RF measurements in CTF3: Phase Calibration and Jitter Alexey Dubrovskiy inputs from Franck Tecker, Luca Timeo and Stephane Ray CLIC/CTF3 experimental verification meeting

Motivation Improve the current measurement of RF phases; Assess the capability of RF measurement systems to detect RF jitter Outline Part 1: Calibration of mixer phase detectors; Part 2: Measurement of RF Jitter; Part 3: Correlation between mixer and diode signals.

Part 1: Calibration of mixer phase detectors

RF measurement layout Klystron LO High-power RF Directional coupler RF phase shifter Diode Mixer ADC RF phase shifter LLRF High voltage modulator Passive devices Controlled devices Measurement All RF feed-backs and phase waveform generators were disabled.

Algebra of the RF measurement Power measurement: Phase measurement:

MKS03: RF phase calibration Calibration Fitted parameters: Error: Phase scan with a step of 10 at a given PFN voltage and at a given time within the pulse

MKS03: calibration at different power levels RF phases

MKS03: Phase in the pulse RF phases New treated: Calibrated: fitted parameter All three measurements are consistent.

MKS03: Phase at different PFNs Difference of RF phases measured at two different PFNs The current threated signal shows a relatively small phase dependence on the power level

Summary of calibration parameters Klystron (PKI) MKS MKS MKS MKS MKS07* RF phase resolution is much smaller for MKS02 and MKS03 (*) Calibration issue on the next slide

Calibration issue: MKS RF Power should not change at all when the comp. phase changes!

Other issues: MKS02 and MKS The current scaling factors of the treaded phase signals PKI02P and PKI05P are off by a factor of about 2 and 4.

Part 2: Measurement of RF Jitter

Algebra of the RF jitter

Mixer and diode signals jitters Similar power jitters were measured using the mixer and diode signals for MKS03 and MKS05 MKS03

MKS02: Power jitter Measured by diode Measured by mixer 42% The jitter corresponds to ~0.7 bit std in both cases. => Both measurements are limited by the ADC sensitivity, but the mixer signal gives a better estimate.

MKS06: Power jitter Measured by diode Measured by mixer 96% The mixer jitter corresponds to ~1 bit std and the diode jitter corresponds to ~1.8 bit std. => The mixer signal gives a better estimate. And there is a strong noise in the diode signal. Unexplained high jitter level

Part 3: Correlation between mixer and diode signals

Correlation between mixer and diode signals Case 1: The RF power deviation linearly depends on the phase deviation, for example, like in the case of a pure high voltage jitter: Then the correlation is given by: Case 2: There is only RF power deviations, which induces jitter on both signals: Case 3: case 1+ case 2 Then the correlation depends on the phase shift and ratio k 1 to k 2. Case 4: case 1+ case 2 + measurement noise Then the correlation depends on the phase shift, k 1, k 2 and noise levels.

Correlation between mixer and diode signals Cases 1, 2 and 3 Case 4 with measurement noise Case 1 (k 2 =0) Case 2 (k 1 =0)

MKS05: Correlation between mixer and diode signals Model parameters: Modulator voltage jitter Power jitter Diode noise Mixer noise => Measured RF jitter is induced by the klystron modulator

MKS03: Correlation between mixer and diode signals Model parameters: Modulator voltage jitter Power jitter Diode noise Mixer noise => Measured RF jitter is substantially given by the measurement noises

MKS06: Correlation between mixer and diode signals Model parameters: Modulator voltage jitter Power jitter Diode noise Mixer noise => Measured RF jitter is primary given by the diode measurement noise

Summary Part 1: Calibration of mixer phase detectors: – New RF phase detection algorithm will provide a slightly better measurement; – The phase comp. changes the power measurement KPI07A; – PKI02P and PKI05P to be recalibrated. Part 2: Measurement of the RF Jitter: – Mixers give significantly better estimates of RF power jitter; – The power jitter measurements are limited by ADC sensitivities. Part 3: Correlation between mixer and diode signals: – Measured PKI05 jitter is induced by the klystron voltage jitter; – MKS06 measured RF jitter is primary given by the diode measurement noise; – MKS02 and MKS03 measured RF jitters are limited by low ADC sensitivity for diode signals.

MKS05: Power jitter