Collective Effects and Beam Measurements in Particle Accelerators

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, F. Ruggiero CERN ideas, curiosities Univ. “La Sapienza”, Rome, 20– 24 March 2006

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 CERN Collective Effects and Beam Measurements

TRISIM 3 D simulation of a LEP bunch E = 22 Ge. V, Qs = 0. 092, I = 0. 3 m. A • • • 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 CERN Collective Effects and Beam Measurements

CERN Linac 4 layout and parameters 95 ke. V H- 3 Me. V RFQ Radio Frequency Quadrupole 352 MHz 6 m 1 Klystron 1 MW 3 Me. V CHOPPER Chopper 352 MHz 3. 6 m Drift Tube Linac 352 MHz 13. 4 m 3 tanks 5 klystrons 4 MW Courtesy A. Lombardi CERN 90 Me. V 160 Me. V CCDTL SCL Cell-Coupled Drift Tube Linac 352 MHz 25. 3 m 24 tanks 8 klystrons 6. 5 MW Side Coupled Linac Duty cycle: 0. 1% phase 1 (Linac 4) 3 -4% phase 2 (SPL) (RF design: 15%) Total Linac 4: 80 m, 18 klystrons F. Ruggiero DTL 40 Me. V 704 MHz 28 m 20 tanks 4 klystrons 12 MW 4 different structures, (RFQ, DTL, CCDTL, SCL) 2 frequencies current: 40 m. A (avg. in pulse), 65 m. A (bunch) Collective Effects and Beam Measurements

Transverse tune depression Instabilities in a Linac =Longitudinal to transverse phase advanc F. Ruggiero CERN Courtesy A. Lombardi 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 6 D phase space Nb/(e 2 szsd) F. Ruggiero CERN IBS growth times for long super-bunches in the LHC as a function of the rms momentum spread sd Collective Effects and Beam Measurements