Plasmas with electromagnetic fields turbulent at sub-Larmor scales are a feature of a wide variety of high-energy-density environments and are essential to the description of many astrophysical and laboratory plasma phenomena. Radiation from particles, whether they are relativistic or nonrelativistic, moving through small-scale magnetic turbulence has spectral characteristics distinct from both synchrotron and cyclotron radiation. The radiation, carrying information on the statistical properties of the magnetic turbulence, is also intimately related to the particle diffusive transport. We have investigated, both theoretically and numerically, the transport of nonrelativistic and trans-relativistic particles in plasmas with high-amplitude isotropic sub-Larmor-scale magnetic turbulence, and its relation to the spectra of radiation simultaneously produced by these particles. Consequently, the diffusive and radiative properties of plasmas turbulent on sub-Larmor scales may serve as a powerful tool to diagnosis laboratory and astrophysical plasmas.

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High-amplitude, chaotic or turbulent electromagnetic fluctuations are ubiquitous in high-energy-density laboratory and astrophysical plasmas, where they can be excited by various kinetic-streaming and/or anisotropy-driven instabilities, such as the Weibel instability. These fields typically exist on "sub-Larmor scales"-scales smaller than the electron Larmor radius. Electrons moving through such magnetic fields undergo small-angle stochastic deflections of their pitch angles, thus establishing diffusive transport on long time scales. We show that this behavior, under certain conditions, is equivalent to Coulomb collisions in collisional plasmas. The magnetic pitch-angle diffusion coefficient, which acts as an effective "collision" frequency, may be substantial in these, otherwise, collisionless environments. We show that this effect, colloquially referred to as the plasma "quasicollisionality," may radically alter the expected radiative transport properties of candidate plasmas. We argue that the modified magneto-optic effects in these plasmas provide an attractive, radiative diagnostic tool for the exploration and characterization of small-scale magnetic turbulence, as well as affect inertial confinement fusion and other laser-plasma experiments.

This paper presents the design, prototyping, and testing of an S-Band conformal array on a partial wing surface. The array elements are series fed microstrip patch antennas fabricated entirely through additive manufacturing (AM) technology using a combination of fused deposition modeling and thermal spray. A robust material set of ULTEM 9085 and copper alloy is used for a good balance of mechanical/environmental robustness and RF performance, while also offering a viable path forward for a future fielded design. The focus of this paper is on AM multi-material fabrication, fundamental print settings and material characterization, and antenna testing. AM characterization coupons are utilized to improve the accuracy of the RF antenna model, which showed excellent agreement with the prototype measurements.