Mechanical design of the beam current transformers for the HERA proton ring

The HERA proton ring consists of four warm straight sections operating at roughly tunnel temperature and the cold arcs with their superconducting magnets in a continuous cryostat. All current monitors are placed in the warm section and are subject to vacuum bakeout of temperatures up to 300 degrees C. The current monitoring system has to supply the following information: bunch shape, fill status of the different buckets, total beam current and beam lifetime. The bunch shape is measured by two coaxial monitors with extremely wide bandwidth, the bucket fill status is measured by fast and integrating current transformers, and the last two properties are measured by up to three precision DC parametric current transformers. All three types of transformer monitors are based on toroids. The design of the beam current transformers is described. They consist of the vacuum pipe with its DC gap, two heating jackets, thermal insulation, a heat dissipating system, and the toroid. The DC monitor also has an extra 5-layer magnetic shield.<>