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S. Son

Publications and source records attributed to S. Son.

At least 37 records · Page 2Linked to original sources
arXiv2013

THz radiation by the frequency down-shift of Nd:YAG lasers

The interaction between an intense laser and a relativistic dense electron beam propagating in the same direction could down-shift the laser frequency. This process, which can be used to generate a coherent THz radiation, is theoretically analyzed. With a set of practically relevant parameters, it is suggested that the radiation energy could reach the order of 1 mJ per shot in the duration of 100 pico-second, or the temporal radiation power of 10 MW.

physics.optics↗
arXiv2013

THz radiation by beating Langmuir waves

An intense terahertz (THz) radiation generated by the beating of two Langmuir waves, which are excited by the forward Raman scattering, is analyzed theoretically. The radiation energy per shot can be as high as 0.1 J, with the duration of 10 pico-second. Appropriate plasma density and the laser characteristics are examined.

physics.optics↗
arXiv2012

Unstable electromagnetic modes in strongly magnetized plasmas

The electromagnetic modes possibly unstable in strongly magnetized plasmas are identified. The regime where this instability might stand out compared to the incoherent electron-cyclotron radiation is explored. These modes are relevant to the inertial confinement fusion and the gamma ray burst.

physics.plasm-ph↗
arXiv2012

Cyclotron Resonance in Strongly Magnetized Plasmas and Gamma Ray Burst

A plausible scenario for the gamma ray and the hard x-ray burst in a strongly magnetized plasma, based on the collective plasma maser instability, is proposed. The physical parameters with which this scenario becomes relevant are estimated. The attractive feature of this scenario over the conventional cyclotron radiation theory is discussed.

physics.plasm-ph↗
arXiv2012

Entropy Maximization and Instability of Uniformly Magnetized Plasma

A regime where a uniformly magnetized plasma could be unstable to a spatial perturbation in the magnetic field is explored. In this regime, a uniformly magnetized state does not maximize the entropy. The physical implication is discussed in the context of the current generation, the magnetic reconnection, and the dynamo effect.

physics.plasm-ph↗
arXiv2012

Overcoming the Child-Langmuir law via the magnetic mirror effect

The maximum current in a vacuum tube prescribed by the classical Child-Langmuir law can be overcome, when the space-charge effect of the induced potential is mitigated by the mirror effect in a spatially varying magnetic field. The current could exceed the Child-Langmuir value by as much as a few factors. The regime of practical interest is examined.

physics.plasm-ph↗
arXiv2012

Hard x-ray or gamma ray laser by a dense electron beam

A coherent x-ray or gamma ray can be created from a dense electron beam propagating through an intense laser undulator. It is analyzed by using the Landau damping theory which suits better than the conventional linear analysis for the free electron laser, as the electron beam energy spread is high. The analysis suggests that the currently available physical parameters would enable the generation of the coherent gamma ray of up to 100 keV. The electron quantum diffraction suppresses the FEL action, by which the maximum radiation energy to be generated is limited.

quant-ph↗
arXiv2011

Helical relativistic electron beam and THz radiation

A THz laser generation utilizing a helical relativistic electron beam propagating through a strong magnetic field is discussed. The initial amplification rate in this scheme is much stronger than that in the conventional free electron laser. A magnetic field of the order of Tesla can yield a radiation in the range of 0.5 to 3 THz, corresponding to the total energy of mJ and the duration of tens of pico-second, or the temporal power of the order of GW.

physics.optics↗
arXiv2011

X-ray Raman compression via two-stream instability in dense plasmas

A Raman compression scheme suitable for x-rays, where the Langmuir wave is created by an intense beam rather than the pondermotive potential between the seed and pump pulses, is proposed. The required intensity of the seed and pump pulses enabling the compression could be mitigated by more than a factor of 100, compared to conventionally available other Raman compression schemes. The relevant wavelength of x-rays ranges from 1 to 10 nm.

physics.plasm-ph↗
arXiv2010

Enhanced damping of ion acoustic waves in dense plasmas

A theory for the ion acoustic wave damping in dense plasmas and warm dense matter, accounting for the Umklapp process, is presented. A higher decay rate compared to the prediction from the Landau damping theory is predicted for high-Z dense plasmas where the electron density ranges from $10^{21}$ to $ 10^{24} \mathrm{cm^{-3}}$ and the electron temperature is moderately higher than the Fermi energy.

physics.plasm-ph↗
arXiv2010

Forward Raman compression via photonic band gap in metals or warm dense matter

The group velocity of a light pulse in photonic band gap material could considerably deviate from the speed of light in vacuum. Different speeds of a forward stoke and a pump pulse would enable the Raman compression in metals or the warm dense matter. A small window of the parameter regime, where the compression is feasible via the forward Raman scattering, is identified.

physics.plasm-ph↗
arXiv2010

Decay of Langmuir wave in dense plasmas and warm dense matter

The decays of the Langmuir waves in dense plasmas are computed using the dielectric function theory widely used in the solid state physics. Four cases are considered: a classical plasma, a Maxwellian plasma, a degenerate quantum plasma, and a partially degenerate plasma. The result is considerably different from the conventional Landau damping theory.

physics.plasm-ph↗
arXiv2010

Theory of plasmon decay in dense plasmas and warm dense matter

The decay of the Langmuir waves in dense plasmas is not accurately predicted by the prevalent Landau damping theory. A dielectric function theory is introduced, predicting much higher damping than the Landau damping theory. This strong damping is in better agreement with the experimentally observed data in metals. It is shown that the strong plasmon decay leads to the existence of a parameter regime where the backward Raman scattering is unstable while the forward Raman scattering is stable. This regime may be used to create intense x-ray pulses, by means of the the backward Raman compression. The optimal pulse duration and intensity is estimated.

physics.plasm-ph↗
arXiv2010

Suppression of Landau damping via electron band gap

The pondermotive potential in the X-ray Raman compression can generate an electron band gap which suppresses the Landau damping. The regime is identified where a Langmuir wave can be driven without damping in the stimulated Raman compression. It is shown that the partial wave breaking and the frequency detuning due to the trapped particles would be greatly reduced.

physics.plasm-ph↗
arXiv2010

Plasmon band gap generated by intense ion acoustic waves

In the presence of an intense ion acoustic wave, the energy-momentum dispersion relation of plasmons is strongly modified to exhibit a band gap structure. The intensity of an ion acoustic wave might be measured from the band gap width. The plasmon band gap can be used to block the nonlinear cascading channel of Langmuir wave decay

physics.plasm-ph↗
arXiv2010

Photonic band gap and x-ray optics in warm dense matter

Photonic band gaps for the soft x-rays, formed in the periodic structures of solids or dense plasmas, are theoretically investigated. Optical manipulation mechanisms for the soft x-rays, which are based on these band gaps, are computationally demonstrated. The reflection and amplification of the soft x-rays, and the compression and stretching of chirped soft x-ray pulses are discussed. A scheme for lasing with atoms with two energy levels, utilizing the band gap, is also studied.

physics.plasm-ph↗
arXiv2010

Backward Raman compression of x-rays in metals and warm dense matters

Experimentally observed decay rate of the long wavelength Langmuir wave in metals and dense plasmas is orders of magnitude larger than the prediction of the prevalent Landau damping theory. The discrepancy is explored, and the existence of a regime where the forward Raman scattering is stable and the backward Raman scattering is unstable is examined. The amplification of an x-ray pulse in this regime, via the backward Raman compression, is computationally demonstrated, and the optimal pulse duration and intensity is estimated.

physics.plasm-ph↗