The pressure and gas composition evolution during the operation of the LEP accelerator at 100GeV

Billy, Juliette; Bojon, J P; Henrist, B.; Hilleret, N.; Jiménez, M.; Laugier, I.; Strubin, P.

doi:10.1016/s0042-207x(00)00383-3

Cited by 8 publications

(5 citation statements)

References 7 publications

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“…The variation of the secondary electron yield (SEY) at 2.5 keV primary electron (PE) energy with increasing electron dose is estimated using equation (1). The SEY value is calculated from the PE beam current, measured with +18 V sample bias, and the sample-toground current, measured with a sample bias of -18 V. SEY 2.5 keV = (I beam -I sample ) / I beam (1) No attempt has been made to optimise the bias voltages and the calculated SEY values are used to show trends but do not correspond to true SEY values.…”

Section: The Sey At 25 Kev As a Function Of Electron Dosementioning

confidence: 99%

“…The internal walls of the ultra high vacuum (UHV) system of particle accelerators are subjected to synchrotron radiation and energetic electron and ion irradiation, which affect the functional surface properties of the wall such as the secondary electron yield (SEY) and the electron stimulated desorption (ESD) yield. This process is usually advantageous for the operation of particle accelerators and it is called surface conditioning or beam scrubbing [1].…”

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confidence: 99%

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An AES study of the room temperature conditioning of technological metal surfaces by electron irradiation

Scheuerlein

Taborelli

Hilleret

et al. 2002

Applied Surface Science

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The modifications to technological copper and niobium surfaces induced by 2.5 keV electron irradiation have been investigated in the context of the conditioning process occurring in particle accelerator ultra high vacuum systems. Changes in the elemental surface composition have been found using Scanning Auger Microscopy (SAM) by monitoring the carbon, oxygen and metal Auger peak intensities as a function of electron irradiation in the dose range 10-6 to 10-2 C mm-2. The surface analysis results are compared with electron dose dependent secondary electron and electron stimulated desorption yield measurements.

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Section: The Sey At 25 Kev As a Function Of Electron Dosementioning

confidence: 99%

mentioning

confidence: 99%

An AES study of the room temperature conditioning of technological metal surfaces by electron irradiation

Scheuerlein

Taborelli

Hilleret

et al. 2002

Applied Surface Science

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“…如(8)式, 约为1.84 × 10 17 photons/(m•s -1 ). 束屏材料束屏材料的选择要求阻抗不能过高, 以免束流在阻抗壁面感应出镜像电流, 引起过多欧姆耗散 [12] ; 需要有足够的结构强度, 以保持在强磁场下的屈服强度 [20,36] ; 要求光子致气体解吸产额尽量低 [26] . 综合考虑, 束屏材料一般选择不锈钢, 并在内表面镀一层铜涂层.…”

Section: 根据实验装置参数及测试参数对束屏内的动unclassified

Gas density evolution in beam screen of super proton-proton collider

You¹,

Wang²,

Gao³

et al. 2021

Acta Phys. Sin.

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Vacuum stability is one of the key issues in the design of particle accelerators, especially high-energy super proton-proton colliders. The synchrotron radiation generated by proton beams in the bending area will desorb and crack the gas molecules which have adsorbed on the wall of the cold bore. The collision or scattering between the proton beam and the desorbed gas molecules may result in the degradation of the beam quality and the reduction of beam life time, and even the collapse of the beam. Usually a copper coated stainless steel beam screen is installed in the cold bore to intercept synchrotron radiation and reduce gas desorption. Based on the design parameters of the Super Proton-Proton Collider, in this paper the source of gas in the beam screen is analyzed. By considering the photon-induced desorption process and the gas molecule cracking process, the gas dynamic model in the beam screen is established. Moreover, the calculation of the evolution of the gas density in the beam screen with the beam operating time is carried out, and the effect of TiZrV non-evaporable getter film coated beam screen on the dynamic gas density is explored. The results show that H2 is the main desorption gas in the beam, the next is CO, while the molecular density of CO2 and CH4 are limited by molecular cracking. The maximum gas density in the beam screen appears at the initial stage of operation, and the gas density decreases with time going by. In order to strengthen adsorption and reduce desorption, TiZrV coated beam screen is discussed in this paper. In the case of TiZrV coated stainless steel beam screen, the maximum equivalent H2 density is about two order of magnitude lower than in the case of copper coated stainless steel beam screen. The non-evaporable getter(NEG) for beam screen material can significantly improve vacuum performance. The calculation results can qualitatively reflect the dynamic vacuum evolution in the beam screen during the beam operation and provide a reference for designing vacuum systems.

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“…Significant efforts were devoted to developing and qualifying the effectiveness of chemical recipes for cleaning vacuum materials [16] and to developing discharge cleaning methods using argon and argon/oxygen mixtures [17]. These surface conditioning studies were extended to aluminum surfaces [18] in the 1980's as CERN focused on the design of the 27 km Large Electron Positron (LEP) collider which operated from 1989 to 2000 [19].…”

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confidence: 99%

“…Measurements to study the phenomenon were first done with electron sources to simulate the photoelectron emission, including the early measurements by the SPEAR vacuum design team. Later, actual measurements of photoinduced desorption coefficients were obtained using beam lines on storage ring light sources by the vacuum groups at CERN [8,19], Brookhaven [21], and KEK [22]. Measured desorption coefficients start out in the range of 10 -2 to 10 -1 depending on whether the substrate is stainless steel, aluminum or copper, and generally decrease inversely with the photon dose to 10 -5 or 10 -6 after a beam exposure that is typically 1 to 10 ampere-hours, corresponding to a photon dose of 10 22 to 10 23 photons per meter of vacuum vessel.…”

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confidence: 99%

Development of ultrahigh and extreme high vacuum technology for physics research

Dylla¹

2003

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Over the last 50 years increasingly large and more sophisticated devices have been designed and put into operation for the study of particle and nuclear physics, magnetic confinement of high temperature plasmas for thermonuclear fusion research, and gravity wave observatories based on laser interferometers. The evolution of these devices has generated many developments in ultrahigh and extreme high vacuum technology that were required for these devices to meet their operational goals. The technologies that were developed included unique ultrahigh vacuum vessel structures, ultrahigh vacuum compatible materials, surface conditioning techniques, specialized vacuum pumps and vacuum diagnostics. Associated with these technological developments are scientific advancements in the understanding of outgassing limits of UHV-compatible materials and particle-induced desorption effects. a)

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The pressure and gas composition evolution during the operation of the LEP accelerator at 100GeV

Cited by 8 publications

References 7 publications

An AES study of the room temperature conditioning of technological metal surfaces by electron irradiation

An AES study of the room temperature conditioning of technological metal surfaces by electron irradiation

Gas density evolution in beam screen of super proton-proton collider

Development of ultrahigh and extreme high vacuum technology for physics research

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