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Introduction

This proposal aims to develop a high-precision RF phase monitor for CLIC and CTF3, enabling very precise synchronization between main and drive beams. The monitor will have an important diagnostic role in CTF3 and will require feedback/feedforward to reduce error to ~0.1 degree. Two complementary FP7 proposals are being considered, one using electro-optic sampling and the other using RF pick-up. The feasibility and performance of the monitor will be tested in CTF3 with high precision electronics.

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Introduction

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  1. Introduction Motivation for phase monitor • Very precise synchronization between main and drive beams is required in CLIC to avoid excessive luminosity loss due to energy variations • Will require feedback/feedforward to reduce error to ~ 0.1 degree • Feasibility issue for CLIC • Monitor will have important diagnostic role in CTF3 Two complementary FP7 proposals • PSI: electro-optic sampling • LNF & CERN: RF pick-up

  2. Precision RF phase measurement in CTF3 EUROTeV TPMON • Demonstrate feasibility of electronics for an RF phase measurement with 0.1 degree resolution up to the bandwidth of the accelerating structure • Electronics being tested in CTF 3 (without purpose-built monitor) • 10fs (0.1 degree at 30GHz) resolution in 100MHz bandwidth has been demonstrated • So now need a monitor! • Not a single bunch measurement • Measure drive beam’s 12GHz component

  3. RF phase monitor proposal by Igor Syratchev RF in Schematic view Beam induced signal Special requirements • Low impedance • Immune to RF noise in beam pipe Drive beam 12 GHz Resonant volume RF noise RF noise Multi-moded rejection filters Example: TM01 choke-type rejection filter  23 mm

  4. Verification of performance in CTF3 • Three monitors in series in TBL • First monitor without filter • Requires high precision electronics for all three monitors

  5. Alternative plan with reduced funds • Reduce cost by 25% • Two monitors and “standard” electronics • Measure effectiveness of filter with no beam through monitor

  6. Bunch phase monitoring using Electro optical sampling • Original idea from DESY: Use periodic train of laser pulses to sample signal from wide bandwidth beam pickup Sampling near zero crossing – variations in the bunch phase get converted to amplitude changes Electro optical sampling allows direct use of high precision signals from fiber laser based timing/synchronization system

  7. Pros and Cons Single bunch measurement High resolution: 50 fs demonstrated by DESY Optional use of multiple EOS modules to obtain intra bunch charge distribution for longer bunches Need wide bandwidth pickup: Deterioration of resolution due to beam echos/wake fields in the beam chamber?

  8. R&D • Pickup: • Optimize bandwidth and slew rate of output signal to increase resolution • Minimize spurious signals from beam echos and wakes by adequate chamber design • Make Electronics 'real time feedback' ready: • Minimum measurement latency • Reliability and stability of system

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