# Your search: "author:"Venturini, A""

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## Scholarly Works (65 results)

Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.

We determine the second-order correction to the gain function of the microbunching instability in single-pass systems of interest for the next generation of light sources. The calculation applies to the case where the instability is seeded by shot noise. We examine an analytically treatable model of beam dynamics where collective forces are active only in non-dispersive sections of the linac. We find that the second order term can augment the linear gain significantly while affecting the spectrum of the overall gain only marginally. The weight of the second-order correction relative to the linear gain is found to scale quadratically with respect to R56. The qualitative behavior predicted by the model is consistent with exact numerical solutions of the Vlasov equations for realistic lattices.

We simulate electron cloud build-up in a grooved vacuum chamber including the effect of space charge from the electrons. We identify conditions for e-cloud suppression and make contact with previous estimates of an effective secondary electron yield for grooved surfaces.

Characterization of single-bunch instabilities in the International Linear Collider (ILC) damping rings (DRs) has been indicated as a high-priority activity toward completion of an engineering design. In this paper we report on a first estimate of the current thresholds for the instability using numerical and analytical models of the wake potentials associated with the various machine components. The numerical models were derived (upon appropriate scaling) from designs of the corresponding components installed in existing machines. The current thresholds for instabilities were determined by numerical solution of the Vlasov equation for the longitudinal dynamics. For the DR baseline lattice as of Feb. 2007 we find the critical current for instability to be safely above the design specifications leaving room for further optimization of the choice of the momentum compaction.

Space-charge effects in the low-energy ring of the proposed Super-B Factory are studied using a weak-strong model of dynamics as implemented in the code Marylie/Impact (MLI). The impact of space charge appears noticeable but our results suggest the existence of workable regions of the tune space where the design emittance is minimally affected. However, additional studies are recommended to fully substantiate this conclusion.

Using first-order perturbation theory for maps, we extend the familiar formulae for space-charge tuneshift to encompass the case of a fully coupled lattice.