The Hadron Electron Ring Accelerator, HERA, is the first electron-proton collider in the world; it will be the only such facility for many years.
HERA offers the unique possibility to study, at very high energies, scattering between electrons of 30 GeV and protons of 820 GeV. (1 electron Volt (eV) is the energy (E) gained by an electron when it is accelerated through a potential of 1 Volt; 1 Giga electron Volt (GeV) = 1 000 000 000 eV.)
The construction of this two-ring accelerator took from May 1984 until November 1990. The commissioning of the machine proceeded during 1991.
The HERA tunnel runs for most of its length of 6.3km outside the site of DESY and 10 m - 25 m deep under ground. There are four experimental halls with sizes of about 25 m x 43 m.
The HERA ring tunnel has an inner diameter of 5.2 m The two storage rings for the electron (e) and proton (p) beams are mounted on top of each other. The magnets of the electron storage ring (lower) contain normal conductors and operate at room temperature.
The magnets of the proton storage ring (upper) need to produce a magnetic field of 4.7 Tesla for bending the high momentum proton beam in the arcs of the ring. To accomplish this, superconducting (s.c.) magnets which operate at a temperature of 4.4 K (-269 C) have been constructed.