HERA [4] is a double storage ring designed for colliding
a 820 GeV proton beam with a 30 GeV electron beam
.
The rings with a length of 6335.8 m, their complicated injector chain
and the four interaction regions
are shown in Fig. 3.
Figure 3: The HERA e-p ring at DESY in Hamburg.
H1 and ZEUS are general purpose e-p experiments, the HERMES experiment in the east hall exclusively uses the polarized electron beam. The west straight section was rebuilt in the 1995/96 shutdown. All previously installed machine elements have been removed from the area to allow the installation of the 20 m long HERA-B detector in the west hall. In addition the optics was modified to comply with the various HERA-B requirements:
