There are more than fifteen thousand particle accelerators in the world, ranging from the linear accelerators used for cancer therapy in modern hospitals to the giant 'atom-smashers' at international particle physics laboratories used to unlock the secrets of creation. For many decades these scientific instruments have formed one of the main pillars of modern research across scientific disciplines and countries.The optimization of the performance of any particle accelerator critically depends on an in-depth understanding of the beam dynamics in the machine, the availability of simulation tools to study and continuously improve all accelerator components from beam handling elements to rf cavities, a complete set of beam diagnostics methods to monitor all important machine and beam parameters with high precision, and a control and data acquisition system that links all the above.The oPAC consortium proposes to carry out collaborative research into all the above aspects, with the aim to optimize the performance of present and future accelerators that lie at the heart of many research infrastructures. The network brings together leading research centers, universities, and industry partners to jointly train the next generation of researchers in this interdisciplinary field. oPAC aims at developing long term collaboration and links between the involved teams across sectors and disciplinary boundaries and to thus help defining improved research and training standards in this important field.