USTRAT/SUPA, Glasgow
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
Pulsar Physics, Eindhoven
Recent progress in developing laser-plasma accelerators is raising the possibility of a compact coherent radiation source that could be housed in a medium sized university department. Beam properties from laser-plasma accelerators have been traditionally considered as not being of sufficient quality to produce amplification. Our work shows that this is not the case. Here we present a study of the beam characteristics of a laser-plasma accelerator. We also highlight the latest results on the ALPHA-X compact FEL. We show how the beam properties of the ALPHA-X beam line have been optimized in order to drive a FEL. We discuss the implementation of a focussing system consisting of a triplet of permanent magnet quadrupoles and a triplet of electromagnetic quadrupoles. The design of these devices has been carried out using the GPT (General Particle Tracer "*") code, which considers space charge effects and allows a realistic estimate of electron beam properties along the beam line. The latest measurements of energy spread and emittance will be presented. Currently we have measured energy spreads less than 0.7% and, using a pepper pot, put an upper limit on the emittance of 5 pi mm mrad.
"*" S.B. van der Geer and M.J. de Loos, “General Particle Tracer code: design, implementation and application” (2001);
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
The ALICE (Accelerators and Lasers in Combined Experiments) facility (formerly known as ERLP) is currently being commissioned at Daresbury Laboratory. It serves as a test facility for novel accelerator and photon science applications. As part of this facility, an oscillator-type FEL will be commissioned later in 2009. The FEL will be used to test energy recovery with a disrupted beam and to provide output for a select experimental programme. The FEL output will be measured and used to determine the accuracy of FEL modelling techniques. The facility could also potentially be used as a testbed for novel FEL concepts. In this paper, an overview of the FEL design is presented, together with an update of the status of commissioning preparations, including time-dependent modelling using the expected electron beam parameters.
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
STFC/DL, Daresbury, Warrington, Cheshire
The choice of undulator design and minimum magnet gap is crucial in the definition of every short wavelength FEL and is ultimately a cost driver for that project. The magnet gap selection is a compromise between wanting to minimise harmful wakefield effects whilst at the same time generating high magnetic fields with short periods. The NLS project has tried to take a holistic approach in the definition of the undulators. This has been carried out by first assessing the impact of resistive wall wakefields in general on the FEL performance and then selecting the maximum level of wakefield which has a just tolerable impact on the FEL. This wakefield is then translated into equivalent circular and elliptical vessel geometries. Suitable vessel thickness and mechanical tolerances are then added to define the undulator magnet gap for the case of a circular vessel (Delta undulator) and an elliptical vessel (APPLE-2 undulator). Finally, the two types of undulator have been modelled, their parameters compared, and a selection made. This paper summarises this global self-consistent approach to undulator definition and reports on the result for the NLS.
