A theory of the beam loss-induced vacuum instability applied to the heavy-ion synchrotron SIS18

Heavy-Ion-Induced Electronic Desorption of Gas from Metals

“…Similar yields of 1:1-2:7 10 4 molecules/ion were measured at the GSI Darmstadt SIS 18 for 8:9 MeV=u U 28 ions impacting near grazing incidence onto baked stainless steel vacuum chambers [15]. In a dedicated test stand (GSI-HLI) yields were 300 for 1:4 MeV=u Cr 7 and 1900 for 1:4 MeV=u Pb 27 perpendicularly impacting on stainless steel.…”

“…In preparation for the heavy-ion program of the Large Hadron Collider at CERN, beam-loss induced molecular desorption was intensively studied in ultra-highvacuum chambers at CERN's Heavy-Ion Accelerator (LINAC 3) [13] and the Super Proton Synchrotron (SPS) [14]. Large effective desorption yields of up to 2 10 4 molecules=Pb 53 ion (4:2 MeV=u) and 3:7 10 4 molecules=In 49 ion (158 GeV=u) were measured for ions impacting under various angles [ 0 (perpendicular), 84.8 , 89.2 at LINAC 3, and 88.3 at the SPS] onto stainless steel samples which were chemically cleaned, 950 C vacuum fired, and in situ baked at 300 C.Similar yields of 1:1-2:7 10 4 molecules/ion were measured at the GSI Darmstadt SIS 18 for 8:9 MeV=u U 28 ions impacting near grazing incidence onto baked stainless steel vacuum chambers [15]. In a dedicated test stand (GSI-HLI) yields were 300 for 1:4 MeV=u Cr 7 and 1900 for 1:4 MeV=u Pb 27 perpendicularly impacting on stainless steel.…”

Review of heavy-ion induced desorption studies for particle accelerators

“…The experimental setups used in the different laboratories can be classified in two types: first, purpose-built experiments that have been installed at accelerator beam lines like LINAC 3 [27][28][29][30][31] and SPS [32] at CERN, HLI [33,34] and HHT [35,36] at GSI, TSL [26] at Uppsala, HCX at LBNL and STS-500 at LLNL [37], and Tandem [38] at BNL; second, studies at synchrotrons either during normal machine operation or machine developments, for example LEAR [3] at CERN, SIS 18 [6,39,40] at GSI, AGS Booster [4,5], and RHIC [23] at BNL. Ion-desorption machine studies with synchrotrons are described in detail in the literature; here we focus on dedicated setups used at beam lines.…”

“…The dashed curves indicate the power law (n ¼ 2) for the electronic component of dE=dx [37]. The measurements were made at BNL [5,22,23], CERN [29][30][31], GSI [7,33,36,45,46,53], LBNL [37], and Uppsala [47,53]. sorption rates are lower than for grazing incidence angles.…”

“…In 2001 a vacuum pressure increase was observed during a highintensity U 28þ run in the heavy-ion synchrotron SIS 18 at GSI [6]. It was found that the beam lifetime was no longer independent of the injected ion current and that injection losses, either at the vacuum chamber wall or at aperture limiting devices, were responsible for large pressure ex-cursions [6,7]. The Relativistic Heavy Ion Collider (RHIC) at BNL started operation in 2000; since 2001 dynamic pressure rises were observed that limited the intensity of the Au 79þ beam [8].…”