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Jonathan Smith (Lancaster University/Cockcroft Institute). Towards Improved Collimation for the ILC. Outline. Damage Studies Merlin Simulations Bench Tests T480@ESA EM Simulation activity Plans. LC-ABD WP5.3 /EUROTeV WP2 (BDS) - PowerPoint PPT Presentation
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Jonathan Smith, LC-ABD, 12th April 07, RHUL1
Towards Improved Collimation for the ILC
Jonathan Smith(Lancaster University/Cockcroft Institute)
Jonathan Smith, LC-ABD, 12th April 07, RHUL2
Outline
● Damage Studies● Merlin Simulations● Bench Tests● T480@ESA● EM Simulation
activity● Plans
• LC-ABD WP5.3 /EUROTeV WP2 (BDS)
• Collimation is crucial for beam delivery and detector protection/performance
http://hepunx.rl.ac.uk/swmd/talks/
Jonathan Smith, LC-ABD, 12th April 07, RHUL3
People● “Spoiler Wakefield and Mechanical Design” task● Details on project web: http://hepunx.rl.ac.uk/swmd/
● Birmingham: N.Watson● CCLRC: C.Beard,G.Ellwood,J.Greenhalgh,J.O'Dell,L.Fernandez ● CERN: F.Zimmermann,G.Rumolo,D.Schulte● [DESY: I.Zagorodnov]● Lancaster: D.Burton,R.Carter,N.Shales,J.Smith,A.Sopczak,R.Tucker● Manchester: R.Barlow,A.Bungau,R.Jones● TEMF, Darmstadt: vice-M.Kärkkäinen,W.Müller,T.Weiland
● For ESA tests, working closely with– CCLRC on optics for wakefield and beam damage studies– SLAC Steve Molloy et al. for all aspects
Jonathan Smith, LC-ABD, 12th April 07, RHUL4
SLAC T-480 Experiment
Vertical mover
BPMBPM
2 doublets
~40m
BPM BPM
Two triplets
~16m
• Wakefields measured in running machines: move beam towards fixed collimators
• Problem– Beam movement oscillations– Hard to separate wakefield effect
• Solution– Beam fixed, move collimators around beam– Measure deflection from wakefields vs. beam-collimator separation– Many ideas for collimator design to test…
Jonathan Smith, LC-ABD, 12th April 07, RHUL5
Vertical mover
BPMBPM
2 doublets
~40m
BPM BPM
Two triplets
~16m
• Wakefields measured in running machines: move beam towards fixed collimators
• Problem– Beam movement oscillations– Hard to separate wakefield effect
• Solution– Beam fixed, move collimators around beam– Measure deflection from wakefields vs. beam-collimator separation– Many ideas for collimator design to test…
Jonathan Smith, LC-ABD, 12th April 07, RHUL6
ESA beamline layout (2006 version)
• Measure kick factor using incoming/outgoing beam trajectory, scanning collimator gap through beam
• 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 – ½ shift for access– Physics runs, Mar 2007, Jul 2006, May 2006 + Jul’07?
Wakefield box
Beam
Jonathan Smith, LC-ABD, 12th April 07, RHUL7
=298mrad
=168mrad
r1 =3.8mm
r2 =1.4mm
4
1=/2 rad
2 =168mrad
r1 =3.8mm
r2 =1.4mm
3
168mrad
r=1.4mm2
=/2rad
r=1.4mm1
Beam viewSide viewSlot
=298mrad
=168mrad
r1 =3.8mm
r2 =1.4mm
4
1=/2 rad
2 =168mrad
r1 =3.8mm
r2 =1.4mm
3
168mrad
r=1.4mm2
=/2rad
r=1.4mm1
Beam viewSide viewSlot
h=38 mmh=38 mm
38 m
m38
mm
7 mm
208mm
28mm
159mm=/2rad
r=3.8mm4
335mrad
r=1.4mm3
335mrad
r=1.4mm2
=335mrad
r=1.9mm1
Beam viewSide viewSlot
=/2rad
r=3.8mm4
335mrad
r=1.4mm3
335mrad
r=1.4mm2
=335mrad
r=1.9mm1
Beam viewSide viewSlot
h=38 mm
38 m
m
h=38 mmh=38 mm
38 m
m38
mm
L=1000 mmL=1000 mmL=1000 mm
7mm
r=1/2 gate
r=2 mm
Collimator 1 is similar to collimator described in SLAC-PUB-12086
Collimator 2 is like 1 but with a narrower gap
Collimator 3 has the same taper angle and gap as 2. We hope to measure the difference due to resistive wakefield.
Collimator 2, 3 and 4 have same taper angle, but 3 and 4 just in the top. The aim is to measure the difference between each geometry, if there is any. A small taper angle is better to reduce wakefields but it also need longer (more space) collimators. Can be model it?
Jonathan Smith, LC-ABD, 12th April 07, RHUL8
Slot 1
Slot 4
Slot 2
Slot 3L=1000 mm
= 324 mradr = 2 mm
= 324 mradr = 1.4 mm
= /2 r = 3.8 mm
= 324 mradr = 1.4 mm
(r = ½ gap)
Jonathan Smith, LC-ABD, 12th April 07, RHUL9
Collimator Measured4
Kick Factor V/pc/mm (2/dof)
Linear fit
Measured4
Kick Factor V/pc/mm (2/dof)
Linear + Cubic Fit
Analytic Prediction1
Kick Factor V/pc/mm
3-D Modelling
Prediction2
Kick Factor
V/pc/mm
1 1.4 ± 0.1 (1.0)3 1.2 ± 0.3 (1.0) 1.1 1.7
2 1.4 ± 0.1 (1.3) 1.2 ± 0.3 (1.4) 2.3 3.1
3 4.4 ± 0.1 (1.5) 3.7 ± 0.3 (0.8) 6.6 7.1
4 0.9 ± 0.2 (0.8) 0.5 ± 0.4 (0.8) 0.3 0.8
5 1.7 ± 0.3 (2.0) 1.7 ± 0.3 (2.2) 2.3 2.4
6 1.7 ± 0.1 (0.7) 2.2 ± 0.3 (0.5) 2.4 2.7
7 0.9 ± 0.1 (0.9) 0.9 ± 0.3 (1.0) 2.3 2.4
8 3.7 ± 0.1 (7.9) 4.9 ± 0.2 (2.6) 2.3 6.8
1Assumes 500-micron bunch length2Assumes 500-micron bunch length, includes analytic resistive wake; modelling in progress3Kick Factor measured for similar collimator described in SLAC-PUB-12086 was (1.3 ± 0.1) V/pc/mm4Still discussing use of linear and linear+cubic fits to extract kick factors and error bars
→ Goal is to measure kick factors to 10%
Preliminary results:
L=1000 mm
208mm
28mm
159mm
Jonathan Smith, LC-ABD, 12th April 07, RHUL10
GdfidL EM simulations…
beam
Jonathan Smith, LC-ABD, 12th April 07, RHUL11
166mrad
r=1.4mm12
=166mrad
r =1.4mm11
=166mrad
r =1.4mm10
166mrad
r=1.4mm
(1/2 gap)6
Revised
27-Nov-2006Beam viewSide viewCollim.#
h=38 mm
38
mm
Roughened surface, compare with 12Roughened surface, compare with 12
As 10, in Ti-6Al-4V, polished, cf. 12As 10, in Ti-6Al-4V, polished, cf. 12
As 10, in OFE Cu, polished, cf. collim. 6, 13As 10, in OFE Cu, polished, cf. collim. 6, 13
Runs 3, 2007
Exists, from 2006 runs. For reproducibilityExists, from 2006 runs. For reproducibility
~211mm
1.4mm
=21mm
=21mm
=21mm
beam
Jonathan Smith, LC-ABD, 12th April 07, RHUL12
Collim.# Side view (“SLAC sandwich”) Beam view Revised
08-Nov-2006
13
1=/2 rad
2=168mrad
r1=4.0mm
r2=1.4mm
14
1=/2 rad
2=168mrad
r1=4.0mm
r2=1.4mm
15
1=/2 rad
2=50mrad
r1=4.0mm
r2=1.4mm
16=exp., sin
r=1.4mm
h=38 mm
38
mm
21 mm
21 mm
52 mm
Ti6Al4V
OFE Cu
21 mm
125 mm
21 mm
= 0.6Ti6Al4V
Jonathan Smith, LC-ABD, 12th April 07, RHUL13
Data analysis from this run…
● Is ongoing, but here is a preview...
Jonathan Smith, LC-ABD, 12th April 07, RHUL14
Longitudinally Asymmetric?
Jonathan Smith, LC-ABD, 12th April 07, RHUL15
Damage Studies
● EGS/Geant4/FLUKA in agreement● ANSYS modelling of temperature flow done.● Shockwave studies underway● Focus now on manufacturability – e.g. wire erosion● Search for a site to conduct damage tests (CERN?
Discussions at EPAC… )
Last time:
Now:● Wire erosion method tested in manufacture on non-linear
profile collimator.● Proposal for damage tests at ATF in preparation,
awaiting discussion at next ATF users meeting.
Jonathan Smith, LC-ABD, 12th April 07, RHUL17
Including EM simulations into Merlin
Fourier DeconvolutionWbunch(s,m)=Wdelta(s,m)Gaussian
Take FT of ECHO result (here mode=1) and FT of Gaussian
(red and blue are sine and cosine parts)
Divide to obtain FT of delta wake
Back-transform.Horrible! (Look at y axis scale)
But mathematically correct: combined with Gaussian reproduces original
Due to noise in spectra at high frequency. Well known problem
Jonathan Smith, LC-ABD, 12th April 07, RHUL18
Delta wakes: Consistency check
Give the same delta wakes
Use FT to extract delta wakes from the different bunch wakes
Agreement reasonable: method validated
Green oscillation artefact of ECHO2D, not of Fourier extraction
Jonathan Smith, LC-ABD, 12th April 07, RHUL19
Merlin studies: emittance dilution due to wakefield
Looked at emittance dilution due to higher order mode wakefields -> get an increase in the beam size and consequently a decrease in luminosity
Beam excursions due to small offsets are under study.
A.Bungau - Manchester University
Jonathan Smith, LC-ABD, 12th April 07, RHUL20
Cylindrical jobs...
● W modal decomposition
● Jobs still running● w(s,r,r',θ,θ')→w(s,r,θ,m)● Useful for rectangular
geometry?
Jonathan Smith, LC-ABD, 12th April 07, RHUL21
Bench “wire method” setup
● Calculate impedence of structure
● Simulate mode structure
● Use where wire is not interfering with the mode, or use simulation results to subtract wire induced effects
Plot from S.F.Hill and M.J.Pugh, paper at EPAC'94
Jonathan Smith, LC-ABD, 12th April 07, RHUL22
Summary● Run 3 at ESA successful, data analysis well
advanced● Collimator damage simulations in 2006…
– ATF proposal in preparation, submission 2 May 2007
● EM simulations – Being used to design optimal spoiler geometries
● Wire tests– devices in production, test utility of method at DL
● Merlin/Placet simulations with wakefields– Quantify effect of higher order modes