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Magnetic fields spontaneously grow at unstable interfaces around hot-spot asymmetries during inertial confinement fusion implosions. Although difficult to measure, theoretical considerations and numerical simulations predict field strengths exceeding 5kT in current national ignition facility experiments. Magnetic confinement of electrons then reduces the hot-spot heat loss by >5%. We demonstrate this via magnetic post-processing of two-dimensional xRAGE hydrodynamic simulation data at bang time. We then derive a model for the self-magnetization, finding that it varies with the square of the stagnation temperature and inversely with the areal density. The self-magnetized Lawson analysis then gives a slightly reduced ignition threshold. Time dependent hot-spot energy balance models corroborate this finding, with the magnetic field quadrupling the fusion yield for near threshold parameters. The inclusion of magnetized multi-dimensional fluid instabilities could further alter the ignition threshold, and will be the subject of future work.

Over the past few decades, instructional policy supports -- encompassing standards, curricula, and assessments -- have featured centrally in the education reform movement. So, too, have efforts to align them. In this article, we conduct interviews with local educators with responsibility for early education about the alignment of instructional supports in Pre-K and kindergarten. Perceptions among study participants indicate that the degree of alignment among standards, curricula, and assessments is stronger within Pre-K and kindergarten than it is between them. Reported reasons for weak alignment between Pre-K and kindergarten include a debate over the purposes of early childhood education, institutional silos, and procedures that disrupt data sharing and transition practices. We consider what participants identify as the barriers to alignment mean for the development of policies aimed at lifting them. [This is the in press version of an article published in "Early Childhood Research Quarterly" (0885-2006).]

Errors in the Epperlein & Haines [PoF (1986)] transport coefficients were recently found at low electron magnetizations, with new magnetic transport coefficients proposed simultaneously by two teams [Sadler, Walsh & Li, PRL (2021) and Davies, Wen, Ji & Held, PoP (2021)]; these two separate sets of updated coefficients are shown in this paper to be in agreement. The importance of these new coefficients in laser-plasmas with either self-generated or applied magnetic fields is demonstrated. When an external magnetic field is applied, the cross-gradient-Nernst term twists the field structure; this twisting is reduced by the new coefficients in the low magnetization regime. For plasmas where only self-generated magnetic fields are present, the new coefficients are found to result in the magnetic field moving with the Righi-Leduc heat-flow, enhancing the impact of MHD. Simulations of Biermann Battery magnetic fields around ICF hot-spot perturbations are presented, with cross-gradient-Nernst transport increasing spike penetration.

We show that, under Braginskii magneto-hydrodynamics, anti-parallel gradients in average ion charge state and electron temperature can be unstable to the growth of self-generated magnetic fields. The instability is analogous to the field-generating thermomagnetic instability, although it is driven by the collisional thermal force magnetic source term rather than the Biermann battery term. The gradient in ion charge state causes a gradient in collisionality, which couples with temperature perturbations to create a self-generated magnetic field. This magnetic field deflects the electron heat flux in a way that reinforces the temperature perturbation. The derived linearized growth rate, typically on hydrodynamic timescales, includes the resistive and thermal smoothing. It increases with large ion composition gradients and electron heat flux, conditions typical of the hohlraum walls or contaminant mix jets in inertial confinement fusion implosions. However, extended magneto-hydrodynamic simulations indicate that the instability is usually dominated and stabilized by the nonlinear Nernst advection, in a similar manner to the standard thermomagnetic instability.

In Braginskii extended magneto-hydrodynamics (ExMHD), applicable to collisional astrophysical and high energy density plasmas, the electric field and heat flow are described by the $\alpha$, $\beta$ and $\kappa$ transport coefficients. We show that magnetic transport relies primarily on $\beta_\parallel-\beta_\perp$ and $\alpha_\perp-\alpha_\parallel$, rather than $\alpha_\perp$ and $\beta_\perp$ themselves. However, commonly used coefficient fit functions [Epperlein and Haines, Phys. Fluids 29, 1029 (1986)] cannot accurately calculate these quantities. This means that many ExMHD simulations have significantly over-estimated the cross-gradient Nernst advection, resulting in artificial magnetic dissipation and discontinuities. We repeat the kinetic analysis to provide fits that rectify this problem. Use of these in the Gorgon ExMHD code resolves the known discrepancies with kinetic simulations in the literature. Recognizing the fundamental importance of $\alpha_\perp-\alpha_\parallel$ and $\beta_\parallel-\beta_\perp$, we re-cast the set of coefficients to find that each of them now shares the same underlying properties. This makes explicit the symmetry of the magnetic and thermal transport equations, as well as the symmetry of the coefficients themselves.

Laser and beam driven wakefields promise orders of magnitude increases in electric field gradients for particle accelerators for future applications. Key areas to explore include the emittance properties of the generated beams and overcoming the dephasing limit in the plasma. In this paper, the first in-depth study of the self-injection mechanism into wakefield structures from non-homogeneous cluster plasmas is provided using high-resolution two dimensional particle-in-cell simulations. The clusters which are typical structures caused by ejection of gases from a high-pressure gas jet have a diameter much smaller than the laser wavelength. Conclusive evidence is provided for the underlying mechanism that leads to particle trapping, comparing uniform and cluster plasma cases. The accelerated electron beam properties are found to be tunable by changing the cluster parameters. The mechanism explains enhanced beam charge paired with large transverse momentum and energy which has implications for the betatron x-ray flux. Finally, the impact of clusters on the high-power laser propagation behavior is discussed.

Engineering features are known to cause jets of ablator material to enter the fuel hot-spot in inertial confinement fusion implosions. The Biermann battery mechanism wraps them in self-generated magnetic field. We show that higher-Z jets have an additional thermoelectric magnetic source term that is not present for hydrogen jets, verified here through a kinetic simulation. It has similar magnitude to the Biermann term. We then include this in an extended magneto-hydrodynamics approach to post-process an xRAGE radiation-hydrodynamic implosion simulation. The simulation includes an accurate model for the capsule fill tube, producing a dense carbon jet that becomes wrapped in a 4000T magnetic field. A simple spherical carbon mix model shows that this insulates the electron heat conduction enough to cause contraction of the jet to an optically thick equilibrium. The denser magnetized jet hydrodynamics could change its core penetration and therefore the final mix mass, which is known to be well correlated with fusion yield degradation. Fully exploring this will require self-consistent magneto-hydrodynamic simulations. Experimental signatures of this self-magnetization may emerge in the high energy neutron spectrum., Comment: Accepted in Physics of Plasmas

Experimental asymmetries in fusion implosions can lead to magnetic field generation in the hot plasma core. For typical parameters, previous studies found that the magnetisation Hall parameter, given by the product of the electron gyro-frequency and Coulomb collision time, can exceed one. This will affect the hydrodynamics through inhibition and deflection of the electron heat flux. The magnetic field source is the collisionless Biermann term, which arises from the Debye shielding potential in electron pressure gradients. We show that there is an additional source term due to the Z dependence of the Coulomb collision operator. If there are ion composition gradients, such as jets of carbon ablator mix entering the hot-spot, this source term can rapidly exceed the Biermann fields. In addition, the Biermann fields are enhanced due to the increased temperature gradients from carbon radiative cooling. With even stronger self-generated fields, heat loss to the carbon regions will be reduced, potentially reducing the negative effect of carbon mix., Comment: Conference proceedings from the Prospects for High Gain Inertial Fusion Energy meeting at the Royal Society in London, 2-3 March 2020

The electric field in laser-driven plasma wakefield acceleration is orders of magnitude higher than conventional radio-frequency cavities, but the energy gain is limited by dephasing between the ultra-relativistic electron bunch and the wakefield, which travels at the laser group velocity. We present a way to overcome this limit within a single plasma stage. The amplitude of the wakefield behind a train of laser pulses can be controlled in-flight by modulating the density profile. This creates a succession of resonant laser-plasma accelerator sections and non-resonant drift sections, within which the wakefield disappears and the electrons rephase. A two-dimensional particle-in-cell simulation with four 2.5TW laser pulses produces a 50MeV electron energy gain, four times that obtained from a uniform plasma. Although laser red-shift prevents operation in the blowout regime, the technique offers increased energy gain for accelerators limited to the linear regime by the available laser power. This is particularly relevant for laser-plasma x-ray sources capable of operating at high repetition rates, which are highly sought after.

Inertial confinement fusion fuel suffers increased X-ray radiation losses when carbon from the capsule ablator mixes into the hot-spot. Here we present one and two-dimensional ion Vlasov-Fokker-Planck simulations that resolve hot-spot self heating in the presence of a localized spike of carbon mix, totalling 1.9% of the hot-spot mass. The mix region cools and contracts over tens of picoseconds, increasing its alpha particle stopping power and radiative losses. This makes a localized mix region more severe than an equal amount of uniformly distributed mix. There is also a purely kinetic effect that reduces fusion reactivity by several percent, since faster ions in the tail of the distribution are absorbed by the mix region. Radiative cooling and contraction of the spike induces fluid motion, causing neutron spectrum broadening. This artificially increases the inferred experimental ion temperatures and gives line of sight variations.

Proton radiography is a technique extensively used to resolve magnetic field structures in high energy density plasmas, revealing a whole variety of interesting phenomena such as magnetic reconnection and collisionless shocks found in astrophysical systems. Existing methods of analyzing proton radiographs give mostly qualitative results or specific quantitative parameters such as magnetic field strength, and recent work showed that the line-integrated transverse magnetic field can be reconstructed in specific regimes where many simplifying assumptions were needed. Using artificial neural networks, we suggest a novel 3-D reconstruction method that works for a more general case. A proof of concept is presented here, with mean reconstruction errors of less than 5 percent even after introducing noise. We demonstrate that over the long term, this approach is more computationally efficient compared to other techniques. We also highlight the need for proton tomography because (i) certain field structures cannot be reconstructed from a single radiograph and (ii) errors can be further reduced when reconstruction is performed on radiographs generated by proton beams fired in different directions.

Shadowgraphy is a technique widely used to diagnose objects or systems in various fields in physics and engineering. In shadowgraphy, an optical beam is deflected by the object and then the intensity modulation is captured on a screen placed some distance away. However, retrieving quantitative information from the shadowgrams themselves is a challenging task because of the non-linear nature of the process. Here, a novel method to retrieve quantitative information from shadowgrams, based on computational geometry, is presented for the first time. This process can be applied to proton radiography for electric and magnetic field diagnosis in high-energy-density plasmas and has been benchmarked using a toroidal magnetic field as the object, among others. It is shown that the method can accurately retrieve quantitative parameters with error bars less than 10%, even when caustics are present. The method is also shown to be robust enough to process real experimental results with simple pre- and post-processing techniques. This adds a powerful new tool for research in various fields in engineering and physics for both techniques.

The use of Higher Education General Information Survey (HEGIS) data and a software program to compare public university expenditures is discussed. Financial expenditures at the University of North Carolina, Chapel Hill, (UNC) and other public universities were compared using 1981-1982 and 1982-1983 HEGIS data for public university members of the Association of American Universities (AAU) Data Exchange Group. For 24 universities, data are included on full- and part-time enrollments and full-time-equivalent (FTE) enrollments; expenditures for instruction, research, and public service; expenditures for specific activities; and research and instructional expenditures per full-time faculty and FTE student. The NPL Report Writer software was used with "The Chronicle of Higher Education's" machine readable data sets. The peer group consisted of the 24 institutions of the AAU data exchange group. A comparison group was constructed based on criteria such as student full-time-equivalency, faculty size, and total educational expenditures. Commands for the software program to generate different kinds of information are identified. Examples of NPL generated tables are also included. It is noted that while NPL quickly provides different categories of data, it offers virtually no statistical analysis procedures. (SW)