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Laser radiation interaction with hot nonuniform plasma, determining thermal and electromagnetic forces for various temperatures and densities
The various embodiments presented herein relate to extraordinary electromagnetic transmission (EEMT) to enable multiple inefficient (un-matched) but coupled radiators and/or apertures to radiate and/or pass electromagnetic waves efficiently. EEMT can be utilized such that signal transmission from a plurality of antennas and/or apertures occurs at a transmission frequency different to transmission frequencies of the individual antennas and/or aperture elements. The plurality of antennas/apertures can comprise first antenna/aperture having a first radiating area and material(s) and second antenna/aperture having a second radiating area and material(s), whereby the first radiating/aperture area and second radiating/aperture area can be co-located in a periodic compound unit cell. Owing to mutual coupling between the respective antennas/apertures in their arrayed configuration, the transmission frequency of the array can be shifted from the transmission frequencies of the individual elements. EEMT can be utilized for an array of evanescent of inefficient radiators connected to a transmission line(s).
We propose novel numerical schemes based on the Boris method in curved spacetime, incorporating both hadronic and radiative interactions for the first time. Once the proton has lost significant energy due to radiative and hadronic losses, and its gyroradius has decreased below typical scales on which the electromagnetic field varies, we apply a guiding center approximation (GCA). We fundamentally simulate collision processes either with a Monte-Carlo method or, where applicable, as a continuous energy loss, contingent on the local optical depth. To test our algorithm for the first time combining the effects of electromagnetic, gravitational, and radiation fields including hadronic interactions, we simulate highly relativistic protons traveling through various electromagnetic fields and proton backgrounds. We provide unit tests in various spatially dependent electromagnetic and gravitational fields and background photon and proton distributions, comparing the trajectory against analytic results. We propose that our method can be used to analyze hadronic interactions in black hole accretion disks, jets, and coronae to study the neutrino abundance from active galactic nuclei.
Most of the papers within this report deal with electromagnetic processes in nucleus-nucleus collisions which are of concern in the space radiation program. In particular, the removal of one and two nucleons via both electromagnetic and strong interaction processes has been extensively investigated. The theory of relativistic Coulomb fission has also been developed. Several papers on quark models also appear. Finally, note that the theoretical methods developed in this work have been directly applied to the task of radiation protection of astronauts. This has been done by parameterizing the theoretical formalism in such a fashion that it can be used in cosmic ray transport codes.
The NASA Astrophysics Program is an endeavor to understand the origin and fate of the universe, to understand the birth and evolution of the large variety of objects in the universe, from the most benign to the most violent, and to probe the fundamental laws of physics by examining their behavior under extreme physical conditions. These goals are pursued by means of observations across the entire electromagnetic spectrum, and through theoretical interpretation of radiations and fields associated with astrophysical systems. Astrophysics orbital flight programs are structured under one of two operational objectives: (1) the establishment of long duration Great Observatories for viewing the universe in four major wavelength regions of the electromagnetic spectrum (radio/infrared/submillimeter, visible/ultraviolet, X-ray, and gamma ray), and (2) obtaining crucial bridging and supporting measurements via missions with directed objectives of intermediate or small scope conducted within the Explorer and Spacelab programs. Under (1) in this context, the Gamma Ray Observatory (GRO) is one of NASA's four Great Observatories. The other three are the Hubble Space Telescope (HST) for the visible and ultraviolet portion of the spectrum, the Advanced X-ray Astrophysics Facility (AXAF) for the X-ray band, and the Space Infrared Telescope Facility (SIRTF) for infrared wavelengths. GRO's specific mission is to study the sources and astrophysical processes that produce the highest energy electromagnetic radiation from the cosmos. The fundamental physical processes that are known to produce gamma radiation in the universe include nuclear reactions, electron bremsstrahlung, matter-antimatter annihilation, elementary particle production and decay, Compton scattering, synchrotron radiation. GRO will address a variety of questions relevant to understanding the universe, such as: the formation of the elements; the structure and dynamics of the Galaxy; the nature of pulsars; the existence of black holes; the possible existence of large amounts of antimatter, energetic and explosive phenomena occurring in galactic nuclei; the origin of the cosmic diffuse background; particle acceleration in the Sun, stars and stellar systems; processes in supernovae; and the origin and evolution of the universe itself.
Fast z-pinch is a very efficient way of converting electromagnetic energy to radiation. With an 8-10 MA current on primary test stand facility, about 1 MJ electromagnetic energy is delivered to vacuum chamber, which heats z-pinch plasma to radiate soft x-ray. To develop a pulsed high power x-ray source, we studied the applicability of diagnosing x-ray power from tungsten wire array z-pinch with a flat spectral response x-ray diode (FSR-XRD). The detector was originally developed to diagnose radiation of a hohlraum in SG-III prototype laser facility. It utilized a gold cathode XRD and a specially configured compound gold filter to yield a nearly flat spectral response in photon energy range of 0.1-4 keV. In practice, it was critical to avoid surface contamination of gold cathode. It is illustrated that an exposure of an XRD to multiple shots caused a significant change of response. Thus, in diagnosing x-ray power and energy, we used each XRD in only one shot after calibration. In a shot serial, output of FSR-XRD was compared with output of a nickel bolometer. In these shots, the outputs agreed with each other within their uncertainties which were about 12% for FSR-XRD and about 15% for bolometer. Moreover, the ratios between the FSR-XRD and the bolometer among different shots were explored. In 8 shots, the standard deviation of the ratio was 6%. It is comparable to XRD response change of 7%.
One consequence of a high altitude nuclear explosion (HANE) is the creation of an artificial radiation belt that can have severe consequences for space-based infrastructure in low Earth orbit (LEO). A HANE-generated radiation belt is produced when radioactive debris ions beta decay to produce an intense population of magnetically-trapped, high-energy electrons that can affect satellites through increased total dose rates and/or internal charging. Recent results from NASA's Van Allen Probes mission has shown how electromagnetic waves can scatter radiation belt electrons decreasing their intensity and effects. Radiation Belt Remediation (RBR) seeks to exploit those processes to rapidly deplete the intensity of either natural or HANE-produced radiation belts by artificially injecting waves to enhance electron scattering and loss rates. One promising option for producing the required waves is to use modulated medium energy electron beams as a type of 'wireless transmitter'. (author)
A recent paper [Ziebell et al., Phys. Plasmas 21, 010701 (2014)] discusses a new type of radiation emission process for plasmas in a state of quasi-equilibrium between the particles and enhanced Langmuir turbulence. Such a system may be an example of the so-called “turbulent quasi-equilibrium.” In the present paper, it is shown on the basis of electromagnetic weak turbulence theory that an initial thermal equilibrium state (i.e., only electrostatic fluctuations and Maxwellian particle distributions) transitions toward the turbulent quasi-equilibrium state with enhanced electromagnetic radiation spectrum, thus demonstrating that the turbulent quasi-equilibrium discussed in the above paper correctly describes the weakly turbulent plasma dynamically interacting with electromagnetic fluctuations, while maintaining a dynamical steady-state in the average sense.
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For electromagnetic immunity testing of an electronic system, it is desirable to demonstrate its functional integrity when exposed to the full range and intensity of environmental electromagnetic threats that may be encountered over its operational life. As part of this, it is necessary to show proper system operation when exposed to representative threat signal modulations. Modulated signal transition time is easily overlooked, but can be highly significant to system susceptibility. Radiated electromagnetic field immunity testing is increasingly being performed in Mode Stirred Chambers. Because the peak field vs. time relationship is affected by the operation of a reverberating room, it is important to understand how the room may influence any input signal modulation characteristics. This paper will provide insight into the field intensity vs. time relationship within the test environment of a mode stirred chamber. An understanding of this relationship is important to EMC engineers in determining what input signal modulation characteristics will be transferred to the equipment under test. References will be given for the development of this topic, and experimental data will be presented
We analyze the damping of strong, superluminal electromagnetic waves by radiation reaction and Compton drag in the context of pulsar winds. The associated radiation signature is found by estimating the efficiency and the characteristic radiation frequencies. Applying these estimates to the gamma-ray binary containing PSR B1259–63, we show that the GeV flare observed by the Fermi Large Area Telescope can be understood as inverse-Compton emission by particles scattering photons from the companion star, if the pulsar wind termination shock acquires a precursor of superluminal waves roughly 30 days after periastron. This requirement constrains the mass-loading factor of the wind μ=L/ N-dot mc{sup 2}, where L is the luminosity and N-dot is the rate of loss of electrons and positrons, to be roughly 6 × 10{sup 4}.
The investigation indicates that nuclei with excitation energy of a few hundred MeV to BeV are more likely to radiate hot nuclear clusters than neutrons. These daughter clusters could, furthermore, de-excite emitting other hot nuclei, and the chain continues until these nuclei cool off sufficiently to evaporate primarily neutrons. A few GeV excited nuclei could radiate elementary particles preferentially over neutrons. Impact of space radiation with materials (for example, spacecraft) produces highly excited nuclei which cool down emitting electromagnetic and particle radiations. At a few MeV excitation energy, neutron emission becomes more dominant than gamma-ray emission and one often attributes the cooling to take place by successive neutron decay. However, a recent experiment studying the cooling process of 396 MeV excited Hg-190 casts some doubt on this thinking, and the purpose of this investigation is to explore the possibility of other types of nuclear emission which might out-compete with neutron evaporation.
Radioisotope Power Systems (RPS) have been and will be enabling or significantly enhancing for many missions, including several concepts identified in the 2011 Planetary Science Decadal Survey. Some mission planners and science investigators might have concerns about possible impacts from RPS-induced conditions upon the scientific capabilities of their mission concepts. To alleviate these concerns, this paper looks at existing and potential future RPS designs, and examines their potential radiation, thermal, vibration, electromagnetic interference (EMI), and magnetic fields impacts on representative science instruments and science measurements. Radiation impacts from RPS on science instruments are of potential concern for instruments with optical detectors and instruments with high-voltage electronics. The two main areas of concern are noise effects on the instrument measurements, and long-term effects of instrument damage. While RPS by their nature will contribute to total radiation dose, their addition for most missions should be relatively small. For example, the gamma dose rate from one Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) would be an order of magnitude lower than the environmental dose rate at Mars, and would have a correspondingly lower contribution to instrument noise and to any permanent damage to payload sensors. Increasing the number of General Purpose Heat Source (GPHS) modules used in an RPS would be expected to increase the generated radiation proportionally; however, the effect of more GPHS modules is mitigated from a strictly linear relationship by self-shielding effects. The radiation field of an RPS is anisotropic due to the deviation of the modules from a point-source-geometry. For particularly sensitive instruments the total radiation dose could be mitigated with separation or application of spot shielding. Though a new, higher-power RPS could generate more heat per unit than current designs, thermal impact to the flight system could be mitigated with shading and pointing if required by the mission. Alternatively, excess heat could prove beneficial in providing needed heat to spacecraft components and instruments in some thermal environments. Vibration for a new higher-power Stirling Radioisotope Generator (SRG) would be expected to be similar to the recent Advanced Stirling Radioisotope Generator (ASRG) design. While vibration should be low, it must be considered and addressed during spacecraft and instrument design. EMI and magnetic fields for new RPS concepts are expected to be low as for the current RPS, but must be considered and addressed if the mission includes sensitive instruments such as magnetometers. The assessment conducted for this paper focused on orbiter instrument payloads for two representative mission concepts- a Titan Saturn System Mission (TSSM) and a Uranus Orbiter and Probe (UOP)-since both of these Decadal Survey concepts would include many diverse instruments on board. Quick-look design studies using notional new RPS concepts were carried out for these two mission concepts, and their specific instrument packages were analyzed for their interactions with new RPS designs. The original Decadal Survey TSSM and UOP concepts did not have complete instrument performance requirements so typical measurement requirements were used where needed. Then, the general RPS environments were evaluated for impacts to various types of instruments. This paper describes how the potential impacts of the RPS on science instruments and measurements were assessed, which impacts were addressed, proposed mitigation strategies against those impacts, and provides an overview of future work.
The maximum synchrotron burnoff limit of 160 MeV represents a fundamental limit to radiation resulting from electromagnetic particle acceleration in one-zone ideal plasmas. In magnetic reconnection, however, particle acceleration and radiation are decoupled because the electric field is larger than the magnetic field in the diffusion region. We carry out two-dimensional particle-in-cell simulations to determine the extent to which magnetic reconnection can produce synchrotron radiation above the burnoff limit. We use the test particle comparison (TPC) method to isolate the effects of cooling by comparing the trajectories and acceleration efficiencies of test particles incident on such a reconnection region with and without cooling them. We find that the cooled and uncooled particle trajectories are typically similar during acceleration in the reconnection region, and derive an effective limit on particle acceleration that is inversely proportional to the average magnetic field experienced by the particle during acceleration. Using the calculated distribution of this average magnetic field as a function of uncooled final particle energy, we find analytically that cooling does not affect power-law particle energy spectra except at energies far above the synchrotron burnoff limit. Finally, we compare fully cooled and uncooled simulations of reconnection, confirming that the synchrotron burnoff limit does not produce a cutoff in the particle energy spectrum. Our results indicate that the TPC method accurately predicts the effects of cooling on particle acceleration in relativistic reconnection, and that, even far above the burnoff limit, the synchrotron energy of radiation produced in reconnection is not limited by cooling.
This paper discusses the measurements of the electromagnetic interference (EMI) generated during discharges of Mylar samples. The two components of EMI, the conducted emission and the radiated emission, are characterized by the replacement current and the radiated RF spectrum respectively. The measured radiated RF spectra reveal important information on the source of the electromagnetic radiation. The possible sources are the replacement current pulse and the discharged generated plasma. The scaling of the amplitudes of the EMI, as a function of the area of the test sample, is also discussed.
Taking into account results of numerous experiments, the variability of the energy spectra of cosmic rays (protons and helium nuclei) in the energy range of 10 GeV to ~10{sup 7} GeV is explained on the basis of a hypothesis of the existence of two variable sources close to the Sun. The first (soft) surfatron source (with a size of ~100 AU) is located at the periphery of the heliosphere. The second (hard) surfatron source (with a size of ~1 pc) is situated in the Local Interstellar Cloud (LIC) at a distance of <1 pc. The constant background is described by a power-law spectrum with a slope of ~2.75. The variable heliospheric surfatron source is described by a power-law spectrum with a variable amplitude, slope, and cutoff energy, the maximum cutoff energy being in the range of E{sub CH}/Z < 1000 GeV. The variable surfatron source in the LIC is described by a power-law spectrum with a variable amplitude, slope, and cut-off energy, the maximum cut-off energy being E{sub Ð}¡{sub L}/Z ≤ 3 × 10{sup 6} GeV. The proposed model is used to approximate data from several experiments performed at close times. The energy of each cosmic-ray component is calculated. The possibility of surfatron acceleration of Fe nuclei (Z = 26) in the LIC up to an energy of E{sub CL} ~ 10{sup 17} eV and electron and positrons to the “knee” in the energy spectrum is predicted. By numerically solving a system of nonlinear equations describing the interaction between an electromagnetic wave and a charged particle with an energy of up to E/Z ~ 3 × 10{sup 6} GeV, the possibility of trapping, confinement, and acceleration of charged cosmic-ray particles by a quasi-longitudinal plasma wave is demonstrated.
A three-component phenomenological model describing the specific features of the spectrum of cosmic-ray protons and helium nuclei in the rigidity range of 30–2×10{sup 5} GV is proposed. The first component corresponds to the constant background; the second, to the variable “soft” (30–500 GV) heliospheric source; and the third, to the variable “hard” (0.5–200 TV) source located inside a local bubble. The existence and variability of both sources are provided by the corresponding “surfatron accelerators,” whose operation requires the presence of an extended region with an almost uniform (in both magnitude and direction) magnetic field, orthogonally (or obliquely) to which electromagnetic waves propagate. The maximum energy to which cosmic rays can be accelerated is determined by the source size. The soft source with a size of ∼100 AU is located at the periphery of the heliosphere, behind the front of the solar wind shock wave. The hard source with a size of >0.1 pc is located near the boundary of an interstellar cloud at a distance of ∼0.01 pc from the Sun. The presence of a kink in the rigidity spectra of p and He near 230 GV is related to the variability of the physical conditions in the acceleration region and depends on the relation between the amplitudes and power-law exponents in the dependences of the background, soft heliospheric source, and hard near galactic source. The ultrarelativistic acceleration of p and He by an electromagnetic wave propagating in space plasma across the external magnetic field is numerically analyzed. Conditions for particle trapping by the wave and the dynamics of the particle velocity and momentum components are considered. The calculations show that, in contrast to electrons and positrons (e{sup +}), the trapped protons relatively rapidly escape from the effective potential well and cease to accelerate. Due to this effect, the p and He spectra are softer than that of e{sup +}. The possibility that the spectra of accelerated protons deviate from standard power-law dependences due to the surfatron mechanism is discussed.
Magnetized cold plasma motion effect on electromagnetic wave propagation and radiation