# High Flux Femtosecond X-ray Emission from the Electron-Hose Instability in Laser Wakefield Accelerators

## TL;DR

This paper reports on experimental and simulation studies showing that the electron-hose instability in laser wakefield accelerators can dramatically increase X-ray flux through large amplitude oscillations of the electron bunch.

## Contribution

It demonstrates the transition from LWFA to PWFA regimes and links the electron-hose instability to enhanced X-ray emission, supported by experimental data and 3D PIC simulations.

## Key findings

- X-ray flux increases significantly beyond depletion/dephasing lengths.
- Electron-hose instability causes large amplitude oscillations in electron bunches.
- Simulations reveal the time-dependent radiation emission processes.

## Abstract

Bright and ultrashort duration X-ray pulses can be produced by through betatron oscillations of electrons during Laser Wakefield Acceleration (LWFA). Our experimental measurements using the \textsc{Hercules} laser system demonstrate a dramatic increase in X-ray flux for interaction distances beyond the depletion/dephasing lengths, where the initial electron bunch injected into the first wake bucket catches up with the laser pulse front and the laser pulse depletes. A transition from an LWFA regime to a beam-driven plasma wakefield acceleration (PWFA) regime consequently occurs. The drive electron bunch is susceptible to the electron-hose instability and rapidly develops large amplitude oscillations in its tail, which leads to greatly enhanced X-ray radiation emission. We measure the X-ray flux as a function of acceleration length using a variable length gas cell. 3D particle-in-cell (PIC) simulations using a Monte Carlo synchrotron X-ray emission algorithm elucidate the time-dependent variations in the radiation emission processes.