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We use a semi analytical model to investigate the mechanisms underlying the saw tooth instability dynamics in storage rings. We discuss its interplay with other effects, such as the multiple Touschek scattering and derive an upper limit for the power emission associated with such an instability.

We present a phenomenological treatment of free-electron laser storage ring saturation dynamics. The model includes longitudinal instabilities, Touschek intrabeam scattering, and nonzero off-energy-function contributions. The model predictions are compared with Super ACO experimental results and the agreement is shown to be satisfactory.

SPARC and SPARX are two different initiatives toward an ItalianFreeElectronLaser (FEL) source operating in theSelfAmplifiedSpontaneousEmission (SASE) mode, in which several national research institutions are involved. SPARC is a high gain FEL project devoted to provide a source of visible and VUV radiation while exploiting the SASE mechanism. An advanced Photo-Injector system, emittance compensating RF-gun plus a 150 MeV Linac, will inject a high quality e-beam into the undulator to generate high brilliance FEL radiation in the visible region at the fundamental wavelength, (∼500 nm). The production of flat top drive laser beams, high peak current bunches, and emittance compensation scheme will be investigated together with the generation of higher harmonic radiation in the VUV region. SPARX is the direct evolution of such a high gain SASE FEL toward the 13.5 and 1.5 nm operating wavelengths, at 2.5 GeV. To get the required value for the bunch peak current, Ipeak≈ 2.5 kA, the “hybrid” scheme, RF-compression stage plus magnetic chicane, is analyzed and compared with the more standard double stage of magnetic compression. The two options are reviewed considering the tolerance to the drive laser pulse phase jitter.

FELs based on SASE are believed to be powerful tools to explore the frontiers of basic sciences, from physics to chemistry to biology. Intense R&D programs have started in the USA and Europe in order to understand the SASE physics and to prove the feasibility of these sources. The allocation of considerable resources in the Italian National Research Plan (PNR) brought about the formation of a CNR‐ENEA‐INFN‐University of Roma “Tor Vergata” study group. A conceptual design study has been developed and possible schemes for linac sources have been investigated, bringing to the SPARX proposal. We report in this paper the results of a preliminary start to end simulation concerning one option we are considering based on an S‐band normal conducting linac with high brightness photoinjector integrated in a RF compressor.

We develop a rate equation model of the Storage Ring Free Electron Laser dynamics, which includes bunch lengthening and energy spread increasing effects, due to the combined mechanism of potential well distortion and collective random excitations. The model is based on the ordinary storage ring Free Electron Laser equations, coupled to Haissinski-type equations, accounting for the previously quoted effects. The obtained results are shown to provide a reliable tool, yielding a transparent understanding of the interplay between Free Electron Laser and e-beam induced effects.

The construction of the superconducting linac LISA and the transport line to the 25 MeV spectrometer has been completed in July. The commissioning of the whole machine will be carried on starting in September. The installation of the 25 MeV arc to the undulator will be completed by December. Up to now successfully rf power tests and conditioning of 3 out of 4 modules compousing the superconducting accelerator have been accomplished. Conditioning is to be continued also the improve the present results (\\sim 4MeV/m at 25% duty cycle) limited by intense X-ray enission. A technique to measure the quality factor Q_0 by on-line LHe level measurement has been devised [1], taking into account the complex behaviour of LHe in the loop-controlled cryogenic system. The peculiarity of this behaviour is the onset of coupled pressure, temperature and density oscillations which make the LHe evaporated mass evaluation a very indirect measurement.

We report the construction progress of the superconducting (SC) linac LISA and of the FEL experiment SURF at LNF. The design criteria of the 25 MeV transport line from the linac to the undulator are presented and the operation and emittance measurements of the 100 keV gun are described.