NEW OPTICS WITH EMITTANCE REDUCTION AT THE SPRING-8 STORAGE RING

The machine tuning of a new optics has been examined at the SPring-8 storage ring. The natural emittance is reduced to 2.41 nmrad from the past value of 3.49 nmrad without any change of magnet positions. The flux density 1.3 times higher than that of the 3.49 nmrad optics was observed at the diagnostics beamline. The nominal injection efficiency of the order of 80 % has been achieved (the 3.49 nmrad optics: 92 %) by correcting the error of the optics function, by adjusting the strength of the injection magnets and by optimizing the sextupole magnetic fields. The beam lifetime was 13 h at 1 mA / bunch (the 3.49 nmrad optics: 22 h), and the momentum aperture estimated from the measurement of the Touschek lifetime was 2.3 % (the 3.49 nmrad optics: 2.8 %). As verifying the photon beam performance at beamlines, this new optics has been applied to the user operation.