Serafini, L.
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| MOPP015 | Beam Dynamics Studies for the SPARXINO Linac | 67 |
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The first phase of the SPARX project is essentially an R&D activity focused on developing techniques and critical components for future X-ray FEL facilities. The SPARXINO test facility will generate ultra-high peak brightness electron beams at 1 GeV, thanks to the upgrade of the existing Frascati 800 MeV linac. This facility will allow driving a single pass FEL experiment in the range of 3-5 nm, both in SASE and SEEDED FEL configurations. A peculiarity of this linac design is the choice of integrating a rectilinear RF compressor in the early stage of the acceleration, producing a 300-500 A beam, with a magnetic chicane afterwards, for a further compression up to 1 kA. In this paper we discuss the dynamics of the beam, which is in the space charge dominated regime throughout almost all the linac. Start to end simulations and preliminary stability studies taking into account some significant parameter fluctuations are also reported. |
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| MOPP016 | Quantum SASE FEL with a Laser Wiggler | 71 |
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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. |
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| TUOB003 | Velocity and Magnetic Compressions in FEL Drivers | |
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We will compare merits and issues of these two techniques suitable for increasing the peak current of high brightness electron beams. The typical range of applicability is low energy for the velocity bunching and middle to high energy for magnetic compression. Velocity bunching is free from CSR effects but requires very high RF stability (time jitters), as well as a dedicated additional focusing and great cure in the beam transport: it is very well understood theoretically and numerical simulations are pretty straightforward. Several experiments of velocity bunching have been performed in the past few years: none of them, nevertheless, used a photoinjector designed and optimized for that purpose. Magnetic compression is a much more consolidated technique: CSR effects and micro-bunch instabilities are its main drawbacks. There is a large operational experience with chicanes used as magnetic compressors and their theoretical understanding is quite deep, though numerical simulations of real devices are still challenging, in particular for 3D self-consistent modeling. Most of present FEL drivers foresee in their lay-out a multiple-staged magnetic compression that brings the bunch peak current all the way from the photoinjector exit (at typically 50-100 A) up to the linac exit at a multi-kA level (total compression by a factor 30 to 60). As an alternative option, we will discuss how to integrate the two techniques into a typical FEL linac, with the aim to marry the merits of both and to mitigate the issues. |
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| THPP049 | Collective Effects in the Thomson Back-Scattering between a Laser Pulse and a Relativistic Electron Beam | 580 |
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Funding: Università degli Studi di MIlano-INFN Via Celoria,16 MIlano (Italy) Collective effects in the radiation emission process via Thomson back-scattering of an intense optical laser pulse by high brightness electron beams are analyzed. The micro-bunching of the electron beam on the scale of the emitted radiation wavelength and the consequent free-electron-laser instability may enhance significantly the total number of emitted photons. Scalings of the radiation properties, both in the collective and in the incoherent spontaneous regime, versus laser and electron beam parameters are discussed. Transverse effects due to radiation diffraction, finite emittance of the beam, and transverse distribution of the laser energy are studied. |
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| THPP066 | Experimental Studies of Temporal Electron Beam Shaping at the DUV-FEL Accelerator | 632 |
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Funding: Work supported by DOE contracts DE-AC02-76SF00515 and DE-AC02-98CH10886 The photoinjectors for future short wavelength high brightness accelerator driven light sources need to produce an electron beam with ultra-low emittance. At the DUV-FEL facility at BNL, we studied the effect of longitudinally shaping the photocathode laser pulses on the electron beam dynamics. We report on measurements of transverse and longitudinal electron beam emittance and comparisons of the experimental results with simulations. |
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| THPP019 | Status of the SPARX FEL Project | 491 |
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The first phase of the SPARX project, now funded by MIUR (Research Department of Italian Government), is an R&D activity focused on developing techniques and critical components for future X-ray FEL facilities. This project is the natural extension of the activities under development within the ongoing SPARC collaboration. The aim is the generation of electron beams characterized by an ultra-high peak brightness with a linear accelerator based on the upgrade of the existing Frascati 800 MeV LINAC and to drive a single pass FEL experiment in the range of 3-5 nm, both in SASE and SEEDED FEL configurations, exploiting the use of superconducting and exotic undulator sections. In this paper we discuss the present status of the collaboration. |
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