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For many years, scientists around the world have sought an ultra-low-emittance ring-based light source that offers greater performance than existing third-generation light sources. Pioneering work on the seven-bend lattice for MAX IV [1] initiated these efforts. Another significant development was the scheme for nonlinearity control based on “phase-matched” sextupole pairs. This configuration, first introduced in a light source design by the ESRF design group [2], efficiently suppresses strong nonlinear resonances induced by sextupoles for chromaticity correction. Since a small dynamic aperture due to the strong nonlinearities mentioned earlier presents a great obstacle when we attempt to lower the beam emittance of a high-energy light source using individual bending magnets with small deflection angles, the ESRF scheme contributes significantly to the emittance reduction that can be practically achieved. [ABSTRACT FROM PUBLISHER]

A novel scheme to reduce transverse beam emittance in a ring accelerator is proposed by using a pair of coupling cavities as a basic unit to control damping partition numbers. As indicated by Robinson in 1958, a simple rf electromagnetic field (e.g., a TM210 mode by a single coupling cavity) cannot control the damping partition of three eigenoscillation modes in a ring accelerator due to the cancellation between the contributions from the magnetic and electric fields. Based on both analytical and numerical studies, we show that a pair of coupling cavities that satisfy phase and optics matching conditions can overcome this cancellation. The results indicate that the horizontal emittance is reducible to the theoretical limit based on the steady state condition and also, the emittance is reducible below the reduction limit under a nonsteady state by driving the coupling cavities with gated signals. [ABSTRACT FROM AUTHOR]

The CeB6(001) single crystal used as a cathode in a low‐emittance electron gun and operated at the free‐electron laser facility SACLA was investigated using cathode lens electron microscopy combined with X‐ray spectroscopy at SPring‐8 synchrotron radiation facility. Multilateral analysis using thermionic emission electron microscopy, low‐energy electron microscopy, ultraviolet and X‐ray photoemission electron microscopy and hard X‐ray photoemission spectroscopy revealed that the thermionic electrons are emitted strongly and evenly from the CeB6 surface after pre‐activation treatment (annealing at 1500°C for >1 h) and that the thermionic emission intensity as well as elemental composition vary between the central area and the edge of the old CeB6 surface. [ABSTRACT FROM AUTHOR]

An ultra-high-precision clock system for long time delay has been developed for picosecond time-resolved x-ray diffraction measurements using synchrotron radiation (SR) pulses and synchronized femtosecond laser pulses. The time delay control between pump laser pulse and the probe SR pulse was achieved by combining an in-phase quadrature modulator and a synchronous counter. This method allowed us to change the delay time by a nearly infinite amount while maintaining the precision of ±8.40 ps. Time-resolved diffraction measurements using the delay control system were demonstrated for precise measurement of an acoustic velocity in a single crystal of gallium arsenide. [ABSTRACT FROM AUTHOR]