Collective Effects in the LHC

Single-beam collective effects can limit the intensity and thus the performance of the Large Hadron Collider (LHC), unless the impedance of the different vacuum chamber discontinuities seen by the beam is kept below certain limits. This has an impact on the design of several machine components, such as monitors, kickers, bellows, warm sections, experimental beam pipes, rf-cavities, feedback systems and especially on the beam screen, with its millions of pumping slots. Moreover, the large number of hard U.V. photons due to synchrotron radiation liberate photo-electrons, which are pulled towards the positively charged proton bunch. When they hit the opposite wall, they generate secondary electrons which can in turn be accelerated by the next bunch if they are slow enough to survive. This mechanism can lead to the fast build-up of an electron cloud with potential implications for beam stability and heat load on the beam screen.
CERN, SL-AP team, Collaborators, Publications, Computer Codes, Measurements, Others

New EPAC 2000 Papers, LHC99 Beam-Beam Workshop, LHC Impedance Working Group, LHC Beam-Beam Studies, BibTEX Bibliography, WWW page on Electron Cloud, EPAC98 Papers

Impedance Budget Tune Shifts Narrow-Band Impedance Multi-Bunch Instabilities
Parasitic Losses Activity in 1996 Activity in 1997 PUBLICATIONS

The SL-AP team working on collective effects in the LHC consists of

Francesco RUGGIERO Electron cloud, Landau damping, impedance budget
Daniel BRANDT Impedance and instabilities
Oliver BRUNING Impedance calculations and database, simulations
Andrea MOSTACCI (Rome Univ.) Impedance estimates: slots and rough surface
Jocelyn TAN Impedance measurements
Hiroshi TSUTSUI Impedance calculations and measurements, instabilities
Luc VOS IBS, impedances, instabilities and feedback
Xiaolong ZHANG Multipacting tests and electron cloud simulations
Frank ZIMMERMANN Space charge, beam-beam and electron cloud simulations

Other collaborators are

Scott BERG (Indiana Univ.) Multi-bunch instabilities and Landau damping
Fritz CASPERS (CERN PS-RF) Impedance measurements and multipacting tests
Luisa CAPPETTA (Salerno Univ.) Transient space charge with resistive wall
Oleg DANILOV et. al. (BINP) Resistive wall and kicker impedance
Mikhail D'YACHKOV (Triumf) Impedance calculations and microwave instability
Kohji HIRATA (KEK) Beam-beam with crossing angle
Olaf MEINCKE Wakefields and multi-bunch simulations
Michele MORVILLO (CERN PS-RF) Impedance measurements and multipacting tests
Stefania PETRACCA (Salerno Univ.) Laslett tune shifts and space charge
Gennady STUPAKOV (SLAC) Electron cloud build-up

Computer Codes

MathCad Program for Transmission Line calculations (impedance of multi-layered chambers)
Mathematica Notebook for Power Loss through LHC pumping slots
Program for Computing Energy Gain of Photoelectrons
Impedance database ZBASE
Single- and multi-bunch instability package VLASOV
Programs for generating Landau damping curves
Various impedance estimates
BINP codes for electromagnetic calculations
BBC: Program for Beam-Beam Interaction with Crossing Angle
Bibliography on Computer Codes in Accelerator Physics

Measurements

Multipacting tests with a resonant coaxial setup
Surface resistance measurements for the LHC beam screen
WWW page on beam echo measurements in the SPS
Impedance measurements for the pumping holes in the LHC liner

Others

Electron Cloud in the LHC
PAC97 Papers
Special LHC Forum on Future LHC Beam-Beam Studies
Landau damping and octupoles
Transverse Instabilities in the LHC
Single-beam collective effects in the LHC
Anomalous skin effect and resistive wall heating
LHC Forums, Beam Physics Discussions and SL-AP Seminar Calendar
Index of collective
Bibliography: local BibTeX database or SPIRES results


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6 August 1999 Francesco.Ruggiero@cern.ch