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CLIC workshop 2014

CLIC workshop 2014. RF phase and amplitude studies in CTF3 Alexey Dubrovskiy CERN BE/OP Alexey.Dubrovskiy@cern.ch. 06.02.2014. Introduction to the study.

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CLIC workshop 2014

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  1. CLIC workshop 2014 RF phase and amplitude studies in CTF3 Alexey Dubrovskiy CERN BE/OP Alexey.Dubrovskiy@cern.ch 06.02.2014

  2. Introduction to the study The main concernis 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 0.05º 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 0.25º at 1 GHz for the Drive Beam bunch phase are allowed. Current solution: stable RF sources Vendor: unknown Cost: 1% of luminosity + development cost + production cost We study: RF source implementations; Alternative solutions. Today’s main topic CLIC CDR: CLIC workshop, 06.02.2014

  3. Levels of stabilization 4a. Beam feed-forward 4b. Passive stabilization RF Beam 3a. LLRF loop 3b. Detuning of penultimate cavities (not yet verified) Klystron LLRF Pulsed RF Amplifier 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, timing Triggers Timing Pulsed HV Modulator 0a. Independent fully controlled power network; (not considered yet) 220/400V Mains CLIC workshop, 06.02.2014

  4. RF sensitivity to the klystron voltage The RF phase sensitivity to the klystron voltage: has been measured as the following: expected The RF power sensitivityto the klystron voltage: has been measured in the range from 2.7 to 5. CLIC workshop, 06.02.2014

  5. Klystron voltage stability Summary Measurement * CLIC current requirement is 1∙10-5 CLIC workshop, 06.02.2014

  6. Phase-amplitude jitter correlation MKS02 General model Pulse-to-pulse @ a given time Along the pulse of a given pulse where , , and are constants and , and are stochastic independent processes. Typically and * Complex normal distribution The source of the pulse-to-pulse jitter is likely the same as the source of the along the pulse jitter. Total Jdrv Jkly From driver From klystron CLIC workshop, 06.02.2014

  7. Positive off-crest acceleration Normalized energy jitter Off-crest acceleration The minimum of the normalized energy jitter is achieved at the following positive phase off-crest acceleration: (where the voltage of a saturated klystron corresponds to an efficiency close to the best one) Head Tail Minimization of normalized energy jitter: CLIC workshop, 06.02.2014

  8. Experiments with beam in CTF3 Chicane Injector 3 GHz beam Linac Off MKS 06 MKS 15 MKS 05 No No Off Off ~ 2 hours Beam Position monitor: CL.BPM0502 Beam Phase monitor: CL.BPR0475 Beam Position monitors: CT.BPM0215, CT.BPM0285 Beam Phase monitor: CL.BPR0532 On-crest phase Injector phase CLIC workshop, 06.02.2014

  9. Expected result MKS05 RF jitter after the RF compressor The minimum beam energy and phase jitter at the injector phase of about 8 deg. CLIC workshop, 06.02.2014

  10. Measured beam energy jitter BPM 0285 Similar measurements CT.BPM0285: Horizontal CLIC workshop, 06.02.2014

  11. Linac on-crest phase along the pulse RF phases Estimations from RF and beam energy jitter of the linac on-crest phase along the pulse showed similar profiles: 4 2 Phase [deg] -2 -4 Time [ns] CLIC workshop, 06.02.2014

  12. Linac intensity & efficiency BPM 0502 BPM 0215 +7 deg +7 deg +7 deg CLIC workshop, 06.02.2014

  13. Passive phase stabilization in an injector MKS 02 Arc- Chicane R56 MKS 03 The following two relations help to suppressthe beam phase jitter and to reduce the beam energy jitterat the beginning of linac, induced by modulator voltage jitters : 1. Relation among MKS02, MKS03 and Chicane: Energies Stabilized beam phase 2. Relation between MKS03 and off-crest acceleration phase : Bunching and acceleration: considered independent fundamental harmonic rf-jitters with (MKS02) and (MKS03) correlation angles: Or in directive terms: Bunch compression with Positive off-crest acceleration phase ** Conventions: The maximum bunch compression is archived in a chicane with at RF phase. Klystrons: high-voltage, short tube CLIC workshop, 06.02.2014

  14. Simulation of the beam jitter Phase jitter Energy jitter improvement Energy jitter rms [%] improvement CLIC target Phase jitter rms[deg] Initial bunch length r.m.s. [deg] Initial bunch length rms[deg] CLIC workshop, 06.02.2014

  15. Summary Stay at the positive off-crest acceleration phase with the negative R56 and the beam should be stable. Thank you for your attention! CLIC workshop, 06.02.2014

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