference pulses as well as RF reference signals are derived. Optical pulses will be transmitted to pulsed laser and BAM clients over stabilized fiber-optic links whereas the RF signals are transmitted over newly developed stabilized cw fiber-optic links. Both s- and cband reference signals use s-band links, whereupon the C band receiver incorporates an additional ultra-low jitter/drift frequency doubler. Furthermore, ultra-low noise analog laser PLLs have been built. We are presenting concepts and first results of sub-10fsrms jitter and 20fspp long term drift cw links, tested in the SwissFEL Injector Test Facility (SITF).

High-gain free-electron lasers (FELs) are capable of generating femtosecond x-ray pulses with peak brilliances many orders of magnitude higher than at other existing x-ray sources. In order to fully exploit the opportunities offered by these femtosecond light pulses in time-resolved experiments, an unprecedented synchronization accuracy is required. In this Letter, we distributed the pulse train of a mode-locked fiber laser with femtosecond stability to different locations in the linear accelerator of the soft x-ray FEL FLASH. A novel electro-optic detection scheme was applied to measure the electron bunch arrival time with an as yet unrivaled precision of 6 fs (rms). With two beam-based feedback systems we succeeded in stabilizing both the arrival time and the electron bunch compression process within two magnetic chicanes, yielding a significant reduction of the FEL pulse energy jitter.