12 results on '"Vincent Baglin"'
Search Results
2. Electron flux and pressure dynamic in the LHC vacuum pilot sector as a function of beam parameters and beam pipe properties
- Author
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Paolo Chiggiato, Bernard Henrist, Vincent Baglin, Ambrogio Fasoli, and Elena Buratin
- Subjects
Nuclear and High Energy Physics ,education.field_of_study ,nonevaporable getter films ,Materials science ,Physics and Astronomy (miscellaneous) ,Population ,Surfaces and Interfaces ,Electron ,Accelerators and Storage Rings ,Secondary electrons ,Bunches ,Amorphous carbon ,Getter ,Physics::Accelerator Physics ,lcsh:QC770-798 ,lcsh:Nuclear and particle physics. Atomic energy. Radioactivity ,Atomic physics ,education ,Beam (structure) ,Storage ring - Abstract
The Large Hadron Collider (LHC) is affected by the electron cloud (EC) phenomenon that can provoke beam instabilities, detrimental heat loads and pressure increases in the vacuum system. An innovative dedicated system called vacuum pilot sector (VPS) provides a continuous monitoring of the electron flux and of the pressure signals thanks to electron pickup and vacuum gauges. The VPS system is installed in a room temperature, field-free part of the LHC storage ring. Several technical surfaces, such as ex situ nonevaporable getter (NEG), amorphous carbon coating and copper, are simultaneously tested. The main outcomes of this study show that the EC signals have: (1) a linear dependence upon the number of bunches and upon the bunch population in the multipacting regime, (2) a multipacting threshold at a given bunch population, (3) a reduction under beam conditioning, (4) a strong dependence on the filling pattern and beam energy. The comparison between different surfaces shows that amorphous carbon coating reduces drastically the EC buildup, thanks to its low secondary electron yield (SEY) and photoelectron yield (PY), while copper and ex situ NEG coated surfaces suffer of EC multipacting, even after several months of operation. The multipacting rate coefficients are higher for copper than for ex situ NEG, as predicted from the SEY estimation. Other detailed experimental observations are discussed in this paper.
- Published
- 2020
3. The LHC vacuum system: Commissioning up to nominal luminosity
- Author
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Vincent Baglin
- Subjects
Physics ,Large Hadron Collider ,Luminosity (scattering theory) ,Physics::Instrumentation and Detectors ,010308 nuclear & particles physics ,Non-Evaporable Getter ,Synchrotron radiation ,Condensed Matter Physics ,01 natural sciences ,Surfaces, Coatings and Films ,Nuclear physics ,0103 physical sciences ,Higgs boson ,Physics::Accelerator Physics ,High Energy Physics::Experiment ,010306 general physics ,Instrumentation ,Beam (structure) ,Storage ring ,Boson - Abstract
The Large Hadron Collider (LHC), currently under operation at CERN, is colliding intense proton beams at the highest energy frontier up to ∼14 TeV in the centre of mass. This superconducting storage ring is at the origin of the discovery in 2012 of the so-called ‘Higgs’ Boson explaining the origin of the mass of weak bosons W + ,W − and Z also discovered at CERN in 1983. The arc vacuum system, which operates at cryogenic temperatures, consists of a 1.9 K cold bore which houses a 5–20 K beam screen. Beam collisions are performed inside a Non-Evaporable-Getter coated vacuum system located in long straight sections held at room temperature. These vacuum systems were designed to be stable under ion bombardment, to cope with intense VUV synchrotron radiation flux and to mitigate beam induced multipacting effects. In this paper, the LHC beam vacuum system design is recalled. Its operation, challenges and achieved performances during the commissioning phase will be discussed in detail.
- Published
- 2017
4. Vacuum stability and residual gas density estimation for the vacuum chamber upgrade of the ATLAS interaction region of the Large Hadron Collider
- Author
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Giuseppe Bregliozzi, G. Lanza, Vincent Baglin, and J. M. Jimenez
- Subjects
Physics ,Photon ,Large Hadron Collider ,Interaction point ,Physics::Instrumentation and Detectors ,Instrumentation ,Particle accelerator ,Electron ,Condensed Matter Physics ,Surfaces, Coatings and Films ,law.invention ,Nuclear physics ,law ,Physics::Accelerator Physics ,Vacuum chamber ,Beam (structure) - Abstract
The CERN Large Hadron Collider (LHC) has 54 km of ultra-high vacuum (UHV) beam chambers out of which about 90% are at cryogenic temperature (1.9 K) and the rest at room temperature. During operation, the residual gas density in the beam pipes is dominated by beam induced effect such ion, electron and photon-stimulated gas desorption. Therefore, the computation of gas density profile is of great importance to confirm the vacuum stability, and to estimate the beam lifetime. Moreover, the gas density profiles are essential to determine the machine induced background in the experimental areas, and to define the pressure profile in the cryogenic sectors where there is no vacuum instrumentation available. In this paper, the vacuum stability is studied for a newly proposed upgrade of the vacuum chamber at the ATLAS interaction point, using the vacuum stability code called VASCO. The residual gas density profile along the ATLAS vacuum chambers and the effects of photon and electron flux hitting the vacuum chamber walls are presented and analysed.
- Published
- 2012
5. Outgassing measurement of an LHC collimator and estimation for the NEG performances
- Author
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Giuseppe Bregliozzi, J. M. Jimenez, Vincent Baglin, and Junichiro Kamiya
- Subjects
Large Hadron Collider ,Chemistry ,business.industry ,Particle accelerator ,Collimator ,Condensed Matter Physics ,Surfaces, Coatings and Films ,law.invention ,Nuclear physics ,Outgassing ,Optics ,Getter ,law ,Gas composition ,business ,Instrumentation ,Order of magnitude ,Beam (structure) - Abstract
The outgassing rate of the collimators in the Large Hadron Collider (LHC) at CERN has an important role for the life-time of the Non-Evaporable Getter (NEG), and an accurate analysis allows the definition of future activities, like NEG vacuum activation. For these reasons, both, total outgassing rate and gas composition of a secondary collimator have been measured in the laboratory. The outgassing rate decreases by about two orders of magnitude by after bake-out and moreover, repeated bake-out further reduced the outgassing rate. The gas transmission through the NEG coated beam pipes and the resulting pressure distributions near the collimator were also measured in a dedicated setup. It is found that the main gas component after just 2 m of NEG coated beam pipe is CH 4 due to the extreme pumping speed of NEG for the other gases. Large amount of outgassing for H 2 and carbon related molecules are released when moving the collimator jaws. It is found that the NEG is very effective even in such case with large gas load.
- Published
- 2011
6. He leaks in the CERN LHC beam vacuum chambers operating at cryogenic temperatures
- Author
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Vincent Baglin
- Subjects
Superconductivity ,Physics ,Large Hadron Collider ,Physics::Instrumentation and Detectors ,Superconducting magnet ,Cryogenics ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Nuclear physics ,Magnet ,Physics::Accelerator Physics ,High Energy Physics::Experiment ,Vacuum chamber ,Instrumentation ,Storage ring ,Beam (structure) - Abstract
The 27 km long large hadron collider (LHC), currently under construction at CERN, will collide protons beam at 14 TeV in the centre of mass. In the 8 arcs, the superconducting dipoles and quadrupoles of the FODO cells operate with superfluid He at 1.9 K. In the 8 long straight sections, the cold bores of the superconducting magnets are held at 1.9 or 4.5 K. Thus, in the LHC, ∼75% of the beam tube vacuum chamber is cooled with He. In many areas of the machine, He leaks could appear in the beam tube. At cryogenic temperature, the gas condenses onto the cold bores or beam screens, and interacts with the circulating beam. He leaks creates a He front propagating along the vacuum chambers, which might cause magnet quench. We discuss the consequences of He leaks, the possible means of detections, the strategies to localise them and the methods to measure their size.
- Published
- 2007
7. Performance of a cryogenic vacuum system (COLDEX) with an LHC type beam
- Author
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Vincent Baglin, Berthold Jenninger, and I.R. Collins
- Subjects
Cryostat ,Physics ,Large Hadron Collider ,Proton ,Physics::Instrumentation and Detectors ,Condensed Matter Physics ,Super Proton Synchrotron ,Surfaces, Coatings and Films ,Nuclear physics ,Physics::Accelerator Physics ,Heat load ,Cryogenic temperature ,Instrumentation ,Beam (structure) ,Storage ring - Abstract
The cold bore experiment installed in the super proton synchrotron has been used to study the performance of a vacuum system operating at cryogenic temperatures in the presence of a large hadron collider (LHC) type proton beam. The ∼2 m long cryostat, which can be cooled below 3 K, is fitted with an actively cooled beam screen which can be temperature controlled between 5 and 100 K. Molecular desorption and deposited heat load measurements, with or without gas pre-condensation, have been performed. Implications to the LHC design and operation will be discussed.
- Published
- 2004
8. Coupling impendances studies and power loss measurements of the COLDEX upgraded vacuum chamber
- Author
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Luigi Palumbo, D. Alesini, Berthold Jenninger, Andrea Mostacci, Bruno Spataro, Vincent Baglin, Mauro Migliorati, and F. Ruggiero
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Physics ,Coupling ,Nuclear and High Energy Physics ,Power loss ,Physics::Instrumentation and Detectors ,business.industry ,Coupling impedance ,Power (physics) ,Optics ,Nuclear magnetic resonance ,Physics::Accelerator Physics ,Vacuum chamber ,business ,Instrumentation ,Electrical impedance ,Beam (structure) - Abstract
The coupling impedances of the upgraded beam screen and cold/warm transition of the cold bore experiment (COLDEX) vacuum chamber installed in the SPS machine are investigated, and the power dissipated in the circular beam screen with narrow longitudinal slots are evaluated. A comparison with the experimental results is also presented.
- Published
- 2007
9. Electron Cloud Measurements in the SPS in 2004
- Author
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Vincent Baglin, J.M. Jimenez, Gianluigi Arduini, Daniel Schulte, Frank Zimmermann, and F. Ruggiero
- Subjects
Nuclear physics ,Physics ,Large Hadron Collider ,Atomic orbital ,Physics::Instrumentation and Detectors ,Ionization ,Detector ,Physics::Accelerator Physics ,Electron ,Nuclear Experiment ,Accelerators and Storage Rings ,Reflectivity ,Beam (structure) - Abstract
Novel measurements of the electron cloud have been performed in the SPS in 2004. The LHC beam in the SPS consists of a number of short bunch trains. By varying the distance between these trains it is possible to test the survival of the electrons after the bunch passage. In this paper, results from simulations and experiments are compared.
- Published
- 2006
10. Photon reflectivity distributions from the LHC beam screen and their implications on the arc beam vacuum system
- Author
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Luca Pasquali, Vincent Baglin, Maddalena Pedio, I.R. Collins, Angelo Giglia, Stefano Nannarone, Nicola Mahne, and Roberto Cimino
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Physics ,Large Hadron Collider ,business.industry ,Bremsstrahlung ,General Physics and Astronomy ,Synchrotron radiation ,Particle accelerator ,Surfaces and Interfaces ,General Chemistry ,Electron ,Condensed Matter Physics ,Accelerators and Storage Rings ,Electromagnetic radiation ,Surfaces, Coatings and Films ,law.invention ,Optics ,Beamline ,law ,Absorption and reflection spectra: visible and ultraviolet ,beam dynamics ,collective effect and instabilities ,absorption and reflection spectra ,visible and ultraviolet ,Physics::Accelerator Physics ,business ,Beam (structure) - Abstract
In particle accelerators with intense positively charged bunched beams, an electron cloud may induce beam instabilities and the related beam induced electron multipacting (BIEM) can result in an undesired pressure rise. In a cryogenic machine such as the large hadron collider (LHC), the BIEM will introduce additional heat load. When present, synchrotron radiation (SR) may generate a significant number of photoelectrons, that may play a role in determining the onset and the detailed properties of the electron cloud related instability. Since electrons are constrained to move along field lines, those created on the accelerator equator in a strong vertical (dipole) field cannot participate in the e-cloud build-up. Therefore, for the LHC there has been a continuous effort to find solutions to absorb the photons on the equator. The solution adopted for the LHC dipole beam screens is a saw-tooth structure on the illuminated equator. SR from a bending magnet beamline at ELETTRA, Italy (BEAR) has been used to measure the reflectivities (forward, back-scattered and diffuse), for a flat and a saw-tooth structured Cu co-laminated surface using both white light SR, similar to the one emitted by LHC, and monochromatic light. Our data show that the saw-tooth structure does reduce the total reflectivity and modifies the photon energy distribution of the reflected photons. The implications of these results on the LHC arc vacuum system are discussed. © 2004 Elsevier B.V. All rights reserved.
- Published
- 2004
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11. CERN SPS electron cloud heat load measurements and simulations
- Author
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Vincent Baglin and B. Jenninger
- Subjects
Physics ,Nuclear and High Energy Physics ,Large Hadron Collider ,Physics and Astronomy (miscellaneous) ,Proton ,Physics::Instrumentation and Detectors ,Surfaces and Interfaces ,Accelerators and Storage Rings ,Secondary electrons ,Calorimeter ,Nuclear physics ,Dipole ,Atomic orbital ,lcsh:QC770-798 ,Physics::Accelerator Physics ,lcsh:Nuclear and particle physics. Atomic energy. Radioactivity ,Atomic physics ,Scaling ,Beam (structure) - Abstract
A calorimeter, WAMPAC, operating at room temperature has been designed and installed into the SPS to measure directly the electron cloud induced heat load due to the Large Hadron Collider (LHC)-type proton beam. Theoretical behavior, calibrations, measurement protocols, preliminary results, and simulation benchmarking are presented. Scaling of the results to the LHC indicated a linear heating power in a LHC dipole of about $500\text{ }\text{ }\mathrm{mW}\text{ }{\mathrm{m}}^{\ensuremath{-}1}$ for $5\ifmmode\times\else\texttimes\fi{}{10}^{10}\text{ }\mathrm{\text{protons}}/{\mathrm{\text{bunch}}}^{\ensuremath{-}1}$ for a copper surface which is not fully conditioned (maximum of secondary electron yield $\ensuremath{\sim}1.9$).
- Published
- 2003
12. Present understanding of electron cloud effects in the large hadron collider
- Author
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Gianluigi Arduini, F. Ruggiero, B. Henrist, Roberto Cimino, N. Hilleret, M Jiménez, Vincent Baglin, Karel Cornelis, Elena Benedetto, Daniel Schulte, I.R. Collins, Giovanni Rumolo, A. Rossi, Berthold Jenninger, Frank Zimmermann, and Paul Collier
- Subjects
Nuclear physics ,Physics ,Large Hadron Collider ,Atomic orbital ,Thermal emittance ,Heat load ,Accelerators and Storage Rings ,Optical coupling ,Stability (probability) ,Beam (structure) - 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.
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