Plasma-based positron sources at EuPRAXIA

Abstract

Plasma-based positron sources are attracting significant attention from the research community, thanks to rather unique characteristics, which include broad energy tuneability and ultra-short duration, obtainable in a compact and relatively inexpensive setup. Here, we show a detailed numerical study of the positron beam characteristics obtainable at the dedicated user target areas proposed for the EuPRAXIA facility, the first plasma-based particle accelerator to be built as a user facility for applications. It will be shown that MeV-scale positron beams with unique properties for industrial and material science applications can be produced, alongside with GeV-scale positron beams suitable for fundamental science and accelerator physics.

Narrow bandwidth, low-emittance positron beams from a laser-wakefield accelerator

“…All positron beam parameters for different target thicknesses can then be readily obtained using known scaling laws (see, e.g., Refs. 33 , 34 ). For a converter target placed right after the LWFA, our simulations indicate that different electron source size or divergence will have a small effect on the positron beam characteristics, which can anyway be taken into account by adding it in quadrature to the obtained values.…”

“…In terms of future developments, increasing the stability and energy of the primary electron beam is expected to further improve the positron beam characteristics, with significant improvements in electron beam stability already having been reported with state-of-the-art laser systems 4 . Moreover, single-stage LWFA has been demonstrated beyond 5 GeV 48 , which, in conjunction with a minimised drift distance for the LWFA electrons, is expected to readily provide, for instance, nm-scale geometric emittances and a normalised emittance of 10 µm at 3 GeV 33 , 34 .…”

“…However, to effectively enable plasma acceleration of positrons in the laboratory, it is necessary to produce beams that simultaneously have %-level energy spreads, femtosecond-scale duration, and micron-scale normalised emittance 5 , 7 . To date, properties of this kind have only been predicted numerically 29 , 33 , 34 .…”

“…These beams present femtosecond-scale duration and micron-scale normalised emittance, and are thus of sufficient spectral and spatial quality to act as a witness beam in a positron wakefield accelerator, as we demonstrate with proof-of-principle particle-in-cell simulations. Favourable scalings in the beam spectral and spatial characteristics already indicate that even higher quality can be achieved with laser systems of higher peak power 33 , 34 . These results represent a fundamental stepping-stone towards enabling widespread and systematic experimental studies of plasma-based positron acceleration.…”

Laser Generation of Near-GeV Low Emittance Positron Beams

“…Increasing the energy of the primary electron beam is expected to further improve the positron beam characteristics. Single stage LWFA has been demonstrated beyond 5 GeV [33], which along with a minimised drift distance for the LWFA electrons is expected to provide nm-scale geometric emittances and a normalised emittance of 10 µm at 3 GeV [34].…”