Collimation in the ILC BDS

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15 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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Collimation in the ILC BDS

Carl Beard

ASTeC Daresbury Laboratory


People


Requirement


Recent Successes


Future Aims

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

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 23
rd



24
th

November 2006

Need for Collimation


Reduce the background levels in the detector, by removing
halo particles built up over the long linac.




Machine Protection, in the event of a beam miss
-
steer.

Collimators are introduced, as a result of this the change in
impedance has detrimental effects to the beam quality.

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 23
rd



24
th

November 2006


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

Objectives

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

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 10
10


Copper

Fracture temperature ~200
°
C (473 K)

Melting temperature 1085
°
C (1357.77 K)

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

Collimator Proposals

0.3 Xo of Ti alloy each side, central
graphite part (blue).

0.6 Xo of Ti alloy leading taper
(gold), graphite (blue), 1 mm thick
layer of Ti alloy

Ti/C

2 mm,
10mm

250, 500 GeV e
-

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

Cu+Graphite spoiler

∆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.

Carbon zones

Cu zones

500 GeV:

σx

= 79.5
µm,
σ
y= 6.36
µm

250 GeV:

σx

= 111
µm,
σ
y= 9
µm

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

Ti / Graphite Spoiler

∆Tmax = 575 K per a bunch of 2E10 e
-

at 500 GeV

σ
x

= 79.5
µm,
σ
y
= 6.36
µm

270 K

405 K

540 K

2 mm deep from top

Ti alloy and graphite spoiler

400 K

Temperature data in the left only valid the Ti
-
alloy material. Top
increase of temp. in the graphite ~400 K. Dash box: graphite region.

[L.Fernandez, ASTeC]

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

Fluka Benchmark

0
100
200
300
400
500
600
700
0.5
1
1.5
2
2.5
3
Incident e-/um^2 (+/- 2 sigma)x10^7
Melted area (um^2)
Measurements courtesy of SLAC,
Marc Ross et al.

Fluka Prediction of beam Damage
(Evaporated material not considered

Measurements of Beam damage
crater in cooper on the FFTB.


Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

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 23
rd



24
th

November 2006

Wakefield Analysis

Analytical Formula

Simulation

Bench Tests (TDR)

Tests with Beam

Instant solution for only simple geometry

Real life measurements, slow
turnaround time for measurements

Good indicator


poor resolution

Fast Results


Limited by
Resolution/
confidence

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

Simulation and Wire tests

Current TDR and TDT measurements
are limited to 10 ps Pulse lengths.

TDR and TDT are being used
to measure the Impedance of
a vessel and its loss factor

Loss Parameter
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
1E-09
1.2E-09
1.4E-09
1.6E-09
1.8E-09
2E-09
2.2E-09
Time (s)
Volts
Launch Pulse
Transmitted Signal
Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

Achieving a 1 ps Pulse (In development)

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

MAFIA Simulations

y = 0.5856x
3
- 1E-14x
2
+ 0.4088x - 1E-13
-8
-6
-4
-2
0
2
4
6
8
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
2.5
Beam Off set (mm)
Kick Factor (V/pC/mm)
0.5mm Bunch
Poly. (0.5mm Bunch)
-15
-10
-5
0
5
10
15
0
0.001
0.002
0.003
0.004
0.005
0.006
Distance Z (mm)
Wakepotential (V/pC)
500 micron bunch
2mm offset
1.2mm offset
0.8mm offset
0.4mm offset
Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

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

MAFIA/HFSS

GDFIDL /
ECHO 2 &3D

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

Beam Tests in ESA


Simple Shapes to allow benchmarking with Calculations/Code


Geometric Wakefields


Resistive Wall Wakefields


Surface Roughness


=

/2rad
r=3.8mm
4

335mrad
r=1.4mm
3

335mrad
r=1.4mm
2

=335mrad
r=1.9mm
1
Beam view
Side view
Slot

=

/2rad
r=3.8mm
4

335mrad
r=1.4mm
3

335mrad
r=1.4mm
2

=335mrad
r=1.9mm
1
Beam view
Side view
Slot
h=38 mm
38 mm
h=38 mm
h=38 mm
38 mm
38 mm
L=1000 mm
L=1000 mm
L=1000 mm
7mm

r=1/2 gate


=298mrad


=168mrad
r
1
=3.8mm
r
2
=1.4mm
4

1
=

/2
rad

2
=168mrad
r
1
=3.8mm
r
2
=1.4mm
3

168mrad
r=1.4mm
2

=

/2rad
r=1.4mm
1
Beam view
Side view
Slot


=298mrad


=168mrad
r
1
=3.8mm
r
2
=1.4mm
4

1
=

/2
rad

2
=168mrad
r
1
=3.8mm
r
2
=1.4mm
3

168mrad
r=1.4mm
2

=

/2rad
r=1.4mm
1
Beam view
Side view
Slot
h=38 mm
h=38 mm
38 mm
38 mm
7 mm
208mm
28mm
159mm
Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

T
-
480 Experiment

Vertical mover

BPM

BPM

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…

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

T
-
480 Experiment

Vertical mover

BPM

BPM

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…

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

Wakefield Box

ESA

s
z
~ 300
m



ILC nominal


s
y

~ 100
m
洠⡆牡湫/䑥数愠摥獩杮s

䵡杮M琠浯癥爬礠牡湧攠㴠

.4
mmⰠ灲散楳楯渠㴠=
m
m

E
beam
=28.5GeV

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

November 2006

Initial Comparison of Results

Just selecting one ref run (slot 0 ref)
Just selecting one ref run (same slot ref)
run
q1
dq1
chisq/n
run
q1
dq1
chisq/n
599
-1.0117E-11
3.70281E-12
0.556841
599
-7.13552E-12
3.69547E-12
0.811254
624
-1.16155E-13
3.39041E-12
0.861219
624
-6.36929E-13
3.4007E-12
1.153441
1491
1.26302E-11
1.10968E-12
73.30665
1491
1.26302E-11
1.10968E-12
73.30665
w. mean
9.78258E-12
1.01429E-12
w. mean
9.96031E-12
1.01441E-12
w. mean chisq
-4.92422E-12
2.0283E-12
w. mean chisq
-3.13033E-12
2.38158E-12
%
%
kf
1.74034675
0.180444912
10.36833
kf
1.771965811
0.180466779
10.18455
kf (using chisq)
-0.876031954
0.360840007
-41.19028
kf (using chisq)
-0.556893046
0.423690061
-76.08105
Analytical: 0.562 V/pC/mm

MAFIA: 0.408 V/pC/mm

Beam Test 0.556 V/pC/mm

Carl Beard


Cockcroft SAC Meeting 23
rd



24
th

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.


3
rd

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