• Special Issue
  • Laboratory Astrophysics
  • 17 Article (s)
Maser radiation from collisionless shocks: application to astrophysical jets
D. C. Speirs, K. Ronald, A. D. R. Phelps, M. E. Koepke, R. A. Cairns, A. Rigby, F. Cruz, R. M. G. M. Trines, R. Bamford, B. J. Kellett, B. Albertazzi, J. E. Cross, F. Fraschetti, P. Graham, P. M. Kozlowski, Y. Kuramitsu, F. Miniati, T. Morita, M. Oliver, B. Reville, Y. Sakawa, S. Sarkar, C. Spindloe, M. Koenig, L. O. Silva, D. Q. Lamb, P. Tzeferacos, S. Lebedev, G. Gregori, and R. Bingham
This paper describes a model of electron energization and cyclotron-maser emission applicable to astrophysical magnetized collisionless shocks. It is motivated by the work of Begelman, Ergun and Rees [Astrophys. J. 625, 51 (2005)] who argued that the cyclotron-maser instability occurs in localized magnetized collisionless shocks such as those expected in blazar jets. We report on recent research carried out to investigate electron acceleration at collisionless shocks and maser radiation associated with the accelerated electrons. We describe how electrons accelerated by lower-hybrid waves at collisionless shocks generate cyclotron-maser radiation when the accelerated electrons move into regions of stronger magnetic fields. The electrons are accelerated along the magnetic field and magnetically compressed leading to the formation of an electron velocity distribution having a horseshoe shape due to conservation of the electron magnetic moment. Under certain conditions the horseshoe electron velocity distribution function is unstable to the cyclotron-maser instability [Bingham and Cairns, Phys. Plasmas 7, 3089 (2000); Melrose, Rev. Mod. Plasma Phys. 1, 5 (2017)].
High Power Laser Science and Engineering
  • Publication Date: Mar. 14, 2019
  • Vol.7 Issue, 1 01000e17 (2019)
Using the ROSS optical streak camera as a tool to understand laboratory experiments of laser-driven magnetized shock waves
Andy Liao, Patrick Hartigan, Gennady Fiksel, Brent Blue, Peter Graham, John Foster, and Carolyn Kuranz
Supersonic flows with high Mach number are ubiquitous in astrophysics. High-powered lasers also have the ability to drive high Mach number, radiating shock waves in laboratory plasmas, and recent experiments along these lines have made it possible to recreate analogs of high Mach-number astrophysical flows under controlled conditions. Streak cameras such as the Rochester optical streak system (ROSS) are particularly helpful in diagnosing such experiments, because they acquire spatially resolved measurements of the radiating gas continuously over a large time interval, making it easy to observe how any shock waves and ablation fronts present in the system evolve with time. This paper summarizes new ROSS observations of a laboratory analog of the collision of a stellar wind with an ablating planetary atmosphere embedded within a magnetosphere. We find good agreement between the observed ROSS data and numerical models obtained with the FLASH code, but only when the effects of optical depth are properly taken into account.
High Power Laser Science and Engineering
  • Publication Date: May. 21, 2018
  • Vol.6 Issue, 2 02000e22 (2018)
Analytical modelling of the expansion of a solid obstacle interacting with a radiative shock
Th. Michel, E. Falize, B. Albertazzi, G. Rigon, Y. Sakawa, T. Sano, H. Shimogawara, R. Kumar, T. Morita, C. Michaut, A. Casner, P. Barroso, P. Mabey, Y. Kuramitsu, S. Laffite, L. Van Box Som, G. Gregori, R. Kodama, N. Ozaki, P. Tzeferacos, D. Lamb, and M. Koenig
In this paper, we present a model characterizing the interaction of a radiative shock (RS) with a solid material, as described in a recent paper (Koenig et al., Phys. Plasmas, 24, 082707 (2017)), the new model is then related to recent experiments performed on the GEKKO XII laser facility. The RS generated in a xenon gas cell propagates towards a solid obstacle that is ablated by radiation coming from the shock front and the radiative precursor, mimicking processes occurring in astrophysical phenomena. The model presented here calculates the dynamics of the obstacle expansion, which depends on several parameters, notably the geometry and the temperature of the shock. All parameters required for the model have been obtained from experiments. Good agreement between experimental data and the model is found when spherical geometry is taken into account. As a consequence, this model is a useful and easy tool to infer parameters from experimental data (such as the shock temperature), and also to design future experiments.
High Power Laser Science and Engineering
  • Publication Date: Jun. 04, 2018
  • Vol.6 Issue, 2 02000e30 (2018)
Measurement and analysis of K-shell lines of silicon ions in laser plasmas
Bo Han, Feilu Wang, Jiayong Zhong, Guiyun Liang, Huigang Wei, Dawei Yuan, Baojun Zhu, Fang Li, Chang Liu, Yanfei Li, Jiarui Zhao, Zhe Zhang, Chen Wang, Jun Xiong, Guo Jia, Neng Hua, Jianqiang Zhu, Yutong Li, Gang Zhao, and Jie Zhang
We present laboratory measurement and theoretical analysis of silicon K-shell lines in plasmas produced by Shenguang II laser facility, and discuss the application of line ratios to diagnose the electron density and temperature of laser plasmas. Two types of shots were carried out to interpret silicon plasma spectra under two conditions, and the spectra from 6.6 to 6.85 were measured. The radiative-collisional code based on the flexible atomic code (RCF) is used to identify the lines, and it also well simulates the experimental spectra. Satellite lines, which are populated by dielectron capture and large radiative decay rate, influence the spectrum profile significantly. Because of the blending of lines, the traditional value and value are not applicable in diagnosing electron temperature and density of plasma. We take the contribution of satellite lines into the calculation of line ratios of He- lines, and discuss their relations with the electron temperature and density.
High Power Laser Science and Engineering
  • Publication Date: Jun. 05, 2018
  • Vol.6 Issue, 2 02000e31 (2018)
Laboratory radiative accretion shocks on GEKKO XII laser facility for POLAR project
L. Van Box Som, É. Falize, M. Koenig, Y. Sakawa, B. Albertazzi, P. Barroso, J.-M. Bonnet-Bidaud, C. Busschaert, A. Ciardi, Y. Hara, N. Katsuki, R. Kumar, F. Lefevre, C. Michaut, Th. Michel, T. Miura, T. Morita, M. Mouchet, G. Rigon, T. Sano, S. Shiiba, H. Shimogawara, and S. Tomiya
A new target design is presented to model high-energy radiative accretion shocks in polars. In this paper, we present the experimental results obtained on the GEKKO XII laser facility for the POLAR project. The experimental results are compared with 2D FCI2 simulations to characterize the dynamics and the structure of plasma flow before and after the collision. The good agreement between simulations and experimental data confirms the formation of a reverse shock where cooling losses start modifying the post-shock region. With the multi-material structure of the target, a hydrodynamic collimation is exhibited and a radiative structure coupled with the reverse shock is highlighted in both experimental data and simulations. The flexibility of the laser energy produced on GEKKO XII allowed us to produce high-velocity flows and study new and interesting radiation hydrodynamic regimes between those obtained on the LULI2000 and Orion laser facilities.
High Power Laser Science and Engineering
  • Publication Date: Jun. 19, 2018
  • Vol.6 Issue, 2 02000e35 (2018)
Analysis of microscopic properties of radiative shock experiments performed at the Orion laser facility
R. Rodríguez, G. Espinosa, J. M. Gil, F. Suzuki-Vidal, T. Clayson, C. Stehlé, and P. Graham
In this work we have conducted a study on the radiative and spectroscopic properties of the radiative precursor and the post-shock region from experiments with radiative shocks in xenon performed at the Orion laser facility. The study is based on post-processing of radiation-hydrodynamics simulations of the experiment. In particular, we have analyzed the thermodynamic regime of the plasma, the charge state distributions, the monochromatic opacities and emissivities, and the specific intensities for plasma conditions of both regions. The study of the intensities is a useful tool to estimate ranges of electron temperatures present in the xenon plasma in these experiments and the analysis performed of the microscopic properties commented above helps to better understand the intensity spectra. Finally, a theoretical analysis of the possibility of the onset of isobaric thermal instabilities in the post-shock has been made, concluding that the instabilities obtained in the radiative-hydrodynamic simulations could be thermal ones due to strong radiative cooling.
High Power Laser Science and Engineering
  • Publication Date: Jun. 22, 2018
  • Vol.6 Issue, 2 02000e36 (2018)
Physical parameter estimation with MCMC from observations of Vela X-1
Lan Zhang, Feilu Wang, Xiangxiang Xue, Dawei Yuan, Huigang Wei, and Gang Zhao
We present a parameter estimate for continua, and He-like triplets of the high resolution X-ray spectra with a Bayesian inference and a Markov Chain Monte Carlo (MCMC) tool. The method is applied for Vela X-1 with three different orbital phases (), Eclipse, , and , which are adopted from the Chandra High-Energy Transmission Grating Spectrometer (HETGS). A parameterized two-component power-law model [Sako et al., Astrophys. J. 525, 921 (1999)] and a multi-Gaussian model are applied to model these continua and He-like triplets, respectively. A uniform distribution over each parameter is used as the prior belief. Posterior probability distribution functions of parameters and the covariances among them are explored by using the MCMC method. The main advantages are (i) all model-based parameters are set to be free instead of artificially fixing some of the parameters during the data-model fitting; (ii) the contributions from satellite lines are considered; (iii) backgrounds are treated as a correction to the observation errors; and (iv) the confidence interval of each parameter is given. The fitted results show that the column density of scatter component () varies from phase to phase, which imply a non-spherical structure of the stellar wind in Vela X-1. Moreover, the wind velocities derived from main lines of each set of He-like triplets show better self-consistency than those in previous publications, which could provide a reliable approach for the diagnostics of photoionized plasma in astrophysical objects and the laboratory.
High Power Laser Science and Engineering
  • Publication Date: Jun. 25, 2018
  • Vol.6 Issue, 2 02000e37 (2018)
Generation of strong magnetic fields with a laser-driven coil
Zhe Zhang, Baojun Zhu, Yutong Li, Weiman Jiang, Dawei Yuan, Huigang Wei, Guiyun Liang, Feilu Wang, Gang Zhao, Jiayong Zhong, Bo Han, Neng Hua, Baoqiang Zhu, Jianqiang Zhu, Chen Wang, Zhiheng Fang, and Jie Zhang
As a promising new way to generate a controllable strong magnetic field, laser-driven magnetic coils have attracted interest in many research fields. In 2013, a kilotesla level magnetic field was achieved at the Gekko XII laser facility with a capacitor–coil target. A similar approach has been adopted in a number of laboratories, with a variety of targets of different shapes. The peak strength of the magnetic field varies from a few tesla to kilotesla, with different spatio-temporal ranges. The differences are determined by the target geometry and the parameters of the incident laser. Here we present a review of the results of recent experimental studies of laser-driven magnetic field generation, as well as a discussion of the diagnostic techniques required for such rapidly changing magnetic fields. As an extension of the magnetic field generation, some applications are discussed.
High Power Laser Science and Engineering
  • Publication Date: Jul. 04, 2018
  • Vol.6 Issue, 3 03000e38 (2018)