T. P. Pandya

Stability of spheroidal drops in homogeneous electric fields

Abstract The deformation of dielectric drops by uniform electric field is studied theoretically. A first-order approximation shows that if the effects of viscosity are neglected the deformed drop takes the shape of a spheroid. The resulting changes in electrostatic and surface energies are calculated and the stability of the spheroidal drop is discussed. The results are compared with those obtained from earlier studies.

Harmonics in FEL with Plane Polarised Wiggler and Axial Guide Field

Spontaneous and coherent emission of radiation in a FEL with planar wiggler and axial magnetic fields is investigated. The eccentricities of the resulting electron trajectory and spontaneous emission are seen to be different. On interaction with e.m. radiation electron orbits give rise to elliptically polarised coherent emission at principal and harmonic frequencies. Beam amplifications at higher harmonics peak at lower axial field strengths. The peak gains are significantly larger than the gain obtained at the next lower frequency in the absence of axial magnetic fields.

Electron Trajectories and Gains in FEL with an Axial Guide Field

Electron trajectories and small signal gains have been evaluated for a FEL with a constant wiggler and strong axial guide field. Two different injections into the wiggler are considered in this paper. The first case is that the electron beam is injected into an ideal helical orbit. In the second case, the electrons are injected parallel to the axial guide field. At the Doppler upshifted wiggler frequency the magnitudes of gain for the two types of injection tend to become identical. At the upshifted Larmor frequency the FEL gain is feasible. In the case of axial injection, small gains at frequencies higher than those obtained with perfect beam injection are also found possible. Effects of space charge, including enhancement in gain are discussed.

Electrostatic interaction of liquid molecule with surroundings

Abstract The deformation of a spherical molecule due to its own reaction field is studied theoretically. The spheroidal shape thus obtained is used to calculate the cohesion energy of polar liquids and also their molecular dipole moments. The latter values are found to be in better agreement with moments measured in the gas phase than those obtained earlier. Relevance of the model in molecular theory of liquids is pointed out.

Single Particle Analysis of Free-Electron Laser with Uniform Axial Electrostatic and Magnetic Fields

The possibility of obtaining significant FEL gain at an upshifted Larmor frequency is examined with the help of single particle analysis in the small gain per pass limit.

New radiation frequency in free-electron lasers with axial guide field

The physical processes involved in energy exchange between the radiation field and relativistic electrons in a free-electron laser cavity with an axial guide field have been discussed in the context of the single-particle dynamics as well as the solution of the Vlasov–Maxwell equations. Thus laser gains have been calculated at the new radiation frequency.

Stability of spheroidal drops in the field of a point charge

Abstract The deformation of dielectric drops in the field of point charge is studied theoretically. Neglecting the effects of viscosity, the resulting changes in electrostatic and surface energies are calculated. Both odd and even modes of deformation are found to exist. The effects of field configuration on stability of the modes is examined. Following the analysis the shape of the stable deformed surface can be predicted.