MD 349 Impedance localization with ACdipole N Biancacci

MD 349: Impedance localization with AC-dipole N. Biancacci, L. R. Carver, E. Métral, B. Salvant, R. Tomàs & OMC team LSWG 22/09/2015 Acknowledgements: G. Baud, V. Kain, G. Papotti, B. Salvachua, PS &SPS OPs

Introduction • Turn by turn BPM measurements with bunches of different intensities can reveal the impedance distribution of an accelerator machine: 1. Done kicking single bunches to observe impedance induced phase advance variations with intensity. § § Few 100 s of turns Emittance blow up Particle losses Not ideal for small tune shifts

Introduction • Turn by turn BPM measurements with bunches of different intensities can reveal the impedance distribution of an accelerator machine: 1. Done kicking single bunches to observe impedance induced phase advance variations with intensity. 2. Done applying an AC dipole kick to observe impedance induced driven phase advance variations with intensity. § § Few 100 s of turns Emittance blow up Particle losses Not ideal for small tune shifts § § > 5 k turns Limited emittance blow up Limited particle losses Fixed frequency

Introduction • Turn by turn BPM measurements with bunches of different intensities can reveal the impedance distribution of an accelerator machine: 1. Done kicking single bunches to observe impedance induced phase advance variations with intensity. 2. Done applying an AC dipole kick to observe impedance induced driven phase advance variations with intensity. § § Few 100 s of turns Emittance blow up Particle losses Not ideal for small tune shifts Up-Kick: only seen in simulations. Need to check with measurements § § > 5 k turns Limited emittance blow up Limited particle losses Fixed frequency

Introduction • Turn by turn BPM measurements with bunches of different intensities can reveal the impedance distribution of an accelerator machine: 1. Done kicking single bunches to observe impedance induced phase advance variations with intensity. 2. Done applying an AC dipole kick to observe impedance induced driven phase advance variations with intensity. § § Few 100 s of turns Emittance blow up Particle losses Not ideal for small tune shifts § § > 5 k turns Limited emittance blow up Limited particle losses Fixed frequency Up-Kick: only seen in simulations. Need to check with measurements Step = total machine tune shift

2015 -08 -09 exploratory MD Injection settings • • “ + TDI open “ “ + TCSG. D 4 L 7 open “ + all TCSGs open 4 bunches with increasing intensities (6 e 10, 8 e 10, 10 e 10, 12 e 10) + 1 pilot. Octupoles @ 10 A, no damper. AC dipole kick and BPMs record 1 bunch after the other. 30’ each measurement scan (4 points/bunch).

2015 -08 -09 exploratory MD

2015 -08 -09 exploratory MD Resistive wall + collimators ΔQ~1. 5 e-3

2015 -08 -09 exploratory MD Resistive wall + collimators ΔQ~1. 5 e-3 • • Small tune drift (few 1 e-4) thanks to the MD placement after OMC team MD. Very good BPM noise over signal ratio ~5% B 1 data still under study for the different cases. B 2 data have sync problems (can’t correlate BPMs data with oscillating bunches).

2015 -08 -09 exploratory MD Resistive wall + collimators ΔQ~1. 5 e-3 Promising: first time that we can measure this effect!. . next steps: • Re-acquire for B 2 • More points data acquisition -> reduce the error bars

Many thanks!