First emittance measurement of the beam-driven plasma wakefield accelerated electron beam

V Shpakov ,S Romeo ,G Costa ,Alessio Del Dotto ,A Liedl ,M Bellaveglia ,Monica Cesarini ,A R Rossi ,L Magnisi ,M Croia ,A Mostacci ,R Pompili ,Mario Galletti ,M Ferrario ,F Villa ,E Chiadroni ,M Diomede ,Mostafa Behtouei ,G Di Pirro ,C Vaccarezza ,Anna Giribono ,M P Anania ,J Scifo ,A Biagioni ,L Piersanti ,Felice Dipace ,V Lollo ,A Cianchi ,A Zigler

doi:10.1103/physrevaccelbeams.24.051301

Abstract

Next-generation plasma-based accelerators can push electron beams to GeV energies within centimetre distances. The plasma, excited by a driver pulse, is indeed able to sustain huge electric fields that can efficiently accelerate a trailing witness bunch, which was experimentally demonstrated on multiple occasions. Thus, the main focus of the current research is being shifted towards achieving a high quality of the beam after the plasma acceleration. In this letter we present beam-driven plasma wakefield acceleration experiment, where initially preformed high-quality witness beam was accelerated inside the plasma and characterized. In this experiment the witness beam quality after the acceleration was maintained on high level, with $0.2\%$ final energy spread and $3.8~\mu m$ resulting normalized transverse emittance after the acceleration. In this article, for the first time to our knowledge, the emittance of the PWFA beam was directly measured.

Highlights

Published by the American Physical SocietyLaser pulses (130 fs, rms), whose delay can be adjusted through an optical delay line
Next-generation plasma-based accelerators can push electron beams to GeV energies within centimeter distances
In this paper we present a beam-driven plasma wakefield acceleration experiment, where initially preformed high-quality witness beam was accelerated inside the plasma and characterized

Summary

Published by the American Physical Society

Laser pulses (130 fs, rms), whose delay can be adjusted through an optical delay line. The driver and witness bunches are focused down to ≈25 μm and ≈13 μm correspondingly, and injected into the plasma with density np ≈ 1.5 × 1015 cm−3, obtained by delaying the beam time of arrival with respect to the discharge trigger. The CCD camera counts of the witness beam with and without plasma were compared and no loss of the charge was detected Considering these parameters, the experiment is carried out in the quasi-nonlinear (QNL) regime [40], where the driver bunch density exceeds the plasma one and induces the blowout process but, due to its relatively small charge, the produced perturbation is linear. By using a combination of the positive energy-chirp (larger energy particles on the head of the bunch) and beam-loading effects we were able to mitigate any energy spread growth, and to achieve a slight reduction of the total energy spread by removing, partially, Energy (MeV)

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Findings

Spot Energy