In the Relativistic Heavy Ion Collider (RHIC) the abort kicker magnets are the limiting aperture. Continuous losses at this location could deteriorate the kicker performance. In addition, losses especially in the triplet area cause backgrounds in the experimental detectors. The RHIC one-stage collimation system was used to reduce these backgrounds as well as losses at the abort kickers. Collimation performance and results from various runs with even and uneven species (Au-Au, pp and d-Au) are presented and compared. Upgrades of the system for the upcoming high luminosity runs are outlined. I

In the shutdown between the RHIC run 2003 and 2004 three additional collimators were installed in each of the RHIC rings. The new collimators are all single plane copper scrapers of 0.45 m length. Since the existing primary collimators are dual plane a total of five scrapers per ring is now available. The total intensity of the heavy ion beams increased considerably compared to the previous runs. With the intensity the need of experiments for background reduction increased as well. In particular the PHENIX detector with its large forward Muon Identification detectors is sensitive to high background rates. In addition to experimental backgrounds loss limitations in RHIC come from quench limits of the superconduction magnets and environmental considerations. The fully automated collimator steering control is based on feedback from both, local loss monitors and detector background signals. This paper presents the upgraded RHIC collimation system, the collimator control software and the achieved results.

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Since the RHIC Au-Au run in the year 2001 the 200 MHz cavity system was used at storage and a 28 MHz system during injection and acceleration. The rebucketing procedure causes significant debunching of heavy ion beams in addition to amplifying debunching due to other mechanisms. At the end of a four hour store, debunched beam can account for more than 30% of the total beam intensity. In order to minimize the risk of magnet quenching due to uncontrolled beam losses at the time of a beam dump, a combination of a fast transverse kicker and copper collimators were used to clean the abort gap. This report gives an overview of the upgraded gap cleaning procedure and the achieved performance. The upgraded procedure in conjunction with a new application allows to measure properties of the debunched beam routinely.

In the Relativistic Heavy ion Collider (RHIC) much larger background signals were occurring at BRAMS, one of the four experiments. This was especially pronounced at the time when vacuum conditions deteriorated due to the beam ionization profile monitor replacements. Recording the beam intensities during the store provided the beam lifetime. Predictions from the beam gas interactions to the above measured values are compared. The ionization gauges simultaneously recorded the vacuum pressure data.