MAIN LINAC DDS DESIGN Outlook CLIC scheme CLIC parameters CLIC complete layout

MAIN LINAC DDS DESIGN Outlook CLIC scheme CLIC parameters CLIC complete layout www.phwiki.com

MAIN LINAC DDS DESIGN Outlook CLIC scheme CLIC parameters CLIC complete layout

Barter, Jim, Morning Drive-Time On-Air Personality has reference to this Academic Journal, PHwiki organized this Journal MAIN LINAC DDS DESIGN Vasim Khan 06.11.09 Bohr seminar series, HEP group, The University of Manchester Outlook CLIC scheme Two Beam Acceleration Optimised parameters What is wakefield Main Linac Design constraints Present structure Our DDS design Comparison Forthcoming V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 1/34 CLIC scheme e- e+ collider C. M. Energy : 3 TeV Normal conducting technology Frequency : 12 GHz Acc. Gradient : 100 MV/m Luminosity : ~ 1034 cm-2 s-1 Novel technique : Two beam acceleration Overall site length 48 km (compact ) V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 2/34

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CLIC parameters H. Braun, et al. , Updated CLIC Parameters, CLIC-Note 764, 2008. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 3/34 CLIC complete layout SECTOR/LINAC: 24 PETS/SCTOR: 1491 No. of acc. Str./PETS: 2 Main Linac Ref: H. Braun, et al. , Updated CLIC Parameters, CLIC-Note 764, 2008. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 4/34 Two Beam Acceleration 140,000 main linac structures. It is difficult to supply power using conventional RF source i.e. Klystron it will require 10,000’s of such klystrons. A low energy high current beam (drive beam) running parallel to the main beam. Drive beam interacts with the impedance of the Power Extraction in addition to Transfer Structures. Drive beam is thus decelerated. The decelerated energy is used to accelerate main beam. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 5/34

Why 1) Linacs 2) Normal conducting 3) X-b in addition to frequency of 12 GHz Synchrotron radiation [1] Energy loss per revolution [1] Assume a circular CLIC collider (very impractical) [1] S.Y. Lee, Accelerator Physics. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 6/34 Is there any energy loss in linear acceleration Assume if CLIC was proposed to accelerate with accelerating gradient of ~2.75 GeV/m (an impossibly large gradient) In Linac we consider the power radiated to the power supplied by an external source [1] [1] S.Y. Lee, Accelerator Physics. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 7/34 Frequency scaling of rf parameters Need high gradient as long as a feasible site length High gradient cavities will have high surface fields Super conducting (SC) cavities can be operated up to ~ 40 MV/m High gradient in SC cavities will quench the superconductivity. Possible option is Normal Conducting (NC) cavities. Normal conducting V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 8/34

X-b in addition to (8-12 GHz) Initial proposal was 150 MV/m @ 30 GHz Operation with these parameters will suffer major breakdown issues The optimisation procedure has resulted in 100 MV/m gradient with 12 & 14 GHz frequency option. 12 GHz frequency was chosen to utilise more than two decades of R & D in the NLC/GLC project which was also proposed at 12 GHz. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 9/34 What is wakefield V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 10/34 What is wakefield Fields excited by the ultra relativistic (v~c) particles Short range wake :tail of the bunch experiences field excited by the head of the bunch Long range wake : trailing bunches experience fields excited by the leading bunches Transverse wake : emittance dilution luminosity dilution Longitudinal : energy spread = Emittance = Beam size = Beta function L=Luminosity V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 10/34

Main Linac ~25 cm V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 11/34 Fundamental concepts Synchronous mode : Most dominating mode in an accelerating cell, its phase vel. is in synchronous with speed of light B in addition to width : Difference between the synchronous frequencies of the end cells (lowest dipole ) Large BW : 3.3 GHz Small BW : 1 GHz Moderate BW : 2.3 GHz Heavy Damping : Q ~10[1] Moderate Damping : Q ~500-1000[2] Ref: [1]: A. Grudiev in addition to W. Wuenschs, LINAC08 . [2]: R. Jones, et al. , PRSTAB 9, 102001, (2006). V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 12/34 Constraints RF breakdown constraint [1],[2] 1) 2) Pulsed surface heating 3) Cost factor Beam dynamics constraints [1],[2] For a given structure, no. of particles per bunch N is decided by the / in addition to a/ Maximum allowed wake on the first trailing bunch Rest of the bunches should see a wake less than this wake(i.e. No recoherence). Ref: [1]: A. Grudiev in addition to W. Wuensch, Design of an x-b in addition to accelerating structure as long as the CLIC main linacs, LINAC08 . [2]: H. Braun, et al. , Updated CLIC Parameters, CLIC-Note 764, 2008. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 13/34

Accelerating cells : Several designs 4.5 mm V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 14/34 Wakefield suppression in CLIC main linacs To minimise the breakdown probability in addition to reduce the pulse surface heating, we are looking into an alternative scheme as long as the main accelerating structures: Detuning the first dipole b in addition to by as long as cing the cell parameters to have Gaussian spread in the frequencies Considering the moderate damping Q~500 The present main accelerating structure (WDS) as long as the CLIC relies on linear tapering of cell parameters in addition to heavy damping with a Q of ~10. The wake-field suppression in this case entails locating the dielectric damping materials in relatively close proximity to the location of the accelerating cells. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 15/34 CLIC-G: Present baseline waveguide damped design Ref: A. Grudiev, W. Wuensch, Design of an x-b in addition to accelerating structure as long as the CLIC main linacs, LINAC08 Ref: R. Jones, PRSTAB 12, 104801, (2009). V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 16/34

Damped in addition to detuned design Detuning: A smooth variation in the iris radii spreads the dipole frequencies. This spread does not allow wake to add in phase Error function distribution to the iris radii varion results in a rapid decay of wakefield. Due to limited number of cells in a structure (trunated Gaussian) wakefield recoheres. Damping: The recoherence of the wakefield is suppressed by means of a damping waveguide like structure (manifold). Interleaving neighbouring structure frequencies help enhance the wake suppression V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 17/34 NLC/GLC DDS design Ref: R. Jones, et al. , PRSTAB 9, 102001, (2006). V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 18/34 Advantages Moderate damping scheme: Breakdown probability is reduced Pulse temperature rise is reduced Manifolds can be used as long as beam position monitoring in addition to remote measurements of cell alignments. Disadvantages Need bigger b in addition to width as long as adequate detunig in addition to hence more input power to achieve desired accelerating gradient Ref: R. Jones, et al. , SLAC-PUB 7388, 1996. R. Jones, et al. , SLAC-PUB 7539, 1997 Cell offsets of DDS1 obtained by coordinate measurement machine (CMM), indicated by red connected dots in addition to , inferred from the energy radiated from the HOM ports (Pmin), indicated by a black dashed line. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 19/34

Key parameters as long as designing an accelerating structure @ 12 GHz & 100 MV/m Iris radii of the end cells Iris thickness / Group velocity No. of cells per structure Bunch spacing Bunch charge No. of bunches in a train => pulse length V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 20/34 Large b in addition to width structure Error function distribution V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 21/34 Eight fold interleaved structure 3.3 GHz structure does satisfy beam dynamics constraints but does not satisfy RF breakdown constraints. Finite no of modes leads to a recoherance at ~ 85 ns. But as long as a damping Q of ~1000 the amplitude wake is still below 1V/pc/mm/m Why not 3.3 GHz structure V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 22/34

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Small b in addition to width structure : Zero crossing scheme Parameters closely tied to that of CLIC-G with two major changes Gaussian distribution of cell parameters Q= 500 V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 23/34 CLIC-ZC structure V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 24/34 Why not zero crossing scheme Though RF breakdown constraints are satisfied it will be very challenging to achieve zero crossing scheme due to tight tolerances. It may not be feasible to build a structure based on zero crossing scheme. Need many beam dynamics simulations with realistic offsets in addition to r in addition to om errors. Possible option is a moderate b in addition to width. V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 25/34

f = 3.6 = 2.3 GHz f/fc =13.75 % /=0.126 A 2.3 GHz Damped-detuned structure V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 26/34 Typical DDS cell Manifold mode E-field in a quarter symmetry DDS cell V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 27/34 Spectral function -(IFT) Wake function Ref: R. Jones, et al. , PRSTAB 9, 102001, (2006). V. Khan Bohr seminar series, HEP group, The University of Manchester 06.11.09 28/34

Additional slides List of Publications Khan in addition to Jones, Investigation of an alternate means of wakefield suppression in the main linacs of CLIC, PAC09, Canada. Khan in addition to Jones, An alternate design as long as CLIC main linac wakefield suppression, XB08, U.K. Khan in addition to Jones, Beam dynamics in addition to wakefield simulations as long as the CLIC main linacs, LINAC08, Canada. Khan in addition to Jones, Wakefield suppression in hte CLIC main linac, EPAC08, Italy.

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