University of Oxford, Clarendon Laboratory, Oxford
Diamond, Oxfordshire
Ultrashort electron bunches from laser-driven plasma accelerators hold promise as drivers for short-wavelength free electron lasers*. While full 3-D FEL simulation techniques have been successful in simulating lasing at present-day facilities, the novel sources investigated here are likely to violate a number of widely-held assumptions. For instance the HHG seed radiation, as well as the radiation generated by the bunch, do not conform to the slowly-varying envelope approximation (SVEA) on which the majority of codes are based. Additionally, the longitudinal macroparticle binning precludes the full physics of the system from being modeled. In order to more completely simulate the arising sub-wavelength effect we have developed an unaveraged 1-D time-dependent code without the SVEA. We highlight some of the additional features that these new systems present through analytical and numerical analyses. We discuss the regimes in which these effects become important, and investigate how they may be used to enhance the lasing process. Finally we outline a framework for full 3-D simulation of a short-wavelength FEL driven by a laser-plasma accelerator.
* Leemans et al., Nat. Phys. 2, 696 (2006); Gruner et al., Appl. Phys. B 86, 431 (2007).
Diamond, Oxfordshire
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
LBNL, Berkeley, California
The New Light Source (NLS) project was launched in April 2008 by the UK Science and Technology Facilities Council (STFC) to consider the scientific case and develop a conceptual design for a possible next generation light source based on a combination of advanced conventional laser and free-electron laser sources. In this paper we present the results of the optimisation of a single pass superconducting LINAC as a driver for the the NLS FELs. The optimisation process requires the analysis of complicated electron beam dynamics in the presence of CSR, wakefields and space charge and has specifically taken into account the requirements for FEL operation in a seeded harmonic cascade scheme.
Diamond, Oxfordshire
We discuss the possible operation of the UK New Light Source in the single spike regime with photon energies ranging from 50 eV to 1 keV. The optimisation process of the beam dynamics in the single spike regime is outlined and we present the results of full start-to-end simulations to show that few-fs to sub-fs pulses can be obtained, depending on the photon energy, with interesting power level. The analysis of the jitter of the SASE output characteristic is also reported.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
JAI, Oxford
Cockcroft Institute, Warrington, Cheshire
We describe a design for a two-pass recirculating 1.3 GHz superconducting linac as a driver for the suite of free-electron lasers proposed in the UK New Light Source project. The machine will deliver longitudinally compressed electron bunches with repetition rates of 1 kHz with an initial upgrade path to increase this to 1 MHz. A modular philosophy is employed to separate beam injection and extraction from a three stage compression scheme. Results show that the necessary high peak currents can be achieved whilst preserving beam quality.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
JAI, Oxford
USTRAT/SUPA, Glasgow
The New Light Source (NLS) project was launched in April 2008 by the UK Science and Technology Facilities Council (STFC) to consider the scientific case and develop a conceptual design for a possible next generation light source based on a combination of synchronised conventional laser and free-electron laser sources. The requirement identified for the FELs was continuous coverage of the photon energy range 50-1000eV with variable polarisation, 20fs pulse widths and good temporal coherence to as high a photon energy as possible. This paper presents a design study of three separate FELs which in combination satisfy these requirements. It is proposed to use an HHG seed source tunable from 50-100eV giving direct seeding at the fundamental FEL wavelength up to 100eV, then one or two stages of harmonic upconversion within the FEL to reach the higher photon energies. FEL simulations using realistic electron beam distributions tracked from the gun to the FEL will be presented, illustrating the predicted coherence properties of the FEL output at different photon energies.