Efficient post-acceleration of protons in helical coil targets driven by sub-ps laser pulses

Year: 2017

Authors: Ahmed H., Kar S., Cantono G., Hadjisolomou P., Poye A., Gwynne D., Lewis CLS., Macchi A., Naughton K., Nersisyan G., Tikhonchuk V., Willi O., Borghesi M.

Autors Affiliation: Queens Univ Belfast, Sch Math & Phys, Ctr Plasma Phys, Belfast BT7 1NN, Antrim, North Ireland; Rutherford Appleton Lab, Cent Laser Facil, Didcot OX11 OQX, Oxon, England; Univ Pisa, Dept Phys E Fermi, Largo B Pontecorvo 3, I-56127 Pisa, Italy; Univ Claude Bernard, Univ Lyon, Ens Lyon, CNRS,Lab Phys, F-69342 Lyon, France; Natl Res Council CNR INO, Natl Inst Opt, A Gozzini Unit, I-56124 Pisa, Italy; Univ Bordeaux, CNRS, CEA, Ctr Laser Intenses & Applicat, F-33405 Talence, France; Heinrich Heine Univ, Inst Laser & Plasmaphys, D-40225 Dusseldorf, Germany.

Abstract: The characteristics of laser driven proton beams can be efficiently controlled and optimised by employing a recently developed helical coil technique, which exploits the transient self-charging of solid targets irradiated by intense laser pulses. Here we demonstrate a well collimated (<1 degrees divergence) and narrow bandwidth (similar to 10% energy spread) proton beamlet of similar to 10(7) particles at 10 +/- 0.5 MeV obtained by irradiating helical coil targets with a few joules, sub-ps laser pulses at an intensity of similar to 2 x 10(19) W cm(-2). The experimental data are in good agreement with particle tracing simulations suggesting post-acceleration of protons inside the coil at a rate similar to 0.7 MeV/mm, which is comparable to the results obtained from a similar coil target irradiated by a fs class laser at an order of magnitude higher intensity, as reported in S. Kar et al., Nat. Commun, 7, 10792 (2016). The dynamics of hot electron escape from the laser irradiated target was studied numerically for these two irradiation regimes, which shows that the target self-charging can be optimised at a pulse duration of few hundreds of fs. This information is highly beneficial for maximising the post-acceleration gradient in future experiments. Journal/Review: SCIENTIFIC REPORTS

Volume: 7      Pages from: 10891-1  to: 10891-6

More Information: The authors acknowledge funding from EPSRC, [EP/J002550/1-Career Acceleration Fellowship held by S.K., EP/L002221/1, EP/K022415/1, EP/J500094/1 and EP/I029206/1], SBF-TR18 and GRK1203, EC-GA284464 and Invest Northern Ireland (POC-329). Authors acknowledge A. Schiavi (Univ. Roma 1, Italy) for the use of the particle tracing code, PTRACE. Data associated with the research published in this article can be accessible at http://dx.doi.org/10.17034/5c1b0a1f-d3f6-4c2f-b467-ab7b77edde83.
KeyWords: Beams
DOI: 10.1038/s41598-017-06985-4

Citations: 15
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