Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session BO05: Laser Plasma InstabilitiesLive Streamed
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Chair: John Palastro, University of Rochester Room: Ballroom 111 B |
Monday, October 17, 2022 9:30AM - 9:42AM |
BO05.00001: Trapping, Landau damping, and Self-focusing of Multiple-ion Acoustic Waves with Interspecies Collisions Richard L Berger, William Arrighi, Jeffrey W Banks, Thomas D Chapman, Andris M Dimits, Benjamin J Winjum The reduction of laser energy deposition in Inertial Confinement Fusion resulting from stimulated Brillouin backscattering (SBS) is a significant constraint on hohlraum and capsule design. One promising option is the use of multiple ion species. Provided nonlinear trapping of the ions in the Ion Acoustic wave (IAW) can be suppressed,[i] multiple ion species increase the IAW damping rate and thereby lower the amplification rate significantly compared to single species materials. In previous work on mixtures of high-Z and low-Z ions, we showed with Vlasov simulations[ii] that light ion trapping, which reduces the damping, can be decreased by collisional scattering of the light ions from the heavy ions. By varying the IAW wave amplitude, we obtain a scaling for the reduction of the damping rate with respect to the wave amplitude and collision strength. The dynamic energy partition among the species and field is discussed. In addition, using 2D LOKI simulations, we find that collisions can suppress IAW self-focusing. [i] R. Berger, Phys. Plasmas 26, 012709 (2019)
[ii] R. Berger, et al, 62 Annual Meeting of the DPP, November 11, 2020
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Monday, October 17, 2022 9:42AM - 9:54AM |
BO05.00002: Predicting hot electron generation in inertial confinement fusion with particle-in-cell simulations Shihui Cao, Dhrumir Patel, Aarne Lees, Varchas Gopalaswamy, Christian Stoeckl, Michael J Rosenberg, Han Wen, Hu Huang, Alexander Shvydky, Riccardo Betti, Chuang Ren The success of inertial confinement fusion requires a comprehensive understanding of laser plasma interactions and the resulting hot electrons generation. We performed a series of 2D Particle-In-Cell simulations with speckled laser drivers to study hot-electron generation in direct-drive inertial confinement fusion on OMEGA. Scaling laws were obtained for hot electron fraction and temperature as functions of laser/plasma conditions in the quarter-critical region. Using these scalings and conditions from hydro simulations, the temporal history of hot electron generation can be predicted. After taking potential inaccuracies in hydro and PIC simulations into account, our prediction agreed with the experimental hard X-ray data within experimental error bars for a collection of OMEGA warm target implosions. |
Monday, October 17, 2022 9:54AM - 10:06AM |
BO05.00003: Stimulated Raman backscatter in the kinetic regime of lasers with orbital angular momentum Sarah E Chase, Benjamin J Winjum, Frank S Tsung, Kyle G Miller, Denise E Hinkel, Warren B Mori Stimulated Raman scattering (SRS) in laser driven inertial confinement fusion (ICF) can result in decreased laser energy coupling to the target and reduced symmetry of the drive. There has been little research on SRS for lasers which carry orbital angular momentum (OAM). Any laser can scatter into a variety of different OAM modes and can drive a plasma wave which may also carry OAM. The OAM in the plasma wave can change the linear and nonlinear damping rates of the wave. In plasmas where the kλDe of the plasma wave is large, the linear and nonlinear damping of the plasma wave affects the growth of SRS. We present preliminary results of SRS of lasers with and without OAM for plasma conditions of interest to ICF using the envelope equation code pF3D and the particle-in-cell code OSIRIS. We examine cases where conditions are near threshold and far above threshold for the onset of SRS. We also investigate Raman amplification of a seed pulse for combinations of pumps and seeds with different or the same OAM. |
Monday, October 17, 2022 10:06AM - 10:18AM |
BO05.00004: Laser beam profile design to mitigate the two plasmon decay instability for inertial confinement fusion conditions Jason F Myatt, Janukan Sivajeyan, Ramy Aboushelbaya The Two Plasmon Decay (TPD) instability is a preheat concern for inertial confinement fusion (ICF), where electron plasma waves are generated by the instability of laser light encountering near quarter-critical plasma densities. This talk characterizes the effect of an incident beam's electromagnetic (EM) orbital angular momentum (OAM) on the growth rate of the TPD instability. Attention is paid to the conservation of angular momentum throughout the TPD process as it is transferred from the OAM of the EM field to the mechanical angular momentum of particles. The light propagation and TPD processes are simulated using the Laser Plasma Simulation Environment (LPSE). Several beam profiles, constructed from the superposition of Laguerre-Gaussian or Hermite Gaussian modes, have been compared with regards to their stability to TPD, culminating with a profile that minimizes the growth rate. The talk concludes with a discussion of how the simulated profiles can be experimentally created through the use of contemporary beam shaping techniques. |
Monday, October 17, 2022 10:18AM - 10:30AM |
BO05.00005: The Effectiveness of Different Laser Smoothing Techniques for Mitigating Inflationary Stimulated Raman Scattering Han Wen, Russell K Follett, Andrei V Maximov, John P Palastro Kinetic inflation exacerbates the threat of the stimulated Raman scattering (SRS) instability to inertial confinement fusion (ICF). Continued growth of the instability requires phase matching between the incident light wave and the decay products, a scattered-light wave, and an electron plasma wave (EPW). In principle, a density inhomogeneity can disrupt the phase matching by changing the frequency of the EPW along the gradient. In reality, electron trapping in the EPW produces a frequency shift that can compensate this change. This autoresonance, or kinetic inflation, can substantially enhance the SRS reflectivity. Here we present a semi-analytic theory and supporting particle-in-cell simulations that describe how laser bandwidth can inhibit inflationary SRS by rapidly moving the location of exact phase matching and reducing the interaction time. The theory predicts the instantaneous SRS reflectivity and the extent to which different laser bandwidth formats, such as random or smoothing by spectral dispersion, can mitigate inflationary SRS. These predictions can inform designs of next-generation, broadband ICF drivers. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856. |
Monday, October 17, 2022 10:30AM - 10:42AM |
BO05.00006: Parameter scan of stimulated Raman scattering in magnetic fields Benjamin J Winjum, Roman Lee, Simon Bolanos, SJ Spencer, Frank S Tsung, Warren B Mori Stimulated Raman scattering (SRS) can be mitigated in the kinetic regime (kλDe > ~0.3) by weak magnetic fields (ωc/ωp << 1) due to the damping of electron plasma waves (EPWs) propagating perpendicular to the magnetic fields. However, we have also found that magnetic fields can interfere with the nonlinear frequency shift of SRS-driven EPWs, and for SRS that is dominated by the dynamics of this frequency shift, magnetic fields can thereby indirectly enhance the frequency resonance between the light and plasma waves involved in SRS. Furthermore, in some parameter regimes, the SRS waves can themselves be unstable (e.g. the backscattered light wave can decay via rescatter and the backscattered EPW can decay via LDI), and for finite-width waves in multi-dimensions, the damping and transverse evolution of SRS EPWs depends sensitively on wave-particle interactions that can be impacted by magnetic fields. We show one- and two-dimensional particle-in-cell simulations that illustrate how magnetic fields impact SRS and EPWs across a wide range of laser and plasma parameters. |
Monday, October 17, 2022 10:42AM - 10:54AM |
BO05.00007: Influence of random phase plates temporal smoothing on the growth of the Backward stimulated Brillouin scatter Charles Ruyer, Adrien Fusaro, Remy Capdessus, Arnaud Debayle, Pascal P Loiseau, Paul-Edouard Masson-Laborde
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Monday, October 17, 2022 10:54AM - 11:06AM |
BO05.00008: Raman Amplification with a 1 x 1015 W/cm2 Seed Jessica L Shaw, Manfred Ambat, Kyle R McMillen, Jeremy Pigeon, Daniel J Haberberger, Dustin Froula We present first experimental results from the Raman amplification experimental platform at the University of Rochester’s Laboratory for Laser Energetics. This platform explores Raman amplification in a unique parameter space that includes a joule-class pump and an adjustable-energy seed with intensities up to 1 x 1015 W/cm2, which is significantly more intense than prior experiments. Initial experiments have demonstrated single-pass Raman amplification with energy-gain factors as high as 10x and efficiencies as high as 6.6%. Scalings with gas-jet backing pressures, pump energy, and seed energy are presented. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856 and the U.S. Department of Energy under Awards DE-SC00215057 and DE-SC0016253. |
Monday, October 17, 2022 11:06AM - 11:18AM |
BO05.00009: Comparison of Optical Smoothing Techniques for LPI Mitigation Joshua Ludwig, Pierre A Michel Intense laser hotspots/speckles are a concern on high power laser facilities due to their role in seeding unwanted instabilities such as SBS (Stimulated Brillouin Scattering). Optical smoothing techniques such as SSD1,2 (Smoothing by Spectral Dispersion) are used to better homogenize the laser focal spot intensity pattern on the time scale of the instabilities. Here we report on a project that examines the laser electric fields of NIF like beams including the effects of SSD, polarization rotation, and beat waves3. An overview of the simulation technique will be presented with updates on characterizing various optical smoothing techniques for mitigating LPI (Laser Plasma Instabilities). |
Monday, October 17, 2022 11:18AM - 11:30AM |
BO05.00010: Effect of Flow on Laser–Plasma Interactions near the Quarter-Critical Density in the Plasmas of Inertial Confinement Fusion Andrei V Maximov, David Turnbull, Dana H Edgell, Russell K Follett, Han Wen, John P Palastro, Dustin Froula In the direct-drive approach to inertial confinement fusion (ICF), the laser–plasma interaction (LPI) in the plasma corona determines the coupling of laser power to the imploding targets. Under conditions of direct-drive ICF experiments on the OMEGA Laser System, the two most important LPI processes are the two-plasmon decay (TPD) in the plasma region near the quarter-critical density and cross-beam energy transfer (CBET). For both TPD and CBET the nonlinear saturation is determined by the level of low-frequency ion-acoustic perturbations. The resonance condition for the ion-acoustic waves strongly depends on the plasma flow, and velocities close to Mach-1 value often result in the highest levels of ion-acoustic waves. We consider the effect of plasma flow on LPI in the region near quarter-critical density where flow influences ion-acoustic perturbations and, consequently, the nonlinear saturation of both TPD and CBET, and the interplay between them. The results of 3-D simulations with the laser-plasma simulation environment (LPSE)1 are compared with the theoretical analysis. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856. [1] J. F. Myatt et al., Phys. Plasmas 24, 056308 (2017).
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Monday, October 17, 2022 11:30AM - 11:42AM |
BO05.00011: Validation of Ray-Based Cross-Beam Energy Transfer Algorithms Russell K Follett, Arnaud Colaitis, Dustin Froula, Dana H Edgell, David Turnbull, John P Palastro Ray-based cross-beam energy transfer (CBET) models have become a common feature of the radiation-hydrodynamic codes used to simulate inertial confinement fusion experiments. These models are necessary for achieving better agreement with experimental measurements, but their detailed implementation can vary widely between codes and often rely on artificial multipliers. The reliance on multipliers makes it difficult to determine whether the model or code is missing physics or if there is a flaw in the implementation. To address this, a series of 2-D and 3-D test cases have been developed with validated solutions from wave-based calculations. Comparisons of various ray-based CBET models to the wave-based calculations highlight the essential physics that is required for accurate ray-based CBET modeling. |
Monday, October 17, 2022 11:42AM - 11:54AM |
BO05.00012: A 3-D Cross-Beam Energy Transfer Model for Direct-Drive ICF Philip W Moloney, Aidan C Crilly, Jeremy P Chittenden In direct-drive ICF, 3D effects in the laser drive can significantly degrade the implosion performance. Low mode, hydrodynamic perturbations can lead to un-stagnated flows at peak compression and an inefficient conversion of kinetic to internal energy. Cross-Beam Energy Transfer (CBET) can also strongly modify 3D asymmetries in the laser absorption [1]. |
Monday, October 17, 2022 11:54AM - 12:06PM |
BO05.00013: Saturation of Cross-Beam Energy Transfer in Conditions Relevant to OMEGA Implosions Khanh Linh Nguyen, Lin Yin, Brian J Albright, Dana H Edgell, Russell K Follett, David Turnbull, Dustin Froula, John P Palastro In cross-beam energy transfer (CBET), the dynamic interference of two laser beams ponderomotively drives an ion-acoustic wave that coherently scatters light from one beam into the other. This redirection of laser energy can severely inhibit the performance of direct-drive inertial confinement fusion. Recent experiments fielded on the OMEGA laser demonstrated that CBET can saturate through a resonance detuning resulting from ion heating [1,2]. The experiments employed one set of OMEGA laser beams to heat a gas jet plasma and a second set as pump beams for transferring energy to a frequency-detuned seed beam. In contrast, CBET in OMEGA implosions occurs between frequency-degenerate beams in a hotter, denser, inhomogeneous flowing plasma. To determine how CBET saturates in these conditions, we have conducted a series of vector particle-in-cell (VPIC) simulations using plasma profiles from a radiation hydrodynamics simulation of an OMEGA implosion. Results from the VPIC simulations can be used to refine the reduced models for CBET that are implemented in radiation hydrodynamics codes, improving their predictive capability. |
Monday, October 17, 2022 12:06PM - 12:18PM |
BO05.00014: Time-dependent saturation of cross-beam energy transfer relevant to indirect-drive ICF Lin Yin, Truong Nguyen, Guangye Chen, Luis Chacon, David J Stark, Lauren Green, Brian M Haines Cross-beam energy transfer (CBET) allows crossing laser beams to exchange energy and is critically important for ICF/HED experiments. The nonlinear physics of CBET for multi-speckled laser beams is examined using particle-in-cell simulations for a range of plasma conditions, laser intensities, and crossing angles relevant to indirect-drive ICF experiments. The time-dependent growth and saturation of CBET involve complex, nonlinear ion and electron dynamics, including ion trapping-induced enhancement and detuning, ion acoustic wave (IAW) nonlinearity, oblique forward stimulated Raman scattering (FSRS), and backward stimulated Brillouin scattering (BSBS) in a CBET-amplified seed beam. Ion-trapping-induced detuning of CBET is captured in the kinetic linear response by a new δf-Gaussian-mixture algorithm, enabling an accurate characterization of trapping-induced non-Maxwellian distributions. Nonlinear effects lead to deviation of CBET gain from linear theory based on a single-Maxwellian distribution and are found to determine the time-dependent nature and level of CBET gain as the system approaches steady state. |
Monday, October 17, 2022 12:18PM - 12:30PM |
BO05.00015: Dependence of Hot Electron Generation on Hydrogen Concentration of Target Materials for Shock Ignition Scheme of Direct-Drive Inertial Confinement Fusion Koki Kawasaki, Syunnosuke Matsuo, Tomoyuki Idesaka, Yoichiro Hironaka, Daisuke Tanaka, Hideo Nagatomo, Masyasu Hata, Ryunosuke Takizawa, Shinsuke Fujioka, Akifumi Yogo, Yasuhiko Sentoku, Yasunobu Arikawa, Norimasa Ozaki, ryosuke Kodama, Kento Katagiri, Kunioki Mima, Yoshitaka Mori, Tomoyuki Jozaki, Hideaki Yamada, Dimitri Batani, Gabriele Cristoforetti, Keisuke Shigemori Shock ignition (SI) scheme is one of promising approaches for controlled nuclear fusion where a fuel capsule is imploded in two stages: compression stage and ignition stage, which requires more than 30 TPa of ultrahigh pressure creation by high intensity spike pulse irradiation in the ignition stage. In spike pulse (1016 W/cm2), hot electrons are produced by parametric instabilities and hot electron assisted laser ablation is considered. Although hot electrons should be avoided in terms of fuel preheating in compression stage, it is pointed out that hot electrons enhance ablation pressure in the SI scheme since compressed capsule in ignition stage already has high arial density, which indicates the control of hot electrons is crucial. We aim to control hot electron generation by target-based approach. Ablator materials of different H concentration: polyethylene (CH2, 66 at%), polystyrene (CH, 50 at%), and diamond (C, 0 at%) were explored in the SI relevant conditions at GEKKO-XII laser facility, where a planer target can be irradiated by pseudo-single beam bundled 12 laser beams. In the presentation, we will show the experimental results for hot electron characterization with simulation calculations which explain hot electron generation increases with increasing H concentration. |
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