1 Ben Constance 7 th January 2010 FONT5 December 2009 feedback results • During the final shift we ran K1-to-P2 position feedback • 151.2ns bunch spacing, quadrupoles on • 5 gain settings with charge normalisation (2000 – 2400) • 8 ZV6X settings at each gain to generate t-shirt data (~250 micron range in P2) • Some gain settings taken with interleaved feedback on/off • To save time, some settings were only FB on with occasional FB off runs taken • Additionally, throughout: • Calibration constant of 0.0022 used • Low bunch charge cut by threshold • Fliers removed at 3 sigma • All averages over ~50 pulses per point
Transcript
1Ben Constance 7th January 2010
FONT5 December 2009 feedback results
• During the final shift we ran K1-to-P2 position feedback
• 151.2ns bunch spacing, quadrupoles on
• 5 gain settings with charge normalisation (2000 – 2400)
• 8 ZV6X settings at each gain to generate t-shirt data (~250 micron range in P2)
• Some gain settings taken with interleaved feedback on/off
• To save time, some settings were only FB on with occasional FB off runs taken
• Additionally, throughout:
• Calibration constant of 0.0022 used
• Low bunch charge cut by threshold
• Fliers removed at 3 sigma
• All averages over ~50 pulses per point
2Ben Constance 7th January 2010
Baseline subtraction effects
• The firmware does NOT subtract baseline when forming feedback signal
• The true position y0 is:
• While feedback sees:
• With calibration constant of 0.0022:
Σ0 ~ 300
∆b ~Σb ~ 30
Charge - dependent
3Ben Constance 7th January 2010
Gain setting
• Gain set to converge on yFB = 0
• Decided in FONT meeting to add GUI switch to disable base subtraction in plots
• Previous shift data suggested gain ~2200 to give yFB = 0
• In real terms, feedback converges on -∆b / (Σ0 + Σb) [few micron variation]
• Dotted line shows the average position to which the feedback should converge
• To avoid confusion, all following plots are analysed with baseline subtraction, i.e. they correspond the true position
Analysed with baseline subtraction
Analysed without baseline subtraction
4Ben Constance 7th January 2010
T-shirt plots
• Following 8 slides show t-shirt plots for gain -2100
• Gain -2100 gave best results
• Each point averaged over ~50 pulses
• Error bars show the RMS jitter
• Data are interleaved feedback on/off
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Kicker probably saturating
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Gain comparison
• Overlaid T-shirt plots
• Data with feedback on at each corrector setting are overlaid on the next 5 slides
• One plot for each gain setting
• Staircase plots
• The final 5 slides show the equivalent staircase plots in P2
