arXiv subjects

Philip Franke

Publications and source records attributed to Philip Franke.

4 recordsLinked to original sources

arXiv2026

Laser-Wakefield-Driven Photonuclear and Laser-Driven DD Fusion Neutron Sources for Fast Neutron Capture: A Start-to-End Simulation Study

Laser-driven neutron sources offer ultrashort pulse durations and extreme peak fluxes inaccessible to conventional facilities, enabling novel time-of-flight(TOF) spectroscopy and nuclear astrophysics measurements. We present the first complete start-to-end simulation comparison of deuterium-deuterium (DD) bulk fusion and laser wakefield acceleration-driven photonuclear neutron sources, evaluated for fast neutron capture relevant to the r-process. The simulation chain couples particle-in-cell modeling of the laser-plasma interaction, Geant4 Monte Carlo neutron transport with shielding and background characterization, and a NON-SMOKER-based event generator for multi-neutron capture on Au197 and Rh103. We derive scaling laws for neutron yield, pulse duration, and peak flux from 1J terawatt to 250J petawatt-class systems, including DD bulk fusion scaling laws specific to the short-pulse regime where volumetric ion heating via plasma expansion timescales governs yield. Under realistic experimental conditions, DD fusion produces quasi-monoenergetic 2.45MeV neutrons with less than 20ps pulses, 100 micro source size, and peak fluxes exceeding 10^22 cm^(-2) s^(-1), ideal for high-resolution TOF spectroscopy. LWFA sources generate broader spectra with larger than 50ps pulses, but high repetition rates (up to 100 Hz) yield a 36x advantage in cumulative capture events for short-lived isomers. We conclude these sources are complementary: DD fusion maximizes per-shot peak brightness, while LWFA provides high-throughput accumulation for systematic studies. These results establish design criteria for the first direct laser-driven rapid neutron capture experiments at facilities including PHELIX, ELI-NP, and TW-class systems such as UT3.

physics.plasm-ph↗

arXiv2021

Optical Shock-Enhanced Self-Photon Acceleration

Photon accelerators can spectrally broaden laser pulses with high efficiency in moving electron density gradients. When driven by a conventional laser pulse, the group velocity walk-off experienced by the accelerated photons and deterioration of the gradient from diffraction and refraction limit the extent of spectral broadening. Here we show that a laser pulse with a shaped space-time and transverse intensity profile overcomes these limitations by creating a guiding density profile at a tunable velocity. Self-photon acceleration in this profile leads to dramatic spectral broadening and intensity steepening, forming an optical shock that further enhances the rate of spectral broadening. In this new regime, multi-octave spectra extending from $400 nm - 60 nm$ wavelengths, which support near-transform limited $< 400 as$ pulses, are generated over $<100 μ$m of interaction length.

physics.optics↗

arXiv2020

Nonlinear spatiotemporal control of laser intensity

Spatiotemporal control over the intensity of a laser pulse has the potential to enable or revolutionize a wide range of laser-based applications that currently suffer from the poor flexibility offered by conventional optics. Specifically, these optics limit the region of high intensity to the Rayleigh range and provide little to no control over the trajectory of the peak intensity. Here, we introduce a nonlinear technique for spatiotemporal control, the "self-flying focus," that produces an arbitrary trajectory intensity peak that can be sustained for distances comparable to the focal length. The technique combines temporal pulse shaping and the inherent nonlinearity of a medium to customize the time and location at which each temporal slice within the pulse comes to its focus. As an example of its utility, simulations show that the self-flying focus can form a highly uniform, meter-scale plasma suitable for advanced plasma-based accelerators.

physics.optics↗

arXiv2020

Vacuum acceleration of electrons in a dynamic laser pulse

A planar laser pulse propagating in vacuum can exhibit an extremely large ponderomotive force. This force, however, cannot impart net energy to an electron: As the pulse overtakes the electron, the initial impulse from its rising edge is completely undone by an equal and opposite impulse from its trailing edge. Here we show that planar-like "flying focus" pulses can break this symmetry, imparting relativistic energies to electrons. The intensity peak of a flying focus-a moving focal point resulting from a chirped laser pulse focused by a chromatic lens-can travel at any subluminal velocity, forwards or backwards. As a result, an electron can gain enough momentum in the rising edge of the intensity peak to outrun and avoid the trailing edge. Accelerating the intensity peak can further boost the momentum gain. Theory and simulations demonstrate that these dynamic intensity peaks can backwards accelerate electrons to the MeV energies required for radiation and electron diffraction probes of high energy density materials.

physics.acc-ph↗