Towards an Upgrade of the Swiss Light Source

An upgrade of the Swiss Light Source (SLS) is planned for the period 2021-24. The existing 12-TBA (triple bend achromat) lattice will be exchanged by a 12-7BA (7-bend achromat) lattice in order to reduce the emittance from present 5.5 nm down to about 125 pm at 2.4 GeV / 400 mA (IBS included). The new lattice is based on longitudinal gradient bends and reverse bends to realize low emittance despite the small circumference of 290 m. A conceptual design has been established. We present project status, lattice design and work in progress with emphasis on beam dynamics issues.