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Roger M. Jones Contribution from Cockcroft Institute and The University of Manchester

Roger M. Jones Contribution from Cockcroft Institute and The University of Manchester. Wake Function Suppression for CLIC -Staff. 2. FP420 –RF Staff. Roger M. Jones (Univ. of Manchester faculty) Alessandro D’Elia (Dec 2008, Univ. of Manchester PDRA based at CERN)

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Roger M. Jones Contribution from Cockcroft Institute and The University of Manchester

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  1. Roger M. JonesContribution from Cockcroft Institute andThe University of Manchester

  2. Wake Function Suppression for CLIC -Staff 2. FP420 –RF Staff • Roger M. Jones (Univ. of Manchester faculty) • Alessandro D’Elia (Dec 2008, Univ. of Manchester PDRA based at CERN) • Vasim Khan (Ph.D. student, Sept 2007) • Part of EuCard ( European Coordination for Accelerator Research and Development) FP7 NCLinac Task 9.2 • Collaborators: W. Wuensch, A. Grudiev, R. Zennaro (CERN) A. D’Elia, CI/Univ. of Manchester PDRA based at CERN (former CERN Fellow). V. Khan, CI/Univ. of Manchester Ph.D. student (pictured at EPAC 08)

  3. Baseline CLIC_G Design => DDS1  Variation Bandwidth Variation Lowest dipole ∆f ~ 1GHz Q~ 10  CLIC_DDS Uncoupled Design CLIC_G

  4. DDS1: Relaxed parameters (RP)–Wakefunction ∆fmin = 65 MHz ∆tmax =15.38 ns ∆s = 4.61 m ∆fmin = 32.5 MHz ∆tmax =30.76 ns ∆s = 9.22 m Fails design criterion! Single Structure Wake Two-fold interleaving ∆fmin = 8.12 MHz ∆tmax =123 ns ∆s = 36.92 m ∆fmin = 16.25 MHz ∆tmax = 61.52 ns ∆s = 18.46 m Meets design criterion! Eight-fold interleaving Four-fold interleaving <a>/λ=0.12 , ∆f = 3.6σ= 2.3 GHz, ∆f/favg= 13.75% %

  5. DDS1: RF Summary [1] A. Grudiev, CLIC-ACE, JAN 08 [2] H. Braun, CLIC Note 764, 2008 * Mean value of 8 structures

  6. DDS Prototype CERN Tests • A first prototype of a single non-interleaved structure will be fabricated. • Initial DDS, will be fabricated with a view to ensure it sustains High gradients. • Mechanical realization will be done at CERN –Alessandro D’Elia will ensure this is completed (full engineering design). • Aim at High Gradient tests by the end of 2010.

  7. DDS2 Wakefield and High Gradient Optimisation • As a result of the Oct 2009 collaborative 2-week CERN visit by Vasim further optimisation of the DDS is envisaged. • Vasim, Riccardo and Alessandro have settled on a revised geometry • Potential to reduce surface pulse temperature heating • Initial design indicate T ~ 20% less than DDS1 Elliptical geometry

  8. DDS2 Preliminary Simulations • Tolerable limit ~ 247 MV/m • Tolerable limit ~ 56 K ~40 K Single structure 8-fold interleaved 8-fold interleaved Single structure

  9. DDS2 Prototype CERN Tests • October 2009, Vasim visited CERN for 2 weeks in order to collaborate with Alessandro and Riccardo • The original structure has been reviewed and a significant change in cell geometry has been proposed • The new geometry exhibits promising surface fields: Hsur/Eacc~ 4.45mA/V (limit  5.1-5.2mA/V) in cell 1 Esur/Eacc~1.66 (limit  1.8) in cell 24(consistent HFSS + MWS/CST simulations) • Initial simulations indicate wakefield is well-damped (f ~ 2.16 GHz ~ 3.48 ) • Calculations made on the overall efficiency of DDS2 are comparable to CLIC_G • Further simulations are needed to refine this design –in progress!

  10. Recent Publications • **V. Khan and R.M. Jones, Investigation of an alternate means of wakefield suppression in the main linacs of CLIC, Proceedings of Particle Accelerator Conference (PAC 09), Vancouver, BC, Canada, 4-8 May 2009. • **R. M. Jones, Wake field Suppression in High gradient linacs for lepton linear colliders, Phys. Rev. ST Accel. Beams 12, 104801, 2009, 14pp. • R. M. Jones, V. A. Dolgashev, and J. W. Wang, Dispersion and energy compensation in high-gradient linacs for lepton colliders, Phys. Rev. ST Accel. Beams 12, 051001 2009, 11pp. • R.M. Jones, C.E. Adolphsen, R.H. Miller, J.W. Wang , T. Higo, Influence of fabrication errors on wake function suppression in NC X-band accelerating structures for linear colliders, New J. Phys.11:033013,2009, 13pp. • ** Published during period of FP7. • We (UMAN) are pleased to acknowledge a fruitful collaboration with R. Zennaro, A. Grudiev, G. Riddone and W. Wuensch! Acknowledgements

  11. Summary of CLIC DDS • DDS1, as reported in detail at the SLAC workshop, has been abandoned in order to focus on a new geometry, DDS2, which offers superior surface fields (max TDDS2 ~ 40K, cf TDDS1~ 51K ) • First draft of the main geometrical parameters for first and last cell will be available this month –not expected to change radically during further optimisation in Jan/Feb 2010. • Prior toChristmas break technicians will be provided with preliminary parameters for mechanical feasibility design. • Optimization of the new cell geometry is expected to be finalised by, at the latest, Jan/Feb 2010. • Vasim will visit CERN for 3 weeks in Feb (2 weeks to finalise design and,1 week to verify HFSS simulations) • Structure will be high power tested towards end of 2010

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