| 1. |
- Raadu, Michael, et al.
(author)
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Charge fluctuation effects on solitary waves in dusty plasmas
- 2005
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In: New Vistas in Dusty Plasmas. - : AIP. - 0735402876 ; , s. 486-489
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Conference paper (peer-reviewed)abstract
- In a dusty plasma the charge on a moving dust grain changes in response to the variations in the local plasma conditions. The charge on a slowly moving grain should be close to a locally determined equilibrium. For a time independent electrostatic structure an integral of motion for a grain with varying charge can then be found. Solutions of Vlasov's equation are given by arbitrary functions of these integrals of motion, so that, using the Poisson equation, a generalised Sagdeev (Classical) potential can be found (Raadu, 2003, Phys. Scripta vol.68, 266). Solitary wave solutions may be investigated making use of this generalised Sagdeev potential. The influence of charge fluctuations on the range of parameters for the existence of solitary waves is considered here. A modified form of the relation between the amplitude and the wave velocity is found.
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| 2. |
- Shafiq, Mohammad, et al.
(author)
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Delayed shielding of a test charge due to dynamical grain charging in a dusty plasma
- 2004
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In: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 32, s. 627-631
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Journal article (peer-reviewed)abstract
- The dynamical charging of grains in a dusty plasma modifies the plasma dielectric response function and the nature of the electrostatic wave modes. The grain charging leads to an additional shielding effect that acts in the same way as Debye shielding. Both the additional shielding and the charging rate are important in determining the response of a dusty plasma to a moving test charge. The dynamics of the charging can be approximated by using a time delay. An alternative analysis of the potential of a slowly moving test charge is performed introducing a delay operator for the grain charge response. The terms in the potential that depend on the charging dynamics involve a spatial shift given by the test charge velocity and the charging time. This gives a physical interpretation of earlier results which are identical to first order in the test charge velocity.
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| 3. |
- Shafiq, Mohammad, et al.
(author)
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Effect of grain charging dynamics on the wake potential of a moving test charge in a dusty plasma
- 2007
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In: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 14:1, s. 012102-
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Journal article (peer-reviewed)abstract
- The response potential of a dusty (complex) plasma to a moving test charge strongly depends on its velocity. For a test charge moving with a velocity exceeding the dust-acoustic speed, a distinctive wake-field is produced trailing behind the test charge. Here the response to a fast moving test charge, when dispersion effects are small and the dust behaves as a cold plasma component, is considered. The effects of dynamical grain charging are included, and the cases with and without these effects are analyzed and compared. The plasma dielectric function is chosen assuming that all grains are of the same size and includes a response term for charging dynamics. The wake field potential is found either explicitly in terms of known functions or by using numerical methods for the integral expression. Maximum response is found on the wake cone with apex angle determined by the ratio between the dust acoustic velocity and the test charge velocity. The structure of the wake field stretches in the direction of the test charge velocity when this increases. The functional form of the field is given by separately changing the length scales parallel and perpendicular to the velocity. The potential on the axis gives an electric field close behind the test charge that can attract charges with the same sign. The grain charging dynamics leads to a spatial damping and a phase shift in the potential response.
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| 4. |
- Shafiq, Mohammad, et al.
(author)
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Energy loss of test charges in a dusty plasma in the presence of dynamical grain charging, in New Vistas in Dusty Plasmas
- 2005
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In: New Vistas in Dusty Plasmas. - : AIP. - 0735402876 ; , s. 490-493
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Conference paper (peer-reviewed)abstract
- Thedynamical charging of dust grains is an important process andis found to enhance the shielding of a test chargepassing through a multi-component dusty plasma. In the present work,the energy loss of a test charge projectile passing througha dusty plasma in the presence of dynamical grain chargingis studied. The electric forces can be written in termsof the Maxwell stress tensor for a sphere around thetest charge. For sphere with radius tending to zero theforce is just that on the test charge. For afinite radius, forces on the plasma are also included whichmakes it possible to see how the force on thetest charge is balanced by the force on the plasma.The method fails for the zero radius but the dragforce can be found from a simple physical model. Thegeneral analytical results are presented and are compared with theprevious results.
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| 5. |
- Shafiq, Mohammad, et al.
(author)
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Test charge response for a dusty plasma with both grain size distribution and dynamical charging
- 2007
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In: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 14:1, s. 012105-
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Journal article (peer-reviewed)abstract
- The form of the grain size distribution strongly influences the linear dielectric response of a dusty plasma. For a class of size distributions and a thermal velocity distribution, there is an equivalence to a Lorentzian distribution of monosized particles. The electrostatic response to a slowly moving test charge can then be found. Dynamical charging of grains in a dusty plasma leads to an enhanced time-dependent shielding of a test charge. Here the combined effect of both grain size distribution and dynamical grain charging on the response to a slowly moving test charge is analyzed. The dynamical charging contribution to the plasma dielectric has a complicated dependence on the parameters for the size distribution and on the charging rate. However, this dependence can be expressed in terms of known functions. Series expansions are used to derive the potential response to a slowly moving test charge. Previously known results may be recovered as special limiting cases of this investigation. The analytical expression for the plasma dielectric may be used for more general cases and is applicable to the study of electrostatic waves.
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| 6. |
- Shafiq, Rehan, et al.
(author)
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Optical Transmission Plasmonic Color Filter with Wider Color Gamut Based on X-Shaped Nanostructure
- 2022
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In: Photonics. - : MDPI. - 2304-6732. ; 9:4
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Journal article (peer-reviewed)abstract
- Extraordinary Optical Transmission Plasmonic Color Filters (EOT-PCFs) with nanostructures have the advantages of consistent color, small size, and excellent color reproduction, making them a suitable replacement for colorant-based filters. Currently, the color gamut created by plasmonic filters is limited to the standard red, green, blue (sRGB) color space, which limits their use in the future. To address this limitation, we propose a surface plasmon resonance (SPR) color filter scheme, which may provide a RGB-wide color gamut while exceeding the sRGB color space. On the surface of the aluminum film, a unique nanopattern structure is etched. The nanohole functions as a coupled grating that matches photon momentum to plasma when exposed to natural light. Metals and surfaces create surface plasmon resonances as light passes through the metal film. The plasmon resonance wavelength can be modified by modifying the structural parameters of the nanopattern to obtain varied transmission spectra. The International Commission on Illumination (CIE 1931) chromaticity diagram can convert the transmission spectrum into color coordinates and convert the spectrum into various colors. The color range and saturation can outperform existing color filters.
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