Gas desorption and electron emission from 1 MeV potassium ion bombardment of stainless steel

Molvik, A.W.; Covo, M. Kireeff; Bieniosek, F.M.; Prost, L.; Seidl, P.A.; Bača, D.; Coorey, A.; Sakumi, A.

doi:10.1103/physrevstab.7.093202

Cited by 40 publications

(56 citation statements)

References 30 publications

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“…For heavy ions striking a chamber wall, such as Au 79+ used at RHIC, the electron yield is significantly higher than for protons [20]. For K + ions used in present HIF test drivers, the yield appears to be comparable to that for protons at the PSR, at least a low ion energies [21]. In order to minimize activation, designs of newer spallation neutron sources place a premium on minimizing particle losses [22].…”

Section: Primary Sources Of Electrons and Secondary Electron Emissionmentioning

confidence: 99%

Electron-cloud build-up in hadron machines

Furman¹

2004

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The first observations of electron-proton coupling effect for coasting beams and for long-bunch beams were made at the earliest proton storage rings at the Budker Institute of Nuclear Physics (BINP) in the mid-60's [1]. The effect was mainly a form of the two-stream instability. This phenomenon reappeared at the CERN ISR in the early 70's, where it was accompanied by an intense vacuum pressure rise. When the ISR was operated in bunched-beam mode while testing aluminum vacuum chambers, a resonant effect was observed in which the electron traversal time across the chamber was comparable to the bunch spacing [2]. This effect ("beam-induced multipacting"), being resonant in nature, is a dramatic manifestation of an electron cloud sharing the vacuum chamber with a positively-charged beam. An electron-cloud-induced instability has been observed since the mid-80's at the PSR (LANL) [3]; in this case, there is a strong transverse instability accompanied by fast beam losses when the beam current exceeds a certain threshold. The effect was observed for the first time for a positron beam in the early 90's at the Photon Factory (PF) at KEK, where the most prominent manifestation was a coupled-bunch instability that was absent when the machine was operated with an electron beam under otherwise identical conditions [4]. Since then, with the advent of ever more intense positron and hadron beams, and the development and deployment of specialized electron detectors [5][6][7][8][9], the effect has been observed directly or indirectly, and sometimes studied systematically, at most lepton and hadron machines when operated with sufficiently intense beams. The effect is expected in various forms and to various degrees in accelerators under design or construction.The electron-cloud effect (ECE) has been the subject of various meetings [10][11][12][13][14][15]. Two excellent reviews, covering the phenomenology, measurements, simulations and historical development, have been recently given by Frank Zimmermann [16,17]. In this article we focus on the mechanisms of electron-cloud buildup and dissipation for hadronic beams, particularly those with very long, intense, bunches. Primary sources of electrons and secondary electron emissionDepending upon the type of machine, the EC is seeded by primary electrons from three main sources: photoelectrons, ionization of residual gas, and electrons generated when stray beam particles hit the chamber walls. In addition, for HIF drivers, an important expected source of electrons is a combination of two of the above, namely: gas will be desorbed by stray ions striking the chamber walls which will subsequently be ionized by the beam. These electrons get kicked by successive bunches mostly in the * Published as Sec. 2.9 of the ICFA Beam Dynamics Newsletter No. 33, July 2004, p. 70. 2 direction perpendicular to the beam; as they strike the walls of the chamber, they generate secondary electrons which add to the existing electron population.Of all hadron machines presently existing or under construction...

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Section: Primary Sources Of Electrons and Secondary Electron Emissionmentioning

confidence: 99%

Electron-cloud build-up in hadron machines

Furman¹

2004

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“…Measurements of electron emission show that it scales as 1/cos(θ), where θ is the angle of incidence measured from normal to the surface. Electron emission decreases by factors ~20 from grazing to normal incidence, whereas desorption scales as a fractional power of 1/cos, decreasing by factors 2-3 over the same range of angles [27,28]. Both electron emission and gas desorption are minimized for impact near 0°, i.e., normal incidence and scale with the electronic component of ion energy loss in matter dE e /dx [2,3].…”

Section: Issuementioning

confidence: 99%

Critical issues for high-brightness heavy-ion beams --prioritized

Molvik¹,

Cohen²,

Davidson³

et al. 2007

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SUMMARYThis study group was initiated to consider whether there were any "show-stopper" issues with accelerators for heavy-ion warm-dense matter (WDM) and heavy-ion inertial fusion energy (HIF), and to prioritize them. Showstopper issues would appear as limits to beam current; that is, the beam would be well-behaved below the current limit, and significantly degraded in current or emittance if the current limit were exceeded at some region of an accelerator. We identified 14 issues: 1-6 could be addressed in the near term, 7-10 are potentially attractive solutions to performance and cost issues but are not yet fully characterized, 11-12 involve multibeam effects that cannot be more than partially studied in near-term facilities, and 13-14 involve new issues that are present in some novel driver concepts. Comparing the issues with the new experimental, simulation, and theoretical tools that we have developed, it is apparent that our new capabilities provide an opportunity to re-examine and significantly increase our understanding of the number one issue -halo growth and mitigation.

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“…The energy loss for 10 MeV C and protons in aluminum was calculated to be 121.1 and 0:9 eV= A, respectively, resulting in yields at normal incidence of e 13:3 for C ions and 0.4 for protons. Molvik et al [27] determined that e scales as 1= cos, where is relative to normal incidence. In a RITS-6 simulation, ions emitted from the dustbin wall may impact the knob at large angles of incidence (typical values on the sides of the knob are around 60 ), so the actual average yield will be higher than the calculated values.…”

Section: B Stimulated Emission Parametersmentioning

confidence: 99%

Modeling particle emission and power flow in pulsed-power driven, nonuniform transmission lines

Bruner

Genoni

Madrid

et al. 2008

Phys. Rev. ST Accel. Beams

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Pulsed-power driven x-ray radiographic systems are being developed to operate at higher power in an effort to increase source brightness and penetration power. Essential to the design of these systems is a thorough understanding of electron power flow in the transmission line that couples the pulsed-power driver to the load. In this paper, analytic theory and fully relativistic particle-in-cell simulations are used to model power flow in several experimental transmission-line geometries fielded on Sandia National Laboratories' upgraded Radiographic Integrated Test Stand [IEEE Trans. Plasma Sci. 28, 1653 (2000)]. Good agreement with measured electrical currents is demonstrated on a shot-by-shot basis for simulations which include detailed models accounting for space-charge-limited electron emission, surface heating, and stimulated particle emission. Resonant cavity modes related to the transmission-line impedance transitions are also shown to be excited by electron power flow. These modes can drive oscillations in the output power of the system, degrading radiographic resolution.

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Gas desorption and electron emission from 1 MeV potassium ion bombardment of stainless steel

Cited by 40 publications

References 30 publications

Electron-cloud build-up in hadron machines

Electron-cloud build-up in hadron machines

Critical issues for high-brightness heavy-ion beams --prioritized

Modeling particle emission and power flow in pulsed-power driven, nonuniform transmission lines

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