Review of heavy-ion induced desorption studies for particle accelerators

Mahner, E.

doi:10.1103/physrevstab.11.104801

Cited by 38 publications

(31 citation statements)

References 24 publications

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“…The influence of various surface preparation techniques like vacuum firing at 950 C, glow discharge cleaning with Ar-O 2 and He-O 2 , in situ baking, chemical etching, electropolishing, and coatings with noble metals (Au, Ag, Pd) or nonevaporable getters (TiZrV) had been previously studied at CERN and found to affect desorption significantly [13,26]. Our results for ions incident on metals show a scaling of desorption FIG.…”

supporting

confidence: 53%

“…Surface properties of stainless steel play a crucial role for the desorption coefficients [13,26]. The influence of various surface preparation techniques like vacuum firing at 950 C, glow discharge cleaning with Ar-O 2 and He-O 2 , in situ baking, chemical etching, electropolishing, and coatings with noble metals (Au, Ag, Pd) or nonevaporable getters (TiZrV) had been previously studied at CERN and found to affect desorption significantly [13,26].…”

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confidence: 99%

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Heavy-Ion-Induced Electronic Desorption of Gas from Metals

et al. 2007

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During heavy-ion operation in several particle accelerators worldwide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ioninduced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion-induced gas desorption scales with the electronic energy loss (dE e =dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering. DOI: 10.1103/PhysRevLett.98.064801 PACS numbers: 41.75.Ak, 34.50.Dy, 79.20.Rf Energetic ions incident on matter sputter target material and also desorb gas from the target surface. The sputter and desorption yields (number of sputtered or desorbed particles per ion impact) are known to be linked to the energy loss of the projectile inside the target. Two energy loss regimes, nuclear and electronic, have been known for decades. An example for potassium ions impacting onto stainless steel, calculated with the SRIM code [1], is shown in Fig. 1. Here for low projectile energies the nuclear energy loss dominates and for higher energies the electronic energy loss dominates the total energy loss. Sputter and desorption yield measurements from 1 m thick targets in the regime of electronic energy loss have shown that both scale with the electronic energy loss dE e =dx n to the power of n 1-3. This was observed for targets of frozen gases [2 -5], for sputtering from micron-thick coatings of protein [6,7], and for desorption of nitrogen from a conductor (carbon) by 6-13 MeV=u ions (u is the nucleon mass) [8,9]. Electronic sputtering and desorption from 1 m thick targets is found to vary with the ion impact angle from normal, , as 1=cos m to the first or higher power of m [5,10].Our research was motivated by the copious gas desorption that results from lost heavy ions striking particle accelerator vacuum chambers leading to dynamic pressure rises which limit the beam intensity in a number of heavyion accelerators [11]. Related work dates back more than 30 years, when a vacuum instability in the Intersecting Storage Rings (ISR) at CERN was identified above a critical beam current [12]. Recent requirements for orders of magnitude increase in beam intensity have motivated our search for further understanding and mitigation mechanisms. 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...

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confidence: 53%

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confidence: 99%

Heavy-Ion-Induced Electronic Desorption of Gas from Metals

et al. 2007

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“…Measured desorption yields η ionloss (gas molecules released per lost ion) vary widely and some measurements show values higher than 10 5 [43]. The ion-impact desorption yield is dependent on the ion energy and impact angle (with higher η ionloss values for grazing angles), and the surface properties of the beam pipe wall (with large η ionloss values for surfaces with many mono-layers of adsorbed gas).…”

Section: Dynamic Vacuum Pressure Risementioning

confidence: 99%

Ion Colliders

Fischer

Jowett

2014

Rev. Accl. Sci. Tech.

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High-energy ion colliders are large research tools in nuclear physics to study the QuarkGluon-Plasma (QGP). The range of collision energy and high luminosity are important design and operational considerations. The experiments also expect flexibility with frequent changes in the collision energy, detector fields, and ion species. Ion species range from protons, including polarized protons in RHIC, to heavy nuclei like gold, lead and uranium. Asymmetric collision combinations (e.g. protons against heavy ions) are also essential. For the creation, acceleration, and storage of bright intense ion beams, limits are set by space charge, charge change, and intrabeam scattering effects, as well as beam losses due to a variety of other phenomena. Currently, there are two operating ion colliders, the Relativistic Heavy Ion Collider (RHIC) at BNL, and the Large Hadron Collider (LHC) at CERN.

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“…With physical sputtering from the nuclear scattering, it is difficult to get coefficients greater than a few tens, but electronic sputtering is energetically capable of producing desorption coefficients in the range of thousands as observed here and at CERN [11].…”

Section: Gas Desorptionmentioning

confidence: 95%

“…Ion gauges have an analogous difficulty, they can only measure volatile molecules that can impinge walls many times without sticking. Measurements at CERN found the dominant desorbed gases to be CO, CO 2 , H 2 , and CH 4 [11], all insulators in solid or liquid form.…”

Section: Gas Desorptionmentioning

confidence: 99%

Initial experimental studies of electron accumulation in a heavy-ion beam

Molvik

Bača

Bieniosek

et al.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)

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Accelerators for heavy-ion inertial fusion energy (HIF) have an economic incentive to fit beam tubes tightly to beams, putting them at risk from electron clouds produced by emission of electrons and gas from walls. Theory and PIC simulations suggest that the electrons will be radially trapped in the ≥1 kV ion-beam potential. We are beginning studies on the High-Current Experiment (HCX) with unique capabilities to characterize electron production and trapping, the effects on ion beams, and mitigation techniques. We are measuring the flux of electrons and gas evolved from a target, whose angle to the beam can be varied between 78° and 88° from normal incidence. Quadrupole magnets are operating with a variety of internal charged particle diagnostics to measure the beam halo loss, net charge, electron ionization rate, and gas density.

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Review of heavy-ion induced desorption studies for particle accelerators

Cited by 38 publications

References 24 publications

Heavy-Ion-Induced Electronic Desorption of Gas from Metals

Heavy-Ion-Induced Electronic Desorption of Gas from Metals

Ion Colliders

Initial experimental studies of electron accumulation in a heavy-ion beam

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