SPOILER WAKEFIELDS and MECHANICAL DESIGN

1
SPOILER WAKEFIELDS and
MECHANICAL DESIGN

• 
  
• 
  Adriana Bungau
• 
  The University of Manchester
• 
  
• 
  
  
• 
  
  
  Manchester, 24/04/2006

2
Outline

• Motivation
• Wakefield simulations
• 2.1 Progress for ESA tests
• - ESA experiment
• - Collimator
  fabrication
• 2.2 Wakefield studies
• - Gdfidl/Mafia
• - Merlin studies
• 3 Material damage
• - Geant4/Fluka
  studies
• - Ansys studies
• 4. Future plans

3
Motivation

• Aim optimal design of the ILC colimators to
  minimise wakefield effects

• Transverse wakefields excited can lead to
• emittance dilution
• amplification of position jitter at the IP

N.Watson
1 halo is enough to damage a thick collimator
(L.Keller)

• Damage near the edge is easier than in the
  middle of the solid volume

Main goal the collimators should be able to
survive at 2 bunches at 250 GeV and 1 bunch
at 500 GeV
4
People

• Birmingham N.K.Watson (D.Adey, M.Stockton)
• CCLRC C.Beard,G.Ellwood,J.Greenhalgh,J.O'Dell,L.F
  ernandez
• CERN F.Zimmermann,D.Schulte EUROTeV
• DESY I.Zagorodnov EUROTeV
• Lancaster J.Smith,A.Sopczak
• Manchester R.Barlow,A.Bungau,G.Kourevlev,
  A.Mercer, R.Jones
• TEMF, Darmstadt M.Kärkkäinen,W.Müller,T.Weiland
  EUROTeV
• For ESA tests, working closely with
• F.Jackson (CCLRC) on optics for wakefield and
  beam damage studies
• M.Woods, P.Tenenbaum, R.Arnold, (SLAC) for all
  aspects
• For evolving damage studies, L.Keller, M.Ross,
  M.Seidel, DESY/SLAC/

Project web http//hepunx.rl.ac.uk/swmd/
5
ESA Experimental tests

• 
  
• 
  Procedure (P.Tenenbaum)
• 
  - insert collimators in beam path (x
  mover)
• 
  - move collimator vertically
  (y mover)
• 
  - measure centroid kick to
  beam via BPMs
• 
  - Analyse kick angle vs
  collimator position
• Commissioning 4-9 Jan 2006 (4 old collimators)
  - Successful
• Physics 24 Apr 8 May (8 new collimators
  CCLRC)
• People N. Watson, J. Smith, C.Beard, L.
  Fernandez, A.Sopczak, F.Jackson

Next run 3 17 Jul 2006
6
ESA
View upstream from 3BPM9-11
View downstream from 3C2
7
ESA
View downstream from the 3WS2
3BPM 3-5
8
ESA the collimators

• Collimators made at RAL (J.Greenhalg, J. ODell)

Col . No. R (mm) H (mm) Angle (mrad) L (mm)
1 2 18.05 324 102.06
2 1.4 17.05 324 105.63
3 1.4 16.05 324 1105.11
4 4 15.05 0 7 (not ref)
5 1.4 14.05 0 7 (not ref)
6 1.4 13.05 166 210.96
7 1.4 12.05 0 31.3
8 1.4 11.05 289 132.54

• The full set of collimators is at SLAC (four of
  
• these are in the sandwich box, second
• sandwich yet to be prepared)
• Carry out a swap of the sandwiches at the
• beamline -gt measurements with 8 collimators
• within 2 weeks is a big step forward
• Commissioning run starts on 24 April

9
Wakefields Gdfidl / Mafia
(J.Smith - Lancaster, C. Beard -Astec)

• Gdfidl/Mafia simulations of longitudinal wakes
  are in acceptable agreement
• ( Chos results (EPAC paper) still to be
  understood result of assumed
• symmetry ?)
• Performed comparison with ABCI for very simple
  configurations (pillbox cavity as test, with
  varying bunch length)
• R.Jones (expertise in this field area)
• However
• Short timescale for getting results to compare
  with test data at SLAC, even shorter for
  prediction of kicks

10
Wakefields in Merlin

• The Existing Code
• Wakefield formalism implemented in Merlin
• Wakefield effects previously studied by R.Barlow,
  G. Kourevlev, A. Mercer
• SLAC tests were simulated -gt good agreement with
  the data when higher order modes are included
• But the wakepotential the same for all
  accelerator components

11
Wakefields in Merlin
r, ?

• Changes and Additions to the Code
• Cm ? rm cos (m?) Sm ? rm sin (m?)
• wL ? Wm (s) rm Cm cos (m?) Sm sin (m?)
• wX ? mWm (s) rm-1 Cm cos (m-1)? Sm sin
  (m-1)?
• wY ? mWm (s) rm-1 Sm cos (m-1)? Cm sin
  (m-1)?
• define new derived classes SpoilerWakeProcess
  (Cm, Sm), WakePotentials (aperture information),
  SpoilerWakePotentials (longitudinal and
  transverse wakes)
• Work currently ongoing (A.Bungau, R.Barlow)

s
z
r, ?
12
Material Damage Geant4 /Fluka
Simulate energy deposits (Fluka L.Fernandez,
Geant4 A.Bungau) -gtinstantaneous T rise Beam
profile as in ILC FF9 optics at SP2/4 locations
Various spoiler design considered (solid
material/combination of two materials) Results
passed on for transient state studies

• Discussions started with
• L.Keller (Nov 2005)
• Agreement between three
• codes EGS/Fluka/Geant4

0.6 Xo of Ti alloy leading taper (gold),
graphite (blue), 1 mm thick layer of Ti alloy
0.3 Xo of Ti alloy each side, central graphite
part (blue).
L.Fernandez, ASTeC
A.Bungau (Manchester)
13
Material Damage - ANSYS

• Study of steady/transient state heating effects
• used Edep from Fluka/Geant4
• good agreement between simulation
  
• and analytic calculations
• predicted the stress induced in a 3d
• solid (variation with different spoiler
• geometries and beam impact
• locations)

G. Ellwood (RAL)

• Studies from beam damage compiled into a proposal
• To be discussed with people from SLAC/DESY
• Various EPAC06 abstracts were submitted
• EUROTeV reports submitted for review (Fluka and
  Geant4 studies)

14
Future Plans

• Analyse the data from the first round of tests
  24/4 08/05
• Compare with analytic calculations and e.m.
  simulations
• Design/build a new set of collimators to test at
  ESA (input also from ECHO-3D code)
• Extend the damage simulations into real
  experimental tests with beam
• Post-April 2007 development of real collimators
  (not just jaws materialgeometry)