Effect of magnetic field tapering on whistler pumped free electron laser

Manish Kumar

doi:10.1063/1.5064751

Abstract

An analytical formalism of whistler pumped free electron laser (FEL) with tapered magnetic field is developed. The tapering raises the efficiency of the device to 7% for typical parameters. The frequency and power of the FEL can be controlled by tuning the plasma density and/or magnetic field also by increasing the energy of electron beam. The angle of injection of electron beam is very crucial for higher efficiency of FEL. Presence of plasma ensures the space charge and current neutralization and larger power handling capacity of the device.

Highlights

The conventional terahertz sources offered very little energies of the order of 10–100 μJ per pulse for the beat excitation of THz radiation using Gaussian laser beams copropagating along the direction of ambient magnetic field in a rippled density plasma channel.1 The measured value of the coherence properties of SACLA (Spring-8 Angstrom Compact Free Electron Laser) on the basis of a single shot at an X-ray are 4 – 30 keV, time of 0.1 fs and a pulse duration of 5.2 fs respectively.2 Vogt, Faatz, Feldhaus, Honkavaara, Schreiber, Treusch3 have examined the free-electron laser FLASH at DESY routinely produces up to several thousand photon pulses per second with 44 nm down to 4.2 nm wavelength at up to 500 μJ pulse energies
We study an effect of linear tapering of the magnetic field on whistler pumped free electron laser and proposed to use a gyrotron source of an electromagnetic wiggler wave that offers the possibility of generating short radiation wavelengths using tapered magnetic field in presence of the uniform background plasma medium
To generate the free electron laser (FEL) in THz frequency range we propose to use gyrotron powered electromagnetic wave wiggler with power density ∼ 2 GW/cm2 at 30 GHz

Summary

Introduction

The conventional terahertz sources offered very little energies of the order of 10–100 μJ per pulse for the beat excitation of THz radiation using Gaussian laser beams copropagating along the direction of ambient magnetic field in a rippled density plasma channel.1 The measured value of the coherence properties of SACLA (Spring-8 Angstrom Compact Free Electron Laser) on the basis of a single shot at an X-ray are 4 – 30 keV, time of 0.1 fs and a pulse duration of 5.2 fs respectively.2 Vogt, Faatz, Feldhaus, Honkavaara, Schreiber, Treusch3 have examined the free-electron laser FLASH at DESY routinely produces up to several thousand photon pulses per second with 44 nm down to 4.2 nm wavelength at up to 500 μJ pulse energies.

Results

Conclusion