Bunch lengthening in single-bunch mode of UVSOR storage ring

The bunch lengthening and widening in the single-bunch mode of the UVSOR electron storage ring were measured. Certain thresholds were observed in the measurement and they were consistent with the thresholds determined by the balance between the bunch lengthening due to the distortion of the acceleration potential well and the microwave instability. The longitudinal coupling impedance of the UVSOR ring was obtained with the threshold current. The horizontal bunch widening of the beam was also observed above the threshold current. (author)