## 6 Conclusions and Outlook  
The SwissFEL project has made remarkable progress since it first broke ground in 2013, culminating in first SASE lasing in the soft X-ray domain in May 2017. The Aramis hard X-ray branch of SwissFEL will be operational for users in 2018, with its first call for proposals in the beginning of 2018. Installation of the Athos soft X-ray branch has begun, with expected user operation after 2020 on three photon beamlines. In addition to the components and systems we have described in this review the project has several near-term future upgrades planned, including hard X-ray self-seeding [168,180] and the addition of a third experimental station (Cristallina). Beyond the currently defined Aramis and Athos accelerator infrastructure there are plans to add a third undulator beamline. The building was designed to allow space for this installation in the accelerator tunnel and internal discussions have begun on what the parameters of this project might be. We look forward to joining the thriving hard X-ray free electron laser community [209, 210, 2112] and welcoming researchers from around the world to our exciting new facility in the coming years.  
The authors would like to extend their profound thanks to all of the facilities with whom we have collaborated on this project: ASTeC (Daresbury, UK), SPring-8 (JASRI/RIKEN, Hyogo, Japan), CERN (Geneva, Switzerland), SLAC (Stanford, CA, USA), Elettra Sincrotrone Trieste (Basovizza, Italy), DESY (Hamburg, Germany), and the European XFEL (Schenefeld, Germany). Furthermore the authors acknowledge the advice and support they received throughout the preparation and realization of SwissFEL by the members of the FLAC advisory committee, chaired by [PERSON] (DESY and University of Hamburg), the ESA Review Panel, chaired by [PERSON] (European XFEL and Jan Kochanowski University), the ESB Review Panel, chaired by [PERSON] (ETH Zurich), and the ESB-MX Review Panel, chaired by [PERSON] (LLNL). We would also like to acknowledge the funding and support we have received from the Swiss Federal Government, the ETH Council, the government of the Canton of Aargau, the Swiss National Science Foundation, the town of Wurenlingen, and the Swiss Lottery Fund (Swisslos). Finally we would like to acknowledge the support and effort from all the groups at PSI who have contributed to this project. All authors have contributed in some way to the concept, design, installation and commissioning of different aspects of the SwissFEL project. All authors contributed to the paper either during the writing or editing phases.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
ADC Analog-to-digital converter AGIPD Adaptive Gain Integrating Pixel Detector API Application programming interface ASIC Application-specific integrated circuit BAM Electron bunch arrival-time monitor BBO beta barium borate BC Bunch compressor BOL Barrel open cavity BPM Beam position monitor CDS Correlated double sampling COTR Coherent optical transition radiation CPA Chirped-pulse amplification CRL compound refractive lenses CSPAD Cornell-SLAC Pixel Array Detector CVD Chemical vapour deposition DCM double-crystal monochromator DAQ Data acquisition e.n.c.  Equipment noise charge in electrons EPICS Experimental Physics and Industrial Control System ESA Experimental Station Alvra ESB Experimental Station Bernina