WP5.3 Report: Spoiler Wakefield and Mechanical Design

1
WP5.3 ReportSpoiler Wakefield and Mechanical
Design

• Review programme
• Updates
• Theoretical studies
• EM Modelling
• RF bench tests
• Caspers discussion
• SLAC beam test
• proposal/optics study
• collimator design
• simulation studies
• Next steps
• Project web http//hepunx.rl.ac.uk/swmd/

2
Programme

• RF impedance bench tests within CI (calibration,
  etc.) Beard, Sopczak, J. Smith, R.Carter
• Benchmark against known spoiler profile, large
  taper angle, MAFIA etc. simulation
• Carl Beard started to set up MAFIA simulations,
  survey h/w
• Use cold test results to
• Provide data to assist development of improved
  e.m. modelling in problematic regimes
• Also within UK, build up expertise (non-LC
  applications)
• (Within EUROTeV) collaborate with TU Darmstadt
• Alternative spoiler profiles, (at least) relative
  performance
• Theoretical studies Tucker, Burton, Shales
  (Lanc.)
• Direct beam measurement at SLAC CCLRC, Lanc.,
  Birmingham
• With FP6 funding, extend into material damage
  studies
• CCLRC Engineering Department, Manchester,
  Birmingham

3
TDR setup

• From SRS tests (sz6mm)
• Consider vertical plane operation to avoid sag
• Critical issue
• Pulse speed!
• Time LC bunch sz
• 1 ps
• Quick survey, fastest available off the shelf
  pulse generator for TDR 10ps (Tek. 80E04
  modulePSPL module TDS8200 scope)
• Options
• Build fast rise source
• Scale up spoilers (but x10?!)
• Alternative approaches (Caspers, CERN)

1.7m
From HillPugh, EPAC94
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Carl Beard
Impedance Rig
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Impedance Rig 2
Matching Parts
Test Vessels
Launch cone
6
Decided bench tests less urgent/critical Will not
use to design test beam proposal Useful
training/education
Impedance Rig 3
Tektronics 7854 TDR Scope
6 GHz NA S-parameter test set
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Opportunities

• ERLP Test beam 2-3 ps bunch length _at_ 35 MeV
• Similarity with LC-ABD UCL Spectrometry Group
• GDFIDL
• Bench tests
• Beam tests

8
Comparison MAGIC-Theory
Developing novel ultrarelativistic expansion
scheme Next, relate expansion parameter to
physical observables

• Test consists of a comparison between simulation
  and calculations for Brillouin flow
• Analytic solutions exist in literature
• Comparison of BB(req,Ibeam,Vbeam)
• Literature review
• MAGIC
• Analytical solutions using MAPLE.
• Agreement of BB between MAGIC analytic formula
  of 20
• Er(r) and ?(r) fields inconsistent between
  calculations and model
• Spurious Ez?0 field

Burton, Shales, J.Smith,Sopczak,Tucker
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Standard MAGIC algorithm fails for large ?
(200keV, ?1.4,1A,BBB)
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Collimator Wakefield ESA beam test

• ESA tests central to EUROTeV/LC-ABD Spoiler
  Wakefield/Mechanical Design
• Related activity
• Development of ECHO-3D code (TEMF) for shallow
  tapers/short bunches
• Merlin studies calculations ? German
  Kourevlev/Adam Mercer, WP1.2 Report
• Collimator damage estimates
• Overall ESA programme driven by Mike Woods
• http//www.project.slac.stanford.edu/ilc/testfac/
  ESA/esa.html
• SLAC Proposal T-480 (Tenenbaum, Watson et al),
  see
• http//www-project.slac.stanford.edu/ilc/testfac/
  ESA/files/ColWake_TestBeamRequest.pdf
• Beam Requirements
• Momentum 28.5 GeV
• Particles 1010 single bunch, variable by
  2Rep. Rate 10 Hz
• Bunch length 300mm and variable 100ltszlt500mm
• Purpose
• Commision WF box in ESA
• Additional study of resistive wakes in Cu
• First study of 2-step tapers

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Test Beam Responsibilities

• Birmingham (Nigel Watson)
• Programme, analysis, beam test operation
• CCLRC ASTeC (Deepa Angal-Kalinin, Carl Beard,
  Frank Jacksonnew recruit)
• Wakefield simulations, optics design
• Data analysis, instrumentation/signal processing
  support
• Misc. cables (electronics modules t.b.d.?)
• CCLRC ED (Chris Densham, Justin Greenhalgh)
• Collimator insertion design/fabrication
• Lancaster (Jonny Smith, Andre Sopczak, David
  Burton, Robin Tucker, Nick Shales)
• Wakefield simulations and analytic calculations
• Manchester (Roger Barlow, Adam Mercer, German
  Kurevlev)
• Impact of collimator form on emittance dilution
• DESY (Igor Zagorodnov), TEMF TU Darmstadt
  (Wolfgang Mueller, Thomas Weiland)
• Development/validation of 3-d code to model short
  bunch/long structures, optimisation of collimator
  form.
• SLAC (Ray Arnold, Carsten Hast, Doug McCormick,
  Marc Ross and Zen Szalata, Peter Tenenbaum, Mike
  Woods)
• Programme, ESA co-ordinating and infrastructure,
  logistics/beamline support

12
SLAC specific

• Alignment/survey
• DAQ infrastructure and support
• Upstream BPMs 31, 32, 41, 42
• 4 Linac-style 0.8 diameter cavity rf BPMs (part
  of T-474)
• BPMs (angle and position) upstream of WF box
• Wire scanners
• Experiment protection system for beam loss
  monitoring (common to other ESA tests)
• Bunch length diagnostics t.b.d
• Effort for
• Cabling
• Movement of wakefield box to ESA
• Replacement of seals in wakefield box for each
  sandwich
• Utilities

13
ESA Test Update

• Draft distributed last week, comments end 15/4,
• http//hepunx.rl.ac.uk/swmd/
• Comments very welcome!
• Purpose
• Commision WF box in ESA
• Additional study resistive wakes in Cu
• First study of 2-step tapers
• Status Report

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ESA Facility

• Moving quickly
• Two approved projects (T-474,T475)
• Coll. Wakefields
• VXD3 EMI study
• Mike Woods leading project with growing number of
  participants
• Weekly working meetings (phone/SLAC)
• Information collected on web at

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ESA beamline layout
Wakefield box

• Measure kick factor using incoming/outgoing beam
  trajectory, scanning collimator gap through beam
• Stage 1, 5 rf cavity BPMs, 1 stripline BPM, 2
  wire scanners
• Wakefield box, proposal for 2 sets of four pairs
  of spoiler jaws
• Each set mounted in separate sandwich to swap
  into WF box
• (relatively) rapid change over, in situ
• 1 week run, Nov. 2005 (t.b.c., going through
  approval process)

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Optical design

• Optical design of A-line for WF expt. by Frank
  Jackson/Deepa A-K.

sy100mm and flat in vicinity of WF box
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Wakefield box
ESA sz 300mm ILC nominal sy 100mm
(Frank/Deepa design)
Magnet mover, y range ?1.4mm, precision 1mm
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Mechanical Design

• Baseline mechanical designs from SLAC c/o Ray
  Arnold
• Drawings for assembly, sandwich, etc.
• Saves us time/effort (money)
• CCLRC/RAL ED will draw/fabricate new sets for ESA
  run
• Discussions with Joe ODell/Justin Greenhalgh,
  started looking at CAD drawings

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a
r1/2 gate
As per last set in Sector 2, commissioning
Extend last set, smaller r, resistive WF in Cu
7mm
cf. same r, tapered
20
7 mm
Cf. slot 4, set A, smaller r
Cf. slot 2, same r
208mm
28mm
Cf. slot 4, set A,and slot 2
159mm
Cf. slot 3, and same step in/out earlier data
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Spoiler fabrication

• CCLRC ED (Greenhalgh/ODell)
• 1st draft drawings from Joe ODell this week
• Iteration with SLAC on important details (screw
  sizes, locations, tolerances, etc.)
• Required at SLAC 7 Oct.
• Release final drawings for fabrication, 1 Aug.

22
Computer Simulations of Spoiler designs
Carl Beard

• Codes being developed/used to measure the
  impedance of vessels
• ECHO2D, MWStudio, HFSS, GDFIDL, MAFIA, etc etc
• Calculation errors due to small angle of taper
• Off axis measurements

1mm
1m
The length of the structure and the frequency
make simulation time very long
user defined pulse possible
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Longitudinal Wakefield Calculations
Integrating the long-range wake with the bunch
shape the loss factors are obtained.
2-plane symmetry for longitudinal Wake potential
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Transverse Wakefield Calculations Set-up
If the structure is symmetric and the beam is on
axis then the transverse components are zero
Only single plane of symmetry in x-axis
The kick factor is produced by integrating the
transverse wake with the bunch shape
y beam off-set N Number of electrons -
classical electron radius - Relativistic
factor
Y-axis displacement
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Transverse Wake Results
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SummaryConclusion

• Much improved status of WF studies at ESA
• T-480 proposal en route to approval in near
  future
• Integrated UK with EUROTeV programmes
• Programme of
• RF bench tests (ASTeC, Lanc.)
• E.M. modelling
• WF beam test
• Damage studies
• We need to
• Extend WF simulations to GDFIDL (help from UCL)
  and ECHO-3D (TEMF)
• Simulate ESA experimental setup (BPM
  resolution/locations)
• Build/deliver spoiler inserts
• Firm up UK technical contribution (e.g. misc.
  cables, modules)
• Fill advertised EUROTeV post at ASTeC (closing
  5-Aug)
• More ideas!