Dds design status
This presentation is the property of its rightful owner.
Sponsored Links
1 / 27

DDS design status PowerPoint PPT Presentation

  • Uploaded on
  • Presentation posted in: General

DDS design status . Alessandro D’Elia. Outline. General overview of DDS working principle CLIC_DDS_A design status Towards CLIC_DDS_B: wakefield simulations and impedances HOM coupler design Some conclusion. Damped and detuned design.

Download Presentation

DDS design status

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Dds design status

DDS design status

Alessandro D’Elia



  • General overview of DDS working principle

  • CLIC_DDS_A design status

  • Towards CLIC_DDS_B:

    • wakefield simulations and impedances

    • HOM coupler design

  • Some conclusion

Damped and detuned design

Damped and 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 variation results in a rapid decay of wakefield.

  • Due to limited number of cells in a structure (truncated Gaussian) wakefieldrecoheres.

  • 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

Nlc glc dds design

Acceleration cells

Beam tube


HOM coupler

High power

rf coupler

NLC/GLC DDS design

Ref: R. Jones, et al. , PRSTAB 9, 102001, (2006).

Large bandwidth structure

Large bandwidth structure

Error function distribution

Courtesy of R. M. Jones



Courtesy of V. Khan

Why a detuning damping structure dds for clic

Why a Detuning Damping Structure (DDS) for CLIC

  • Huge reduction of the absorbing loads: just 4x2 loads per structure

  • Inbuilt Wakefield Monitors, Beam Position Monitors that can be used as remote measurements of cell alignments

  • In principle, lower pulse temperature rise

  • Consequently (still in principle) lower probability of breakdown events

  • Huge reduction of the outer diameter of the machined disks

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


Dds design status

CLIC_DDS_A: regular cell optimization

The chose of the cell geometry is crucial to meet at the same time:

Wakefield suppression

Surface fields in the specs



Consequences on wake function

Cell shape optimization for fields

Clic dds a regular cells final design

CLIC_DDS_A: regular cells, final design

Roundings enhance the magnetic field however a reduction of the slot size mitigates this enhancement and RF parameters are back within required limits. Also the wake damping is still in the limits with margins for a further improvement.

  • Further information:

  • Manifold dimensions are uniform throughout the structure

  • The manifold radius is now parameterised in order to keep the lowest manifold mode above 12 GHz.

Clic dds a full structure

CLIC_DDS_A full structure

Clic dds a some further detail

CLIC_DDS_A some further detail



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

Next future

First steps toward clic dds b

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

Comparison between GdfidL and Circuit Model



Recalculation of kicks and q s from the impedance

Recalculation of Kicks and Q’s from the impedance

Lorentzian fit of the peaks



Kick factor

Comparison between gdfidl and reconstructed wake

Comparison between GdfidL and reconstructed wake

Comparison of fsyn q s and kicks

Comparison of fsyn, Q’s and Kicks

Dds design status

A possible geometry for the HOM Coupler

  • J. W. Wang and al. “Progress toward NLC/JLC prototype accelerator structure”, LINAC04








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

How much is the bandwidth?

A first na f consideration

A first naÏf consideration

CLIC_DDS_A Impedance

Build up of the wake signal

Build up of the wake signal




Obviously this analysis is qualitative and in the build up we are neglecting the effect of the bunches on the following ones

Some example

Some example







Nb 312


“Built wake”

Bunch train

A last interesting consideration

A last interesting consideration

Preliminary hom coupler thoughts

Preliminary HOM coupler thoughts

My understanding is that, for first dipole band the most dangerous frequency is ~18GHz. Then I’m trying to match the HOM coupler at this frequency.

Same technique as for matching cells

No common minima yet @ 18GHz



  • A first prototype, CLIC_DDS_A, has been fully designed and is going to be produced (hopefully at the end of the year)

  • The study for the HOM coupler which is the fundamental device for CLIC_DDS_B has started

  • New ideas to improve DDS performances are under investigation

  • Login