Collective Effects and Beam Measurements in Particle Accelerators beam diagnostics and fundamental limitations to the performance of high-intensity accelerators http://ab-abp-rlc.web.cern.ch/ab-abp-rlc/ See also slides on Measurements, ideas, curiosities F. Ruggiero

Wakefield for a pill-box cavity Animation showing a bunch of charged particles moving on the cavity axis and the corresponding electric field lines computed by the program ABCI Courtesy Andreas Wagner http://awagner.home.cern.ch/awagner/ F. Ruggiero Collective Effects and Beam Measurements

TRISIM3D simulation of a LEP bunch E = 22 GeV, Qs = 0.092, I = 0.3 mA 3-dimensional computer simulation of single bunch collective effects in particle accelerators top and side view of the particle distribution turn by turn, over 60 turns Courtesy Andreas Wagner http://awagner.home.cern.ch/awagner/ F. Ruggiero Collective Effects and Beam Measurements

CERN Linac4 layout and parameters 95keV 3MeV 3MeV 40MeV 90MeV 160MeV H- RFQ CHOPPER DTL CCDTL SCL Radio Frequency Quadrupole 352 MHz 6 m 1 Klystron 1 MW Chopper 352 MHz 3.6 m Drift Tube Linac 352 MHz 13.4 m 3 tanks 5 klystrons 4 MW Cell-Coupled Drift Tube Linac 352 MHz 25.3 m 24 tanks 8 klystrons 6.5 MW Side Coupled Linac 704 MHz 28 m 20 tanks 4 klystrons 12 MW Duty cycle: 0.1% phase 1 (Linac4) 3-4% phase 2 (SPL) (RF design: 15%) 4 different structures, (RFQ, DTL, CCDTL, SCL) 2 frequencies Total Linac4: 80 m, 18 klystrons current: 40 mA (avg. in pulse), 65 mA (bunch) Courtesy A. Lombardi F. Ruggiero Collective Effects and Beam Measurements

Instabilities in a Linac Transverse tune depression =Longitudinal to transverse phase advance Courtesy A. Lombardi F. Ruggiero Collective Effects and Beam Measurements

Intra-Beam Scattering (simplified formulae by K. Bane, EPAC 2002) For the LHC, the average dispersion invariant is <Hx>~0.03 m, bav~100 m, and the Coulomb logarithm (log)~24 Note that the transverse IBS growth rate is about proportional to the particle density in the 6D phase space Nb/(e2szsd) IBS growth times for long super-bunches in the LHC as a function of the rms momentum spread sd F. Ruggiero Collective Effects and Beam Measurements