Author: Bratman, V.L.
Paper Title Page
MOP009 Efficient Electron Sources of Coherent Spontaneous Radiation with Combined Helical and Uniform Magnetic Fields 43
  • N. Balal, V.L. Bratman, E. Magori
    Ariel University, Ariel, Israel
  • V.L. Bratman
    IAP/RAS, Nizhny Novgorod, Russia
  We discuss two methods to mitigate repulsion of particles in dense electron bunches from photo-injectors and to enhance the power of terahertz radiation. First, the repulsion may be reduced with both very short bunches and undulator periods, reducing the length of a radiation section. According to simulations bunches with duration (50-100) fs, charge (50-200) pC, and energy 6 MeV could fairly effectively radiate at frequencies up to (10-20) THz. The undulator for such a source can be formed by means of redistribution of a solenoid field by a non-magnetized iron helix and a permanently magnetized helix. The second source is based on an idea proposed by A.V. Savilov for electron bunching under conditions when the cyclotron electron frequency is larger than the undulator frequency, and an increase of particle energy in the bunch Coulomb field leads to a decrease in longitudinal momentum and attraction of particles (this effect is analogous to the cyclotron negative-mass instability). A large value of the required uniform field can be used to easily obtain the needed undulator field by placing a simple iron helix inside a pulsed solenoid. Simulations confirm that the corresponding particle attraction can provide a powerful and narrowband radiation at the frequencies (1-3) THz.  
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