Effects of emittance and energy spread in an electron bunch on THz radiation generated by a super-radiant source : report III of the series of reports by the Swedish FEL Center and FREIA Group

In this report we summarize our results on simulation of a super-radiant sourceoperating at the THz spectral range. We consider an open-type undulator com-prising plane magnets but without any guiding structure for generated THz eld.The undulator is assumed to be driven by electron bunches of femtosecond durationwhich are produced by an rf Linac. Using a numerical model developed, we analyzeeects of the bunch parameters on output performance of the super-radiant sourceand reveal some surprising results. Specically, we show that degradation in bunchspatial quality (increase in the bunch emittance) should lead to decrease in angulardivergence and spectral narrowing of the THz radiation. We also demonstrate thatelectron energy spread which commonly leads to bunch broadening and radiativeenergy drop can be eventually suppressed under appropriate conditions

Effects of emittance and energy spread in an electron bunch on THz radiation generated by a super-radiant source : report III of the series of reports by the Swedish FEL Center and FREIA Group

In this report we summarize our results on simulation of a super-radiant sourceoperating at the THz spectral range. We consider an open-type undulator com-prising plane magnets but without any guiding structure for generated THz eld.The undulator is assumed to be driven by electron bunches of femtosecond durationwhich are produced by an rf Linac. Using a numerical model developed, we analyzeeects of the bunch parameters on output performance of the super-radiant sourceand reveal some surprising results. Specically, we show that degradation in bunchspatial quality (increase in the bunch emittance) should lead to decrease in angulardivergence and spectral narrowing of the THz radiation. We also demonstrate thatelectron energy spread which commonly leads to bunch broadening and radiativeenergy drop can be eventually suppressed under appropriate conditions

Effects of emittance and energy spread in an electron bunch on THz radiation generated by a super-radiant source : report III of the series of reports by the Swedish FEL Center and FREIA Group

In this report we summarize our results on simulation of a super-radiant sourceoperating at the THz spectral range. We consider an open-type undulator com-prising plane magnets but without any guiding structure for generated THz eld.The undulator is assumed to be driven by electron bunches of femtosecond durationwhich are produced by an rf Linac. Using a numerical model developed, we analyzeeects of the bunch parameters on output performance of the super-radiant sourceand reveal some surprising results. Specically, we show that degradation in bunchspatial quality (increase in the bunch emittance) should lead to decrease in angulardivergence and spectral narrowing of the THz radiation. We also demonstrate thatelectron energy spread which commonly leads to bunch broadening and radiativeenergy drop can be eventually suppressed under appropriate conditions

Multimode dynamics in a short-pulse THz free electron laser

The interaction of waveguide modes and consequences on laser operation are studied numerically in a THz free electron laser (FEL) driven by short electron bunches. The considered FEL cavity configuration is represented by a parallel-plate waveguide extending over the complete distance between cylindrical cavity mirrors with energy out-coupling through a rectangular slit in one of the mirrors. We describe the multimode FEL cavity desynchronization dynamics and predict strong enhancement in FEL power at special cavity configurations, when modes are degenerate. Furthermore, we predict that simultaneous excitation of several waveguide modes can occur but do not negatively influence the lasing process

High-resolution measurement of the electron affinity of cesium

Negative ions are unique quantum systems where electron correlation plays a decisive role in determining their properties. The lack of optically allowed transitions prevents traditional optical spectroscopy and the electron affinity is, therefore, for most elements, the only atomic quantity that can be determined with high accuracy. In this work, we present a high-precision experimental determination of the electron affinity of cesium. A collinear laser-ion beam apparatus was used to investigate the partial photodetachment cross section for the cesium anion, leaving the neutral atom in the 6p2P3/2 excited state. A resonance ionization scheme was used to obtain final-state selectivity, which enabled the investigation of a sharp onset of the cross section associated with a Wigner s-wave threshold behavior. The electron affinity was determined to be 0.471 598 3(38) eV