Coherent light sources and optical techniques for Thomson scattering and Laser-Plasma experiments

Recent progress in accelerators and lasers technology opens new perspectives in terms of particle-photon colliders luminosity: low cross section processes can be therefore utilized to create specific radiation sources. Indeed, exploiting the inverse Compton scattering or Thomson back-scattering process, the interaction between relativistic electron beams (γ >> 1) and near-infrared laser pulses (λ ≈ 1μm) yields electromagnetic waves in the X-ray and γ-ray range. The energy, the flux and the spectrum of such kind of generated radiation are suitable for many purposes, e.g. dynamical studies and imaging of solid, molecular and biological systems. Nevertheless, the big development in the high power laser field, begun in the ’80s thanks to the chirped pulse amplification (CPA) scheme [66], has provided systems to be employed in the study of the laser wakefield acceleration (LWFA). As stated by Tajima and Dawson in 1979, an intense laser pulse, propagating through a plasma, can stimulate plasma waves able to accelerate electrons with accelerating gradients greater than 100 GV/m, i.e. some orders of magnitude more than the conventional RF-based LINAC. Moreover, with TW-class laser systems and intensity more than 10^18 W/cm^2, the relativistic regime occurs and electrons can be self-injected into the plasma accelerating structure. This opens the possibility to build much more compact particle accelerators, even though the beam quality, in terms of emittance and energy spread, is not yet comparable to the standard linear accelerator. In this work, the activity related to Thomson back-scattering and laser-plasma interaction pursued at SPARC_LAB Facility in Frascati (Italy) will be presented. SPARC_LAB (Sources for Plasma Accelerators and Radiation Compton with Lasers and Beams) is a multi-disciplinary facility aiming to test new radiation source (THz, XUV, X-Ray) exploiting different phenomena such Free Electron Laser (FEL), Coherent Transition Radiation (CTR) and Thomson back-scattering, thank to the high brightness electron beam that it can provide. The peculiarity of SPARC_LAB is the presence of 300 TW FLAME laser together with the high brightness LINAC. This kind of laser represents a powerful tool to study Thomson back-scattering, when combining it with the linear accelerator, as well as the interaction with the matter, mainly to perform experiments related to LWFA, both in self-injection and external-injection regime. Furthermore, a development of a new diagnostics tool able to measure electron beam emittance in a single shot way will be presented. This novel technique seems to be very useful for beam from plasma accelerators, since they suffer shot-by-shot instabilities. Therefore, a statistical measurement would me meaningless while a single shot diagnostics can provide a more useful description of electron beam parameters. Simulations and some preliminary results will be provided. In addiction, also a research activity on interaction with solid target has been conducted in order to study the possibility to optimize the ion acceleration without increasing the laser energy but opportunely shaping the target itself

Ray optics hamiltonian approach to relativistic self focusing of ultraintense lasers in underdense plasmas

The relativistic self focusing of an ultraintense laser propagating through an underdense plasma is analyzed from a geometrical optics point of view, exploiting the classical hamiltonian formalism. The distribution of the laser intensity along the self-generated plasma channel is studied and compared to measurements

Ray optics hamiltonian approach to relativistic self focusing of ultraintense lasers in underdense plasmas

The relativistic self focusing of an ultraintense laser propagating through an underdense plasma is analyzed from a geometrical optics point of view, exploiting the classical hamiltonian formalism. The distribution of the laser intensity along the self-generated plasma channel is studied and compared to measurements

Ray optics hamiltonian approach to relativistic self focusing of ultraintense lasers in underdense plasmas

The relativistic self focusing of an ultraintense laser propagating through an underdense plasma is analyzed from a geometrical optics point of view, exploiting the classical hamiltonian formalism. The distribution of the laser intensity along the self-generated plasma channel is studied and compared to measurements

An ultra short pulse reconstruction software applied to the GEMINI high power laser system

The GRENOUILLE traces of Gemini pulses (15 J, 30 fs, PW, shot per 20 s) were acquired in the Gemini Target Area PetaWatt at the Central Laser Facility (CLF), Rutherford Appleton Laboratory (RAL). A comparison between the characterizations of the laser pulse parameters made using two different types of algorithms: Video Frog and GRenouille/FrOG (GROG), was made. The temporal and spectral parameters came out to be in great agreement for the two kinds of algorithms. In this experimental campaign it has been showed how GROG, the developed algorithm, works as well as VideoFrog algorithm with the PetaWatt pulse class

Simulation of the transition radiation transport through an optic system

Optical Transition Radiation (OTR) screens are widely used for beam profile measurements. The radiation is emitted when a charged particle beam crosses the boundary between two media with different optical properties. The main advantages of OTR are the instantaneous emission process allowing fast single shot measurements (i.e. bunch by bunch measurements in a multi bunch machine), and the good linearity with the beam charge (if coherent effects can be neglected). Furthermore, OTR angular distribution strongly depends on beam energy. Since OTR screens are typically placed in several positions along the Linac to monitor beam envelope, one may perform a distributed energy measurement along the machine: this will be useful, for instance, during the commissioning phase of a machine. This paper deals with the studies of an algorithm to optimize the generation and the transport of the transition radiation through an optic system using the simulation tool Zemax. The algorithm, in combination with a particle tracking code (i.e. Elegant), will allow to simulate the radiation generated by a beam and, so, to take into account beam divergence and energy spread or chromatic effects in the optic system

The FLAME laser at SPARC_LAB

FLAME is a high power laser system installed at the SPARC_LAB Test Facility in Frascati (Italy). The ultra-intense laser pulses are employed to study the interaction with matter for many purposes: electron acceleration through LWFA, ion and proton generation exploiting the TNSA mechanism, study of new radiation sources and development of new electron diagnostics. In this work, an overview of the FLAME laser system will be given, together with recent experimental results

Stability study for matching in laser driven plasma acceleration

In a recent paper [14], a scheme for inserting and extracting high brightness electron beams to/from a plasma based acceleration stage was presented and proved to be effective with an ideal bi-Gaussian beam, as could be delivered by a conventional photo-injector. In this paper, we extend that study, assessing the method stability against some jitters in the properties of the injected beam. We find that the effects of jitters in Twiss parameters are not symmetric in results; we find a promising configuration that yields better performances than the setting proposed in 041 Moreover we show and interpret what happens when the beam charge profiles are modified