Sprecher
Beschreibung
The advent of chirped-pulse-amplified CO2 lasers [1] has yielded picosecond, long-wavelength infrared (λ=10 μm) laser pulses of terawatt (TW) peak power suitable for driving laser wakefield accelerators (LWFAs) with high ponderomotive force (∼Iλ2) in low-density (1016 cm-3 < ne <1018 cm-3) plasma [2]. Such pulses can drive GeV plasma accelerating structures large enough (λp up to hundreds of μm) to enable precise injection of <1%-energy-spread lepton bunches from external linacs and detailed 4D imaging of wake density [3] and field [4] profiles via optical [3] and electron [4] probing. The AE-71 project at Brookhaven’s Accelerator Test Facility (ATF) is devoted to exploring these opportunities. We report time/space-resolved optical measurements of the electron density structure of self-modulated wakes driven by CO2 laser pulses (4 ps, 0.5 J, focus w0 ≈ 25 μm) [5] in fully self-ionized hydrogen (0.4< ne <3 1018 cm-3) with new experimental and simulation results. Wake amplitude and dynamics were observed by monitoring collective Thomson scattering (CTS) of a co-propagating 532 nm, 4 ps, electronically synchronized probe pulse (jitter ∼200 fs). First- and second-order CTS sidebands, at Δω=±ωp, ±2ωp from the center probe frequency, were observed as a function of pump-probe time delay Δt, plasma density ne, drive laser peak power P, and focus position within the gas jet. SPACE [6] and OSIRIS [7] simulations explain key observations, including unexpected spectral splitting of sidebands at Δt≈0, wake lifetimes of ∼10 ps, and dependence of wake amplitude on ne and P.
[1] M. N. Polyanskiy et al., Optica 2, 675 (2015).
[2] I. Pogorelsky and I. Ben-Zvi, Plasma Phys. Control. Fusion 56, 084017 (2014).
[3] S. P. LeBlanc et al., Phys. Rev. Lett. 77, 5381 (1996).
[4] C. Zhang et al., Plasma Phys. Control. Fusion 60, 044013 (2018).
[5] N. Andreev, Phys. Rev. STAB 6, 041301 (2003).
[6] K. Yu et al., “SPACE code for beam-plasma interaction,” 6th IPAC 2015 (2015).
[7] R.A.Fonseca et al., LNCS (2331) 342, 2002
| Working group | Laser-driven electron acceleration |
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