Design of a low-emittance 2.5-GeV pohang light source lattice
The Pohang Light Source (PLS) storage ring is a synchrotron light source with the emittance of 18.9 nm at 2.5 GeV. We designed a new lattice with an achromat of the emittance of 13 nm that may provide more brilliant synchrotron radiation. We investigated dependence of the dynamic aperture on the betatron tune to search for large dynamic aperture in the low-emittance lattice by a simulation method. We examined the dynamic apertures by a tune survey within a specified tune space without and with machine errors. It is also shown that how large is the dynamic aperture in the storage ring after correction of a closed orbit distortion. The operating tune for the low-emittance lattice can be chosen on the view point of dynamic apertures obtained from a tune survey. The low-emittance lattice with the achromat shows the reduced horizontal and vertical beam sizes by 10% and 29% in the positions of insertion devices and by 31% and 52% in the bending magnets than the present lattice, respectively. It is also shown that the low-emittance lattice with 13 nm may provide sufficient dynamic aperture without changing of configuration of magnets in the storage ring.
Lattice related brilliance increase at the ESRF
The ESRF brilliance is currently being increased by more than two orders of magnitude with respect to the original design target value of 1018 photons/sec/mm2/mrad2/0.1% relative bandwidth by acting on the stored beam current, the refinement of the insertion device technology and beam emittances. This paper reviews the lattice-related contribution to the on-going improvements of the initial performances in brilliance of the source: modifications in the tuning of the basic Chasman-Green lattice enabling the reduction of the horizontal emittance from the design 7 nm down to 4 nm, strategy to control the coupling below 1%, optimization of the beta functions in the insertion devices. This already brought a factor of 30 in brilliance. The potential for a further improvement in the brilliance by a factor of ten is described.
POSSIBLE RETUNING OF THE ESRF STORAGE RING LATTICE FOR REDUCING THE BEAM EMITTANCE
The possibility of reducing the emittance in the ESRF storage ring in order to increase the brilliance of emitted photon beams has been investigated. In this paper, it is shown that by breaking the doub!y achromatic condiifion of the Chasman-Green lattice, a reduction by a factor of about two of the horizontal emittance looks feasible.