A single-pass THz free-electron laser (FEL) at the Photo Injector Test facility at DESY in Zeuthen (PITZ) was designed and implemented for a proof-of-principle experiment on a tunable high-power THz source for pump-probe experiments at the European XFEL. THz pulses are generated at a radiation wavelength of 100 μm within a 3.5 m long, strongly focusing planar LCLS-I undulator. High gain is achieved by driving the FEL with high brightness beams from the PITZ photoinjector at 17 MeV and a bunch charge of up to several nC. In addition to the mechanisms of self-amplified spontaneous emission (SASE), seeding of the THz-FEL by electron bunch modulation at the photocathode is also being investigated. The experimental results, including the gain curves and spectral properties of the THz-FEL radiation, are presented in comparison with theoretical predictions and numerical simulations.

The first operational high peak and average power THz self-amplified spontaneous emission (SASE) free electron laser (FEL) at the Photo Injector Test facility at DESY in Zeuthen (PITZ) has demonstrated up to 100 uj single pulse energy at a center frequency of 3 THz from electron bunches of 2-3 nC. The measured shot-to-shot radiation pulse energy has a fluctuation of 10%. Shot-to-shot stability and temporal coherence in FELs can be greatly enhanced by the seeding method. In this paper, we propose the use of dielectric-lined waveguides (DLW) to enhance the initial seeding signal. Simulations of using electromagnetic wakefield in DLW to introduce energy modulation to the beam, controlling the conversion between energy modulation and density modulation, and space charge dominated beam matching in the chicane bunch compressor and the undulator will be presented.

Due to improvements of the performance of FELs, the measurements of the beam’s slice energy spread is becoming increasingly important for optimization of the brightness. Of particular interest are measurements of the uncorrelated energy spread near the gun as this determines the lower limit of the energy spread for the rest of the machine. At the Photo Injector Test facility at DESY in Zeuthen (PITZ), the uncorrelated energy spread is measured of an electron beam generated from an L-band electron gun and accelerated to 20 MeV with a booster cavity. The energy spread of the central time slice is measured using a transverse deflecting structure (TDS) and a dispersive arm to image the longitudinal phase space. Scans of the TDS voltage and quadrupole strengths are used to remove the contributions from the TDS, transverse emittance, and imaging resolution. Presented is an overview of the measurement procedure, resolution, and results of measurements tests.

At the Photo Injector Test facility at DESY in Zeuthen (PITZ), an R&D platform for electron FLASH cancer radiation therapy and radiation biology is being prepared: FLASHlab@PITZ. The design of the full beamline with optimized beam properties was finished; the setup is currently being finalized and the mechanical design and manufacturing is underway. The beamline runs in parallel to the SASE THz beamline at PITZ and is connected to it with a dogleg. Beam dynamics simulations were conducted to assure excellent beam quality at the experimental area. A fast kicker system will be installed which is capable of distributing electron bunches from a single bunch train freely over an area of 25mm x 25mm within one microsecond. When the full FLASHlab@PITZ beamline is ready in 2024, the accelerator will deliver 22 MeV electrons to generate dose rates from 0.01 Gy/s up to 10e+14 Gy/s to an experimental area, which can accommodate a variety of setups for irradiation studies. The flexible arrangement of the experimental area will make it possible for external users to collaborate with PITZ and conduct experiments with existing or newly designed irradiation setups.