1. Collective Effects and Beam Measurements in Particle Accelerators
beam diagnostics and fundamental limitations to the performance of high-intensity accelerators
See also slides on Measurements, ideas, curiosities
F. Ruggiero

2. 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
F. Ruggiero
Collective Effects and Beam Measurements

3. 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
F. Ruggiero
Collective Effects and Beam Measurements

4. 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

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

6. 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