Search

The infrastructure of Extreme Light Infrastructure (ELI) provides an unprecedented opportunity for a broad range of frontier science. Its highest ever intensity of lasers, as well as high fluence, high power, and/or ultrafast optical characteristics carve out new territories of discovery, ranging from attosecond science to photonuclear science, laser acceleration and associated beams, and high field science (Four Pillars of ELI). Its applications span from medicine, biology, engineering, energy, chemistry, physics, and fundamental understanding of the Universe. The relativistic optics that intense lasers have begun exploring may be extended into a new regime of ultra‐relativistic regime, where even protons fly relativistically in the optical fields. ELI provides the highest intensity to date such that photon fields begin to feel even the texture of vacuum. This is a singular appeal of ELI with its relatively modest infrastructure (compared to the contemporary largest scientific infrastructures), yet provides an exceptional avenue along which the 21st Century science and society need to answer the toughest questions. The intensity frontier simultaneously brings in the energy horizon (TeV and PeV) as well as temporal frontier (attoseconds and zeptoseconds). It also turns over optics of atoms and molecules into that of nuclei with the ability to produce monoenergetic collimated γ‐ray photons. As such, the ELI concept acutely demands an effort to encompass and integrate its Four Pillars.

The post‐acceleration of laser‐generated protons through conventional drift tube linear accelerators has been simulated with the particle code Parmela. The proton source is generated on the rear surface of a target irradiated by an high‐intensity (1019 W⋅cm−2) short‐pulse (350 fs) laser and focused by a microlens that allows selecting collimated protons at 7±0.1 MeV with rms unnormalized emittance of 0.180 mm.mrad. The simulations show that protons can be accelerated by one drift tube linac tank to more than 14 MeV with unnormalized emittance growth of 8 in x and 22.6 in y directions when considering a total proton charge of 0.112 mA. This result shows for the first time that coupling between laser‐plasma accelerators with traditional accelerators is possible, allowing a luminosity gain for the final beam.

We discuss the design of and initial results from an experiment in space‐charge dominated beam dynamics which explores a new regime of high‐brightness electron beam generation at the SPARC photoinjector. The scheme under study employs the tendency of intense electron beams to rearrange to produce uniform density, giving a nearly ideal beam from the viewpoint of space charge‐induced emittance. The experiments are aimed at testing the marriage of this idea with a related concept, emittance compensation. We show that this new regime of operating photoinjector may be the preferred method of obtaining highest brightness beams with lower energy spread. We discuss the design of the experiment, including developing of a novel time‐dependent, aerogel‐based imaging system. This system has been installed at SPARC, and first evidence for nearly uniformly filled ellipsoidal charge distributions recorded.

Assuming the validity of the Boussard criterion for the determination of the microwave instability threshold, we derive two coupled non linear differential equations which describe the time evolution of the energy spread and of the instability growth rate under different conditions. The equations reproduce the characteristic features of the saw tooth instability and are in agreement with the results of a time domain simulation code.

This working group was charged with reviewing the general area of plasma phenomena in beams. The group reviewed our present understanding and discussed critical issues for a wide variety of topics, including longitudinal and transverse wakefield instabilities in high intensity rings, numerical computation of wakes at short scale length, ion instabilities, wakefields and emittance growth from coherent synchrotron radiation, the nature of self-amplified spontaneous emission (SASE), soliton theory and its role in beam physics, the control of transverse instabilities by feedback or by temporal variation of ring parameters, and the use of plasma concepts in beam dynamics, particularly applications of beam echo measurements.

Experimental observations on FEL Storage Rings (Aco, Super-Aco, VEPP3, TERAS) have shown that in a storage ring with an operating FEL there is a mutual effect between the FEL operational mode and the beam longitudinal distribution. The main effects are the birth of a macro-temporal structure of the FEL radiation and a suppression of the synchrotron sidebands, evidence of beam stabilisation against the microwave instabilities. In this paper we discuss the main features of the beam dynamics analysed with a simulation code recently developed, which includes the FEL-beam interaction. Furtherly, we propose an heuristic model which enable to describe in a simple way the overall system.