overview of clic main linac accelerating structure design
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Overview of CLIC main linac accelerating structure design
21/10/2010A.Grudiev (CERN)
C L I CC L I C
CLIC-ACE, 16 Jan. 2008Alexej Grudiev, Structure optimization.
RF design constraints for CLIC
Beam dynamics (BD) constraints based on the simulation of the main linac, BDS and beam-beam collision at the IP:
• N – bunch population depends on <a>/λ, Δa/<a> because of short-range wakes
• Ns – bunch separation depends on the long-range dipole wake suppression
RF breakdown and pulsed surface heating (PSH) constraints:
• ΔTmax(Hsurfmax, tp) < 56 K (accelerating structure life time
issues)
• Esurfmax < 250 MV/m
• Pin/Cin·(tp)1/3 < 18 MW/mm · ns1/3
• (Sc = Re{S} + Im{S}/6)·(tp)1/3 < 4 MW/mm2 · (200 ns)1/3
RF constraints: data analysis 1RF design name f [GHz]
dphi [deg] vg1 [%]
1 DDS1 11.424 120 11.72 T53VG5R 11.424 120 53 T53VG3MC 11.424 120 3.34 H90VG3 11.424 150 35 H60VG3 11.424 150 2.86 H60VG3R18 11.424 150 3.37 H60VG3R17 11.424 150 3.68 H75VG4R18 11.424 150 49 H60VG4R17 11.424 150 4.510 HDX11-Cu 11.424 60 5.111 CLIC-X-band 11.424 120 1.112 T18VG2.6-In 11.424 120 2.613 T18VG2.6-Out 11.424 120 1.0314 T18VG2.6-Rev 11.424 120 1.0315 T26VG3-In 11.424 120 3.316 T26VG3-Out 11.424 120 1.6517 TD18_KEK_In 11.424 120 2.418 TD18_KEK_Out 11.424 120 0.919 SW20A3p75 11.424 180 020 SW1A5p65T4p6 11.424 180 021 SW1A3p75T2p6 11.424 180 022 SW1A3p75T1p66 11.424 180 023 2pi/3 29.985 120 4.724 pi/2 29.985 90 7.425 HDS60-In 29.985 60 826 HDS60-Out 29.985 60 5.127 HDS60-Rev 29.985 60 5.128 HDS4Th 29.985 150 2.629 HDS4Th 29.985 150 2.630 PETS9mm 29.985 120 39.8
constBDR
tE pa 530
High power test results has been scaled to tp=200 nsBDR=1e-6 bpp/m using power scaling lower
based on the fitting the data
3
RF constraints: data analysis 2Data has been scaled to tp=200 ns BDR=1e-6 bpp/m
6/ImRe SS cS4
In TD18, all quantities are close to T18 at the same average gradient, except for the pulsed surface heating temperature rise which is factor 5 higher in the last cell.
0 2 4 6 8 10 12 14 16 180
50
100
150
200
250
iris number
P [
MW
] (b
lack
), E
s (
gre
en),
Ea (
red
) [M
V/m
],
T
[K
] (b
lue)
, S
c*50
[MW
/mm
2 ] (m
agen
ta)
30.6
49.4
157
234
3.3
4.5
79
120
56.8
33.8
Pinload = 56.8 MW, P
outload = 33.8 MW
Eff = 0.0 % tr = 0.0 ns, t
f = 0.0 ns, t
p = 100.0 ns
0 2 4 6 8 10 12 14 16 180
50
100
150
200
250
iris number
P [
MW
] (b
lack
), E
s (
gre
en),
Ea (
red
) [M
V/m
],
T
[K
] (b
lue)
, S
c*50
[MW
/mm
2 ] (m
agen
ta)
8.1 12.5
148
232
2.7
4.4
76
126
53.0
37.4
Pinload = 53.0 MW, P
outload = 37.4 MW
Eff = 0.0 % tr = 0.0 ns, t
f = 0.0 ns, t
p = 100.0 ns
1st generation of CLIC X-band test structure prototypes T18/TD18Parameters at tp=100 ns, <Ea>=100 MV/mT18_vg2.6_disk: TD18_vg2.4_disk:
Very strong tapering inspired by the idea of having constant P/C along the structure
High surface fields
5
2007
0 5 10 15 200
50
100
150
200
250
iris number
P [
MW
] (b
lack
), E
s (
gre
en),
Ea (
red
) [M
V/m
],
T
[K
] (b
lue)
, S
c*50
[MW
/mm
2 ] (m
agen
ta)
26.8 25.1
183193
3.5
3.0
94102
44.4
20.6
Pinload = 44.4 MW, P
outload = 20.6 MW
Eff = 0.0 % tr = 0.0 ns, t
f = 0.0 ns, t
p = 100.0 ns
0 4 8 12 16 20 24240
50
100
150
200
250
iris number
P [
MW
] (b
lack
), E
s (
gre
en),
Ea (
red
) [M
V/m
],
T
[K
] (b
lue)
, S
c*50
[MW
/mm
2 ] (m
agen
ta)
7.5 8.4
176
205
3.03.2
90
108
41.1
23.4
Pinload = 41.1 MW, P
outload = 23.4 MW
Eff = 0.0 % tr = 0.0 ns, t
f = 0.0 ns, t
p = 100.0 ns
In TD24, all quantities are lower than in TD18 at the same average gradient. In particular pulsed surface heating temperature rise reduced by factor 2.
2nd generation of CLIC X-band test structure prototypes T24/TD24Parameters at tp=100 ns, <Ea>=100 MV/mT24_vg1.8_disk: TD24_vg1.8_disk:
Weaker tapering (quasi const gradient) together with smaller aperture (11% instead of 12.8%) reduce surface fields significantly compared to T18/TD18.
6
2007
From RF design to a piece of Copper
IWLC2010 Walter Wuensch 19 October 2010
Scaling to CLIC conditions: Scaled from lowest measured BDR to BDR=4*10-7 and =180 ns (CLIC flat-top is 170 ns), using standard E295/BDR =const. Correction to compensate for beam loading not included – expected to be less than about 7%.
T18 by KEK/SLAC at SLAC #1
T18 by KEK/SLACat KEK
T18 by CERNat SLAC
TD18 by KEK/SLACat SLAC
TD18 by KEK/SLACat KEK
unloaded gradient [MV/m]
Synthesis of accelerating structure test results scaled to CLIC breakdown rate
T24 by KEK/SLACat SLAC
1400
3900
550
Total testing time [hr]
1300
3200
200
T18 by KEK/SLACat SLAC #2
280
60 70 80 90 100 110
HOM damping
HOM damping
Comparison at tp=252 ns, BDR=1e-6 bpp/m
0 2 4 6 8 10 12 14 16 180
50
100
150
200
250
iris number
P [
MW
] (b
lack
), E
s (
gre
en),
Ea (
red
) [M
V/m
],
T
[K
] (b
lue)
, S
c*50
[MW
/mm
2 ] (m
agen
ta)
T18--KEK, tp=252 ns, BDR = 1e-5 bpp/m, <E
a> = 101 MV/m,
13.120.3
149
235
2.7
4.5
76
127
54.1
38.2
Pinload = 54.1 MW, P
outload = 38.2 MW
Eff = 0.0 % tr = 0.0 ns, t
f = 0.0 ns, t
p = 252.0 ns
P/C*tp^(1/3) = 13.4 [MW/mm*ns^(1/3)] P/C*tp^(1/3) = 10.6 [MW/mm*ns^(1/3)]
T18: <Ea> = 101 MW/m TD18: <Ea> = 86.6 MW/m
In TD18, all quantities are lower than in T18 measured at the same tp and BDR, except for the pulsed surface heating temperature rise which is factor 3 higher ???
0 2 4 6 8 10 12 14 16 180
50
100
150
200
250
iris number
P [
MW
] (b
lack
), E
s (
gre
en),
Ea (
red
) [M
V/m
],
T
[K
] (b
lue)
, S
c*50
[MW
/mm
2 ] (m
agen
ta)
TD18--KEK, tp = 252 ns, BDR = 1e-6 bpp/m, <Ea. = 86.6 MV/m
36.5
59.0
136
202
2.5
3.3
68
104
42.6
25.4
Pinload = 42.6 MW, P
outload = 25.4 MW
Eff = 0.0 % tr = 0.0 ns, t
f = 0.0 ns, t
p = 252.0 ns
9
Comparing last cell at tp=252 ns, BDR=1e-6 bpp/mT18: <Ea> = 101 MW/m, Ea = 127 MV/m TD18: <Ea> = 86.6 MW/m; Ea = 104 MV/m
10
0 5 10 15 200
50
100
150
200
250
iris number
P [
MW
] (b
lack
), E
s (
gre
en),
Ea (
red
) [M
V/m
],
T
[K
] (b
lue)
, S
c*50
[MW
/mm
2 ] (m
agen
ta)
21.1 19.0
184194
3.7
3.1
94102
40.5
18.7
Pinload = 40.5 MW, P
outload = 18.7 MW
Eff = 0.0 % tr = 0.0 ns, t
f = 0.0 ns, t
p = 100.0 ns
Near term plans
0 2 4 6 8 10 12 14 16 180
50
100
150
200
250
iris number
P [
MW
] (b
lack
), E
s (
gre
en),
Ea (
red
) [M
V/m
],
T
[K
] (b
lue)
, S
c*50
[MW
/mm
2 ] (m
agen
ta)
30.6
49.4
157
234
3.3
4.5
79
120
56.8
33.8
Pinload = 56.8 MW, P
outload = 33.8 MW
Eff = 0.0 % tr = 0.0 ns, t
f = 0.0 ns, t
p = 100.0 ns
TD18_vg2.4_disk:
0 5 10 15 200
50
100
150
200
250
iris number
P [M
W] (
blac
k), E
s (g
reen
), E
a (red
) [M
V/m
],
T [K
] (bl
ue),
Sc*5
0 [M
W/m
m2 ] (
mag
enta
)26.8 25.1
183193
3.5
3.0
94102
44.4
20.6
Pinload = 44.4 MW, Pout
load = 20.6 MW
Eff = 0.0 % tr = 0.0 ns, tf = 0.0 ns, tp = 100.0 ns
TD24_vg1.8_disk:At 11.424 GHz testing of T24/TD24 should come this year.
Very interesting because TD24 has 2 times lower PSH ΔT than TD18
0 5 10 15 200
50
100
150
200
250
iris number
P [M
W] (
blac
k), E
s (g
reen
), E
a (red
) [M
V/m
],
T [K
] (bl
ue),
Sc*5
0 [M
W/m
m2 ] (
mag
enta
)
27.7 26.9
184193
3.7
3.1
94102
40.7
18.6
Pinload = 40.7 MW, P
outload = 18.6 MW
Eff = 0.0 % tr = 0.0 ns, t
f = 0.0 ns, t
p = 100.0 nsAt 11.994 GHz testing of
T24/TD24/TD24_R05 are planed for the next year.
TD24 TD24_R05 provides further reduction of PSH ΔT by 1/3
TD24_vg1.8_disk TD24_vg1.8_R05:
11
Geometry difference between TD24_vg1.8_disk TD24_vg1.8_R05
12
Design of the HOM Damping Load
Tip size 1x1 mmTip length 20 mm or 30 mmBase size 5.6 x 5 or 5.5 mmBase length 10 mmWaveguide width awd = 10.1 mm or 11 mm50.00 60.00 70.00 80.00 90.00 100.00 110.00
sdw [mm]
3000.00
3500.00
4000.00
4500.00
5000.00
5500.00
6000.00
Y1
Ansoft Corporation f0_45_adw11mmXY Plot 1
Curve Info
Q(1)Setup1 : LastAdaptive
Q(1)1Imported
thick line: awg = 11mm, thin line: awg = 10.1 mm
Will be used for CLIC module prototype and for a structure prototype for high power testing with damping load inside (TD24_vg1.8_R05_SiC)
SiC properties from M.Luong, 1999
13
Will be used for CLIC module prototype and for a structure prototype for high power testing with damped compact coupler (TD26_vg1.8_R05_CC)
Design of the damped compact coupler
14
Beyond CLIC_G• Next step in rf design will be a structure with a degree of tapering lower than TD18 (41%) and TD24 (8%)• For example, ~ 20-25 %• It will probably have bigger average aperture if CLIC main beam bunch charge can be increased accordingly.• A detailed optimization of the parameters and rf design will be done soon
0 5 10 15 200
50
100
150
200
250
iris number
TD18 vg2.4 disk
29.147.0
155
226
3.2
4.4
79
120
57.5
34.3
41%
0 5 10 15 20 250
50
100
150
200
250
iris number
TD24 vg1.7 disk
24.621.7
183193
3.3
2.9
94102
44.4
20.6
8%
15
Quadrants/halves familyHALVES
Here T18_vg2.6_quad design is used. It has no slots.
QUADs with SLOTST18_vg2.6_quad design is used but rounded 4 slots of 0.2 mm are introduced.
16
Symmetrical disk design
It has a number of pros and cons:+ higher Q― higher cost― requires axial alignment ― tuning is more difficult and it is not implement―
The structure is in the production
17
Alternative damping designs1. DDS type is underdevelopment at 12 GHz by Cockcroft Institute and
Manchester University (R. Jones, A. D’Elia, V. Khan).2. Choke-mode type is under development in collaboration with
Tsinghua University (J. Shi)1. Minimum gap acceptable from the point of view rf breakdowns
to be determined using CD10_choke with different gaps: 1mm, 2mm, etc.
2. Damping design of the full structure is under way aiming at full structure prototype high power test
18
The choke mode cavity and radial choke
19
Damping simulation with Gdfidl/HFSS
(Model in HFSS)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 210
-1
100
101
102
103
Wy /
[V
/pC
/m/m
m]
s / m
gap 1mm
gap 1.5mmgap 2mm
0 10 20 30 40 50 60 70 80 90-10
0
10
20
30
40
Z y / k
/m
/mm
f / GHz
gap 1mm
gap 1.5mmgap 2mm
Gap 1mm 2mm Good damping forfirst dipole
Mode reflected by the choke, to be studied…
E field, fundamental mode
E field of a dipole mode that is reflected by the choke Impedance and wakefield simulated in Gdfidl 20
Design of CD-10-Choke
• CD10-Choke for demonstration– RF Design for Gap 1mm, 1.5mm, 2mm– Mechanical Design finished for 1mm-gap– Qualification disks and bonding test
• To the production pipeline and High Power testing
21
• Limited number of cells (N=24) in a structure (poor sampling of a Gaussian) means truncation of Gaussian leading to re-coherence of the wake (t=1/Δfmin)
• Re-coherence of the wake is suppressed by moderate damping: Coupling out the HOMs using a waveguide like structure i.e. manifolds running parallel to the accelerating cells
• Interleaving neighboring structure frequencies improves wake suppression
• Gaussian distribution of cell parameters is chosen in this (CLIC_DDS) structure which causes Wakefield to decay in nearly Gaussian fashion for short time scale (few nsec)
Damped Detuned Structure
• This is a similar technique to that experimentally verified and successful employed for the NLC/JLC program
• Potential benefits include, reduced pulse temperature heating (In principle true but not for CLIC_DDS_A: pulse heating is greater than CLIC_G), ability to optimally locate loads, built-in beam and structure diagnostic (provides cell to cell alignment) via HOM radiation. Provides a fall-back solution too!
24
Disk cross-section.
Parameter Value
a (mm) 3.8523
b (mm) 11.0031
t (mm) 3.8884
ε 1.0203
g (mm) 4.3316
CLIC_DDS_A: Regular disk #1 Section profile and Parameters Table
Parameters table.L
= t +
g
t
a
b
t/2
ε*t/2
Ellipse
25
CLIC_DDS_A: E-Field profile along the structure
Thank you
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