High energy and high quality electron bunches are needed for advanced all-optical X/gamma-ray secondary sources. In this context, schemes relying on the decoupling of the ionization process from the plasma wave excitation are highly desirable and actively pursued. Efficient plasma waves can be resonantly excited using trains of ultrashort pulses instead of a single pulse. This is exploited, for instance, in the recently proposed ReMPI scheme, which holds the promise for producing remarkably high quality bunches, while keeping at the same time a reasonable complexity.
The generation of ultrashort pulse trains is not so straightforward; over the past few years, not so many schemes have been proposed and, possibly, experimentally studied. Most often, these schemes lead to the loss of a sizeable fraction of the available laser energy; this is of a particular concern for the design of high rep rate (tentatively accessing the 100Hz level) systems aimed to drive secondary sources, such as, for instance, the lasers currently under design for the envisioned EuPRAXIA facility.
Here we report on the study of novel optical schemes leading to the generation of ultrashort pulse trains with negligible energy losses. Two different schemes will be presented, based on the splitting of the original pulse at different levels of the laser transport and focusing chain. Results from both numerical simulations and experimental tests will be shown, and the perspectives for scaling to the pulse requirements of large scale facilities discussed.
Laser Wake Field accelerated electrons need to exhibit a good beam-quality to comply with requirements of FEL or high brilliance Thomson Scattering sources, or to be post-accelerated in a further LWFA stage towards TeV energy scale. Controlling electron injection, plasma density profile and laser pulse evolution are therefore crucial tasks for high-quality e-bunch production. A new bunch injection scheme, the Resonant Multi-Pulse Ionization Injection (RMPII), is based on a single, ultrashort Ti:Sa laser system. In the RMPII the main portion of the pulse is temporally shaped as a sequence of resonant sub-pulses, while a minor portion acts as an ionizing pulse. Simulations show that high-quality electron bunches with energies in the range 265MeV −1.15GeV , normalized emittance as low as 0.08 mm·mrad and 0.65% energy spread can be obtained with a single 250 TW Ti:Sa laser system. Applications of the e-beam in high-brilliance Thomson Scattering source, including 1.5 - 26.4 MeV γ sources with peak brilliance up to 1 · 1028ph/(s · mm2 • mrad2 • 0.1%bw), are reported.
The INFN Strategic Project PLASMONX (PLASma acceleration and MONochromatic X-ray production) deals with
the creation of a High Intensity Laser Laboratory at LNF (HILL@LNF) beside the SPARC bunker, with which it will
communicate via a channel for the propagation of laser beams. In this laboratory FLAME ( Frascati Laser for
Acceleration and Multidisciplinary Experiments), a 200TW, 30fs, 10Hz Ti:Sapphire Laser, will be set up.
The main goals of this project are:
1) demonstration of high-gradient acceleration of relativistic electrons injected into electron plasma waves excited
by ultra-short, super-intense laser pulses;
2) development of a monochromatic and tuneable X-ray source in the 20-1000 keV range, based on Thomson
Scattering of laser pulses by the 20-200 MeV electrons of the LINAC of the SPARC project.
One of the aims of the project consists in the realization of a pulsed source of ionizing radiation for R&D activity in
Guiding focused pulses along path lengths much larger than the depth of focus is one of the major tasks for the
progress of laser acceleration of electrons in plasmas. We will present the results of the production of hollow
plasmas to be used as guiding medium, obtained inducing optical breakdown in Helium subsonic gas-jet with
nanosecond laser pulses similar to the Amplified Spontaneous Emission (ASE) pedestal of a powerful ultrashort
laser pulse. These plasmas have been then carefully characterized by the deconvolution, with original algorithms,
of high quality interferograms obtained with high resolution interferometry and the relevant channel parameters
were measured, including length, width, electron density at the channel axis and at its boundary. The electron
density profiles we obtained match the requirements for an efficient guiding in laser wakefield acceleration (LWFA)
experiments. The acceleration length can be further increased by using longer gas-jets and larger f/N numbers.
New studies are planned with supersonic gas-jets, providing more homogeneous density profiles and steeper
Novel sources of energetic photons are currently studied and developed at the Intense Laser Irradiation Laboratory of
Pisa. They include: i) X-rays generated by plasmas produced with nanosecond and picosecond laser pulses. This kind of
source has been recently optimised in terms of intensity, repetition rate, monochromaticity, which allowed novel
techniques to be successfully tested as micro-radiography and differential mapping of tracing elements. ii) K-a X-ray
emission of short duration due to the collision of energetic electrons generated during ultra-short femtosecond laser-solid
interactions. iii) Monochromatic and ultra-short X-rays pulses generated via Thomson scattering of intense sub-
picosecond pulses by relativistic electron bunches are currently being studied theoretically also with the aid of numerical
codes. Electron bunches produced by both conventional beamlines and laser acceleration of electrons in plasmas are