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Ultra-short electron beams, produced through the velocity bunching compression technique, are used to drive the SPARC linear accelerator based source, which relies on the emission of coherent transition radiation in the terahertz range. This paper reports on the main features of this radiation, as terahertz source, with spectral coverage up to 5 THz and pulse duration down to 200 fs, with an energy per pulse of the order of several micro-joule, and as electron beam longitudinal diagnostics. [ABSTRACT FROM AUTHOR]

Abstract Plasma wake-field acceleration experiments are performed at the SPARC_LAB test facility by using a gas-filled capillary plasma source composed of a dielectric capillary. The electron can reach GeV energy in a few centimeters, with an accelerating gradient orders of magnitude larger than provided by conventional techniques. In this acceleration scheme, wake fields produced by passing electron beams through dielectric structures can determine a strong beam instability that represents an important hurdle towards the capability to focus high-current electron beams in the transverse plane. For these reasons, the estimation of the transverse wake-field amplitudes assumes a fundamental role in the implementation of the plasma wake-field acceleration. In this work, it presented a study to investigate which parameters affect the wake-field formation inside a cylindrical dielectric structure, both the capillary dimensions and the beam parameters, and it is introduced a quantitative evaluation of the longitudinal and transverse electric fields. Highlights • Gas-filled capillary plasma source. • Wake fields produced by passing electron beams through dielectric capillaries. • Experimental and theoretical evaluation of the electric fields inside a dielectric capillary. [ABSTRACT FROM AUTHOR]

Abstract: In order to produce a high brightness electron beam for the Frascati Linac coherent light source (SPARC) the use of an accelerating section with frequency equal to the fourth harmonic of the main S-Band Linac frequency is needed. This paper discusses the design and the realization of a compact X-Band linear accelerating section for obtaining 5MV average accelerating gradient, working at a frequency of 11.424GHz and operating on the standing wave mode. Numerical predictions compared with measurements made on a copper prototype at room temperature are reported. [Copyright &y& Elsevier]