000219008 001__ 219008
000219008 005__ 20190509132557.0
000219008 0247_ $$2doi$$a10.5075/epfl-thesis-7077
000219008 02470 $$2urn$$aurn:nbn:ch:bel-epfl-thesis7077-8
000219008 02471 $$2nebis$$a10674357
000219008 037__ $$aTHESIS 000219008 041__$$aeng
000219008 088__ $$a7077 000219008 245__$$aLongitudinal intensity effects in the CERN Large Hadron Collider
000219008 269__ $$a2016 000219008 260__$$bEPFL$$c2016$$aLausanne
000219008 300__ $$a158 000219008 336__$$aTheses
000219008 502__ $$aProf. Romuald Houdré (président) ; Prof. Leonid Rivkin, Dr Elena Shaposhnikova (directeurs) ; Dr Lukas Stingelin, Prof. Mauro Migliorati, Dr Giovanni Rumolo (rapporteurs) 000219008 520__$$aThis PhD thesis provides an improved knowledge of the LHC longitudinal impedance model and a better understanding of the longitudinal intensity effects. These effects can limit the LHC performance and lead to a reduction of the integrated luminosity. The LHC longitudinal impedance was measured with beams. Results obtained using traditional techniques are consistent with the expectations based on the impedance model, although the measurement precision was proven insufficient for the low impedance of the LHC. Innovative methods to probe the LHC reactive impedance were successfully used. One of the methods is based on exciting the beam with a sinusoidal rf phase modulation to estimate the synchrotron frequency shift from potential-well distortion. In the second method, the impedance is estimated from the loss of Landau damping threshold, which is also found to be in good agreement with analytical estimations. Beam-based impedance measurements agree well with estimations using the LHC impedance model. Macroparticle simulations of loss of Landau damping reproduce the measurements precisely and are used to determine the current stability limits. The single-bunch stability is analyzed for the HL-LHC, for a bunch intensity almost twice higher than the nominal LHC intensity. The effect of an additional rf system installed for double rf operation provides an increased stability margin in the absence of a wideband longitudinal damper system. The differences between the bunch-shortening and bunch-lengthening operation modes are presented, as well as the effect of an error in the phase synchronization between both rf systems. Several options for the rf parameters are considered, and their advantages and drawbacks under different circumstances are analyzed. A novel diagnostic tool for e-cloud monitoring based on bunch phase measurements has been fully developed. An advanced post-processing was implemented to improve the measurement accuracy up to the required level by reducing systematic and random errors. The tool is available at the CERN Control Room and shows the e-cloud build-up structure along the bunch trains and the total beam power loss due to e-cloud. Phase shift measurements are in good agreement with simulations of the e-cloud buildup and can be used to estimate the heat load in the cryogenic system. The use of this method in operation has been proven to ease the scrubbing run optimization and can eventually be used as an additional input for the cryogenic system.
000219008 6531_ $$aAccelerator 000219008 6531_$$abeam dynamics
000219008 6531_ $$abeam-based measurements 000219008 6531_$$acollective effects
000219008 6531_ $$aelectron cloud 000219008 6531_$$ahigh-intensity beams
000219008 6531_ $$aHL-LHC 000219008 6531_$$aimpedance
000219008 6531_ $$aLHC 000219008 6531_$$alongitudinal
000219008 6531_ $$amacroparticle simulations 000219008 6531_$$aradiofrequency (rf)
000219008 6531_ $$asingle-bunch stability 000219008 6531_$$awakefield
000219008 700__ $$0247762$$g235539$$aEsteban Müller, Juan Federico 000219008 720_2$$aRivkin, Leonid$$edir.$$g173996$$0244707 000219008 720_2$$aShaposhnikova, Elena$$edir. 000219008 8564_$$uhttps://infoscience.epfl.ch/record/219008/files/EPFL_TH7077.pdf$$zn/a$$s7252890$$yn/a 000219008 909C0$$xU10658$$0252363$$pLPAP
000219008 909CO $$pthesis-bn2018$$pDOI$$pSB$$ooai:infoscience.tind.io:219008$$qDOI2$$qGLOBAL_SET$$pthesis 000219008 917Z8$$x108898
000219008 917Z8 $$x108898 000219008 917Z8$$x108898
000219008 918__ $$dEDPY$$aSB
000219008 919__ $$aLPAP 000219008 920__$$b2016$$a2016-6-28 000219008 970__$$a7077/THESES
000219008 973__ $$sPUBLISHED$$aEPFL
000219008 980__ aTHESIS