285 research outputs found
Coupling impedances studies and power loss measurements of the COLDEX upgraded vacuum chamber
No full textThe 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
Impedances of the cold bore experiment, COLDEX, installed in the SPS machine
No full textThis paper focuses on the impedances evaluation of the cold bore experiment called COLDEX, and installed in the SPS machine. A comparison between analytical model and numerical results is presented. Tests on power losses are also shown. (c) 2006 Elsevier B.V. All rights reserved
Estimation of Thermal Resistance from Room Temperature Electrical Resistance Measurements for Different LHC Beam Screen Support Systems
No full textIn this note the thermal resistance between the LHC beam screen and cold bore is estimated from room temperature electrical resistance measurements. The results indicate that the beam screen without supports should have a comparable, if not better, thermal performance than the one with the existing spring supports. This prediction from electrical resistance measurements is confirmed by recent preliminary thermal measurements
Gas Condensates onto a LHC Type Cryogenic Vacuum System Subjected to Electron Cloud
No full textIn the Large Hadron Collider (LHC), the gas desorbed via photon stimulated molecular desorption or electron stimulated molecular desorption will be physisorbed onto the beam screen held between 5 and 20 K. Studies of the effects of the electron cloud onto a LHC type cryogenic vacuum chamber have been done with the cold bore experiment (COLDEX) installed in the CERN Super Proton Synchrotron (SPS). Experiments performed with gas condensates such as H2, H2O, CO and CO2 are described. Implications for the LHC design and operation are discussed
CERN SPS electron cloud heat load measurements and simulations
No full textA 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 mW m^{-1} for 5×10^{10} protons/bunch^{-1} for a copper surface which is not fully conditioned (maximum of secondary electron yield ∼1.9)
Pressure and Heat Load in a LHC Type Cryogenic Vacuum System Subjected to Electron Cloud
No full textThe electron cloud is of major concern for most of the storage rings operating with large bunch currents and low bunch spacing. The Large Hadron Collider (LHC) operated at cryogenic temperature will have to face the electron cloud when running with proton beams. For this reason, the first experimental studies related to the electron cloud in a LHC type cryogenic vacuum system have been launched in 2002 after the closure of the Electron Positron Accumulator (EPA) synchrotron radiation experimental program. The cold bore experiment (COLDEX) has been installed in the CERN Super Proton Synchrotron (SPS) where electron clouds could be produced with proton beams. The detailed results of the investigations, which include measurements of the dynamic heat deposition, dynamic total pressure rise and residual gas composition as a function of beam operation dose will be presented. The beam conditioning efficiency is studied as a function of temperature. The results of dedicated experiments with pre-condensed gas layers onto the beam screen are shown. The preliminary results with 75 ns bunch spacing are presented. The experimental results obtained as a function of beam operation dose are compared to the outputs of the ECLOUD simulation code. Finally, the implications to the LHC design and operation are discussed
Birgit-Nicole Krebs: Sprachhandlung und Sprachwirkung. Untersuchungen zur Rhetorik, Sprachkrititk und zum Fall Jenninger
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