Abstract
We report on experimental results on laser-driven proton acceleration using high-intensity laser pulses. We present power law scalings of the maximum proton energy with laser pulse energy and show that the scaling exponent $\ensuremath{\xi}$ strongly depends on the scale length of the preplasma, which is affected by the temporal intensity contrast. At lower laser intensities, a shortening of the scale length leads to a transition from a square root toward a linear scaling. Above a certain threshold, however, a significant deviation from this scaling is observed. Two-dimensional particle-in-cell simulations show that, in this case, the electric field accelerating the ions is generated earlier and has a higher amplitude. However, since the acceleration process starts earlier as well, the fastest protons outrun the region of highest field strength, ultimately rendering the acceleration less effective. Our investigations thus point to a principle limitation of the proton energy in the target normal sheath acceleration regime, which would explain why a significant increase of the maximum proton energy above the limit of $100\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ has not yet been achieved.
Highlights
The availability of proton pulses accelerated to kinetic energies well above 10 MeV during laser-plasma interactions bears great potential for applications in fundamental science, inertial fusion energy [1,2], time-resolved radiography of plasmas [3,4], as a frontend for conventional accelerators [5,6,7], for material sciences [8,9,10], and radiation therapy [11,12]
We report on experimental results on laser-driven proton acceleration using high-intensity laser pulses
We present power law scalings of the maximum proton energy with laser pulse energy and show that the scaling exponent ξ strongly depends on the scale length of the preplasma, which is affected by the temporal intensity contrast
Summary
The availability of proton pulses accelerated to kinetic energies well above 10 MeV during laser-plasma interactions bears great potential for applications in fundamental science, inertial fusion energy [1,2], time-resolved radiography of plasmas [3,4], as a frontend for conventional accelerators [5,6,7], for material sciences [8,9,10], and radiation therapy [11,12]. To further increase the proton energy, the driving-laser technology is continuously improved and acceleration schemes are investigated These include radiation pressure acceleration [14], collisionless shock acceleration [15,16], or mechanisms dominant in the near-critical density or induced-transparency regime [17,18]. Relativistic electrons are generated during the interaction of a high-intensity laser with preplasma formed at the front side of a solid target—typically a thin foil. Such preplasma can be generated by prepulses, amplified spontaneous emission (ASE), or the rising edge of the driving laser pulse itself
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.