collimator design and short range wakefields
DESCRIPTION
Collimator design and short range wakefields. Adriana Bungau University of Manchester. CERN, Dec 2006. ILC-BDS spoilers. Must satisfy several competing requirements: Thickness: 0.5 and 1.0 r.l -> avoids particle multiplication in e.m. showers and high energy density - PowerPoint PPT PresentationTRANSCRIPT
Collimator design and short range wakefields
Adriana Bungau
University of Manchester
CERN, Dec 2006
ILC-BDS spoilers
Must satisfy several competing requirements:
• Thickness: 0.5 and 1.0 r.l -> avoids particle multiplication in e.m.
showers and high energy density• Survivable ( 1 bunch at 250 GeV and 2 bunches at 500 GeV)• Include tapers section (leading and trailing tapers)-> reduces the
wakefield components induced by change in aperture• high electrical conductivity ->mitigates the resistive wall effects
Understanding the effect the concentrated energy deposition has on the collimator material is an important design consideration
Impossible to test the ILC candidate spoiler in the exact beam
conditions of size and energy as the ILC ->rely heavily on simulation
Bunch charge: 2.1010 e-, energy=250 GeV
Spoiler Beam size
(m) X Y
EGS4
T (K)
FLUKA
T (K)
GEANT4
T (K)
0.6 r.l.
Ti alloy 28 6 1380 1560 2000
0.6 r.l.
Ti alloy111 9 290 255 255
1.0 r.l.
Ti alloy104 15 260 300 310
30 cm Cu 20 1.4 25000 25000 25600
Collimator design - GEANT4
Benchmarking for simple titanium alloy targets
Spoiler Beam size
(m) X Y
EGS4
T (K)
FLUKA
T (K)
GEANT4
T (K)
0.6 r.l.
Ti alloy 28√2 6√2 2770 3180 3200
0.6 r.l.
Ti alloy111√2 9√2 560 450 435
1.0 r.l.
Ti alloy 58 11 720 760 770
30 cm Cu 20√2 1.4√2 60000 69000 70000
Benchmarking for simple titanium alloy targets
Bunch charge: 2.1010 e-, Energy=500 GeV
GEANT4 simulations of the spoilers
Two types of spoilers:• a full metal spoiler • a combination of metal and graphite
Choice of material:
Material r.l. T (K) Conductivity
(.m)-1
Ti6Al4V 3.56 1941 -
Copper 1.43 1358 6.0*10-7
Aluminium 8.9 933 3.8*10-7
Beam profile:
- at energy 250 GeV:
x = 111 m
y = 9 m
- at energy 500 GeV:
x = 78.48 m
y = 6.36 m
Charge: 2*1010 e-
The beam was sent through the collimators at 2 depths: 2mm and 10 mm from the top at beam energy 250 GeV and 500 GeV for each depth.
Full metal spoiler
Ti alloy spoiler
width = 38 mmheight = 17 mmlength = 122.64 mmupper region = 21.4 mmangle = 324 mrad
Al spoiler
width = 38 mmheight = 17 mmlength = 154.64 mmupper region = 53.4 mmangle = 324 mrad
Cu spoiler
width = 38 mmheight = 17 mmlength = 109.82 mmupper region = 8.58 mmangle = 324 mrad
zy
x
Ti alloy Aluminium
Depth T(K) at
250 GeV
T(K) at
500 GeV
2 mm 376 827
10 mm 818 1951
Difference 117% 135%
Depth T(K) at
250 GeV
T(K) at
500 GeV
2 mm 201 372
10 mm 276 586
Difference 37% 58%
Instantaneous T rise
Fracture T (489 K) exceeded!
Copper
Depth T at 250 GeV T at 500 GeV
2 mm 1206 2438
10 mm 3060 7800
Difference 153% 219%
Instantaneous T rise
Metal-graphite spoiler
same dimensions as Ti alloy
graphite prism:
z =100.23 mm long
offset from spoiler centre:
z = 10.18 mm
y = 0.16 mm
zy
x
same dimensions as for Al
graphite prism:
z =100.23 mm long
offset from spoiler centre:
z = 26.07 mm
y = 0.16 mm
same dimensions as for Cu
graphite prism:
z =100.23 mm long
offset from spoiler centre:
z = 3.76 mm
y = 0.16 mm
Instantaneous T rise
Ti alloy-Graphite Aluminium-Graphite
Depth T at 250 GeV T at 500 GeV
2 mm 238 456
10 mm 304 527
Difference 27% 15%
Depth T at 250 GeV T at 500 GeV
2 mm 190 352
10 mm 192 381
Difference 1% 8%
Depth T at 250 GeV T at 500 GeV
2 mm 517 743
10 mm 330 850
Difference -36% 14%
Instantaneous T rise
Copper-Graphite
Summary
• the combination of metal-graphite spoiler is a safer option ( the melting T was not reached in any of these cases)
• attractive candidates are TiAlloy-Graphite and Al-graphite spoilers
What about particle multiplicities and energy spectra?
e.m. shower for one 250 GeV e- at 2 mm depth e.m. shower for one 250 GeV e- at 10 mm depth
Particle Multiplicities and Energy Spectra
Ti alloy-Graphite
Ti alloy-Graphite
Al-Graphite
Al-Graphite
Conclusion - collimator damage
• Energy deposition profile from Geant4/Fluka used for ANSYS studies at RAL (steady state, transient effects, fractures)
• Simulation studies are now written up (see EUROTeV reports)
• Beam damage test to follow (SLAC, CERN ?)
Ti alloy - graphite spoiler is the best option
Wakefield simulations with Merlin
Current situation:
• mathematical formalism developed by R. Barlow for incorporating higher order mode wakefields
• formalism implemented in the Merlin code • SLAC beam tests simulated -> good agreement between analytical
calculations and experiment• so far, only simple beamlines were studied (ie. Drift, Collimator, Drift)
Roger Barlow, Adriana Bungau - “Simulation of High Order Short Range Wakefields”
(EUROTeV-Report-2006-051)
No Name Type Z (m) Aperture
1 CEBSY1 Ecollimator 37.26 ~
2 CEBSY2 Ecollimator 56.06 ~
3 CEBSY3 Ecollimator 75.86 ~
4 CEBSYE Rcollimator 431.41 ~
5 SP1 Rcollimator 1066.61 x99y99
6 AB2 Rcollimator 1165.65 x4y4
7 SP2 Rcollimator 1165.66 x1.8y1.0
8 PC1 Ecollimator 1229.52 x6y6
9 AB3 Rcollimator 1264.28 x4y4
10 SP3 Rcollimator 1264.29 x99y99
11 PC2 Ecollimator 1295.61 x6y6
12 PC3 Ecollimator 1351.73 x6y6
13 AB4 Rcollimator 1362.90 x4y4
14 SP4 Rcollimator 1362.91 x1.4y1.0
15 PC4 Ecollimator 1370.64 x6y6
16 PC5 Ecollimator 1407.90 x6y6
17 AB5 Rcollimator 1449.83 x4y4
No Name Type Z (m) Aperture
18 SP5 Rcollimator 1449.84 x99y99
19 PC6 Ecollimator 1491.52 x6y6
20 PDUMP Ecollimator 1530.72 x4y4
21 PC7 Ecollimator 1641.42 x120y10
22 SPEX Rcollimator 1658.54 x2.0y1.6
23 PC8 Ecollimator 1673.22 x6y6
24 PC9 Ecollimator 1724.92 x6y6
25 PC10 Ecollimator 1774.12 x6y6
26 ABE Ecollimator 1823.21 x4y4
27 PC11 Ecollimator 1862.52 x6y6
28 AB10 Rcollimator 2105.21 x14y14
29 AB9 Rcollimator 2125.91 x20y9
30 AB7 Rcollimator 2199.91 x8.8y3.2
31 MSK1 Rcollimator 2599.22 x15.6y8.0
32 MSKCRAB Ecollimator 2633.52 x21y21
33 MSK2 Rcollimator 2637.76 x14.8y9
Next plans:• extend the studies to the ILC-BDS beamline (33 collimators involved)• interested in the emittance growth given by wakefield modes as a function of beam offset, bunch profile at IP• work is in progress.
Wakefield Measurements at SLAC-ESA
Motivation:
to optimize the collimator design by studying various ways of minimising wakefield effects while achieving the required performance for halo removal
SLAC beam has similar parameters as for the ILC bunch for bunch charge, bunch length and bunch energy spreadCommissioning: Jan 2006 (4 old collimators) - SuccessfulPhysics: first run: Apr/May second run: July (8 new collimators – CCLRC) People: N. Watson, S.Molloy, J. Smith, A.Bungau, L. Fernandez, C.Beard,
A.Sopczak, F.Jackson (optics modeller)
ESA – Experimental tests
- 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
1500mm
- collimators fabricated and polished at RAL
Sandwich 2, slot 4
Reconstructed kick vs collimator position
good run: 1206
horizontal axis in mm, vertical axis in urad position of the BPMs
-performed calibrations before each of the collimators (ie. a BMP calibration for each collimator to protect against any BPM drifts);
-monitored the beam size, length etc as such a long scan would allow larger drifts in these cases;
bad run: 1388
Next plans :
• data analysis work not complete-> reprocessing with new BPM calibration algorithm
• Manchester cluster set up for BPM recalibration - complete
• seven new collimator designs agreed for run3-ESA ->sent to manufacturing company
• new beam tests at ESA in 2007 with new collimators