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Results for “cyclotron radiation”

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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NASA NTRS1972

A resonant instability of model proton radiation belts in the Jovian magnetosphere

The ion cyclotron instability and characteristics of the ion cyclotron wave are discussed. A mathematical perturbation technique is applied to the dispersion relations, and the results are applied to the case of propagation parallel to the magnetic field. The ion cyclotron wave is determined in its damping and growth characteristics by resonant protons and electrons, found in momentum space on resonant surfaces. In the relativistic case the resonant surfaces are hyperbolas of revolution around the magnetic field, and protons can have a stabilizing effect. Instability rates are calculated for the region in the equatorial plane with the Ioannidis and Brice density model. The upper limit of proton flux which gives an energy density of the same order of magnitude as the magnetic field energy density is obtained. The upper limit is plotted with respect to distance from Jupiter and the minimum resonant energy contributing to the instability is also plotted.

Neubauer, F. M.↗

NASA NTRS1985

The stopping of deuterons in lithium

The interaction of 52 MeV deuterons with lithium was investigated, in view of the optimization of a lithium target for an intense neutron source based on the d-Li stripping reaction. The experimental results are compared with theoretical calculations obtained from an updated version of the Bragg code. This code describes in detail the interaction of charged particles with matter. Within the experimental uncertainties the theoretical results are well reproduced by the experiments.

NASA Program Space Medicine↗

DOE OSTI2021

A proton beam energy modulator for rapid proton therapy

We present the design for a rapid proton energy modulator with radiofrequency accelerator cavities, which can deliver the proton radiation dose to varied depth in human tissues much faster than traditional mechanical beam energy degraders. The proton energy modulator is designed as a multi-cell 1-m long accelerator working at 2.856 GHz. Each individual accelerator cavity is powered by a 400 kW compact klystron to provide an accelerating/decelerating gradient of 30 MV/m. The high gradient is enabled by the individual power coupling regime, which provides a high shunt impedance. Beam dynamics simulations were performed, showing that the energy modulator can provide ±30 MeV of beam energy change for a 150 MeV, 7 mm long (full length) proton bunch, and the total energy spread of 3 MeV is satisfactory to clinical needs. A prototype experiment of a single cell has been built and tested, and the low-power microwave measurement results agree very well with simulations. The energy modulator is optimized for the 150 MeV cyclotron proton beam, while this approach can work with different beam energies.

47 OTHER INSTRUMENTATION↗

NASA NTRS1992

Synchrotron emission from a cosmological jet as a model of gamma-ray bursts

The nonthermal rapidly varying spectra of gamma-ray bursts require relativistic beaming if the source is at a cosmological distance. Limits on the Lorentz factors and magnetic fields of extragalactic jet models of gamma-ray bursts are derived from the synchrotron source function, the position of the fundamental cyclotron resonance, the Thomson optical depth of radiating electrons, and the Thomson optical depth of electron-positron pairs created in photon-photon collisions of Compton upscattered radiation. The last of these constraints is the strongest, and it is satisfied by the observations if the jet's Lorentz factor is greater than 100. The limit from the position of the cyclotron fundamental requires a magnetic field strength below approximately 10 exp 10 G. Jet models producing observable cyclotron lines are allowed. The acceleration region in the burst must be separate from the emission region. The similarity of gamma-ray burst jet models to models of quasars and BL Lac objects suggest that if gamma-ray bursts are cosmological sources, they are a type of active galaxy.

Brainerd, J. J.↗

NASA NTRS1981

Absorption and emission of extraordinary-mode electromagnetic waves near cyclotron frequency in nonequilibrium plasmas

An investigation is presented of two cases: (1) weakly relativistic electrons with a loss-cone type distribution, and (2) electrons with a drift velocity parallel to the ambient magnetic field. Numerical computations are given for physical parameters close to those in the polar region of the earth magnetosphere and laboratory experiments, with attention to the fast extraordinary-mode radiation whose frequency is near that of the electron cyclotron frequency. The fast extraordinary mode can escape from a strong field region to the weaker field region and may therefore be measured outside the plasma. It is found that the X mode radiation can be amplified by means of a cyclotron maser effect when the electrons have a loss-cone distribution, and it is concluded that, when the electron energy is sufficiently high, the X mode cutoff frequency may be lower than the cyclotron frequency.

Wu, C. S.↗

NASA NTRS1986

Coronal plasmas on the sun and nearby stars

The current understanding of the quiescent, or non-flaring, microwave emission from solar active regions is summarized. The thermal radiation mechanisms that account for most of the quiescent emission is reviewed, while it is also pointed out that current-amplified magnetic fields or non-thermal radiation may be required in some instances. The 20 cm radiation of coronal loops and the thermal cyclotron lines that accurately specify their magnetic field strength are discussed. The 20 cm and X ray emission of the coronal plasma are then compared. The coronae of nearby stars is next discussed, where coherent radiation processes seem to prevail. Some thoughts toward directions for future exploration are given.

Lang, Kenneth R.↗

NASA NTRS2017

Spectra of KeV Protons Related to Ion-Cyclotron Wave Packets

We use the Fokker-Planck-Kolmogorov equation to study the statistical aspects of stochastic dynamics of the radiation belt (RB) protons driven by nonlinear electromagnetic ion-cyclotron (EMIC) wave packets. We obtain the spectra of keV protons scattered by these waves that showsteeping near the gyroresonance, the signature of resonant wave-particle interaction that cannot be described by a simple power law. The most likely mechanism for proton precipitation events in RBs is shown to be nonlinear wave-particle interaction, namely, the scattering of RB protons into the loss cone by EMIC waves.

electromagnetic ion-cyclotron↗

DOE OSTI2024

MCTrans++: a 0-D model for centrifugal mirrors

The centrifugal mirror confinement scheme incorporates supersonic rotation of a plasma into a magnetic mirror device. This concept has been shown experimentally to drastically decrease parallel losses and increase plasma stability as compared with prior axisymmetric mirrors. MCTrans++ is a dimensionless (0-D) scoping tool which rapidly models experimental operating points in the Centrifugal Mirror Fusion Experiment (CMFX) at the University of Maryland. In the low-collisionality regime, parallel losses can be modelled analytically. A confining potential is set up that is partially ambipolar and partially centrifugal. Due to the stabilizing effects of flow shear, the perpendicular losses can be modelled as classical. Radiation losses such as bremsstrahlung and cyclotron emission are taken into account. A neutrals model is included, and, in some circumstances, charge-exchange losses are found to exceed all other loss mechanisms. We use the SUNDIALS ARKODE library to solve the underlying equations of this model; the resulting software is suitable for scanning large parameter spaces, and can also be used to model time-dependent phenomena such as a capacitive discharge. MCTrans++ has been used to verify results from prior centrifugal mirrors, create an experimental plan for CMFX and find configurations for future reactor-scale fusion devices.

Schwartz, Nick R. (ORCID:0000000296846435)↗

DOE OSTI2020

Cold-hot coupled waves in a flowing magnetized plasma

Abstract Nonlinear coupling of cold and hot waves in a flowing magnetized plasma is analyzed with the Vlasov equation. An analytical solution is obtained for cold waves of a small amplitude (weak flow) and a long wavelength. The distribution function is obtained by integrating the kinetic equation along a perturbed phase-space trajectory for a time-varying plasma flow. The kinetic description presents a generalized dispersion relation that involves resonances depending on cold and hot wave dispersions. Coherent fluid motion leads to radiation peaks in addition to the cyclotron harmonics, where the wavenumber of the cold wave determines the peak frequencies. The peaks appear narrow when the wave propagates perpendicular to the time-averaged flow while they become broad due to the Doppler effect when the wave propagates parallel to the flow. Fully kinetic particle-in-cell simulations corroborate the theoretical predictions. The dispersion relation and resulting wave spectra provide information about plasma parameters and flow properties.

Physics↗

NASA NTRS1983

Accreting X-ray pulsar atmospheres heated by Coulomb deceleration of protons

Results are presented from detailed self-consistent models of accreting magnetized neutron star atmospheres, heated by the gradual deceleration of infalling protons via Coulomb encounters. The temperature and density gradients are calculated assuming momentum and energy balance, coupled with the radiative transfer for two polarizations. The cyclotron resonance effects were treated approximately. These models are characterized by power-law energy spectra, with single pulses at higher frequencies and multiple pulses at lower ones for some aspect angles, as well as a phase-dependent spectral index.

Meszaros, P.↗

NASA NTRS1985

Recent developments in the theory of AM Her and DQ Her stars

Recent advances in the theory of accreting magnetic white dwarf stars are described and several of the unresolved issues concerning them are discussed. Recently reported Einstein satellite observations are examined and the possibility is considered that the 'soft X-ray puzzle' in the AM Her stars may have disappeared. Based on these observations, the evidence is considered that the region emitting the polarized optical light is separate from the X-ray emission region. Among the theoretical advances described are extensive new calculations of the X-ray emission from accreting magnetic white dwarfs, including soft and hard X-ray pulse profiles and time-dependent behavior; improvements in the treatment of cyclotron emission and the transfer of radiation in magnetoactive plasmas, with application to the polarized optical light from the AM Her stars; new ideas about the stream-magnetosphere interaction region that produces the forest of strong emission lines in the AM Her stars; explanation of the synchronization of the white dwarf in the AM Her stars in terms of an MHD torque; and determination of the magnetic fields in the AM Her and DQ Her stars through analysis of their spin-up behavior.

Lamb, D. Q.↗

NASA NTRS2015

Calibration and Readiness of the ISS-RAD Charged Particle Detector

The International Space Station (ISS) Radiation Assessment Detector (RAD) is an intravehicular energetic particle detector designed to measure a broad spectrum of charged particle and neutron radiation unique to the ISS radiation environment. In this presentation, a summary of calibration and readiness of the RAD Sensor Head (RSH) - also referred to as the Charged Particle Detector (CPD) - for ISS will be presented. Calibration for the RSH consists of p, He, C, O, Si, and Fe ion data collected at the NASA Space Radiation Laboratory (NSRL) and Indiana University Cyclotron Facility (IUCF). The RSH consists of four detectors used in measuring the spectroscopy of charged particles - A, B, C, and D; high-energy neutral particles and charged particles are measured in E; and the last detector - F - is an anti-coincidence detector. A, B, and C are made from Si; D is made from BGO; E and F are made from EJ260XL plastic scintillator.

Rios, R.↗

NASA NTRS1986

Electron-cyclotron maser emission from the planets and the stars

Auroral kilometric radiation (AKR), Jupiter's decametric radio emission, microwave spike bursts from the sun, and related bursts from flare stars and close binaries, have all been attributed to the electron-cyclotron maser instability. Although all of these are produced by the same instability, the plasma conditions in the source regions differ; for the planets the ratio of the plasma frequency to the electron-cyclotron frequency, Omega(e), is less than about unity whereas for the sun and stars it is greater than about 1. It is shown that as this ratio increases, the frequency of the emissions moves to higher harmonics of Omega(e) and the mode changes from electromagnetic to electrostatic. Implications for AKR, microwave spike bursts and related bursts from the stars are discussed.

Winglee, R. M.↗

DOE OSTI2023

Observation of impurity accumulation and its compatibility with high plasma performance in W7-X

At the W7-X stellarator, the bolometer system has measured an intensive radiation zone in the inner plasma region (at a normalized radius $ρ$ ~ 0.3–0.4) in the hydrogen plasma generated by electron cyclotron resonance heating; it differs from the normal plasma radiation distribution with an edge-localized emission zone. Spectroscopic diagnostics have recorded high-Z elements such as iron. This phenomenon happens in the plasma phases after gas supply turn-off, which results in all impurity relevant diagnostic signals increasing for several seconds. Despite the enhancement of the core radiation, the plasma energy confinement is improved. A transport analysis shows that this impurity radiation behavior is associated with a low diffusion coefficient ($D$~ 0.02 m 2 s -1 ) and a reversal of the convection around the radial position of the emission peak, which, under normal conditions, separates the zones of outward convection in the central (|$V$| ~ 0.1 m s -1 ) and inward convection in the outer region (|$V$| ~ 0.3 m s -1 ). An impurity accumulation around this radial position has been identified. The transport coefficients obtained are comparable with the theoretical predictions of collisional impurity transport. In the plasma phases studied, both impurity and energy confinement are enhanced. The mechanism responsible for the improvement is believed to be a reduction of micro-instabilities associated with the observed steepening of the density profile, initiated by a low edge plasma density (<1.0 × 10 19 m -3 ) after switching off the gas fueling. The normalized temperature and density gradients fulfil the condition for the suppression of ITG turbulence.

suppression of ITG turbulence↗

NASA NTRS1984

Calculation of the spontaneous cyclotron emissivity using the complete relativistic resonance condition

An expression for the spectral emissivity of spontaneous synchrotron radiation for a plasma which consists of both thermal and suprathermal electron components is derived using the complete relativistic cyclotron resonance condition. The expression is valid over all angles of propagation. The result is applied to the study of the emission of radiation from an energetic population of electrons with a loss-cone distribution in a relatively low-density plasma (i.e., the electron plasma frequency is less than the cyclotron frequency).

Freund, H. P.↗

NASA NTRS1990

The magnetoionic modes and propagation properties of auroral radio emissions

The nature of the magnetoionic wave modes which accompany the aurora is clarified here by a detailed analysis, using multiple techniques, of DE 1 auroral radio observations. All four of the possible magnetoionic wave modes are found to occur, apparently emitted from two different source regions on the same auroral field line. AKR originates primarily in the X mode near the electron cyclotron frequency, and is frequently also accompanied by a weaker O-mode component from the same location. The next most prominent auroral emission is the W-mode auroral hiss originating from altitudes always well below the DE 1 satellite at frequencies below the local cyclotron frequency. The previously reported Z-mode auroral radiation was also detected, but from sources also below the satellite at the poleward edge of the cavity, and not from the expected AKR source at the cyclotron frequency.

Calvert, Wynne↗

NASA NTRS1986

Electron-cyclotron maser emission from the planets and the stars

Auroral kilometric radiation (AKR), Jupiter's decametric radio emission, microwave spike bursts from the Sun, and related bursts from flare stars and close binaries are discussed. Although all of these are produced by the same instability, the plasma conditions in the source regions differ; for the planets the ratio of the plasma frequency to the electron-cyclotron frequency is less than 1, whereas for the Sun and stars it is greater than or = 1. It is shown that as the ratio increases the frequency of the emissions moves to higher harmonics of the electron-cyclotron frequency and the mode changes from electromagnetic to electrostatic. Implications for AKR, microwave spike bursts, and related bursts from the stars are discussed.

Winglee, R. M.↗

NASA NTRS1986

Jovian VLF chorus and Io torus aurora

A test particle model of the cyclotron resonance interaction of waves and trapped radiation belt particles is used to estimate the energetic electron fluxes precipitated by Jovian VLF chorus waves observed on the Voyager 1 and 2 spacecraft near the Io torus. The precipitation fluxes induced by 1-s-long chorus wave packets at L = 7.6 and 8.6 are estimated to be bursts of 5s duration with a peak of 0.3-3 and 0.7-7 ergs/sq cm s that consist of electrons of 5-100 keV energy and that arrives at the ionosphere 15 s after the generation of the chorus wave at the equatorial plane. The effects in the Jovian ionosphere of the chorus-induced precipitation are estimated using existing ionospheric models. A possible experiment for measuring Jovian chorus-induced aurora is proposed and discussed.

Inan, U. S.↗