Integrated Modeling of Beam Dynamics, Pulse Propagation and Lasing to Design Next-Generation Free Electron Lasers

It is a priority of the DOE Office of Basic Energy Sciences to upgrade present free-electron laser (FEL) facilities, such as the Linac Coherent Light Source, and to develop fundamentally new FEL concepts. Simulation will play an essential role. The codes GENESIS and GINGER accurately model present FEL facilities. However, some future concepts require the development of new codes to relax long-standing approximations. Also, existing algorithms need to make more effective use of parallel computers. Effective optimization and design requires integrated modeling of electron beams and radiation pulses in complicated configurations, including separated undulators. The present approach requires use of multiple codes, and subtle details are lost when translating (for example) particle data between a beam tracking code and an FEL code. Future concepts of interest include: the optics-free FEL oscillator, high gain harmonic generation, echo enabled harmonic generation and the self-seeding scheme for producing transform-limited pulses. Successful completion of the proposed effort will produce commercial quality software, including a state-of-the-art graphical user interface for Windows, Mac OSX and Linux. Use of present-day al- gorithms will enable fast modeling. Fully time-dependent algorithms will also be provided to enable self-consistent modeling of emerging concepts on multi-core desktops and other parallel computers. During Phase I, we will implement standard FEL radiation field algorithms in the parallel VOR- PAL framework, integrating them with existing particle push and space charge algorithms. Correct modeling of self-amplified spontaneous emission (SASE) FELs will be explored via comparison with existing codes. The cost and performance of VORPALs general space charge algorithm will be compared with a simplified model in an existing code. We will also explore the suitability of complex-weight macroparticles for controlling shot noise in SASE FELs and for simulation of high harmonic content. Commercial applications and other benefits: FEL technology has advanced dramatically in the past decade, with a corresponding increase in the number of operating facilities. The majority of FEL facilities are for scientific research; however, industrial and defense applications are increasing. For example, the Laser Processing Consortium at Jefferson Lab has been active for over 10 years, with many partners from industry and defense. Industrial applications include pulsed laser ablation and deposition, laser nitriding and microfabrication. FELs are also being used for processing of polymers, ceramics, metals, water, waste products and food. As these applications move from the R & amp;D stage to deployable systems, the number of operating FELs will increase, together with the need for modeling to optimize performance and efficiency. The US Navy has identified FELs as a key technology for future shipboard self defense.