DORIS III is an electron-positron storage ring which was originally designed primarily for high energy physics experiments involving collisions but was also used as a source of synchrotron radiation in experiments covering a wide range of topics. Up until May '93 DORIS III alternated between two modes of operation. In parasitic mode the ring was typically run at energies of and stored both electrons and positrons. Priority was given to high energy physics experiments but synchrotron radiation was still available. In dedicated mode the ring was operated at lower energies of around with only electrons used to supply synchrotron radiation to beam lines at the wiggler and bending magnet stations. After May 1993 the source became dedicated to the production of synchrotron radiation. The consequences were an improvement in source stability leading to higher electron currents and a smaller source size. Table shows the typical operating parameters of DORIS III for the three cases mentioned above. The parameters shown are the electron energy at which the ring is operated; the critical energy, , of the ring defined as that energy which bisects the distribution of radiated power of the synchrotron, (i.e. half of the total radiated power is above and half below); the current circulating as electrons in the ring, ; the radiated power in one milliradian of horizontal arc at maximum ; the number of electron bunches circulating in the ring at any one time; the typical electron beam lifetime; and the emittance defined as the area of the phase space ellipse describing the positional and orientation distribution of the particle trajectories.
Table: DORIS III storage ring parameters in both modes of operation.
Figure: Bending and Wiggler magnet lines of the DORIS III storage at DESY in Hamburg (kindly provided by Dr H. Brefeld, HASYLAB.
Fig. shows the position of the wigglers and bending magnets around the storage ring. The two bending magnets, and , support six of the EMBL beam lines, two of which, X31 and X11, are used solely for protein crystallography.