Tunable and precise two-bunch generation at FLASHForward

Beam-driven plasma-wakefield acceleration based on external injection has the potential to significantly reduce the size of future accelerators. Stability and quality of the acceleration process substantially depends on the incoming bunch parameters. Precise control of the current profile is essential for optimising energy-transfer efficiency and preserving energy spread. At the FLASHForward facility, driver–witness bunch pairs of adjustable bunch length and separation are generated by a set of collimators in a dispersive section, which enables fs-level control of the longitudinal bunch profile. The design of the collimator apparatus and its commissioning is presented

Investigation of advanced electron bunch generation and diagnostics in the BOND laboratory at DESY

Laser driven plasma wakefield accelerators have been explored as a potential compact, reproducible source of relativistic electron bunches, utilising an electric field of many GV/m. Control over injection of electrons into the wakefield is of crucial importance in producing stable, mono-energetic electron bunches. Density tailoring of the target, to control the acceleration process, can also be used to improve the quality of the bunch. By using gas jets to provide tailored targets it is possible to provide good access for plasma diagnostics while also producing sharp density gradients for density down-ramp injection. OpenFOAM hydrodynamic simulations were used to investigate the possibility of producing tailored density targets in a supersonic gas jet. Particle-in-cell simulations of the resulting density profiles modelled the effect of the tailored density on the properties of the accelerated electron bunch. Here, we present the simulation results together with preliminary experimental measurements of electron and x-ray properties from LPWA experiments using gas jet targets and a 25 TW, 25 fs Ti:Sa laser system at DESY

X-Band TDS Project

Based on the success of the X-Band Transverse Deflecting Structure (TDS) diagnostic at LCLS*, a collaboration between DESY, PSI and CERN has formed with the aim of developing and building an advanced modular X-Band TDS system. The designed TDS has the new feature of providing variable polarization of the deflecting field**. The possibility of changing the orientation of the streaking field of the TDS to an arbitrary azimuthal angle allows for 3D characterization of the phase space using tomographic methods***. Moreover the complete 6D characterization of the beam phase space is possible by combining this technique with quadrupole scans and a dipole spectrometer. As this new cavity design requires very high manufacturing precision to guarantee highest azimuthal symmetry of the structure to avoid the deterioration of the polarization of the streaking field, the high precision tuning-free assembly procedures developed at PSI for the SwissFEL C-band accelerating structures will be used for the manufacturing****. The high-power rf system is based on the CERN-based X-band test stands. We summarize in this work the status of the projects and its main technical parameters

Future-oriented wakefield-accelerator research and development at FLASH

FLASHForward is a beam-driven plasma wakefield acceleration facility,currently under construction at DESY (Hamburg, Germany),aiming at the stable generation of electron beams of several \si{\GeV} with small energy spread and emittance.High-quality 1 GeV-class electron beams from the free-electron laser FLASH will act as the wake driver.The setup will allow studies on external injection as well as on various internal injection techniques, such as density-downramp or ionisation injection.With a triangular-shaped drive beam electron energies of up to 5 GeV from a few centimeters of plasma can be anticipated.Particle-In-Cell simulations are used to assess the feasibility of each technique and to predict properties of the accelerated electron bunches.In this contribution the physics case and the current status of FLASHForward will be reviewed.Concepts of the main components - the extraction beamline from the FLASH linac, the target area, the plasma cell and the post-plasma beam transport and diagnostics - will be described

FLASHForward - A Future-Oriented Wakefield-Accelerator Research and Development Facility at FLASH

FLASHForward is a beam-driven plasma wakefield acceleration facility, currently under construction at DESY (Hamburg, Germany), aiming at the stable generation of electron beams of several GeV with small energy spread and emittance. High-quality 1 GeV-class electron beams from the free-electron laser FLASH will act as the wake driver. The setup will allow studies of external injection as well as density-downramp injection. With a triangular-shaped driver beam electron energies of up to 5 GeV from a few centimeters of plasma can be anticipated. Particle-In-Cell simulations are used to assess the feasibility of each technique and to predict properties of the accelerated electron bunches. In this contribution the current status of FLASHForward, along with recent experimental developments and upcoming scientific plans, will be reviewed

X-Band TDS simulations and commissioning

Understanding of both driver and witness bunches in beam-driven plasma-wakefield acceleration (PWFA) experiments is critical in order to gain a deeper insight into what happens behind the scenes of the plasma cell i.e. validation of theory and control over the acceleration processes. However, witness bunches with lengths on the order of several femtoseconds are difficult to temporally resolve with traditional diagnostic methods. In order to characterise the longitudinal phase space of these short bunches a new polarisable transverse deflection RF structure (TDS) working in the X-Band range (11.99 GHz) will be installed at the FLASHForward facility at DESY. To assess the capabilities and limitations of this device during its upcoming operation, as well as to optimise the sometimes challenging transport of the accelerated electrons from the plasma cell to the TDS, particle tracking simulations have been performed. Here the results of these simulations for scenarios including external and internal injection will be presented

Plasma Wakefield Accelerated Beams for Demonstration of FEL Gain at FLASHForward

FLASHForward is the Future-ORiented Wakefield Accelerator Research and Development project at the DESY free-electron laser (FEL) facility FLASH. It aims to produce high-quality, GeV-energy electron beams over a plasma cell of a few centimeters. The plasma is created by means of a 25 TW Ti:Sapphire laser system. The plasma wakefield will be driven by high-current-density electron beams extracted from the FLASH accelerator. The project focuses on the advancement of plasma-based particle acceleration technology through the exploration of both external and internal witness-beam injection schemes. Multiple conventional and cutting-edge diagnostic tools, suitable for diagnosis of short electron beams, are under development. The design of the post-plasma beamline sections will be finalized based on the result of these aforementioned diagnostics. In this paper, the status of the project, as well as the progress towards achieving its overarching goal of demonstrating FEL gain via plasma wakefield acceleration, is discussed