Jeroen van Tilborg

Ultrafast dynamics in acetylene clocked in a femtosecond XUV stopwatch

Few-photon induced ultrafast dynamics in acetylene (C2H2) leading to several dissociation channels—deprotonation (H++C2H+ and H++C2H2+), symmetric break-up (CH++CH+) and isomerization (C++CH2+)-–were investigated employing the (XUV; extreme ultra-violet)-pump–(XUV; extreme ultra-violet)-probe scheme at the free-electron laser in Hamburg, combined with multi-hit coincidence detection. The kinetic energy releases and fragment-ion momentum distributions for various decay channels are presented. The C++CH2+ and H++C2H2+ channels reveal clear signatures of ultrafast molecular mechanisms, demonstrating potential applications of our pump-probe technique to complex systems in order to study a large variety of ultrafast phenomena in the XUV regime.

Powerful, pulsed, THz radiation from laser accelerated relativistic electron bunches

Coherent THz radiation was produced from relativistic electron bunches of subpicosecond duration. The electron beam was produced by strongly focused (≈ 6 μm), high peak power (up to 10 TW), ultra-short (≥50 fs) laser pulses of a 10 Hz repetition rate Ti:sapphire chirped pulse amplification (CPA) laser system via self-modulated laser wakefield acceleration (SM-LWFA) in a high density (> 1019 cm-3) pulsed gas jet. As the electrons exit the plasma, coherent transition radiation is generated at the plasma-vacuum boundary for wavelengths long compared to the bunch length. Radiation yield in the 0.3 to 19 THz range and at 94 GHz has been measured and found to depend quadratically on the bunch charge. The measured total radiated energy in the THz range for two different collection angles is in good agreement with theory. Modeling indicates that optimization of this table-top source could provide more than 100 μJ/pulse. Together with intrinsic synchronization to the laser pulse, this will enable numerous applications requiring intense terahertz radiation. This radiation can also be applied as a useful tool for measuring the properties of laser accelerated bunches at the exit of the plasma accelerator.

Control of quasi-monoenergetic electron beams from laser-plasma accelerators with adjustable shock density profile

The injection physics in a shock-induced density down-ramp injector was characterized, demonstrating precise control of a laser-plasma accelerator (LPA). Using a jet-blade assembly, experiments systematically varied the shock injector profile, including shock angle, shock position, up-ramp width, and acceleration length. Our work demonstrates that beam energy, energy spread, and pointing can be controlled by adjusting these parameters. As a result, an electron beam that was highly tunable from 25 to 300 MeV with 8% energy spread (ΔEFWHM/E), 1.5 mrad divergence, and 0.35 mrad pointing fluctuation was produced. Particle-in-cell simulation characterized how variation in the shock angle and up-ramp width impacted the injection process. This highly controllable LPA represents a suitable, compact electron beam source for LPA applications such as Thomson sources and free-electron lasers.

Narrow bandwidth Thomson photon source and diagnostic development using laser-plasma accelerators

Compact, high-quality photon sources at MeV energies are being developed based on Laser-Plasma Accelerators (LPAs), and these sources at the same time provide precision diagnostics of beam evolution to support LPA development. We review design of experiments and laser capabilities to realize a photon source, integrating LPA acceleration for compactness, control of scattering to increase photon flux, and electron deceleration to mitigate beam dump size. These experiments are developing a compact photon source system with the potential to enable new monoenergetic photon applications currently restricted by source size, including nuclear nonproliferation. Diagnostic use of the energy-angle spectra of Thomson scattered photons is presented to support development of LPAs to meet the needs of advanced high yield/low-energy-spread photon sources and future high energy physics colliders.

A Free Electron Laser driven by Laser Plasma Acceleration

Ongoing efforts towards a compact free electron laser based on laser-plasma acceleration (LPA) are presented. Recent results [van Tilborg (PRL 2015) and Steinke (Nature, accepted)] demonstrate compact transport and support LPA-based FEL design and simulations. Article not available.

Staging and Transport of Laser Plasma Accelerators

We present experiments on the coupling of two closely-spaced Laser Plasma Accelerators by a plasma mirror, aimed at increasing the electron energy while preserving compactness. The critical role of magnetic transport between stages is investigated.

Multi-GeV Electron Beams at the Berkeley Lab Laser Accelerator

Multi-GeV electron beams from nonlinear laser-plasma acceleration were achieved in cm-scale plasma waveguides. Self-focusing caused trapping in multiple plasma periods. These processes are strongly parameter dependent, requiring precise plasma control for stable acceleration.

Staged, Guided Laser-Plasma Accelerators Towards Thomson Photon Sources and High Energy Physics

Experiments characterize two high-gradient laser-plasma accelerators in series, each powered by a separate laser pulse, with application to deceleration for compact high energy photon sources and to high energy future particle physics colliders.

Multi-GeV Laser Plasma Accelerators Using Plasma Waveguides and Integration of Multiple Acceleration Modules

Laser Plasma Accelerators offer high gradients important to compact machines. We present results towards high energies via staged acceleration integrating two independent modules, and multi-GeV e-beams from the BELLA 1Hz petawatt-class laser.

Staged laser plasma accelerators

We present current results on staged electron acceleration in the LOASIS program at the Lawrence Berkeley National Laboratory. The goal is to experimentally demonstrate laser driven electron acceleration in two stages, where each stage is driven by a separate laser pulse. This technology could provide the key to built compact laser driven accelerators which could potentially reach up to TeV in electron energy.