Spectral Control via Multi-Species Effects in PW-Class Laser-Ion Acceleration

Laser-ion acceleration with ultra-short pulse, PW-class lasers is dominated by non-thermal, intra-pulse plasma dynamics. The presence of multiple ion species or multiple charge states in targets leads to characteristic modulations and even mono-energetic features, depending on the choice of target material. As spectral signatures of generated ion beams are frequently used to characterize underlying acceleration mechanisms, thermal, multi-fluid descriptions require a revision for predictive capabilities and control in next-generation particle beam sources. We present an analytical model with explicit inter-species interactions, supported by extensive ab initio simulations. This enables us to derive important ensemble properties from the spectral distribution resulting from those multi-species effects for arbitrary mixtures. We further propose a potential experimental implementation with a novel cryogenic target, delivering jets with variable mixtures of hydrogen and deuterium. Free from contaminants and without strong influence of hardly controllable processes such as ionization dynamics, this would allow a systematic realization of our predictions for the multi-species effect.Comment: 4 pages plus appendix, 11 figures, paper submitted to a journal of the American Physical Societ

A Laser-Plasma Ion Beam Booster Based on Hollow-Channel Magnetic Vortex Acceleration

Laser-driven ion acceleration can provide ultra-short, high-charge, low-emittance beams. Although undergoing extensive research, demonstrated maximum energies for laser-ion sources are non-relativistic, complicating injection into high-$\beta$ accelerator elements and stopping short of desirable energies for pivotal applications, such as proton tumor therapy. In this work, we decouple the efforts towards relativistic beam energies from a single laser-plasma source via a proof-of-principle concept, boosting the beam into this regime through only a few plasma stages. We employ full 3D particle-in-cell simulations to demonstrate the capability for capture of high-charge beams as produced by laser-driven sources, where both source and booster stages utilize readily available laser pulse parameters.Comment: 4 pages, 4 figures, submitted for peer revie

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets.

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (∅ 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (∅ 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions

Defect engineering of silicon with ion pulses from laser acceleration

Defect engineering is foundational to classical electronic device development and for emerging quantum devices. Here, we report on defect engineering of silicon with ion pulses from a laser accelerator in the laser intensity range of 1019 W cm−2 and ion flux levels of up to 1022 ions cm−2 s−1, about five orders of magnitude higher than conventional ion implanters. Low energy ions from plasma expansion of the laser-foil target are implanted near the surface and then diffuse into silicon samples locally pre-heated by high energy ions from the same laser-ion pulse. Silicon crystals exfoliate in the areas of highest energy deposition. Color centers, predominantly W and G-centers, form directly in response to ion pulses without a subsequent annealing step. We find that the linewidth of G-centers increases with high ion flux faster than the linewidth of W-centers, consistent with density functional theory calculations of their electronic structure. Intense ion pulses from a laser-accelerator drive materials far from equilibrium and enable direct local defect engineering and high flux doping of semiconductors.This work was supported by the Office of Science, Office of Fusion Energy Sciences, of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231. Experiments at the BELLA Center were enabled through facilities developed by HEP and LaserNetUS. TS and JGL gratefully acknowledge support by the coordinated research project “F11020” of the International Atomic Energy Agency (IAEA). LZT and JS were supported by the Molecular Foundry, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231Peer reviewe

Supplementary Notes - Defect engineering of silicon with ion pulses from laser acceleration

14 pages. -- Supplementary Note 1. Time lapse movie showing evaporation of the aluminum foil mask during 100 shots. -- Supplementary Note 2. Photoluminescence (PL) and Secondary Ion Mass Spectrometry (SIMS) data correlation to PL data. -- Supplementary Note 3. Details on energy deposition and heat calculations. -- Supplementary Note 4. Details on Nuclear Reaction Analysis (NRA). -- Supplementary Note 5. Details on channeling Rutherford Backscattering (ch-RBS). -- Supplementary Note 6. Supplemental material on Density Functional Theory (DFT) calculations of G and W-centers in silicon.Peer reviewe

Supplementary Data: Spectral Control via Multi-Species Effects in PW-Class Laser-Ion Acceleration

Supplementary materials for our paper "Spectral Control via Multi-Species Effects in PW-Class Laser-Ion Acceleration". Additional high-resolution, raw HDF5 files using the openPMD standard (DOI:10.5281/zenodo.1167843) increase simulation output data to 4.7 TByte and are available from the corresponding author upon reasonable request.This project received funding within the MEPHISTO project (BMBF-Förderkennzeichen 01IH16006C)

Laser-plasma proton acceleration with a combined gas-foil target

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