PETRA

This article is about Physics. For other uses, see Petra (disambiguation).

Positron-Electron Tandem Ring Accelerator (PETRA) is one of the particle accelerators at DESY in Hamburg, Germany. From 1978 to 1986 it was used to study electron-positron collisions. In one of these studies the first direct evidence for gluons was found in three jet events. The modification called PETRA-II is a source of high-energy synchrotron radiation and also a pre-accelerator for the HERA. A planned upgrade in 2007 will convert it to PETRA-III, which will be a high intensity source for synchrotron radiation.