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V M Malkin

Publications and source records attributed to V M Malkin.

9 recordsLinked to original sources
PubMed2004

Pump side scattering in ultrapowerful backward Raman amplifiers.

Extremely large laser power might be obtained by compressing laser pulses through backward Raman amplification (BRA) in plasmas. Premature Raman backscattering of a laser pump by plasma noise might be suppressed by an appropriate detuning of the Raman resonance, even as the desired amplification of the seed persists with a high efficiency. In this paper we analyze side scattering of laser pumps by plasma noise in backward Raman amplifiers. Though its growth rate is smaller than that of backscattering, the side scattering can nevertheless be dangerous, because of a longer path of side-scattered pulses in plasmas and because of an angular dependence of the Raman resonance detuning. We show that side scattering of laser pumps by plasma noise in BRA might be suppressed to a tolerable level at all angles by an appropriate combination of two detuning mechanisms associated with plasma density gradient and pump chirp.

Journal Article↗
PubMed2004

Finite-duration seeding effects in powerful backward Raman amplifiers.

In the process of backward Raman amplification (BRA), the leading layers of the seed laser pulse can shadow the rear layers, thus weakening the effective seeding power and affecting parameters of output pulses in BRA. We study this effect numerically and also analytically by approximating the pumped pulse by the "pi-pulse" manifold (family) of self-similar solutions. We determine how the pumped pulse projection moves within the pi-pulse manifold, and describe quantitatively the effective seeding power evolution. Our results extend the quantitative theory of BRA to regimes where the effective seeding power varies substantially during the amplification. These results might be of broader interest, since the basic equations are general equations for resonant three-wave interactions.

Journal Article↗
PubMed2002

Collective deceleration of relativistic electrons precisely in the core of an inertial-fusion target.

The energy deposition of a relativistic electron beam in a plasma can be managed through turning on or off fast beam-plasma instabilities in desirable regions. This management may enable new ways of realizing the fast-igniter scenario of inertial fusion. Collisional effects alone can decelerate electrons of at most a few MeV within the core of an inertial-fusion target. Beam-excited Langmuir turbulence, however, can decelerate even ultrarelativistic electrons in the core.

Journal Article↗
PubMed2002

Suppression of superluminous precursors in high-power backward Raman amplifiers.

The very promising scheme for producing ultrapowerful laser pulses through Raman backscattering of pump lasers in plasmas can be jeopardized by superluminous precursors. Growing from the leading part of the Raman pumped seed pulse, these precursors can disturb the plasma and the pump ahead of the pumped pulse. These ruinous effects, however, might be averted by a detuning, large enough to suppress the precursors, yet small enough to allow the desired backscatter effect.

Journal Article↗
PubMed2000

Stability of muon beams to Langmuir waves during ionization cooling.

Fast cooling of muon beams will be needed for building either TeV muon colliders that might explore the electroweak gauge symmetry breaking or muon storage rings that could become ultrabright neutrino sources. Stochastic and electron cooling take longer than the muon lifetime, so attention has been focused on the potentially faster but less explored ionization cooling. Addressing recent concerns that excitation of Langmuir waves might be deleterious for ionization cooling techniques, we show that, while the hydrodynamic instability indeed might be dangerous, the waves are, in fact, stabilized through a combination of resistive and kinetic effects at a very modest emittance of the beam.

Journal Article↗
PubMed2000

Stimulated raman scattering of rapidly amplified short laser pulses.

The theory of transient forward stimulated Raman scattering (FSRS) of rapidly amplified short laser pulses is put forth to complement the classical theory for FSRS of stationary pulses. Quantitative conditions for FSRS suppression are identified. In particular, it is shown quantitatively how the limitation imposed by pumped pulse FSRS on the output laser intensity in plasma-based ultrapowerful backward Raman amplifiers can be overcome through a selective detuning of the Stokes resonance.

Journal Article↗
PubMedDate not supplied

[Luminescence of thymine aqueous solutions at the room temperature].

The distinguishing features of luminescence of aqueous thymine solutions at room temperature (a broadening of luminescence spectra as compared with low-temperature spectra and differences between excitation and absorption spectra) are discussed. It is shown that these features are due to bimolecular photochemical reactions that lead to the formation of photoproducts (at the first stages, photoadducts) with a comparatively high luminescence ability.

Luminescence↗
PubMedDate not supplied

[Photochemical revelation of the stacking aggregation of thymine chromophores in water solutions of polythymidylic acid].

The structure heterogeneity of water solutions of polyribothymidylic acid at T(room) was studied from changes caused in their absorption spectra by the photodimerization reaction. Three fractions of thymine chromophores were revealed from the differential absorption spectra: (a) the main fraction consisting of weakly interacting (isolated chromophores) chromophores with the absorption spectrum maximum at approximately 270 nm; (b) pair chromophores of the first type with the absorption spectrum maxima at 260 and 290 nm (exciton splitting 4000 cm(-1)); and (c) pair chromophores of the second type with the absorption spectrum maxima at 250 and 280 nm (exciton splitting 4300 cm(-1)). The revealed aggregates have a relatively high photochemical activity in the photodimerization reaction in comparison with the isolated chromophores. They contribute little to the total absorption spectrum of solutions but make a great contribution to its changes at the initial stages of the UV irradiation of solutions.

Nucleic Acid Conformation↗