At present, the PETRA storage ring is mainly used as a pre-accelerator for the "super microscope" HERA, DESY’s largest particle accelerator. In addition, three test experimental stations are available at PETRA for experiments with intense X-ray radiation. Nearly 300 meters of the 2.3-kilometer-long storage ring have to be rebuilt completely to convert PETRA into a powerful light source, and a new experimental hall has to be constructed. Current plans envision 13 to 15 experimental stations, which will be equipped with so-called undulators: long magnet arrangements delivering X-ray radiation with especially high brilliance. Briefly, high brilliance means that a large number of light particles (photons) are concentrated into a very small area and form an extremely intense light beam. As Dr. Edgar Weckert, the scientific head of the PETRA upgrade program explains: "PETRA will generate an equally high photon flux on an area of a single square millimeter as the ring accelerator DORIS – DESY’s present light source – does today on a few square centimeters!" The significant advantage of such a high photon flux: The highly brilliant X-ray light beam will allow scientists to study even extremely small material samples and to produce an accurate view of their atomic arrangements. Structural biologists for instance will be able to reveal the spatial atomic structure of tiny protein crystals. This kind of information is for certain needed today: Together with human genes, proteins, which are assembled according to the genetic code, rank right at the top of the scientists’ "most wanted list". Applications are expected for example in the development of new drugs which act specifically at the point where the pathogens strike.

The new, brilliant X-ray source will also offer a wide range of possibilities for the whole field of materials research. For some applications, materials scientists require particularly energetic photons with large penetrating power, for instance to examine welding seams or to study fatigue of work pieces. The PETRA storage ring will generate particularly highly energetic radiation of more than 100 kilo-electronvolts with high brilliance – a decisive advantage for many experiments.

The X-ray source PETRA will soon receive support from the new free-electron lasers, which are developed to generate radiation in the X-ray range. These facilities complement each other very well. X-ray lasers offer completely new possibilities and open up many new research areas. The time resolution, brilliance and coherence of their radiation will set new standards. Yet these X-ray lasers are not well suited to ensure the "basic supply" of intense X-ray radiation. An ever-increasing number of users worldwide from all the fields of natural sciences will continue to need also the "conventional" light sources. And these will have to be powerful and internationally competitive – such as the rebuilt PETRA storage ring at DESY.