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CTF3 May 2013 Data Analysis
Phase Profile Plots and ADC Droop Correction with IIR Filter
02/08/2013
FONT Meeting 2nd August 2013
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Overview
• Phase profile with unfiltered Mixer/Diode.• Calibration with IIR filter, Mixer/sqrt(Diode).• Phase profile with filtered, Mixer/sqrt(Diode).• Unfiltered vs. Filtered phase reconstruction.• Mean pulse to pulse phase stability.
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Recap: Unfiltered Mixer/Diode Calibration
• Cancel ADC droop by using Mixer/Diode instead of Mixer/sqrt(Diode).
• Absorb beam current A in to calibration constant a.
• Fitted values for a:– M1: 1.67– M2: 3.11– M3: 1.92
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3 4 8 9Mixer∝ 𝐴sin (𝜙 ) exp (− 𝑡 /𝜏 )
Diode∝ 𝐴2 exp (−𝑡 /𝜏 )
sin (𝜙 )= 1𝑐𝐴MixerDiode
=1𝑎MixerDiode
• Best resolution near zero crossings of LO scan.
• Plots for the points circled here are outlined in red.
• All the plots are mean subtracted.
CALIBRATION LO SCAN
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Phase Profile – No filtering, Mixer/Diode Calibration.
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Phase Profile – No filtering, Mixer/Diode Calibration
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Phase Profile – No filtering, Mixer/Diode Calibration
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• Good agreement between M1 and M3 near zero crossings of ADC output in LO scan.
• Saturation effects near min/max of ADC output in LO scan due to sin(phi)>1 values.
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ADC Droop Exponential Fit
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• Fit an exponential to the diode data then use the fitted decay constants in an IIR filter:
• Fitted values for τ (in 357 MHz samples), Diode ADCs:- M1: 518 ± 1- M2: 440 ± 1- M3: 457 ± 2
• Also have droop in mixer channel but can’t fit exponential to it.- Use the mean of the diode ADCs: τ = 472. - Can get these values from lab tests (on going).
• Fitted values for τ can vary up to ~20% dependent on sampling window used, LO phase etc.
• Resolution seems fairly insensitive to τ.
Diode=𝐴2 exp (− 𝑡 /𝜏 )
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ADC Droop Exponential Fit
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• Left: Points are mean diode channel data for each LO phase setting. Black lines are the exponential fit using the fitted decay constants.
• Seeing cross-talk from Mixer?
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• Implement an IIR filter to remove the exponential droop using the fitted decay constants:
• Can now perform a calibration using Mixer/sqrt(Diode) as planned:
• Fitted values for a:• M1: 52.5• M2: 84.1• M3: 56.9
IIR Filter
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1
)()(k
xkxky
Mixer∝ 𝐴sin (𝜙 ) Diode∝ 𝐴2 sin (𝜙 )=1𝑎Mixer
√Diode
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Phase Profile – Filtered, Mixer/sqrt(Diode) Calibration
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Phase Profile – Filtered, Mixer/sqrt(Diode) Calibration
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Phase Profile – Filtered, Mixer/sqrt(Diode) Calibration
• At a first glance, very similar to the unfiltered calibration plots.
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Resolution Comparison – Filtered vs. Unfiltered
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• Resolution appears to be a bit better for the filtered calibration.
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Comparison – Unfiltered vs. Filtered
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M1
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M1Comparison – Unfiltered vs. Filtered
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M1Comparison – Unfiltered vs. Filtered
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M2Comparison – Unfiltered vs. Filtered
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M2Comparison – Unfiltered vs. Filtered
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M2Comparison – Unfiltered vs. Filtered
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M3Comparison – Unfiltered vs. Filtered
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M3Comparison – Unfiltered vs. Filtered
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M3
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Comparison – Unfiltered vs. Filtered
• There are differences in the relative scale of the reconstructed phase from the two calibrations.
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Filtered vs. Unfiltered Calibration Constant
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• Filtered/unfiltered calibration constants divided by mean to make them comparable.
• Only mean value used in phase reconstruction.
• Differences vs. sample no. will cause phase shifts.
Mean
Mean
Mean
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Mean Pulse Phase Stability
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Mean Pulse Phase Stability
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Mean Pulse Phase Stability
• Only short runs, but around 0.5o – 1.0o of jitter in the mean pulse phase.
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Summary• The IIR filter appears to do a good job but lab tests needed to
accurately determine decay constants.• Difference in relative scale of reconstructed phase for unfiltered
Mixer/Diode and filtered Mixer/sqrt(Diode) calibrations.• Can look in to cross-talk between the mixer and diode.
• Side notes:– Installation of kickers, rearrangement of magnets etc. in TL2 for
the feedforward system in progress.– M2 can’t be repaired due to radiation. Planned to test using
horizontal pickups instead of vertical. 4th monitor will be built.– May be delays in installing M3 in its final location.– Thinking about how to integrate FONT DAQ with CTF3 data.
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