The vacuum system of the HERA electron storage ring

Abstract The 6.3 km long vacuum system for electrons of the new large storage ring HERA 1 at Hamburg consists of about 1400 components having lengths between 0.14 and 12m. These components are mainly made by brazing variously shaped tubes of the copper alloy CuSn 2 instead of using the common aluminium alloy extrusions. This copper alloy absorbs synchrotron light more efficiently than aluminium and therefore reduces radiation shielding problems. The system is mainly pumped by integrated sputter-ion pumps using the fields of the dipole and quadrupole magnets. The impedence of the beam environment is kept small by minimizing the dimensions of the pump slots and avoiding steps of greater than 1 mm inside the vacuum chamber. A vacuum pressure in the 10 −9 mbar range was achieved some days after assembly of the vacuum system and without bake-out in situ . A beam lifetime of more than one hour was observed during the first test runs of HERA.