The Experts below are selected from a list of 17244 Experts worldwide ranked by ideXlab platform
E N Nikolaev - One of the best experts on this subject based on the ideXlab platform.
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dynamically harmonized ft icr cell with specially shaped electrodes for compensation of inhomogeneity of the magnetic field computer simulations of the electric field and ion motion dynamics
Journal of the American Society for Mass Spectrometry, 2012Co-Authors: Yury Kostyukevich, Gleb Vladimirov, E N NikolaevAbstract:The recently introduced ion trap for FT-ICR mass spectrometers with dynamic harmonization showed the highest resolving power ever achieved both for ions with moderate masses 500–1000 Da (peptides) as well as ions with very high masses of up to 200 kDa (proteins). Such results were obtained for superconducting magnets of very high homogeneity of the magnetic field. For magnets with lower homogeneity, the time of transient duration would be smaller. In superconducting magnets used in FT-ICR mass spectrometry the inhomogeneity of the magnetic field in its axial direction prevails over the inhomogeneity in other directions and should be considered as the main factor influencing the synchronic motion of the ion cloud. The inhomogeneity leads to a dependence of the Cyclotron Frequency from the amplitude of axial oscillation in the potential well of the ion trap. As a consequence, ions in an ion cloud become dephased, which leads to signal attenuation and decrease in the resolving power. Ion Cyclotron Frequency is also affected by the radial component of the electric field. Hence, by appropriately adjusting the electric field one can compensate the inhomogeneity of the magnetic field and align the Cyclotron Frequency in the whole range of amplitudes of z-oscillations. A method of magnetic field inhomogeneity compensation in a dynamically harmonized FT-ICR cell is presented, based on adding of extra electrodes into the cell shaped in such a way that the averaged electric field created by these electrodes produces a counter force to the forces caused by the inhomogeneous magnetic field.
G Gabrielse - One of the best experts on this subject based on the ideXlab platform.
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circumventing detector backaction on a quantum Cyclotron
Physical Review Letters, 2021Co-Authors: Xing Fan, G GabrielseAbstract:Detector backaction can be completely evaded when the state of a one-electron quantum Cyclotron is detected, but it nonetheless significantly broadens the quantum-jump resonance line shapes from which the Cyclotron Frequency can be deduced. This limits the accuracy with which the electron magnetic moment can be determined to test the standard model's most precise prediction. A steady-state solution to a master equation, the first quantum calculation for the open quantum Cyclotron system, illustrates a method to circumvent the detection backaction upon the measured Frequency.
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the true Cyclotron Frequency for particles and ions in a penning trap
International Journal of Mass Spectrometry, 2009Co-Authors: G GabrielseAbstract:The true Cyclotron Frequency of a particle or ion, needed for mass spectrometry and other accurate measurements in a Penning trap, cannot be measured directly. It is not one of the oscillation frequencies of the trapped particle, and the three oscillation frequencies that can be measured vary with the misalignment and the harmonic distortion of the trap potential. Two methods to determine the Cyclotron Frequency are discussed. First, when all three eigenfrequencies of a trapped particle can be measured, the true Cyclotron Frequency is given by the prescription of the Brown–Gabrielse invariance theorem. This prescription makes possible a surprising number of the most accurate measurements in particle, nuclear and atomic physics because it accounts exactly for the lowest order electrostatic imperfections and magnetic misalignments. Second, when less accuracy is required, as when the masses of unstable nuclei are measured, a single sideband Frequency is often measured instead—the Frequency of a driving force that optimally couples two of the motions of the ion in the trap. A missing theoretical justification for this alternate method is provided using an expansion of the same invariance theorem. A remarkable suppression of systematic measurement errors is predicted, showing why these are not larger than reported measurement uncertainties, despite the contrary indication of simple estimates.
D. A. Brain - One of the best experts on this subject based on the ideXlab platform.
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temporal variability of waves at the proton Cyclotron Frequency upstream from mars implications for mars distant hydrogen exosphere
arXiv: Space Physics, 2013Co-Authors: Cesar Bertucci, Norberto Romanelli, Jean-yves Chaufray, Christian Mazelle, M. Delva, Ronan Modolo, Daniel O Gomez, Francisco Gonzalezgalindo, D. A. BrainAbstract:We report on the temporal variability of the occurrence of waves at the local proton Cyclotron Frequency upstream from the Martian bow shock from Mars Global Surveyor observations during the first aerobraking and science phasing orbit periods. Observations at high southern latitudes during minimum-to-mean solar activity show that the wave occurrence rate is significantly higher around perihelion southern summer solstice and lower around the same hemisphere's spring and autumn equinoxes. A similar trend is observed in the hydrogen (H) exospheric density profiles over the Martian South Pole obtained from a model including UV thermospheric heating effects. In spite of the complexity in the ion pick-up and plasma wave generation and evolution processes, these results support the idea that variations in the occurrence of waves could be used to study the temporal evolution of the distant Martian H corona and its coupling with the thermosphere at altitudes currently inaccessible to direct measurements.
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Temporal variability of waves at the proton Cyclotron Frequency upstream from Mars: Implications for Mars distant hydrogen exosphere
Geophysical Research Letters, 2013Co-Authors: Cesar Bertucci, Norberto Romanelli, Jean-yves Chaufray, D. Gomez, Christian Mazelle, M. Delva, Ronan Modolo, F. González-galindo, D. A. BrainAbstract:We report on the temporal variability of the occurrence of waves at the local proton Cyclotron Frequency upstream from the Martian bow shock from Mars Global Surveyor observations during the first aerobraking and science phasing orbit periods. Observations at high southern latitudes during minimum-to-mean solar activity show that the wave occurrence rate is significantly higher around perihelion/southern summer solstice than around the spring and autumn equinoxes. A similar trend is observed in the hydrogen (H) exospheric density profiles over the Martian dayside and South Pole obtained from a model including UV thermospheric heating effects. In spite of the complexity in the ion pick-up and plasma wave generation and evolution processes, these results support the idea that variations in the occurrence of waves could be used to study the temporal evolution of the distant Martian H corona and its coupling with the thermosphere at altitudes currently inaccessible to direct measurements.
G G Howes - One of the best experts on this subject based on the ideXlab platform.
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plasma waves near the electron Cyclotron Frequency in the near sun solar wind
Astrophysical Journal Supplement Series, 2020Co-Authors: D Malaspina, J S Halekas, Laura Bercic, D E Larson, Phyllis Whittlesey, S D Bale, J W Bonnell, R E Ergun, G G HowesAbstract:Data from the first two orbits of the Sun by Parker Solar Probe reveal that the solar wind sunward of 50 solar radii is replete with plasma waves and instabilities. One of the most prominent plasma wave power enhancements in this region appears near the electron Cyclotron Frequency (f_ce). Most of this wave power is concentrated in electric field fluctuations near 0.7 f_ce and f_ce, with strong harmonics of both frequencies extending above f_ce. At least two distinct, often concurrent, wave modes are observed, preliminarily identified as electrostatic whistler-mode waves and electron Bernstein waves. Wave intervals range in duration from a few seconds to hours. Both the amplitudes and number of detections of these near-f_ce waves increase significantly with decreasing distance to the Sun, suggesting that they play an important role in the evolution of electron populations in the near-Sun solar wind. Correlations are found between the detection of these waves and properties of solar wind electron populations, including electron core drift, implying that these waves play a role in regulating the heat flux carried by solar wind electrons. Observation of these near-f_ce waves is found to be strongly correlated with near-radial solar wind magnetic field configurations with low levels of magnetic turbulence. A scenario for the growth of these waves is presented which implies that regions of low-turbulence near-radial magnetic field are a prominent feature of solar wind structure near the Sun.
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a model of turbulence in magnetized plasmas implications for the dissipation range in the solar wind
arXiv: Astrophysics, 2007Co-Authors: G G Howes, S C Cowley, W Dorland, G W Hammett, Eliot Quataert, A A SchekochihinAbstract:This paper studies the turbulent cascade of magnetic energy in weakly collisional magnetized plasmas. A cascade model is presented, based on the assumptions of local nonlinear energy transfer in wavenumber space, critical balance between linear propagation and nonlinear interaction times, and the applicability of linear dissipation rates for the nonlinearly turbulent plasma. The model follows the nonlinear cascade of energy from the driving scale in the MHD regime, through the transition at the ion Larmor radius into the kinetic Alfven wave regime, in which the turbulence is dissipated by kinetic processes. The turbulent fluctuations remain at frequencies below the ion Cyclotron Frequency due to the strong anisotropy of the turbulent fluctuations, k_parallel << k_perp (implied by critical balance). In this limit, the turbulence is optimally described by gyrokinetics; it is shown that the gyrokinetic approximation is well satisfied for typical slow solar wind parameters. Wave phase velocity measurements are consistent with a kinetic Alfven wave cascade and not the onset of ion Cyclotron damping. The conditions under which the gyrokinetic cascade reaches the ion Cyclotron Frequency are established. Cascade model solutions imply that collisionless damping provides a natural explanation for the observed range of spectral indices in the dissipation range of the solar wind. The dissipation range spectrum is predicted to be an exponential fall off; the power-law behavior apparent in observations may be an artifact of limited instrumental sensitivity. The cascade model is motivated by a programme of gyrokinetic simulations of turbulence and particle heating in the solar wind.
S Ulmer - One of the best experts on this subject based on the ideXlab platform.
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a cryogenic detection system at 28 9mhz for the non destructive observation of a single proton at low particle energy
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2013Co-Authors: S Ulmer, Klaus Blaum, Holger Kracke, A Mooser, W Quint, Cricia C Rodegheri, J WalzAbstract:Abstract A highly sensitive detection system for the non-destructive measurement of the Cyclotron Frequency of a single proton stored in a cryogenic Penning trap is described. The detector consists of a low noise GaAs field effect transistor amplifier combined with a copper helical resonator with high quality factor. The resonance Frequency can be tuned with a GaAs-varactor diode. Connected to the Penning trap a quality factor of 1250 at 28.9 MHz is achieved. With this detection system the signal of a single proton at a Cyclotron mode-energy of only 10 meV was resolved.
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direct measurement of the free Cyclotron Frequency of a single particle in a penning trap
Physical Review Letters, 2011Co-Authors: S Ulmer, Klaus Blaum, Holger Kracke, A Mooser, W Quint, Cricia C RodegheriAbstract:A measurement scheme for the direct determination of the free Cyclotron Frequency ${\ensuremath{\nu}}_{c}$ of a single particle stored in a Penning trap is described. The method is based on the dressed states of mode coupling. In this novel measurement scheme both radial modes of the single trapped particle are simultaneously coupled to the axial oscillation mode.
