Physics considerations for laser-plasma linear colliders

Abstract

Physics considerations for a next-generation linear collider based on laser-plasma accelerators are discussed. The ultrahigh accelerating gradient of a laser-plasma accelerator and short laser coupling distance between accelerator stages allows for a compact linac. Two regimes of laser-plasma acceleration are discussed. The highly nonlinear regime has the advantages of higher accelerating fields and uniform focusing forces, whereas the quasilinear regime has the advantage of symmetric accelerating properties for electrons and positrons. Scaling of various accelerator and collider parameters with respect to plasma density and laser wavelength are derived. Reduction of beamstrahlung effects implies the use of ultrashort bunches of moderate charge. The total linac length scales inversely with the square root of the plasma density, whereas the total power scales proportional to the square root of the density. A 1 TeV center-ofmass collider based on stages using a plasma density of 10 17 cm À3 requires tens of J of laser energy per stage (using 1 m wavelength lasers) with tens of kHz repetition rate. Coulomb scattering and synchrotron radiation are examined and found not to significantly degrade beam quality. A photon collider based on laser-plasma accelerated beams is also considered. The requirements for the scattering laser energy are comparable to those of a single laser-plasma accelerator stage.

Generalized algorithm for control of numerical dispersion in explicit time-domain electromagnetic simulations

“…Dephasing plays a key role in the design of stages for a high-energy laser-plasma collider [9]. We therefore expect that correct dispersion will be an important aspect of the simulation of such stages.…”

“…Since then, efforts have focused on obtaining beams useful for highenergy particle colliders [9] and radiation sources [16][17][18][19]. This involves developing longer acceleration stages to achieve greater total energy gain, and controlling the injection process for higher beam quality.…”

“…This process is called dephasing and is one limitation on the length of an LPA stage. Dephasing plays a key role in determining the optimal stage length in highenergy LPA collider designs [9] and is sensitively dependent on the laser pulse group velocity, and hence dispersion. Significant theoretical and computational work has gone into LPA stage simulations, and has led to the development of new algorithms [10][11][12].…”

Beamstrahlung considerations in laser-plasma-accelerator-based linear colliders

“…The electron plasma wave has relativistic phase velocity, and can support large electric fields in the direction of propagation of the laser. Rapid progress in the field of laser-plasma acceleration, and in particular the demonstration of high-quality GeV electron beams using cm-scale plasmas at Lawrence Berkeley National Laboratory [4], has increased interest in laserplasma acceleration as a path toward a compact, TeV-class, electron-positron linear collider [5,6].…”

“…[6]. These scaling laws were derived under the assumptions of fixed final focusing to the interaction point (IP), fixed efficiency of the energy conversion, and a fixed center-of-mass energy and luminosity required for highenergy physics experiments.…”