Title Author Date

CLIC workshop 2014RF phase and amplitude studies in CTF3

Alexey DubrovskiyCERN BE/OPAlexey.Dubrovskiy@cern.ch 06.02.20141Introduction to the studyCLIC CDR:CLIC workshop, 06.02.20142The main concern is that energy jitter generated in the Drive Beam accelerator would be transformed into beam-phase jitter during the final bunch compression. The tolerances are extremely tight: about 0.2% for the RF power and 0.05 for the RF phase are required in the Drive Beam accelerator, while a maximum variation of 0.1% for the Drive Beam bunch charge and 0.25 at 1 GHz for the Drive Beam bunch phase are allowed.Vendor: unknownCost: 1% of luminosity + development cost + production costCurrent solution: stable RF sourcesWe study:RF source implementations;Alternative solutions.Todays main topicAlexey Dubrovskiy

Klystron3a. LLRF loop3b. Detuning of penultimate cavities (not yet verified)

2a. Stable LLRF distribution, control and amplification (50-200 W)1a. Stable voltage modulator;(by A. Gobbo, D.Aguglia and F. Cabaleiro)1b. Stable triggers, timing0a. Independent fully controlled power network;(not considered yet)Levels of stabilizationCLIC workshop, 06.02.2014Pulsed HV Modulator220/400V MainsPulsed RF AmplifierLLRF

RF3

TriggersTiming4a. Beam feed-forward4b. Passive stabilization

BeamAlexey DubrovskiyRF sensitivity to the klystron voltageCLIC workshop, 06.02.2014

has been measured as the following:The RF phase sensitivity to the klystron voltage:

4The RF power sensitivity to the klystron voltage: expectedhas been measured in the range from 2.7 to 5.

Alexey DubrovskiyKlystron voltage stabilityCLIC workshop, 06.02.2014Summary

Measurement5* CLIC current requirement is 110-5Alexey Dubrovskiy

Phase-amplitude jitter correlationCLIC workshop, 06.02.2014General modelFrom driverFrom klystronTotal

Pulse-to-pulse @ a given timeMKS02Along the pulse of a given pulse* Complex normal distribution

JklyJdrv6The source of the pulse-to-pulse jitter is likely the same as the source of the along the pulse jitter. Alexey DubrovskiyPositive off-crest acceleration7CLIC workshop, 06.02.2014Minimization of normalized energy jitter:

The minimum of the normalized energy jitter is achieved at the following positive phase off-crest acceleration:HeadTailNormalized energy jitterOff-crest accelerationAlexey DubrovskiyExperiments with beam in CTF3CLIC workshop, 06.02.20148

NoNoInjector 3 GHz beamLinacBeam Position monitor: CL.BPM0502Beam Phase monitor: CL.BPR0475Beam Position monitors: CT.BPM0215, CT.BPM0285Beam Phase monitor:CL.BPR0532OffOff

~ 2 hoursOn-crest phaseInjector phaseOff

MKS05MKS06MKS15Alexey DubrovskiyExpected result CLIC workshop, 06.02.20149

The minimum beam energy and phase jitter at the injector phase of about 8 deg. MKS05 RF jitter after the RF compressor Alexey Dubrovskiy

Measured beam energy jitterCLIC workshop, 06.02.201410

CT.BPM0285: HorizontalBPM0285Similar measurementsAlexey DubrovskiyLinac on-crest phase along the pulse11CLIC workshop, 06.02.2014

Estimations from RF and beam energy jitter of the linac on-crest phase along the pulse showed similar profiles: RF phases

24-2-4Phase [deg]Time [ns]Alexey DubrovskiyLinac intensity & efficiencyCLIC workshop, 06.02.201412

BPM0215BPM0502+7 deg+7 deg+7 degAlexey DubrovskiyPassive phase stabilization in an injector13CLIC workshop, 06.02.2014Klystrons: high-voltage, short tube

MKS02MKS03Arc-ChicaneR561. Relation among MKS02, MKS03 and Chicane:2. Relation between MKS03 and off-crest acceleration phase :EnergiesThe following two relations help to suppress the beam phase jitter and to reduce the beam energy jitter at the beginning of linac, induced by modulator voltage jitters :Stabilizedbeam phaseOr in directive terms:Alexey Dubrovskiy

Simulation of the beam jitterCLIC workshop, 06.02.201414Initial bunch length rms [deg]Phase jitter rms [deg]ModelModulator voltage stabilityR56[mm] CTF35010-549.5CTF32210-549.5CLIC-like310-549.5Proposed5010-5-62.1CLIC target

Energy jitter rms [%]Initial bunch length r.m.s. [deg]Phase jitterEnergy jitterimprovementimprovementAlexey DubrovskiySummaryStay at the positive off-crest acceleration phase with the negative R56 and the beam should be stable.

Thank you for your attention!CLIC workshop, 06.02.201415Alexey Dubrovskiy