1ben constance7 th january 2010 font5 december 2009 feedback results during the final shift we ran...

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


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


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


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


Kicker probably saturating


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

1ben constance7 th january 2010 font5 december 2009 feedback results during the final shift we ran...

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