Neil Fazel

Quasi-monoenergetic laser-plasma acceleration of electrons to 2 GeV

Laser-plasma accelerators of only a centimetre’s length have produced nearly monoenergetic electron bunches with energy as high as 1 GeV. Scaling these compact accelerators to multi-gigaelectronvolt energy would open the prospect of building X-ray free-electron lasers and linear colliders hundreds of times smaller than conventional facilities, but the 1 GeV barrier has so far proven insurmountable. Here, by applying new petawatt laser technology, we produce electron bunches with a spectrum prominently peaked at 2 GeV with only a few per cent energy spread and unprecedented sub-milliradian divergence. Petawatt pulses inject ambient plasma electrons into the laser-driven accelerator at much lower density than was previously possible, thereby overcoming the principal physical barriers to multi-gigaelectronvolt acceleration: dephasing between laser-driven wake and accelerating electrons and laser pulse erosion. Simulations indicate that with improvements in the laser-pulse focus quality, acceleration to nearly 10 GeV should be possible with the available pulse energy.

Generation of dark-current-free quasi-monoenergetic 1.25 GeV electrons by laser wakefield acceleration

We report electron acceleration to 1.25 GeV by petawatt-laser-driven wakefield acceleration at plasma density 5×1017 cm3. Electron beams are dark-current-free, quasi-monoenergetic, highly collimated (<;1mrad divergence), contain tens of pC and have excellent pointing stability.

Self-injected petawatt laser-driven plasma electron acceleration in 10 17 cm −3 plasma

We report observation of electron self-injection and acceleration in a plasma accelerator driven by the Texas petawatt laser at 1017 cm−3 plasma density, an order of magnitude lower density than previous self-injected laser-plasma accelerators.

Interaction between laser pulses and trailing wakefields intersecting at small angle for LWFA charge yield enhancement

Increasing the high energy electron yield from laser wakefield acceleration is crucial to its development as an electron beam source. We present a scheme for charge yield enhancement using two equal-intensity pulses—or hot spots in a single laser pulse—intersecting at a small angle. Experiments on the Texas Petawatt Laser with two well-defined hot spots yielded more than ten times as much charge as the single-hot-spot case. VORPAL particle-in-cell simulations suggest the charge yield enhancement depends on the hot-spot intersection angle and the relative phase between spots.

Betatron x-rays from GeV laser-plasma-accelerated electrons

X-rays are produced when laser-wakefield accelerated electrons oscillate in the transverse electrostatic field of the accelerating structure. The measured characteristics of these betatron x-rays follow scaling laws relating them to the electron energy, charge, plasma density, and other observables. Here we report on the x-rays produced by electrons accelerated to energies >1 GeV and investigate the scaling laws for photon number, critical energy, and beam divergence.

GeV Electrons and High brightness Betatron X-rays from Petawatt-Laser-Driven Plasma Accelerators

We identify three regimes of correlated GeV-electron/keV-betatron-X-ray generation by a laser-plasma accelerator driven by the Texas Petawatt laser, and relate them to variations in strength of blowout, injection geometry and beam loading.

Multi-GeV Electron Generation Using Texas Petawatt Laser

We present simulation results and experimental setup for multi‐GeV electron generation by a laser plasma wake field accelerator (LWFA) driven by the Texas Petawatt (TPW) laser. Simulations show that, in plasma of density ne = 2–4×1017 cm−3, the TPW laser pulse (1.1 PW, 170 fs) can self‐guide over 5 Rayleigh ranges, while electrons self‐injected into the LWFA can accelerate up to 7 GeV. Optical diagnostic methods employed to observe the laser beam self‐guiding, electron trapping and plasma bubble formation and evolution are discussed. Electron beam diagnostics, including optical transition radiation (OTR) and electron gamma ray shower (EGS) generation, are discussed as well.