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