Improvement of the PF ring vacuum system

For an upgrade of the PF ring, about half of the vacuum ducts were replaced by newly made or improved ones, which were designed and manufactured to achieve the required beam lifetime. The concept of pumping was maintained. Every vacuum duct was pre-baked and installed with care so as not to introduce contamination caused by exposure to the atmosphere. The ring vacuum was successfully conditioned without an in situ bake-out. The operating pressure was speedily reduced by beam cleaning as the operation time increased. A low operating pressure and resulting long beam lifetime was achieved within a short operation period. # 2001 Elsevier Science B.V. All rights reserved.