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Jonathan Smith, 1st March, COLSIM, CERN1
Recent Developments with ILC Collimator Wakefield
Calculations
Jonathan Smith(Lancaster University/Cockcroft Institute)
Jonathan Smith, 1st March, COLSIM, CERN2
Introduction/Project Objectives
● LC-ABD WP5.3 (Nigel Watson)/EUROTeV WP2 (BDS)
● Collimation is crucial for beam delivery and detector protection/performance of a particle accelerator
● Quantification of longitudinal and transverse wakefield effects of collimators on the beam
● Optimization of collimator design● Use and understanding of simulation tools,
potential improvements and support of other projects
● Verification by test beam measurement
Jonathan Smith, 1st March, COLSIM, CERN3
Wakefield box
ESA z ~ 300m – ILC nominaly ~ 100m (Frank/Deepa design)
Magnet mover, y range = mm, precision = 1m
1500mm
Ebeam=28.5GeV
Slide reproduced from talk by Nigel Watson
Jonathan Smith, 1st March, COLSIM, CERN4
=/2rad
r=4.0mm4, 4
324mrad
r=1.4mm3, 3
324mrad
r=1.4mm2, 2
=324mrad
r=2.0mm1, 1
Revised
4-May-2006Beam viewSide view (“DESY sandwich”)Collim. #,
slot
h=38 mm
38
mm
L=1000 mm
7mm
r=1/2 gap
As per last set in Sector 2, commissioningAs per last set in Sector 2, commissioning
Extend last set, smaller r, resistive WF in CuExtend last set, smaller r, resistive WF in Cu
cf. same r, taperedcf. same r, tapered Slide reproduced from talk by Nigel Watson
Jonathan Smith, 1st March, COLSIM, CERN5
=/2rad
r=1.4mm5, 4
166mrad
r=1.4mm6, 3
1=/2 rad
2=166mrad
r1=4.0mm
r2=1.4mm
7, 2
r1 =4.0mm
r2 =1.4mm =289mrad
=166mrad
8, 1
Revised
4-May-2006Beam viewSide view (“SLAC sandwich”)Collim.#, slot
h=38 mm
38
mm
7 mmcf. collim. 4 smaller rcf. collim. 4 smaller r
211mmcf. collim. 2, same rcf. collim. 2, same r
31mm
cf. collims. 4 and 6cf. collims. 4 and 6
133mm
cf. collim. 7, and same step in/out earlier datacf. collim. 7, and same step in/out earlier data
Slide reproduced from talk by Nigel Watson
Jonathan Smith, 1st March, COLSIM, CERN6
Small improvement on the
Chisq/n
Run 1206 (ref. 1207)
Multiplying each bunch by its ebpm_x ADC value
Jonathan Smith, 1st March, COLSIM, CERN7
Analytical estimate
● Stupakov says:●Stupakov says:●Stupakov says:●Stupakov says:
●Stupakov asserts that the h»b is met, but is this really valid?
Jonathan Smith, 1st March, COLSIM, CERN8
For SLAC collimators...
Jonathan Smith, 1st March, COLSIM, CERN9
Assessment/Familiarization of Simulation Tools
● MAGIC (easy to use tool for first comparison with new calculations)
● ECHO/ECHO3D– Thomas Weiland, Mikko Karkkainen (TEMF,
Darmstadt) Igor Zagorodnov (DESY). Code development as part of EUROTeV project
● MAFIA– CDB and JS working on comparison with Cho Ng’s results
(PAC 2001)● GdfidL
– Overlapping interest with David Miller and Alexei Liapine (UCL) as part of EUROTeV WP5 (Spectrometry)
● Additional software for research if required:– BCI/TBCI/ABCI (old CERN tools), XWAKE, XOOPIC– Tau3P, Omega, T3P (next generation SLAC codes)– Boundary Element (BEM) codes (Sapporo, Japan)
Jonathan Smith, 1st March, COLSIM, CERN10
EM Simulations with GdfidL
11 22
33
55
66
7744
88
Jonathan Smith, 1st March, COLSIM, CERN11
Wakefields @300µm
(6 cells/sigma)
Jonathan Smith, 1st March, COLSIM, CERN12
Wakefields @500µm
(12 cells/sigma)
Jonathan Smith, 1st March, COLSIM, CERN13
Mesh stability: Collimators 1&2
● Only 3 decent points at 300µm for most collimators
● More at 500µm● 1mm ~ OK – can use
spline fit on data to get an estimate – not done so far – further analysis to see if this takes us closer to ECHO/PBCI.
Jonathan Smith, 1st March, COLSIM, CERN14
What do we do about it? (1)
Jonathan Smith, 1st March, COLSIM, CERN15
What do we do about it?(2)
Jonathan Smith, 1st March, COLSIM, CERN16
Effect of mesh filtering…
Jonathan Smith, 1st March, COLSIM, CERN17
Misallignment
Jonathan Smith, 1st March, COLSIM, CERN18
Further collimator designs
semi-circle, with[9]/without[10] flat, opposing demi-circles[10], 8 with flat[11].
Jonathan Smith, 1st March, COLSIM, CERN19
More possible collimators
7 with flat [13], half exponential[14], 13 with shallower angle[15]exponential profile[16],13 with ellipse connecting 4mm and 1.4mm aperture[17]13 with ellipse connecting beam pipe radius and 1.4mm aperture (also see 9)[18]half cosine taper [19], raised cosine taper [20], tanh tapers [21] (set typically to the length of collimator 6)
Jonathan Smith, 1st March, COLSIM, CERN20
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
Jonathan Smith, 1st March, COLSIM, CERN21
non-linear taper
r=1.4mm16?
1=/2 rad
2=50mrad
r1=4.0mm
r2=1.4mm
15
1=/2 rad
2=166mrad
r1=4.0mm
r2=1.4mm
14
1=/2 rad
2=166mrad
r1=4.0mm
r2=1.4mm
13
Revised
27-Nov-2006Beam viewSide viewCollim.#
h=38 mm
38
mm
cf. ?cf. ?
Polished, cf. collim. 13Polished, cf. collim. 13
Polished, cf. collims. 7, 11, 13Polished, cf. collims. 7, 11, 13
Polished, cf. collim. 7, 12, 13Polished, cf. collim. 7, 12, 13
Ti6Al4V
OFE Cu
OFE Cu=21 mm
Form t.b.d.
= 0.6Ti6Al4V
Runs 3, 2007
~52 mm
=21 mm
~52 mm
=21 mm
~125 mm
=21 mm
Jonathan Smith, 1st March, COLSIM, CERN22
Variation of collimator kick with bunch length
Jonathan Smith, 1st March, COLSIM, CERN23
WB's suggestion:
Chop this bit off as beam will never see wake that has travelled this far from the bunch
Jonathan Smith, 1st March, COLSIM, CERN24
Two possibilities:s_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
xs_ma
x
s_max
“colimator 23”
“colimator 22”
Jonathan Smith, 1st March, COLSIM, CERN25
Longitudinally Asymmetric?
Jonathan Smith, 1st March, COLSIM, CERN26
Results...
Jonathan Smith, 1st March, COLSIM, CERN27
Cylindrical jobs...
● W modal decomposition
● See Adriana's talk...● Jobs still running● w(s,r,r',θ,θ')→w(s,r,θ,m)● Useful for rectangular
geometry?
Jonathan Smith, 1st March, COLSIM, CERN28
GdfidL & PBCI● TEMF working on ECHO/PBCI – 3D,
moving mesh, conformal, non-dispersive solver
s/σ
σ/Δz=6
W║(s
)/(V
/pC
)
GdfidLPBCI
With thanks to Mikko Kärkkäinen