Robb, G.R.M.
| Paper | Title | Page |
|---|---|---|
| MOPP016 | Quantum SASE FEL with a Laser Wiggler | 71 |
|
||
|
Funding: Istituto Nazionale di Fisica Nucleare (INFN), Italy Quantum effects in high-gain FELs become relevant when ρ'=ρ(mcγ/ ћ k)<1. The quantum FEL parameter ρ' rules the maximum number of photons emitted per electrons. It has been shown that when ρ'<1 a "quantum purification" of the SASE regime occurs: in fact, the spectrum of the emitted radiation (randomly spiky in the usual classical SASE regime) shrinks to a very narrow single line, leading to a high degree of temporal coherence. From the definition of ρ it appears that in order to achieve the quantum regime, small values of ρ, beam energy and radiation wavelength are necessary. These requirements can be met only using a laser wiggler. In this work we state the scaling laws necessary to operate a SASE FEL in the Angstrom region. All physical quantities are expressed in terms of the normalized emittance and of two parameters: the ratio between laser and electron beam spot sizes and the ratio between Rayleigh range and electron β-function. The feasibility study of a Quantum SASE FEL experiment using parameters as those foreseen in the SPARC/PLASMONX projects in construction at the INFN Frascati is explicitly discussed. |
||
| THOA005 | Harmonic Lasing in an FEL Amplifier | 434 |
|
||
|
Funding: We acknowledge the support of the European Framework Programme 6 EUROFEL Design Study, CCLRC, and the Scottish Universities Physics Alliance. Recent proof-of-principle simulations have demonstrated a method that allows a planar undulator FEL to lase so that the interaction with an odd harmonic of the radiation field dominates that of the fundamental [1]. This harmonic lasing of the FEL is achieved by disrupting the interaction between the fundamental radiation field and electrons as they propagate through the undulator while allowing the n-th harmonic interaction to evolve unhindered. The disruption of the interaction at the fundamental is achieved by a series of relative phase changes between electrons and the fundamental ponderomotive potential of 2k pi/n (k = 1, 2, 3, . . . ; k not equal to n). The corresponding phase change with the ponderomotive potential of the n-th harmonic is then 2k pi which, at least in a simple steady-state FEL model, will have no deleterious effect upon the harmonic interaction. Such phase changes are relatively easy to implement and indeed some current FEL designs would not require any structural modification. We present a more detailed analysis of harmonic lasing and use this to discuss potential benefits and applications in extending the operational bandwidth of FELs to shorter wavelengths. [1] B.W.J. McNeil, G.R.M. Robb and M.W. Poole, Proceedings of Particle Accelerator Conference, Knoxville, USA (2005) |
||
| THPP025 | Design Considerations for the 4GLS XUV-FEL | 506 |
|
||
|
Funding: We acknowledge the support of the European Framework Programme 6 EUROFEL Design Study, CCLRC, and the Scottish Universities Physics Alliance. An XUV Free-Electron Laser operating in the photon energy range 10-100eV is a key component of the proposed 4th Generation Light Source (4GLS) at Daresbury Laboratory in the UK. The current design proposal is an amplifier FEL seeded by a Higher Harmonic Generation (HHG) source. In this paper we present and discuss the considerations that led to the current design. We also present 3D simulation results that illustrate the potential radiation output characteristics. |
||
| THOC002 | Quantum Theory of SASE-FEL with Propagation Effects | 664 |
|
||
|
We present a proof of principle of the novel regime of quantum SASE with propagation effects. Using a self-consistent system of Schrodinger-Maxwell equations, we show that the dynamics of the system is determined by a properly defined "quantum FEL-parameter", ρ', which rules the number of photons emitted per electron, as well as the electron recoil in units of ћk. In the limit ρ'>>1 the quantum model reproduces the classical SASE regime with random spiking behavior and broad spectrum. In this limit we show that the equation for the Wigner function reduces to the classical Vlasov equation. In the opposite limit, ρ'<1, we demonstrate "quantum purification" of SASE: the classical spiking behavior disappears and the power spectrum becomes very narrow so that the temporal coherence of the SASE spectrum is dramatically improved. Photon statistics, electron-photon entangled states, minimum uncertainty states and quantum limitations on bunching and energy spread will be discussed. |
||