Meter-scale conditioned hydrodynamic optical-field-ionized plasma channels

Abstract

We demonstrate through experiments and numerical simulations that low-density, low-loss, meter-scale plasma channels can be generated by employing a conditioning laser pulse to ionize the neutral gas collar surrounding a hydrodynamic optical-field-ionized (HOFI) plasma channel. We use particle-in-cell simulations to show that the leading edge of the conditioning pulse ionizes the neutral gas collar to generate a deep, low-loss plasma channel which guides the bulk of the conditioning pulse itself as well as any subsequently injected pulses. In proof-of-principle experiments, we generate conditioned HOFI (CHOFI) waveguides with axial electron densities of n e0 ≈ 1×10 17 cm −3 and a matched spot size of 26 μm. The power attenuation length of these CHOFI channels was calculated to be L att = (21 ± 3) m, more than two orders of magnitude longer than achieved by HOFI channels. Hydrodynamic and particle-in-cell simulations demonstrate that meter-scale CHOFI waveguides with attenuation lengths exceeding 1 m could be generated with a total laser pulse energy of only 1.2 J per meter of channel. The properties of CHOFI channels are ideally suited to many applications in high-intensity light-matter interactions, including multi-GeV plasma accelerator stages operating at high pulse repetition rates.

Parametric co-linear axion photon instability

“…Such intensities would correspond to a wavelength of λ a = 9 m. Generating and maintaining long laser focuses might be possible with a variety of approaches in the future. For example, recent plasma-waveguides are capable of maintaining a laser focus over 10 m scales [22,23]. It is also worth pointing out that the focus length decreases mildly with laser power, hence the problem will become marginally simpler in the future.…”

Meter-scale conditioned hydrodynamic optical-field-ionized plasma channels

“…Although the initial temperature is high enough to allow for full ionization of the plasma column, a neutral gas collar appears in the early stages of the expansion. The simulation shows the number of free electrons to remain approximately constant throughout the expansion (see the Supplemental Material [33]), indicating that the accumulation of neutral gas in the region of the shock is caused by the high pressure in the inner regions of the channel.…”

“…The experiments were undertaken with the 5-Hz repetitionrate Astra-Gemini TA2 laser at the Central Laser Facilty, UK. The setup employed has been described previously [27] and is described in detail in the Supplemental Material [33], so here we provide only an outline.…”

Gev-Scale Accelerators Driven by Plasma-Modulated Pulses from Kilohertz Lasers

“…We note that the key components required to realize this new approach have all recently been demonstrated, and in principle all are capable of multi-kilohertz operation. These include: metre-scale, low-loss, all-optical plasma waveguides [64][65][66][67][68][69][70]; 100 mJ-scale, sub-50 fs seed laser pulses [71]; and joule-level, few-picosecond, 1030 nm drive laser pulses [43,45]. The proposed scheme requires tight temporal and spatial overlap of multiple laser beams, the most challenging of which are: (i) control of the delay between the electron bunch and the seed pulse (∼ 10 fs); and (ii) control of the pointing of the seed and drive pulses relative to the waveguide axes (< 10 µrad).…”

“…The proposed scheme requires tight temporal and spatial overlap of multiple laser beams, the most challenging of which are: (i) control of the delay between the electron bunch and the seed pulse (∼ 10 fs); and (ii) control of the pointing of the seed and drive pulses relative to the waveguide axes (< 10 µrad). These requirements have already been met [67,68,70,[72][73][74][75] in experiments operating at f rep = 1 Hz, and even tighter tolerances could be achieved with the improved feedback made possible by kHz operation. In this document we provide additional information on the analytic theory and Particle-In-Cell (PIC) simulations presented in the main paper.…”