We present plans for a positron-source test stand in OSFA. The test stand will be installed in a separate branch downstream of linac-3 to make use of SwissFEL's 6 GeV accelerator as a flexible driver linac. The international FCC study group published in 2019 a Conceptual Design Report for an electron-positron collider with a centre-of-mass energy from 90 to 365 GeV, a circumference of 98 km and beam currents of up to 1.4 A per beam. The high beam currents of this collider create challenging requirements on the injection chain. The e+e- injector linac should provide a minimum beam energy of 6 GeV using S-band and/or C-band normal-conducting RF structures with a bunch population up to 6.7 nC. All aspects of the linac need to be carefully reconsidered and revisited, including the injection time structure. The accelerating field and the RF power generation scheme must be optimised taking into account the infrastructure costs and limitations. Furthermore, two different kinds of e- bunches have to be generated, one for direct injection, the second for e+ generation. These two bunches have different requirements, in particular the bunch population typically differs by a factor of two. For this reason, a comparative study of two solutions for a single gun or two dedicated guns should be carried out. The entire beam dynamics studies for the full linac, damping ring and transfer lines are other major activities of the injector studies. However, a key point is that any increase of positron production and capture efficiency reduces the cost and complexity of the driver linac, the heat and radiation load of the converter system, and increases the operational margin. Therefore, any progress with R&D on the target and capture systems will have a direct benefit for the FCC-ee injector chain. In this context, the positron source demonstrator for novel integrated target and capture concepts is planned at PSI. All these activities are part of a CHART-approved proposal involving a collaboration between PSI and CERN with several external collaborators, such as IJCLab, BINP and LNF/INFN.
