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DDS design status. Alessandro D’Elia on behalf of Roger M. Jones. CLIC_DDS_A. In October 2009 it has been decided to produce a first prototype to be tested at input power of 62 MW to ascertain the suitability of the structure to sustain high e.m . field gradients
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DDS design status Alessandro D’Elia on behalf of Roger M. Jones
CLIC_DDS_A • In October 2009 it has been decided to produce a first prototype to be tested at input power of 62 MW to ascertain the suitability of the structure to sustain high e.m. field gradients • RF and mechanical design completed in Summer 2010 • 4 qualification disks machined by VDL received in Oct 2010 • The 4 disks have been successfully bonded by Bodycote • The whole structure will be machined in Japan by Morikawa under the supervision of KEK • High Power Tests are foreseen as soon as we will get the full structure
CLIC_DDS_A some further detail VDL BODYCOTE
CLIC_DDS_B • The study of a further structure (CLIC_DDS_B) is already started • This structure will be based on CLIC_DDS_A but will be provided with HOM couplers and with a compact coupler for fundamental mode • Both wakefield suppression and high power performances will be tested
First steps toward CLIC_DDS_B Wakefield calculations for DDS are, in the early design stage, based on single infinitely periodic cells. Though cell-to-cell interaction is taken into account to calculate the wakefields, it is important to study full structure properties using computational tools.
Comparison between GdfidL and Circuit Model NB: GdfidL does not include Ohmic losses which are present in Circuit Model
Recalculation of Kicks and external Q’s from the impedance Lorentzian fit of the peaks Procedure Qext Kick factor
Comparison of fsyn, Q’s and Kicks <QloadGdfidL>=1947 <Q Circuit Model>=1647
A possible geometry for the HOM Coupler • J. W. Wang and al. “Progress toward NLC/JLC prototype accelerator structure”, LINAC04 Port2 Port1 Port4 Port3 SLAC PEC PML As a first approach I decided to reproduce the same as done at for NLC/JLC: HOM coupler attached at first and last regular cells Only Matching cells uncoupled
Reflections only from one side of the structure RPrimen=0, RPrime1=1 RPrimen=RPrime1=0 (Original wake) f=1.9874GHz 8-fold, 3.48 (Original structure) RPrimen=1, RPrime1=0 RPrimen=RPrime1=0 (Original wake) Circuit Model shows that only one HOM coupler downstream is enough
HOM coupler matching technique Same technique as for matching cells No common minima yet
Conclusions • Due to tremendous earthquake in Japan, we had some delay in CLIC_DDS_A production; which will be terminated for the end of this year • Comparison between circuit model and GdfidL is done showing a very similar behavior • Studies on HOM coupler for CLIC_DDS_B are ongoing • Studies on a structure with a lower Q in order to minimize the number of interleaved structures and to relax the requirements of the HOM coupler