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ABSTRACT: Each beam arriving from the SPS has to pass through five injection septum magnets before being kicked onto the LHC orbit. The injection layout implies that the vacuum chambers for the two circulating beams pass through the septum magnet yokes at a flange distance from the chamber of the beam to be injected. Specially designed vacuum chambers and interconnections provide the required straightness and alignment precision, thus optimising the aperture for both the circulating and injected beams, without affecting the quality of the magnetic dipole field seen by the injected beam. The circulating beams are shielded against the magnetic stray field by using μ-metal chambers with a thickness of 0.9 mm to avoid saturation of the μ-metal (0.8 T), coated with copper (0.4 mm) for impedance reasons and NEG for pumping and electron cloud purposes. A 2 mm gap between the iron yoke and the μ-metal chamber allows an in-situ bake-out at 200° C, based on a polyimide/stainless steel/polyimide sandwich structure with an overall thickness of 0.2 mm. The constraints are described and the resulting vacuum system design, the apertures and the residual stray field are presented in this paper.
Particle Accelerator Conference, 2005. PAC 2005.; 06/2005
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J.M. Jimenez,
Q. Arduini,
V. Baglin,
P. Collier,
G. Ferioli, B. Henrist,
N. Hilleret,
L. Jensen,
B. Jenninger,
J.M. Laurent,
A. Rossi,
K. Weiss,
F. Zimmermann
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ABSTRACT: A summary of the main results obtained so far from the electron cloud studies using strip detectors, pick-ups, COLDEX and a 100 MHz coaxial resonator will be presented. The spatial and energy distributions of the electrons in the cloud measured by the strip detectors will be detailed and compared to the results obtained with a conventional retarding field detector. The evidence of the scrubbing effect and of the NEG coatings as remedies to reduce the electron cloud activity will also be shown. In a second part, the improved hardware of the experiments will be presented together with the program of measurements foreseen for the 2003 SPS run.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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G. Arduini,
V. Baglin,
E. Benedetto,
R. Cimino,
P. Collier,
I. Collins,
K. Cornelis, B. Henrist,
N. Hilleret,
B. Jenninger,
M. Jimenez,
A. Rossi,
F. Ruggiero,
G. Rumolo,
D. Schulte,
F. Zimmermann
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ABSTRACT: We discuss the predicted electron cloud build up in the arcs and the long straight sections of the LHC, and its possible consequences on heat load, beam stability, long-term emittance preservation, and vacuum. Our predictions are based on computer simulations and analytical estimates, parts of which have been benchmarked against experimental observations at the SPS.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: In the LHC, in addition to the molecular photodesorption due to synchrotron radiation, an electron cloud will produce a significant gas load due to electron stimulated desorption. This electron cloud build-up is strongly dependant on the primary photoelectrons, secondary electron production and on the reflectivity of photons and electrons. The dependence of these phenomena on surface properties and of vacuum chamber materials is discussed. Experiments performed at cryogenic temperatures with the COLDEX apparatus, installed on an external EPA synchrotron radiation beam line, are presented. Photon irradiations at room temperature have been performed to study in detail the scrubbing effect by photons and electrons and will be used to extrapolate to the condition in the SPS and the LHC vacuum systems. Plans for future experiments with LHC-type beams in the SPS, to be performed at room temperature and at cryogenic temperatures, are presented.
04/2001;
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ABSTRACT: The secondary electron yield (SEY) of two different non-evaporable getter (NEG) samples has been measured ‘as received’ and after thermal treatment. The investigated NEGs are TiZr and TiZrV thin film coatings of 1 μm thickness, which are sputter deposited onto copper substrates. The maximum SEY δmax of the air exposed TiZr and TiZrV coating decreases from above 2.0 to below 1.1 during a 2 h heat treatment at 250 and 200°C, respectively.Saturating an activated TiZrV surface under vacuum with the gases typically present in ultra-high vacuum systems increases δmax by about 0.1. Changes in elemental surface composition during the applied heat treatments were monitored by Auger electron spectroscopy (AES). After activation carbon, oxygen and chlorine were detected on the NEG surfaces. The potential of AES for detecting the surface modifications which cause the reduction of SE emission during the applied heat treatments is critically discussed.
Applied Surface Science 01/2001; · 2.10 Impact Factor
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O. Bruning,
F. Caspers,
I.R. Collins,
O. Grobner, B. Henrist,
N. Hilleret,
J.-M. Laurent,
M. Morvillo,
M. Pivi,
F. Ruggiero,
X. Zhang
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ABSTRACT: An adequate dose of photoelectrons, accelerated by low-intensity
proton bunches and hitting the LHC beam screen wall, will substantially
reduce secondary emission and avoid the fast build-up of an electron
cloud for the nominal LHC beam. The conditioning period of the liner
surface can be considerably shortened thanks to secondary electrons,
provided heat load and beam stability can be kept under control; for
example this may be possible using a special proton beam, including
satellite bunches with an intensity of 15-20% of the nominal bunch
intensity and a spacing of one or two RF wavelengths. Based on recent
measurements of secondary electron emission, on multi-pacting tests and
simulation results, we discuss possible `beam scrubbing' scenarios in
the LHC and present an update of electron cloud effects
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
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E N Shaposhnikova,
Gianluigi Arduini,
J Axensalva,
E Benedetto,
S Calatroni,
P Chiggiato,
K. Cornelis,
P Costa-Pinto, B. Henrist,
J M Jiménez,
E Mahner,
G Rumolo,
M Taborelli,
C Yin Vallgren
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ABSTRACT: Electron cloud build-up is a major limitation for the operation of the SPS with LHC beam above nominal intensity. These beams are envisaged in the frame of the LHC luminosity upgrade and will be available from the new injectors LPSPL and PS2. A series of studies have been conducted in order to identify possible means to suppress electron multipacting by coating the existing SPS vacuum chambers with thin films of amorphous carbon. After a description of the experimental apparatus installed in the SPS, the results of the tests performed with beam in 2008 will be presented.
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VV Anashin,
V Baglin,
R Cimino,
IR Collins,
RV Dostovalov,
NV Fedorov,
J Gómez-Goñi,
O Gröbner, B. Henrist,
N Hileret,
AA Krasnov,
J. M. Laurent,
O B Malyshev,
EE Pyata,
M. Pivi
