| Legal Entity | Short Name | Country |
| Politecnico Milano | POLIMI | Italy |
| Max Born Institute | MBI | Germany |
| University of Lund | LUND | Sweden |
| Deutsches Elektronen Synchrotron | DESY | Germany |
| Max Planck Institute for Quantum Optics Garching | MPQ | Germany |
| Aarhus University | AU | Denmark |
| Amplitude Technologies | AMPL | France |
| Commissariat à l’énergie atomique et aux énergies alternatives | CEA | France |
| Foundation for Research and Technology-Hellas | FORTH | Greece |
| Femtolasers | FEMTO | Austria |
| Max Planck Insitute for nuclear physics Heidelberg | MPIK | Germany |
| University of Freiburg | FREIB | Germany |
| TRUMPF scientific lasers | TRUMPF | Germany |
| “Excite Youth for Engineering, Science and Technology” | EYESTyzw | Belgium |
| Museo Nazionale della Scienza e della Tecnologia Leonardo da Vinci | MUST | Italy |
| Venteon | VENT | Germany |
| Universidad Autonoma de Madrid | MAD | Spain |
| Costruzioni Apparecchiature Elettroniche Nucleari | CAEN | Italy |
| Photek | PHOTEK | England |
| Elettra-Sincrotrone Trieste | ELETTRA | Italy |