More Like this

1. Experimental signatures of direct-laser-acceleration-assisted laser wakefield acceleration

   Shaw, J.L.; Lemos, N.; Marsh, K.A.; Froula, D.H.; and Joshi, C. (February 2018, Plasma physics and controlled fusion)
2. Experimental signatures of direct-laser-acceleration-assisted laser wakefield acceleration

   https://doi.org/10.1088/1361-6587/aaade1  

   Shaw, J L; Lemos, N; Marsh, K A; Froula, D H; Joshi, C (April 2018, Plasma Physics and Controlled Fusion)
3. Diffusive shock re-acceleration

   https://doi.org/10.1017/S0022377818000478  

   Caprioli, Damiano; Zhang, Horace; Spitkovsky, Anatoly (June 2018, Journal of Plasma Physics)

   We have performed two-dimensional hybrid simulations of non-relativistic collisionless shocks in the presence of pre-existing energetic particles (‘seeds’); such a study applies, for instance, to the re-acceleration of galactic cosmic rays (CRs) in supernova remnant (SNR) shocks and solar wind energetic particles in heliospheric shocks. Energetic particles can be effectively reflected and accelerated regardless of shock inclination via a process that we call diffusive shock re-acceleration. We find that re-accelerated seeds can drive the streaming instability in the shock upstream and produce effective magnetic field amplification. This can eventually trigger the injection of thermal protons even at oblique shocks that ordinarily cannot inject thermal particles. We characterize the current in reflected seeds, finding that it tends to a universal value $$J\simeq en_{\text{CR}}v_{\text{sh}}$$ , where $$en_{\text{CR}}$$ is the seed charge density and $$v_{\text{sh}}$$ is the shock velocity. When applying our results to SNRs, we find that the re-acceleration of galactic CRs can excite the Bell instability to nonlinear levels in less than $${\sim}10~\text{yr}$$ , thereby providing a minimum level of magnetic field amplification for any SNR shock. Finally, we discuss the relevance of diffusive shock re-acceleration also for other environments, such as heliospheric shocks, galactic superbubbles and clusters of galaxies. 

   more » « less
4. Undepleted direct laser acceleration

   https://doi.org/10.1126/sciadv.adk1947  

   Cohen, Itamar; Meir, Talia; Tangtartharakul, Kavin; Perelmutter, Lior; Elkind, Michal; Gershuni, Yonatan; Levanon, Assaf; Arefiev, Alexey V; Pomerantz, Ishay (January 2024, Science Advances)

   Intense lasers enable generating high-energy particle beams in university-scale laboratories. With the direct laser acceleration (DLA) method, the leading part of the laser pulse ionizes the target material and forms a positively charged ion plasma channel into which electrons are injected and accelerated. The high energy conversion efficiency of DLA makes it ideal for generating large numbers of photonuclear reactions. In this work, we reveal that, for efficient DLA to prevail, a target material of sufficiently high atomic number is required to maintain the injection of ionization electrons at the peak intensity of the pulse when the DLA channel is already formed. We demonstrate experimentally and numerically that, when the atomic number is too low, the target is depleted of its ionization electrons prematurely. Applying this understanding to multi-petawatt laser experiments is expected to result in increased neutron yields, a perquisite for a wide range of research and applications. 

   more » « less
5. Filtering for Anderson Acceleration

   https://doi.org/10.1137/22M1536741  

   Pollock, Sara; Rebholz, Leo G. (August 2023, SIAM Journal on Scientific Computing)