dds design status
Download
Skip this Video
Download Presentation
DDS design status

Loading in 2 Seconds...

play fullscreen
1 / 27

DDS design status - PowerPoint PPT Presentation


  • 125 Views
  • Uploaded on

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.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'DDS design status' - alvaro


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

outline
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
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

Manifold

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

interleaving
Interleaving

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
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

NOW

slide9
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

DDS1_C

DDS2_E

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 b
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.

recalculation of kicks and q s from the impedance
Recalculation of Kicks and Q’s from the impedance

Lorentzian fit of the peaks

Procedure

Qdip

Kick factor

slide20
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

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

W0(t)

….

Wn(t+nt)

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=1

Nb=10

Nb=28

Nb=100

Nb=260

Nb=312

nb 312
Nb=312

“Built wake”

Bunch train

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

conclusions
Conclusions
  • 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
ad