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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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This is a final report to LLNL summarizing results of the project funded by a sub-contract AWD015218 to investigate the generation and confinement of pair electron-positron plasma and its application for high-energy-density physics and astrophysics.
Overview of the Jefferson Lab Long Term Schedule from 12 GeV to positrons and beyond
Potential physics with positrons and the Solid Polarized Target
A photogun to generate a high-intensity, highly spin-polarized electron beam >90% with unprecedented charge lifetime in the kilocoulomb range is envisioned at JLab for a proposed Ce+BAF polarized positron beam source. The electron photogun is expected to provide a CW beam of >1 mA for a month without intervention. A limiting factor is ion-back bom-bardment on the strained-superlattice GaAs-photocathode which can be reduced by improving the photogun vacuum or biasing the anode. Additionally, increasing the laser spot size can help mitigate ion-induced damage. However, eventually the laser size becomes too large for the photogun electrode. An envisioned photogun design will incorporate larger electrodes to accommodate larger and off-center laser spot sizes. Compatible larger conical insulators which operate >300 kV for beam injection into a Beta~1 SRF booster are also necessary.
Reduction-oxidation (redox) reactions that transfer conduction electrons from the anode to the cathode are the fundamental processes responsible for generating power in Li-ion batteries. Electronic and microstructural features of the cathode material are controlled by the nature of the redox orbitals and how they respond to Li intercalation. Thus, redox orbitals play a key role in performance of the battery and its degradation with cycling. We unravel spectroscopic descriptors that can be used to gain an atomic-scale handle on the redox mechanisms underlying Li-ion batteries. Our focus is on X-ray Compton Scattering and Positron Annihilation spectroscopies and the related computational approaches for the purpose of identifying orbitals involved in electrochemical transformations in the cathode. This review provides insight into the workings of lithium-ion batteries and opens a pathway for rational design of next-generation battery materials.
The tropomyosin receptor kinases family (TrkA, TrkB, and TrkC) supports neuronal growth, survival, and differentiation during development, adult life, and aging. TrkA/B/C downregulation is a prominent hallmark of various neurological disorders including Alzheimer’s disease (AD). Abnormally expressed or overexpressed full-length or oncogenic fusion TrkA/B/C proteins were shown to drive tumorigenesis in a variety of neurogenic and non-neurogenic human cancers and are currently the focus of intensive clinical research. Neurologic and oncologic studies of the spatiotemporal alterations in TrkA/B/C expression and density and the determination of target engagement of emerging antineoplastic clinical inhibitors in normal and diseased tissue are crucially needed but have remained largely unexplored due to the lack of suitable non-invasive probes. Here, we review the recent development of carbon-11- and fluorine-18-labeled positron emission tomography (PET) radioligands based on specifically designed small molecule kinase catalytic domain-binding inhibitors of TrkA/B/C. Basic developments in medicinal chemistry, radiolabeling and translational PET imaging in multiple species including humans are highlighted.
Magnetic reconnection is often invoked to explain the nonthermal radiation of relativistic outflows, including jets of active galactic nuclei (AGNs). Motivated by the largely unknown plasma composition of AGN jets, we study reconnection in the unexplored regime of electron–positron–proton (pair-proton) plasmas with large-scale two-dimensional particle-in-cell simulations. We cover a wide range of pair multiplicities (lepton-to-proton number ratio κ = 1–199) for different values of the all-species plasma magnetization (σ = 1, 3, and 10) and electron temperature (${{\rm{\Theta }}}_{e}\equiv {{kT}}_{e}/{m}_{e}{c}^{2}=0.1\mbox{--}100$). We focus on the dependence of the post-reconnection energy partition and lepton energy spectra on the hot pair plasma magnetization ${\sigma }_{e,h}$ (i.e., the ratio of magnetic to pair enthalpy densities). We find that the post-reconnection energy is shared roughly equally between magnetic fields, pairs, and protons for ${\sigma }_{e,h}$ gsim 3. We empirically find that the mean lepton Lorentz factor in the post-reconnection region depends on σ, Θ e , and ${\sigma }_{e,h}$ as $\langle {\gamma }_{e}-1\rangle \approx \sqrt{\sigma }(1+4{{\rm{\Theta }}}_{e})\left(1+{\sigma }_{e,h}/30\right)$, for σ ≥ 1. The high-energy part of the post-reconnection lepton energy distributions can be described by a power law, whose slope is mainly controlled by ${\sigma }_{e,h}$ for κ gsim 3–6, with harder power laws obtained for higher magnetizations. We finally show that reconnection in pair-proton plasmas with multiplicities κ ~ 1–20, magnetizations σ ~ 1–10, and temperatures Θ e ~ 1–10 results in particle power-law slopes and average electron Lorentz factors that are consistent with those inferred in leptonic models of AGN jet emission.
Electron-positron components of primary cosmic radiation, noting energy spectrum, flux, charge composition, origin, etc
Gamma scintillation spectrometer design based on electron-positron pair formation
Scattering resonance below positronium thresholds in positron-hydrogen systems
First order adiabatic correlation function for determining variational bounds in positron-atom scattering
General formula for calculating equilibrium spectra of secondary cosmic ray positrons in galaxy and cosmic annihilation gamma ray spectra
Positronium formation in positron-hydrogen scattering solved by coupled equations
Charge composition of primary electron component from balloon-borne magnetic spectrometer measurements, discussing energy dependence of positron-electron ratio in primary cosmic radiation
Electron-positron pairs production by negative pions in nuclear emulsion, noting possible sources of selection error
Positron-H scattering, discussing possible scattering resonance below positronium thresholds
Antiproton flux in primary cosmic rays, calculating ratio of antiproton to positron production in nuclear collisions
Adiabatic correlation function for variational lower bounds on positron-atom elastic scattering phase shifts for hydrogen and helium atoms