Precision photometric redshifts will be essential for extracting cosmological parameters from the next generation of wide-area imaging surveys. In this paper, we introduce a photometric redshift algorithm, ArborZ, based on the machine-learning technique of boosted decision trees. We study the algorithm using galaxies from the Sloan Digital Sky Survey (SDSS) and from mock catalogs intended to simulate both the SDSS and the upcoming Dark Energy Survey. We show that it improves upon the performance of existing algorithms. Moreover, the method naturally leads to the reconstruction of a full probability density function (PDF) for the photometric redshift of each galaxy, not merely a single "best estimate" and error, and also provides a photo-z quality figure of merit for each galaxy that can be used to reject outliers. We show that the stacked PDFs yield a more accurate reconstruction of the redshift distribution N (z). We discuss limitations of the current algorithm and ideas for future work.

We present synthetic dust polarization maps of simulated molecular clouds with the goal to systematically explore the origin of the relative orientation of the magnetic field ($\mathbf {B}$) with respect to the cloud sub-structure identified in density (n; 3D) and column density (N; 2D). The polarization maps are generated with the radiative transfer code POLARIS, which includes self-consistently calculated efficiencies for radiative torque alignment. The molecular clouds are formed in two sets of 3D magneto-hydrodynamical simulations: (i) in colliding flows (CF), and (ii) in the SILCC-Zoom simulations. In 3D, for the CF simulations with an initial field strength below ∼5 μG, $\mathbf {B}$ is oriented either parallel or randomly with respect to the n-structures. For CF runs with stronger initial fields as well as all SILCC-Zoom simulations, which have an initial field strength of 3 μG, a flip from parallel to perpendicular orientation occurs at high densities of $n_\rm {trans}$ ≃ 102 – 103 cm−3. We suggest that this flip happens if the cloud’s mass-to-flux ratio, μ, is close to or below the critical value of 1. This corresponds to a field strength around 3 – 5 μG, close to the Galactic average. In 2D, we use the method of Projected Rayleigh Statistics (PRS) to study the relative orientation of $\mathbf {B}$. If present, the flip in orientation occurs in the projected maps at $N_\rm {trans}$ ≃ 1021 − 21.5 cm−2. This value is similar to the observed transition value from sub- to supercritical magnetic fields in the interstellar medium. However, projection effects can strongly reduce the predictive power of the PRS method: Depending on the considered cloud or line-of-sight, the projected maps of the SILCC-Zoom simulations do not always show the flip, although it is expected given the 3D morphology. Such projection effects can explain the variety of recently observed field configurations, in particular within a single cloud. Finally, we do not find a correlation between the observed orientation of $\mathbf {B}$ and the N-PDF.

We present experimental results from the first systematic study of performance scaling with drive parameters for a magnetoinertial fusion concept. In magnetized liner inertial fusion experiments, the burnaveraged ion temperature doubles to 3.1 keV and the primary deuterium-deuterium neutron yield increases by more than an order of magnitude to 1.1 × 10 13 (2 kJ deuterium-tritium equivalent) through a simultaneous increase in the applied magnetic field (from 10.4 to 15.9 T), laser preheat energy (from 0.46 to 1.2 kJ), and current coupling (from 16 to 20 MA). Individual parametric scans of the initial magnetic field and laser preheat energy show the expected trends, demonstrating the importance of magnetic insulation and the impact of the Nernst effect for this concept. A drive-current scan shows that present experiments operate close to the point where implosion stability is a limiting factor in performance, demonstrating the need to raise fuel pressure as drive current is increased. Simulations that capture these experimental trends indicate that another order of magnitude increase in yield on the Z facility is possible with additional increases of input parameters.

A laser-driven, magnetized liner inertial fusion (MagLIF) experiment is designed for the OMEGA Laser System by scaling down the Z point design to provide the first experimental data on MagLIF scaling. OMEGA delivers roughly 1000× less energy than Z, so target linear dimensions are reduced by factors of ∼10. Magneto-inertial fusion electrical discharge system could provide an axial magnetic field of 10 T. Two-dimensional hydrocode modeling indicates that a single OMEGA beam can preheat the fuel to a mean temperature of ∼200 eV, limited by mix caused by heat flow into the wall. One-dimensional magnetohydrodynamic (MHD) modeling is used to determine the pulse duration and fuel density that optimize neutron yield at a fuel convergence ratio of roughly 25 or less, matching the Z point design, for a range of shell thicknesses. A relatively thinner shell, giving a higher implosion velocity, is required to give adequate fuel heating on OMEGA compared to Z because of the increase in thermal losses in smaller targets. Two-dimensional MHD modeling of the point design gives roughly a 50% reduction in compressed density, temperature, and magnetic field from 1-D because of end losses. Scaling up the OMEGA point design to the MJ laser energy available on the National Ignition Facility gives a 500-fold increase in neutron yield in 1-D modeling.

Pulsed power accelerators compress electrical energy in space and time to provide versatile experimental platforms for high energy density and inertial confinement fusion science. The 80-TW “Z” pulsed power facility at Sandia National Laboratories is the largest pulsed power device in the world today. Z discharges up to 22 MJ of energy stored in its capacitor banks into a current pulse that rises in 100 ns and peaks at a current as high as 30 MA in low-inductance cylindrical targets. Considerable progress has been made over the past 15 years in the use of pulsed power as a precision scientific tool. This paper reviews developments at Sandia in inertial confinement fusion, dynamic materials science, x-ray radiation science, and pulsed power engineering, with an emphasis on progress since a previous review of research on Z in Physics of Plasmas in 2005.