Advanced Design of a Low Energy Electron Source

A multiphysics-based modeling design of a low energy electron source using a thermionic cathode is described in this paper. The proposed device produces a narrow beam employable in delicate applications where dimensions are critical. The effects of multiple physics influencing factors due to the cathode heating over the beam dynamics have been predicted through a multiphysics design approach. This paper would provide the needed knowledge for virtual prototyping of such devices. For this aim, several strategies have been adopted to obtain a simple model, which shows clearly the investigated mechanisms. According to this study, the appropriate materials and shapes can be chosen

SUB-RADIANCE AND THE COHERENCE LIMITS OF FEL*

Abstract The e-beam and radiation wave dynamics in the radiating and non-radiating beam transport sections of Free Electron Lasers are analyzed in the collective regime by use of a single transverse mode linear response formulation. This is employed to derive conditions for coherent operation of seeded high gain FELs. It is shown that the level of incoherent self-amplified spontaneous emission (SASE) radiation power can be controlled by adjusting the plasma oscillation phase in the non-radiating beam transport sections preceding the FEL, and that at short wavelengths the FEL coherence is limited by energy noise (rather than current shot-noise), and ultimately by quantum noise

Enhancing Electron Beam Radiative Energy Extraction Efficiency in Free-Electron Laser Oscillators Through Beam Energy Ramping

Free-electron lasers are used to generate laser radiation using an accelerated electron beam. In this paper, an electrostatic accelerator was used with a thermionic cathode. Lasing pulses of the order of tens of microseconds were generated by passing the current pulses through a wiggler and resonator combination. The change in lasing power as a result of postsaturation variation of the energy of the electron beam during the lasing period is presented in this paper in the form of experimental measurements and simulations. In the experiments, the initial electron beam energy was similar to 1.4 MeV and the current was 1.13 A, whilst the lasing frequency was always close to 102 GHz. It is shown that postsaturation, positively ramping the beam energy increases the radiation extraction efficiency by around 50%. Whilst a falling beam energy results in a reduction in extraction efficiency

Design of a sub-millimetric electron gun with analysis of thermomechanical effects on beam dynamics

This paper describes a particular design of a thermionic electron gun employable in Sub-millimetric waves vacuum tubes and for spatial environment applications. Design strategies are proposed by providing closed formulas and dimensioning techniques. A multiphysics approach has been employed for studying the effect of multiple physics influencing factors due to the cathode heating over the beam dynamics. Operating temperature, thermal expansion displacements and external environment effects have been considered. This paper would give the academic knowledge for developing electron sources with narrow dimension providing an analytical approach followed by numerical modeling technique for virtual prototypes, which foresee the global behavior of this kind of devices while operating. For this aim, several strategies have been adopted and described in detail to obtain a simple model, which shows clearly these effects and their relations. The proposed modeling can allow for the correct operation in this range of narrow dimensions, where the operation is extremely critical while the cathode heating effects are present. According to this study, the appropriate materials and geometrical shapes for the beam-forming electrodes can be chosen

Superradiant and stimulated-superradiant emission in prebunched electron-beam radiators. II. Radiation enhancement schemes

Further enhancement of the intense coherent superradiant and stimulated-superradiant emission from prebunched electron beams is possible, in schemes of prebunched beam radiation devices, and particularly free electron laser (FEL). The enhancement of coherent power and spectral power by use of a waveguide, particularly at the zero-slippage condition, is evaluated. A special scheme of a stimulated-superradiance FEL oscillator is analyzed and is shown to feature ultimate radiative energy conversion efficiency (near 100%)