During heavy ion operation, large pressure rises, up to a few orders of magnitude, were observed at CERN, GSI, and BNL. The dynamic pressure rises were triggered by lost beam ions that impacted onto the vacuum chamber walls and desorbed about ${10}^4$ to ${10}^7$ molecules per ion. The deterioration of the dynamic vacuum conditions can enhance charge-exchange beam losses and can lead to beam instabilities or even to beam abortion triggered by vacuum interlocks. Consequently, a dedicated measurement of heavy-ion induced molecular desorption in the $\mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{u}$ energy range is important for Large Hadron Collider (LHC) ion operation. In 2003, a desorption experiment was installed at the Super Proton Synchrotron to measure the beam-loss induced pressure rise of potential LHC collimator materials. Samples of bare graphite, sputter coated (Cu, TiZrV) graphite, and 316 LN (low carbon with nitrogen) stainless steel were irradiated under grazing angle with $158\mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{u}$ indium ions. After a description of the new experimental setup, the results of the pressure rise measurements are presented, and the derived desorption yields are compared with data from other experiments.

• Received 20 June 2004

DOI:https://doi.org/10.1103/PhysRevSTAB.7.103202

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