Active Plasma Lensing for Relativistic Laser-Plasma-Accelerated Electron Beams

Abstract

Compact, tunable, radially symmetric focusing of electrons is critical to laser-plasma accelerator (LPA) applications. Experiments are presented demonstrating the use of a discharge-capillary active plasma lens to focus 100-MeV-level LPA beams. The lens can provide tunable field gradients in excess of 3000 T/m, enabling cm-scale focal lengths for GeV-level beam energies and allowing LPA-based electron beams and light sources to maintain their compact footprint. For a range of lens strengths, excellent agreement with simulation was obtained.

Demonstration of a high repetition rate capillary discharge waveguide

“…In addition to providing focusing forces for laser pulses in LPAs, capillary discharge waveguides have also been shown to be an effective focusing element for electron beams via the discharge current and associated magnetic field 21 . This provides a compact, tunable, and symmetric lens for transporting electron beams to targets and between independently powered LPA stages to achieve very high electron beam energy 22 .…”

Density characterization of discharged gas-filled capillaries through common-path two-color spectral-domain interferometry

“…In addition, x-ray lasing [9] and soft x-ray high-harmonic generation [10] have benefited from guiding in pre-formed channels. More recently, discharged plasma structures have been applied to focus relativistic electron beams, exploiting the advantages of radial symmetry, tunability, and strong multi kilo-Tesla/meter focusing gradients [11]. Knowledge of the on-axis plasma density is of critical importance to accelerator applications since the density dominates the plasma response time, self-injection threshold, accelerating field strength, electron beam dephasing length [6], and beam-driven wakefield effects [12].…”

Staging of laser-plasma accelerators

“…Changing the relative delay of the injector pulse and the second stage laser pulse resulted in a charge modulation of the electron beam that allowed determination of the plasma wavelength k p and, hence, the plasma density n e . An active plasma lens 27 was introduced to the setup to focus the injector electron beam at the entrance of the second stage target for maximum coupling to the wake (see Fig. 1(b)).…”