Collimation in the ILC BDS
Carl Beard
ASTeC Daresbury Laboratory
•People
•Requirement
•Recent Successes
•Future Aims
People




Task Leader – Nigel Watson (B’ham)
Damage Studies
 L. Fernandez (ASTeC), A.Bungau (Manc) R. Barlow (Manc) G.
Elwood (RAL), J. Greenhaulgh (RAL).
Wakefield Simulation and TDR
 C. Beard (ASTeC), J. Smith (Lanc), R. Jones (Manc), R.Carter
(Lanc), S Jamison (ASTeC), P Corlett (ASTeC)…
 I. Zagorodnov (DESY),
 M.Kärkkäinen, W.Müller, T.Weiland (TEMF)
Beam Tests (T-480 Experiment)
 Frank Jackson…plus most of the above
 SLAC ESA Team – Steven Malloy, Mike Woods…
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Need for Collimation

Reduce the background levels in the detector, by removing
halo particles built up over the long linac.
Collimators are introduced, as a result of this the change in
impedance has detrimental effects to the beam quality.

Machine Protection, in the event of a beam miss-steer.
The collimators have to be robust to withstand the full
impact of several ILC Bunches.
Design / optimisation of spoiler jaws
(geometry and materials) for wakefield
and beam damage performance
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Objectives





Development of Advanced EM modelling methods
Benchmarking of wakefield calculations against
experiments
 SLAC ESA beam test / data analysis
 RF bench tests (training/code comparisons)
Tracking simulations with best models of wakefields
Simulations of beam damage to spoilers
Material studies using beam test
Submitted 7 papers at EPAC, several EUROTeV reports/memos
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Collimator Parameter and Beam Parameters
Beam Energy, GeV
250, 500
Material
Cu, Ti, C
Penetration (mm)
2 to 10
e- Particles/bunch
2 x 1010
Copper
Fracture temperature ~200 °C (473 K)
Melting temperature 1085 °C (1357.77 K)
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Collimator Proposals
2 mm,
10mm
250, 500 GeV eTi/C
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).
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Cu+Graphite spoiler
Carbon zones
250 GeV:
σx = 111 µm, σy= 9 µm
500 GeV:
σx = 79.5 µm, σy= 6.36 µm
∆T [K]; 250 GeV e-
∆T [K]; 500 GeV e-
2 mm from top
465 K
860 K
10 mm from top
440 K
870 K
Difference
-5%
1%
Fracture temp.
Melting temp.
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Cu zones
Ti / Graphite Spoiler
Temperature data in the left only valid the Ti-alloy material. Top
increase of temp. in the graphite ~400 K. Dash box: graphite region.
540 K
405 K
400 K
270 K
2 mm deep from top
∆Tmax = 575 K per a bunch of 2E10 e- at 500 GeV
Ti alloy and graphite spoiler σx = 79.5 µm, σy= 6.36 µm
Carl Beard – Cockcroft SAC Meeting
23rd
–
24th
November 2006
[L.Fernandez, ASTeC]
Fluka Benchmark
Fluka Prediction of beam Damage
(Evaporated material not considered
Measurements of Beam damage
crater in cooper on the FFTB.
700
Measurements courtesy of SLAC,
Marc Ross et al.
Melted area (um^2)
600
500
400
300
200
100
0
0.5
1
1.5
2
Incident e-/um^2 (+/- 2 sigma)x10^7
2.5
3
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Damage Studies


Beam tests are being planned to benchmark the
Fluka/Geant Simulations
 No electron beam is available with sufficient intensity
 Or probability to hit the same point due to beam jitter.
Dynamic Simulations in ANSYS are being studied in
support of the FLUKA/GEANT Simulations
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Wakefield Analysis
Instant solution for only simple geometry
Analytical Formula
Simulation
Fast Results –
Limited by
Resolution/
confidence
Bench Tests (TDR)
Good indicator –
poor resolution
Tests with Beam
Real life measurements, slow
turnaround time for measurements
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Simulation and Wire tests
Loss Parameter
2.5
2
Launch Pulse
Transmitted Signal
1.5
Volts
1
TDR and TDT are being used
to measure the Impedance of
a vessel and its loss factor
0.5
0
1E-09
-0.5
1.2E-09
1.4E-09
1.6E-09
1.8E-09
2E-09
2.2E-09
-1
-1.5
Time (s)
Current TDR and TDT measurements
are limited to 10 ps Pulse lengths.
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Achieving a 1 ps Pulse (In development)
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
MAFIA Simulations
15
500 micron bunch
10
2mm offset
1.2mm offset
0.8mm offset
0.4mm offset
Wakepotential (V/pC)
5
0
0
0.001
0.002
0.003
0.004
0.005
0.006
-5
-10
-15
Distance Z (mm)
8
y = 0.5856x3 - 1E-14x2 + 0.4088x - 1E-13
6
Kick Factor (V/pC/mm)
4
2
0
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
-2
-4
0.5mm Bunch
-6
Poly. (0.5mm Bunch)
-8
Beam Off set (mm)
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Limitations / Advances
Limiting the simulations to short structures or only
sufficient resolution for >>300 um bunch length.
A new technique is being applied to allow full structures to
be simulated with substantially higher resolution
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
MAFIA/HFSS
GDFIDL /
ECHO 2 &3D
Beam Tests in ESA
Simple Shapes to allow benchmarking with Calculations/Code
 Geometric Wakefields
 Resistive Wall Wakefields
 Surface Roughness
Slot
Side view
Beam view
Side view
Beam view
=/2rad
=335mrad
38 mm

1
Slot
r=1/2 gate
r=1.9mm
1
7 mm
h=38 mm
r=1.4mm
h=38 mm
335mrad
r=1.4mm
2
38 mm

168mrad
r=1.4mm
2
208mm
1=/2 rad
335mrad
3
r=1.4mm
2=168mrad
3
L=1000 mm
28mm
=/2rad
r=3.8mm
4
159mm
4
7mm
r1=3.8mm
r2=1.4mm
=298mrad
=168mrad
r1 =3.8mm
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
r2 =1.4mm
T-480 Experiment
2 doublets
BPM
BPM
Two triplets
BPM
~40m
BPM
~16m
Vertical mover



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…
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
T-480 Experiment
2 doublets
BPM
BPM
Two triplets
BPM
~40m
BPM
~16m
Vertical mover



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…
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Wakefield Box
Ebeam=28.5GeV
ESA
sz ~ 300mm – ILC nominal
sy ~ 100mm (Frank/Deepa design)
Magnet mover, y range = .4mm, precision = 1mm
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Initial Comparison of Results
Analytical: 0.562 V/pC/mm
MAFIA: 0.408 V/pC/mm
Beam Test 0.556 V/pC/mm
Just selecting one ref run (same slot ref)
run
q1
dq1
599 -7.13552E-12 3.69547E-12
624 -6.36929E-13
3.4007E-12
1491
1.26302E-11 1.10968E-12
w. mean
9.96031E-12 1.01441E-12
w. mean chisq-3.13033E-12 2.38158E-12
kf
1.771965811
kf (using chisq)
-0.556893046
chisq/n
0.811254
1.153441
73.30665
%
0.180466779 10.18455
0.423690061 -76.08105
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006
Future Work





Continue study into beam damage/materials
 In the process of designing a 4th beam test
Collimators designed and built in EU, to be installed at
SLAC ESA.
 3rd Physics run Mar/April 2007
Application of the Moving Mesh Technique
TDR Measurements with Optically generated 1 ps Pulse.
Combine information on geometry, material, construction,
to find acceptable baseline design regarding all of
 Wakefield optimisation
 Collimation efficiency
 Damage mitigation
Carl Beard – Cockcroft SAC Meeting 23rd – 24th November 2006