N. Sei et al., BEAM QUALITY IN STORAGE-RING NIJI-IV, Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 393(1-3), 1997, pp. 38-43
Several remedies to achieve a high peak current with storage ring NIJI
-IV are presented. We observe a bunch lengthening and a limitation on
the single-bunch current, which reduces the FEL gain remarkably. To su
ppress with the coupled-bunch instability, we install a longitudinal f
eedback system which consists of the phase detector and phase shifter.
This feedback system effectively suppresses the coupled-bunch instabi
lity and shortens the electron bunch. However. we need a solution to t
he limitation on the single-bunch current originated from a head-tail
instability. Quadrupole and 6-pole magnets have been designed to be in
stalled in a restricted space between bending magnets. Calculations on
the injection orbit and dynamical aperture show that there should be
a large aperture in the ring with the small bore, 45 mm. The installat
ion of these small bore magnets will be started coming Autumn.