Experimental and Numerical Studies of Megagauss Magnetic-Field Generation at LANL-NHMFL

Mielke, C. H.; Novac, B.M.

doi:10.1109/tps.2010.2049507

Cited by 24 publications

(9 citation statements)

References 4 publications

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“…To access ultrahigh magnetic fields, we used the single turn coil (STC) magnet at the National High Magnetic Field Laboratory (NHMFL) in Los Alamos 39,40 [see Fig. 1(a)].…”

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confidence: 99%

Circular polarization dependent cyclotron resonance in large-area graphene in ultrahigh magnetic fields

et al. 2012

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Using ultrahigh magnetic fields up to 170 T and polarized midinfrared radiation with tunable wavelengths from 9.22 to 10.67 μm, we studied cyclotron resonance in large-area graphene grown by chemical vapor deposition. Circular polarization dependent studies reveal strong p-type doping for as-grown graphene, and the dependence of the cyclotron resonance on radiation wavelength allows for a determination of the Fermi energy. Thermal annealing shifts the Fermi energy to near the Dirac point, resulting in the simultaneous appearance of hole and electron cyclotron resonance in the magnetic quantum limit, even though the sample is still p-type, due to graphene's linear dispersion and unique Landau level structure. These high-field studies therefore allow for a clear identification of cyclotron resonance features in large-area, low-mobility graphene samples. The band structure of graphene exhibits a zero-gap linear dispersion relation near each of the Dirac points, which results in a variety of exotic properties of two-dimensional (2D) Dirac fermions. [1][2][3] While a number of electronic transport studies have revealed novel phenomena in the presence of a high magnetic field, including half-integer quantum Hall states observed at room temperature, 1,2,4 magneto-optical properties are expected to be equally unusual, 5-15 especially in the magnetic quantum limit 12 where the Fermi level resides in the lowest Landau level (LL). Even in conventional 2D electron systems such as found in GaAs quantum wells, studies of cyclotron resonance (CR) in the magnetic quantum limit have shown many-body effects, [16][17][18][19] such as spin splitting in the fractional quantum Hall regime, even though CR is not expected to be sensitive to electron-electron interactions due to Kohn's theorem. 20 The linear dispersions of graphene automatically evade this basic requirement for Kohn's theorem, motivating CR studies of graphene in ultrahigh magnetic fields.An applied magnetic field (B) creates LLs for charge carriers both in the conduction and valence bands, and CR measures resonant optical transitions between adjacent LLs ( n = ±1, where n is the Landau level index). 21 CR is a well-established and powerful technique to determine many fundamental parameters of a sample, such as carrier effective masses, densities, mobilities, and scattering rates. When performed with circularly polarized radiation, the sign of the charge carriers can also be determined. Furthermore, owing to graphene's nonparabolic (i.e., linear) dispersion, LL energies are not equally spaced; rather, they follow E n,± = ±c * √ 2ehBn, where n 0 and c * ≈ 1.0 × 10 6 m/s corresponds to the slope of the linear dispersions. Thus, different inter-Landau level (LL) transitions occur at different energies or magnetic fields. Hence, the absence or presence of a certain resonance can determine the Fermi energy. This is in marked contrast to conventional materials with parabolic dispersions, which form equally spaced LLs in a magnetic field [E n = (n + 1/2)ehB/m * , where m * is ...

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“…To access ultrahigh magnetic fields, we used the single turn coil (STC) magnet at the National High Magnetic Field Laboratory (NHMFL) in Los Alamos 39,40 [see Fig. 1(a)].…”

mentioning

confidence: 99%

Circular polarization dependent cyclotron resonance in large-area graphene in ultrahigh magnetic fields

et al. 2012

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“…The 2D filamentary model has been used to predict this non-uniform current distribution in the past [2] as well as the filamentary current distribution in various other geometries [3].…”

Section: A Overviewmentioning

confidence: 99%

A novel current density distribution sensor for use in parallel plate transmission lines

Omar

Graneau

Novac

et al. 2014

2014 17th International Symposium on Electromagnetic Launch Technology

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“…A number of original features have recently been introduced into the standard approach (also termed network mesh or meshmatrix method), mostly related to the fast dynamics of imploding/exploding metallic structures. The technique has been successfully applied by Loughborough along the years in a very wide range of pulsed power applications, including pulsed ultrahigh magnetic field coils [12], explosively driven fluxcompression generators [13], [14], single and multiturn electromagnetic launchers [15]- [17], electromagnetic launchers [15]- [17], electromagnetic compression [18], and the design of various types of high-voltage air core pulsed transformers [19].…”

Section: A Generalitiesmentioning

confidence: 99%

“…The system is firstly solved algebraically for the time rate of change of the unknowns and then integrated using the initial conditions. More information about the implementation of the 2-D filamentary technique can be found in [12].…”

Section: Flyer 2-d Dynamicsmentioning

confidence: 99%

Numerical Modelling of a Flyer Plate Electromagnetic Accelerator

Novac

Omar²,

Graneau³

et al. 2012

IEEE Trans. Plasma Sci.

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A joint program involving the study and practical performance of a foil-flyer electromagnetic accelerator has recently been initiated by Atomic Weapons Establishment, Aldermaston, and Loughborough University. As an initial phase of the work, both 0-D and 2-D numerical models for the foil-flyer accelerator have been developed. The 0-D model, although very crude, is capable of providing an insight into the accelerator phenomena and is currently used for parametric design studies. The 2-D model is based on the well-proven Loughborough filamentary modeling technique and is capable of accurately calculating the 2-D distribution of current, velocity, acceleration, and temperature of the flyer, together with the complete distribution of the magnetic and electric fields generated during a shot. The paper presents the two models and compares typical theoretical predictions with the corresponding experimental results.

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Experimental and Numerical Studies of Megagauss Magnetic-Field Generation at LANL-NHMFL

Cited by 24 publications

References 4 publications

Circular polarization dependent cyclotron resonance in large-area graphene in ultrahigh magnetic fields

Circular polarization dependent cyclotron resonance in large-area graphene in ultrahigh magnetic fields

A novel current density distribution sensor for use in parallel plate transmission lines

Numerical Modelling of a Flyer Plate Electromagnetic Accelerator

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