Laser wake-field acceleration in pre-formed plasma channel created by pre-pulse pedestal of terawatt laser pulse

Abstract

The role of nanosecond duration pre-pulse pedestal (Amplified Spontaneous Emission (ASE) pre-pulse) in the propagation of 45 fs, 4 TW Ti:Sapphire laser pulse through a helium gas jet target has been investigated. We observed that the pre-pulse pedestal of about 1 ns duration and intensity 3 × 1012 W/cm2 creates pre-formed plasma with optical guiding channel like structure in the gas-jet at density around 3 × 1019 cm−3. Guiding of the 45 fs laser pulse (IL = 3 × 1018 W/cm2) in the pre-formed plasma channel, over a distance much longer than the Rayleigh length was also observed. The guiding of the laser pulse resulted in the generation of high energy electron beam by laser wake-field acceleration of self-injected electrons. The accelerated electron beam was quasi-monoenergetic with peak energy up to 50 MeV, low divergence in the range of 3–6 mrad, and bunch charge up to 100 pC.

High-quality stable electron beams from laser wakefield acceleration in high density plasma

“…Simultaneous measurement of nonlinear Thomson side-scattering images showed smooth and stable selfguiding channels with length 490 μm. Increasing the level of prepulse reduced the stability of the electron beam as observed in our earlier investigations [14].…”

“…Although the electron energy in the present study is relatively less compared to Ref. [14], a low level of prepulse in the present study is found to contribute to improvement in the stability of the electron beam parameters as observed in an earlier study [23].…”

“…In that experiment, the wakefield excitation and the electron acceleration occurred as a result of strong selfmodulation seeded by the forward Raman scattering instability [22], which is inherently susceptible to shot-to-shot fluctuations. It was noted in another previous experiment that an amplified spontaneous emission prepulse with sufficient intensity and duration forms preplasma that helps to guide the main laser beam in the low density plasma channel and accelerate the electrons to higher energies [14]. However, the inherent shot-to-shot variation of the prepulse parameters causes fluctuation in electron beam parameters.…”

A comparative study of the inner-shell and the ionic line radiation from ultra-short laser-produced magnesium plasma

“…The ASE pre-pulse and replica pulse contrast ratios were measured using a fast photo-diode with a 0.8 ns rise time on a 500 MHz digital oscilloscope. The typical ASE pre-pulse pedestals for two different switching times of the Pockels cell were similar to those in [18]. The duration of the ASE pre-pulse pedestal was controlled by changing the switching-on time of the high voltage pulse on the Pockels cell of the pulse cleaner (located after the regenerative amplifier) in the Ti:sapphire laser system.…”

Direct electron acceleration by chirped laser pulse in a cylindrical plasma channel*

“…The threshold can be altered by changing the polarization angle of the laser pulse, [42] and it can increase the maximum energy of electrons. [40,[43][44][45][46][47][48] Therefore, the direct laser acceleration of electrons in under-dense density plasma channel has attracted much attention. However, the coupling characteristics between chirped laser pulse and plasma channel and its effect on electron acceleration are still unclear.…”