Influence of various vacuum surface treatments on the secondary electron yield of niobium

Calder, R.; Dominichini, G.; Hilleret, N.

doi:10.1016/0168-583x(86)90581-1

Cited by 23 publications

(22 citation statements)

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“…δ max of a freshly deposited Nb thin film increases during a 2 h air exposure to a value of 1.7, which is much below the δ max value of 2.2, reported for chemically polished Nb [8]. Also for copper it has been found that after an identical air exposure time the SEY of chemically cleaned copper is much higher than the SEY of a copper surface that was sputter-cleaned before the air exposure [5].…”

Section: The Influence Of Chemical Cleaning Procedures On the Sey Of mentioning

confidence: 99%

“…However, the effect of an air exposure on the SEY can be evaluated at best on a sample that is atomically clean before the air exposure. In the present study this has been achieved by preparing a clean Nb coating under vacuum by sputterdeposition.The influence of thermal treatments on the SEY has been measured and the results are compared with SEY results, which have been obtained previously on chemically polished Nb with the same experimental set-up [8]. In parallel variations of the surface composition are monitored by Auger electron spectroscopy (AES) and by Static Secondary Ion Mass Spectroscopy (SSIMS).…”

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confidence: 99%

“…Electron doses as low as 10 -6 C mm -2 remove efficiently a part of the surface species and, as a result, reduce the SEY [7]. Therefore, measurements on air exposed metal surfaces provide in some cases the SEY of an electron beam damaged surface, which has a much lower SEY than the as-received surface.Several SEY and surface analysis measurements of differently treated air exposed Nb surfaces have been reported [8,9]. However, the effect of an air exposure on the SEY can be evaluated at best on a sample that is atomically clean before the air exposure.…”

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confidence: 99%

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The secondary-electron yield of air-exposed metal surfaces

Hilleret

Scheuerlein

Taborelli

2003

Applied Physics A: Materials Science & Processing

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The secondary electron yield (SEY) variation of atomically clean metal surfaces due to air exposures and during subsequent heat treatments is described with the example of a sputter-deposited Nb thin film. Corresponding variations of the surface chemical composition have been monitored using AES and SSIMS. On the basis of these results and of previously obtained SEY results on metals and metal oxides the origin of the SEY variations is discussed.The SEY increase, which is generally observed during long lasting air exposures of clean metals, is mainly caused by the adsorption of an airborne carbonaceous contamination layer. The estimated value of about 3 for the maximum SEY of this layer is higher than that of all pure metals.Only in some cases the air-formed oxide can contribute to the air exposure induced SEY increase while many oxides have a lower SEY than their parent metals. From the experimental data it can also be excluded that the SEY increase during air exposures is mainly due to an increased secondary electron escape probability. Paper submitted to Applied Physics A Geneva, SwitzerlandJune 2002 -2- INTRODUCTIONThe secondary electron yield (SEY) of the internal surfaces of ultra high vacuum systems is of great importance for devices the operation of which can be perturbed by the occurrence of a resonant electron multiplication (multipacting) [1]. Examples for such devices are superconducting RF cavities for particle acceleration [2], and the beam vacuum system of CERN's next accelerator, the Large Hadron Collider (LHC) [3].Reliable SEY data for most atomically clean metals have been published already several decades ago [4]. However, despite the fact that for many applications the SEY of air exposed surfaces is more relevant than the SEY of atomically clean surfaces, SEY data of air exposed surfaces are rare and the reasons for the SEY variation during air exposures of atomically clean metals are still discussed controversially. There are mainly two reasons for this.Firstly, it is difficult to define precisely an air exposed surface because of the many parameters influencing the surface properties (e.g. initial sample state, air exposure time, humidity, concentration of contaminants in the ambient air, etc.). For initially clean copper, as an example, the maximum SEY value after air exposure can vary between 1.2 and above 2 for an air exposure lasting a few minutes and a few days, respectively [5].The second reason why SEY data of air exposed surfaces is often questionable is the fact that the SEY of such surfaces is much more sensitive to electron irradiation than the SEY of atomically clean surfaces [6]. Electron doses as low as 10 -6 C mm -2 remove efficiently a part of the surface species and, as a result, reduce the SEY [7]. Therefore, measurements on air exposed metal surfaces provide in some cases the SEY of an electron beam damaged surface, which has a much lower SEY than the as-received surface.Several SEY and surface analysis measurements of differently treated air exposed Nb surfaces h...

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Section: The Influence Of Chemical Cleaning Procedures On the Sey Of mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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The secondary-electron yield of air-exposed metal surfaces

Hilleret

Scheuerlein

Taborelli

2003

Applied Physics A: Materials Science & Processing

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“…However, soft multipacting barriers may exist in an rf cavity and may be a limiting factor depending on the conditions of the inner surface. The multipacting levels were analyzed for the 400 MHz rf-dipole cavity using the TRACK3P package from the SLAC ACE3P code suite [36] for an impact energy range of 20-2000 eV, which is the critical level in secondary emission for Nb [31,37]. Because of the similarity to a parallel platelike geometry multipacting conditions may exist in the rf-dipole geometry [38].…”

Section: A Multipactingmentioning

confidence: 99%

Cryogenic test of a proof-of-principle superconducting rf-dipole deflecting and crabbing cavity

Silva

Delayen

2013

Phys. Rev. ST Accel. Beams

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Recent applications in need of compact low-frequency deflecting and crabbing cavities have initiated the design and development of new superconducting structures operating at high gradients with low losses. Previously, TM 110 -type deflecting and crabbing cavities were developed and have also been operated successfully. However, these geometries are not favorable designs for low operating frequencies. The superconducting rf-dipole cavity is the first compact deflecting and crabbing geometry that has demonstrated high gradients and high shunt impedance. Since the fundamental operating mode is the lowest mode and is widely separated from the nearest higher order mode, the rf-dipole design is an attractive geometry for effective damping of the higher order modes in high current applications. A 400 MHz rf-dipole cavity was designed, fabricated, and tested as a proof-of-principle cavity. The cavity achieved high operating gradients, and the multipacting levels were easily processed and did not reoccur.

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“…With respect to ion bombardment behaviour, it is known that a glow discharge (Argon or Nitrogen) (ArGD or NGD) bombardment on technical surfaces will sputter-clean the surface to such an extent that its SEY will be very close from the atomically clean surface [12,13]. We can expect that such plasma will also work on thin films.…”

Section: δ =mentioning

confidence: 99%

The effect of gas ion bombardment on the secondary electron yield of TiN, TiCN and TiZrV coatings for suppressing collective electron effects in storage rings

Pimpec

Kirby

King

et al. 2006

Nuclear Instruments and Methods in Physics Research Section A:

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In many accelerator storage rings running positively charged beams, multipactoring due to secondary electron emission (SEE) in the beam pipe will give rise to an electron cloud which can cause beam blow-up or loss of the circulating beam. A preventative measure that suppresses electron cloud formation is to ensure that the vacuum wall has a low secondary emission yield (SEY). The SEY of thin films of TiN, sputter deposited Non-Evaporable Getters and a novel TiCN alloy were measured under a variety of conditions, including the effect of re-contamination from residual gas.

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Influence of various vacuum surface treatments on the secondary electron yield of niobium

Cited by 23 publications

References 2 publications

The secondary-electron yield of air-exposed metal surfaces

The secondary-electron yield of air-exposed metal surfaces

Cryogenic test of a proof-of-principle superconducting rf-dipole deflecting and crabbing cavity

The effect of gas ion bombardment on the secondary electron yield of TiN, TiCN and TiZrV coatings for suppressing collective electron effects in storage rings

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