apex bbtf 11Apr07
Preliminary results:Preliminary results:Beam-Beam Transfer Function Beam-Beam Transfer Function for Luminosity Optimization for Luminosity Optimization
P. Cameron, A. Drees, A. Dellapenna,…
apex bbtf 11Apr07
SummarySummary• The approach at CESR
– Radiation damping means they can kick hard– Look off resonance
• The approach at RHIC – Excitation power is limited by emittance growth– Excite ‘on resonance’ to enhance the coupling
• Results– We observed anti-correlation between ZDC’s and BBTF!
• This is not understood, no obvious cause
– Higher excitation levels caused emittance growth– No plan to further pursue on-resonance excitation
• Future request– 2 hours in 2 weeks to study off-resonance excitation
apex bbtf 11Apr07
CESR CESR systemsystem
apex bbtf 11Apr07
The APEX procedure as The APEX procedure as originally conceivedoriginally conceived
• Take swept BBTF to find zero phase• Lock BBQ thru the continuous BBTF• Do vernier scan• Compare amplitude of BBTF and vernier scan results
• This can be done parasitically early in the run, to get preliminary results?
apex bbtf 11Apr07
The APEX procedure as doneThe APEX procedure as done
• Concern with effects of phase shifts due to beam-beam corrupting the ‘tune-tracking’ approach
• Solution was– Excite beam in one ring with white noise – more robust, does not require locking BBQ to
beam– Do vernier scan– Record data with BTM DAQ for offline analysis– Initial offline analysis is spectral power within a specified tune window
apex bbtf 11Apr07
blue beamyellow beam
Beam Transfer Function measure here excite here
Beam-Beam Transfer Function excite here measure here
apex bbtf 11Apr07
Blue beam response to white noise excitation in yellow (both planes), as seen by the ‘back-up’ DAQ (turned out to be un-needed)
H
V
apex bbtf 11Apr07
ZDC signals during the first two position scans
apex bbtf 11Apr07
BPM signals during the first position scan
apex bbtf 11Apr07
3D AFE signals during the first position scan
apex bbtf 11Apr07
apex bbtf 11Apr07
Integral of 3D AFE FFT in the tune window from .215 to .24 during the first position scan
BTF – yellow excitation
BBTF – blue responseBBTF – blue response
apex bbtf 11Apr07
BBTF – blue vert response
BBTF – blue horizresponse
apex bbtf 11Apr07
The vernier scan app for the first position scan
apex bbtf 11Apr07
1st scan 2nd scan
forgot to turn kicker off
apex bbtf 11Apr07
1st scan 2nd scan
IPM
Schottky
apex bbtf 11Apr07
1st scan
2nd scan
apex bbtf 11Apr07
apex bbtf 11Apr07
apex bbtf 11Apr07
SummarySummary• The approach at CESR
– Radiation damping means they can kick hard– Look off resonance
• The approach at RHIC – Excitation power is limited by emittance growth– Excite ‘on resonance’ to enhance the coupling
• Results– We observed anti-correlation between ZDC’s and BBTF!
• This is not understood, no obvious cause
– Higher excitation levels caused emittance growth– No plan to further pursue on-resonance excitation
• Future request– 2 hours in 2 weeks to study off-resonance excitation
