PHY Research Publications (till 2011)

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    Mössbauer spectral analysis and magnetic properties of the superparamagnetic Mn$_{0.5}$Zn$_{0.5}$Fe$_{2}$O$_{4}$ ferrite nanocomposites
    (Elsevier Ltd, 2023-12) Moustafa, M.G.; Hamdeh, Hussein H.; Sebak, M.A.; Mahmoud, Mohamed H.
    Manganese-zinc (Mn-Zn) ferrites of the composition Mn$_{0.5}$Zn$_{0.5}$Fe$_{2}$O$_{4}$ are synthesized by solid-state reactions. Portions of the synthesized material are then ball milled for 1, 2, 4, 8, and 12 h. Their physical properties are subsequently analyzed by XRD, Mössbauer spectroscopy, and magnetization measurements. The XRD analysis reveals the cubic spinel structure for all milled samples. Upon ball milling, however, the crystalline size decreased while the microstrain increased significantly. Moreover, the magnetic order is enhanced by ball milling, as shown by the Mössbauer effect and magnetization measurements. The observed magnetic characteristics are consistent with ball milling changing the chemical order at the two sites of the spinel structure. The distribution of cations for the composition of these samples is suggested by considering the Fe$^{3+}$ ions amounts that exist at the octahedral and tetrahedral sites. Interestingly, the milling process played a crucial role in enhancing the magnetization of these Mn-Zn ferrites. The remarkable magnetization of these Mn-Zn ferrites is useful for energy-related applications.
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    Age of FGK Dwarfs Observed with LAMOST and GALAH: Considering the Oxygen Enhancement
    (American Astronomical Society, 2023-09) Sun, Tiancheng; Ge, Zhishuai; Chen, Xunzhou; Bi, Shaolan; Li, Tanda; Zhang, Xianfei; Li, Yaguang; Wu, Yaqian; Bird, Sarah A.; Ferguson, Jason W.; Zhou, Jianzhao; Ye, Lifei; Long, Liu; Zhang, Jinghua
    Varying oxygen abundance could impact modeling-inferred ages. This work aims to estimate the ages of dwarfs considering observed oxygen abundance. To characterize 67,503 LAMOST and 4006 GALAH FGK-type dwarf stars, we construct a grid of stellar models, which take into account oxygen abundance as an independent model input. Compared with ages determined with commonly used α-enhanced models, we find a difference of ~9% on average when the observed oxygen abundance is considered. The age differences between the two types of models are correlated to [Fe/H] and [O/α], and they are relatively significant on stars with [Fe/H] ≲ -0.6 dex. Generally, varying 0.2 dex in [O/α] will alter the age estimates of metal-rich (-0.2 < [Fe/H] < 0.2) stars by ~10% and relatively metal-poor (-1 < [Fe/H] < -0.2) stars by ~15%. Of the low-O stars with [Fe/H] < 0.1 dex and [O/α] ~-0.2 dex, many have fractional age differences of ~10% and even reach up to 27%. The fractional age difference of high-O stars with [O/α] ~0.4 dex reaches up to -33% to -42% at [Fe/H] ≲ -0.6 dex. We also analyze the chemical properties of these stars. We find a decreasing trend of [Fe/H] with ages from 7.5-9 Gyr to 5-6.5 Gyr for the stars from the LAMOST and GALAH. The [O/Fe] of these stars increases with decreasing age from 7.5-9 Gyr to 3-4 Gyr, indicating that the younger population is more O rich.
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    Design and testing of a 3U CubeSat to test the in-situ vetoing for the vSOL Solar Neutrino Detector
    (International Astronautical Federation, IAF, 2022-09) Folkerts, Jonathan
    For years, earth-based neutrino detectors have been run and operated to detect the elusive neutrino. These have historically been enormous underground detectors. The neutrino Solar Orbiting Laboratory (vSOL) project is working to design a technical demonstration to show that a much smaller neutrino detector can be operated in near-solar environments for a future spaceflight mission. At a closest approach of 3 solar radii, there is a ten thousand-fold increase in the neutrino flux. This would allow a 100 kg payload to be the equivalent of a 1 kTon earth-based payload, larger than the first neutrino experiment in the Homestake mine. As a continuing step towards this goal, the vSOL project will fly a 3U CubeSat for testing the detector's passive shielding design, active vetoing system in a space environment, and the rate of false double-pulse signals in a space environment. I go into technical detail about the characterization of the central detector in simuo and in the lab. The first test is a characterization of energy resolution and calibration through the use of radioactive sources. We will continue testing by measuring the veto success rate with ground-level cosmic rays. For the final ground testing, we will use the Fermilab test beam to characterize the central detector and veto performance at specific particle energies. Veto performance on the previous detector design has been promising, and we were able to veto a high percentage of all particles that can penetrate the passive shielding of the satellite. These laboratory results and simulations of the CubeSat detector design will raise the technological readiness level of the planned technological demonstrator flight to the sun, and the current level of shielding performance is promising for a successful CubeSat test flight.
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    Pourable and destroyable Cosmic Ray radiation shield for spacecraft
    (International Astronautical Federation, IAF, 2022-09) Novak, Jarred
    Historically, materials such as lead, tungsten, and iron have been used in spacecraft to shield scientific detectors from Cosmic Rays. These materials work well when re-entry to Earth is not an issue. The typical strategy is to have a controlled descent of the spacecraft or to have extremely limited shielding, if any, due to NASA's requirement that all impacting parts must impact with no greater than 15J of energy. Given the nature of this mission neither a controlled descent nor having no shielding was not an option. This is the issue Wichita State University (WSU) nuSOL (Neutrino Solar Orbiting Laboratory) team is facing for its 3U CubeSat demonstrator. The CubeSat will be equipped with scientific equipment with the purpose of detecting solar neutrinos, and the less background noise from Cosmic Rays the better the study will be. Through simulations, density tests, and burn tests, WSU was able to develop an epoxy-based shield doped with either iron or tungsten powder. The simulations were conducted by firing electrons, protons, alpha particles, and oxygen and iron nuclei into the shield material with energies ranging from 1MeV until consistent failure rate using Geant4 (Geometry and Tracking). The standards for these simulations are the base epoxy at 1.15g/cm3 to solid steel at 8g/cm3. Mixing tests have determined for iron, a density of 4g/cm3 is achievable, which is 53% iron by volume. tungsten epoxy with a density of 7.5g/cm3 is more easily achieved, and results in 40% tungsten by volume. These ratios are concrete in texture, pourable, and homogeneous. With the data collected, several prototypes of varying densities were made by pouring the mixture into molds. The results indicate that the 4g/cm3 iron doped epoxy does not have a 90% punch-through until 40MeV for electrons and 74MeV for protons. The tungsten fared better at 1GeV and 90MeV respectively, with the proton never exceeding 94% punch-through at 1GeV. The steel 90% fail are 250MeV for electron and 125MeV for proton. Due to the current requirements of the mission, the densities of iron 4g/cm3 and tungsten 7.5g/cm3 have been determined to be the best fit for the nuSOL project. Both materials have been tested to determine if they burn upon re-entry and neither shield survived past 425°C. A vibration test is planned to ensure survival of launch along with a test to measure the science package and shielding capabilities for accelerator particles to ensure efficiency.
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    Concept study for observing Galactic Neutrinos in Neptune's atmosphere
    (International Astronautical Federation, IAF, 2022-09) English, Trent; Solomey, Nickolas
    I discuss the feasibility of a conceptual space-based neutrino detector that utilizes the Ice Giants as Targets for Galactic Neutrinos. The purpose of this research stems from the concept of wanting to find a new method of observing the Galactic Core (GC) of the Milky way and the Supermassive black hole, Sag A*. Observations of the GC have been made in every accessible wavelength except for the regions of space that are too dense for photons to probe. In these regions, we may instead use neutrinos. Neutrinos from the Active Galactic Nucleus are emitted at extreme energies, 10 GeV to EeV scales, but have an extremely low flux measured here at Earth. Neutrino telescopes such as the IceCube Observatory have only been able to measure a handful of neutrinos that might correlate to the GC. But using Gravitational lensing, our sun can be used as a lens which increases the "light" collection power for neutrinos by a factor of 1013, with the trade-off that the minimum focal point is located at 22 AU. This means that Uranus and Neptune are suitable natural targets for these neutrinos to interact with and observe the effects from a spacecraft in orbit. Initial studies use GEANT4, a particle physics simulation toolbox developed by CERN, to facilitate the propagation of energetic particles passing through the atmosphere of Neptune. Various aspects are studied ranging from the wavelength of the photons that are being measured at the detector, timing of the hits, and distribution of the photons leaving the atmosphere. For each of these aspects, we modify several variables such as particle type, energy, interaction depth, and orbital distance from the surface. I also discuss the versatility of this neutrino detector which has the possibility of mapping out the inner structure of the Ice Giants, in-depth studies of the neutrinos coming from the GC, and possibilities to use this method for other cosmic neutrino sources. This detector would be of great interest to planetary science, particle physics, and astrophysics communities.