Highly coupled off-resonance lattice design in diffraction-limited light sources

The round-beam operation presents many benefits for scientific experiments regarding synchrotron radiation and the weak-ening influences of intra-beam scattering in diffraction-limited synchrotron light sources.A round-beam generation method based on the global setting of skew quadrupoles and the application of a non-dominated sorting genetic algorithm was pro-posed in this study.Two schemes,including large-emittance coupling introduced via betatron coupling and vertical disper-sion,were explored in a candidate lattice for an upgrade-proposal of the Shanghai synchrotron radiation facility.Emittance variations with lattice imperfections and their influence on the beam dynamics of beam optic distortions were investigated.The results demonstrated that a precise coupling control ranging from 10 to 100%was achieved under low optical distortion,whereas full-coupling generation and its robustness were achieved by our proposed method by adjusting the skew quadrupole components located in the dispersion-free sections.The Touschek lifetime increased by a factor of 2–2.5.

High resolution spectroscopy of Rb in magnetic field by far-detuning electromagnetically induced transparency

We have presented a high resolution spectroscopy of Rb in magnetic field by far-detuning electromagnetically induced transparency(EIT).The EIT spectrum in theΞ-type configuration is usually companied by a double resonance optical pumping(DROP)due to the strong optical coupling between the two upper states,leading to the spectral lines seriously deformed and widely broadened for complex relaxation processes in DROP.Here we demonstrate a high resolution spectroscopy by far-detuning EIT for^(87)Rb 5S_(1/2)→5P_(3/2)→5D_(5/2)in magnetic fields.The method of far-detuning eliminates the relaxation in DROP to the most extent and decreases the spectral linewidth from more than 20 MHz down to its natural linewidth limit(6 MHz).The deformation of the spectral lines also disappears and the observed spectra are well in accordance with the theoretical calculation.Our work shows that far-detuning EIT is a reliable high resolution spectroscopic method when the relaxation in DROP cannot be neglected,especially for the case of transition to low excited states.

Improving the off-resonance energy harvesting performance using dynamic magnetic preloading

Piezoelectric stack transducers in d33 mode have a much higher mechanical-to-electric energy conversion efficiency compared with d3l mode piezoelectric harvesters.However,multilayered piezoelectric stacks usually operate in off-resonance due to the higher stiffness and thereby have a lower power output under low-frequency excitations.This paper proposes to apply the dynamic magnetic pre-loading to a piezoelectric stack transducer to significantly increase the power output.The energy harvesting system consists of a multilayered piezoelectric stack with a compliant force amplification frame,a proof mass,and two magnets configured in attraction.The static force-displacement relationship of the magnets is identified from experiments and extended to a dynamic model capable of characterizing the dynamic magnetic interaction.An electromechanical model is developed based on the theoretical derivation and the experimentally identified parameters to predict the voltage outputs under different resistive loads.Approximate analytical solutions are derived by using the harmonic balance method and show good agreements with the numerical and experimental results.The performance of the system is examined and compared with that of the harvester without magnetic pre-loading.The influences of the distance between the two magnets and the electrical resistive loads on the power output are investigated.Results indicate the energy harvesting system with magnetic pre-loading can produce over thousand times more power than the system without magnetic pre-loading at the base excitation of 3 Hz and 0.5 m/s……2,far below the resonance at 243 Hz.