A whistler-pumped free electron laser

Abstract

A relativistic electron beam in the presence of a whistler wave excites a negative-energy beam space charge mode and a high frequency laser radiation (ω1≫ωc). The instability is explosive for a copropagating beam and the whistler pump, resulting in the excitation of an intense laser in a short pulse. The explosion time τ={(4/kv0)[(ω1−k1vb−ωc) γ0ω1/(ω1−k1vb)ω′pb]1/2}. For both the counterpropagating beam and the whistler wave, the instability is nonexplosive. The laser frequency in this case is somewhat larger, whereas the exponentiation time is comparable to the explosion time of the earlier case.

Stimulated Brillouin scattering of a laser beam in a plasma channel

“…one (5) where vo = eEo/imojo and vi = eEi/imu>i are the oscillatory velocity of plasma electrons due to the pump and the sideband (backscattered) electromagnetic waves. The ponderomotive and self-consistent low-frequency forces eV((f> + 4>p) on the electrons drive a low-frequency density perturbation n e at (to, k).…”

“…Balakirev et al have predicted an explosive mode of operation of FEL with the employment of slow Langmuir waves. Sharma and Tripathi [5] have proposed the scheme of a whistler-pumped FEL which offers high gain in the vicinity of cyclotron resonance. Chen and Dawson [6]-[8] have recently proposed yet another exciting concept of an ion ripple laser (IRL) which can produce short wavelengths with the modest energy electron beams.…”

Effect of axial magnetic field tapering on whistler-pumped FEL amplifier in collective Raman regime operation

“…The HUMAN BODY is the best example of free electron lasers that produces radiated energy after gyrated foods (seed-signal) into the human body chamber interact with water as e-beams and finally dumped it through depressed collector. Sharma et al [9] examined the operation of the electromagnetic and electrostatic wiggler with whistler pumped free electron laser for the higher frequencies. They have also studied the feasibility of the FELs in the low-current Compton Regime (CR), however practically, in the Compton regime, the whistler wave does not exist as suitable wiggler for FEL Amplifier operation due to requirements of extremely high pump power density (10)(11)(12)(13)(14)(15) Tesla for operating frequencies scaled upto 200-250 GHz) for reasonable growth rate, hence including the effect of finite space charged mode, Raman Regime operation plays an important role in whistler-pumped FEL only [10] [11].…”

Numerical investigations on the effects of geometrical parameters on free electron laser instability

“…Granatstein and Sprangle [11] and Carmel et al [12] have proposed a theory of a FEL pumped by an electromagnetic wave as a wiggler. Sharma and Tripathi [13] have proposed the use of a whistler wave as a pump in a FEL. Jaiman and Tripathi [14] have studied the parametric up-conversion of a transverse magnetic TM mode.…”