Accelerating structure
prototypes for 2011
(proposal)
A.Grudiev
6/07/11
Outline
• T18++ at 11.424 GHz
• Alternative to CLIC-G for CLIC main linac
–
–
–
–
Same last iris (CLIC-M)
Similar <a> (CLIC-N)
Same degree of tapering as T18 (CLIC-O)
XXL tapering (CLIC-P)
• Single feed input/output couplers for CLIC_G
How can we improve T18
T18-vg2p6-disk
76
30
20
10
53.0
50
Percent of BKD Events
126
37.4
tp = 100.0 ns
0
5
12.5
10
iris number
0
0
5
15
10
Cell No.
15
20
moment about the hot cell
#7, the BDR is higher in the
last cell, where field
quantities are higher.
• So reducing tapering
should help ???
• N.B., in T24, the BDR
distribution is more flat but
there are also other
differences
6
250
Pload
= 41.1 MW, P load
= 23.4 MW
in
out
Eff = 0.0 %
tr = 0.0 ns, tf = 0.0 ns, tp = 100.0 ns
T24_SLAC
205
5
3.2
4
200
176
a
3.0
150
T24_vg1.8_disk
3
T24_KEK
s
108
Events
s
148
2.7
8.1
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
394 BKDs within 0~250hrs
193 BKDs within 250~500hrs
298 BKDs within 500~750hrs
57 BKDs within 750~900hrs
74 BKDs within 900~1000hrs
34 BKDs within 1000~1200hrs
24 BKDs within 1200~1400hrs
40
100
0
P [MW] (black), E (green), E (red) [MV/m],
T18_SLAC#1
200
150
• If we forget for the
50
232
4.4
T18_vg2.6_disk
a
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
P [MW] (black), E (green), E (red) [MV/m],
250
100
90
2
50
41.1
23.4
0
0
1
8.4
7.5
4
8
12
iris number
16
20
24
0
0
5
10
15
Cell No.
20
25
From T18 to T35 at 11.424 GHz
T18-vg2p6-disk
T35-vg2p6-disk
200
a
148
2.7
150
126
s
s
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
0.16 m active length
250
P [MW] (black), E (green), E (red) [MV/m],
232
4.4
a
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
P [MW] (black), E (green), E (red) [MV/m],
250
100
76
53.0
50
37.4
8.1
0
0
tp = 100.0 ns
12.5
0.31 m active length
200
10
iris number
15
3.8
161
3.2
150
117
100
83
63.3
50
32.5
tp = 100.0 ns
9.6
0
5
217
0
5
10
15
20
iris number
10.9
25
30
35
New cells
are in red
• New prototype T35_vg2.6_disk is proposed at 11.424 GHz
• Due to doubling the length all peak field values in the last cells are lower by ~10% but
the values in the first cell become higher by the same amount
• It does not make since to do it at 12 GHz because there is no T18@12GHz
• There is no need for a new RF design. RF design of T18_vg2.6_disk can be used
including matching cells. Dimensions of the regular cells have to be redefined when
introducing 17 new cells between 18 regular cells of T18_vg2.6_disk.
Making it even longer (T52_vg2.6_disk)
T18-vg2p6-disk
T52-vg2p6-disk
250
0.46 m active length
197
200
3.7
173
3.2
a
148
2.7
150
126
s
s
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
200
P [MW] (black), E (green), E (red) [MV/m],
232
4.4
0.16 m active length
a
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
P [MW] (black), E (green), E (red) [MV/m],
250
100
76
53.0
50
37.4
8.1
0
0
tp = 100.0 ns
5
10
iris number
12.5
15
150
107
100
89
72.8
50
0
0
27.0
tp = 100.0 ns
11.1
5
10
15
20
25
30
iris number
9.0
35
40
45
• Even longer prototype T52_vg2.6_disk is proposed at 11.424 GHz
• Due to tripling the length all peak field values in the last cells are lower. It is close to a
constant gradient structure. This is also more practical in terms of length.
• It does not make since to do it at 12 GHz because there is no T18@12GHz
• There is no need for a new RF design. RF design of T18_vg2.6_disk can be used
including matching cells. Dimensions of the regular cells have to be redefined when
introducing 2*17 new cells between 18 regular cells of T18_vg2.6_disk.
50
T18-vg2p6-disk
250
232
4.4
Summary for T18++
structure proposals
200
148
2.7
150
126
100
76
53.0
c
s
a
P [MW] (black), E (green), E (red) [MV/m],
s
a
T [K] (blue), S *50 [MW/mm 2] (magenta)

2
c
 T [K] (blue), S *50 [MW/mm ] (magenta)
P [MW] (black), E (green), E (red) [MV/m],
50
37.4
8.1
250
0
0
, tp = 100.0 ns
5
12.5
T35-vg2p6-disk
10
iris number
T35_vg2.6_disk
15
200
217
3.8
161
3.2
150
117
100
83
63.3
50
9.6
0
250
0
200
32.5
tp = 100.0 ns
5
10.9
T52-vg2p6-disk
10
15
20
iris number
25
30
T52_vg2.6_disk
35
197
3.7
173
3.2
150
107
100
89
72.8
50
0
0
27.0
9.0
tp = 100.0 ns
11.1
5
10
15
20
25
iris number
30
35
40
45
50
CLIC-G disk R05 regular cells
200
200
194
3.1
160
24 regular cells unloaded
180
160
3.0
26 regular cells unloaded
140
60
40.5
21.1
20
0
19.0
18.7
5
10
15
iris number
20
• The difference between TD24 and TD26 is only 1-2 % in field
quantities, which is most probably un-measurable in highgradient experiments
• That means
•we can compare TD24_vg1.7_R05 <-> TD26_vg1.7_R05CC
for compact coupler performance evaluation
•we can also use it for comparison with possible alternatives
to CLIC_G with “mode launcher” power coupler
Pload
= 41.8 MW, P load
= 18.1 MW
in
out
96 Eff = 0.0 %
tr = 0.0 ns, tf = 0.0 ns, tp = 100.0 ns
100
80
100
60
41.8
40
18.1
21.8
20
0
300
18.4
0
5
5.4
a
40
120
250
10
15
20
200
25
26 regular
cells loaded,
iris number
N=3.72e9, Nb=312
224
229
4.3
Pload
= 60.0 MW, P load
= 9.8 MW
in
out
Eff = 27.9 %
tr = 22.4 ns, tf = 62.6 ns, tp = 240.5 ns
150
s
80
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
100
102
s
Pload
= 40.5 MW, P load
= 18.7 MW
in
out
94 Eff = 0.0 %
tr = 0.0 ns, tf = 0.0 ns, tp = 100.0 ns
P [MW] (black), E (green), E (red) [MV/m],
s
120
0
191
187
3.8
a
140
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
3.7
P [MW] (black), E (green), E (red) [MV/m],
180
a
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
P [MW] (black), E (green), E (red) [MV/m],
184
120
115
100
60.0
44.7
50
0
0
37.8
26.0
5
10
15
iris number
20
25
Constant Sc with the same last iris: CLIC-M
300
TD26_vg2.0_diskR05
a
206
200
3.5
3.5
173
26 regular cells loaded,
N=3.72e9, Nb=322
4.9
4.9
250
243
200
150
203
Pload
= 63.3 MW, P load
= 12.5 MW
in
out
Eff = 27.3 %
tr = 22.4 ns, tf = 57.4 ns, tp = 240.3 ns
128
s
s
150
108
100
88
45.7
5
10
15
iris number
20
Parameter changes CLIC-G -> CLIC-M:
1st iris radii [mm]: 3.15 -> 3.41
Input group velocity [%]: 1.65 -> 1.99
<a>/lambda: 0.11 -> 0.117
N: 3.72e9 -> 4.1e9
Nb: 312 -> 322
25
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
0
63.3
50
43.0
29.3
39.8
300
0
0
a
tp = 100.0 ns
104
100
5
10
15
20
N=4.1e9,
Nb = 322
iris number
5.0
250
25
5.0
246
206
200
Pload
= 65.2 MW, P load
= 11.8 MW
in
out
Eff = 29.2 %
150 tr = 22.4 ns, tf = 57.4 ns, tp = 240.3 ns
130
s
21.2
21.5
19.9
P [MW] (black), E (green), E (red) [MV/m],
50
0
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
250
P [MW] (black), E (green), E (red) [MV/m],
26 regular cells unloaded
a
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
P [MW] (black), E (green), E (red) [MV/m],
300
105
100
65.2
50
44.1
40.9
30.2
0
0
5
10
15
iris number
20
25
Constant Sc with the reduced last iris: CLIC-N
300
172
3.4
3.4
150
108
100
88
50
42.2
20.7
18.4
19.3
0
tp = 100.0 ns
0
5
10
15
iris number
20
25
Parameter changes CLIC-G -> CLIC-N:
1st, last iris radii [mm]: {3.15,2.35} -> {3.342.24}
Input,output vg/c [%]: {1.65,0.83} -> {1.89,0.74}
<a>/lambda: 0.11 -> 0.1116
N is the same
Nb: 312 -> 306
250
245
4.9
4.8
205
200
Pload
= 60.4 MW, P load
= 10.1 MW
in
out
Eff = 27.3 %
tr = 25.7 ns, tf = 62.3 ns, tp = 240.6 ns
a
200
26 regular cells loaded,
N=3.74e9, Nb=306
150
130
s
205
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
TD26_vg1.9_diskR05
s
a
250
P [MW] (black), E (green), E (red) [MV/m],
26 regular cells unloaded
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
P [MW] (black), E (green), E (red) [MV/m],
300
105
100
60.4
50
0
42.1
26.3
39.3
0
5
10
15
iris number
20
25
Same degree of tapering as T18: CLIC-O
153
150
3.0
120
100
78
50
42.7
24.0
16.5
0
0
tp = 100.0 ns
5
10
15
iris number
250
4.2
a
200
5.6
268
26 regular cells loaded,
N=3.73e9, Nb=295
200
s
3.9
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
225
TD26_vg2.3_diskR05
s
a
250
P [MW] (black), E (green), E (red) [MV/m],
300
26 regular cells unloaded
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
P [MW] (black), E (green), E (red) [MV/m],
300
Pload
= 60.7 MW, P load
= 10.3 MW
in
out
150
Eff = 26.1 %
tr = 31.0 ns, tf = 62.4 ns, tp = 240.4 ns
182
100
143
93
60.7
50
48.2
33.0
26.4
18.6
20
25
Parameter changes CLIC-G -> CLIC-O:
1st, last iris radii [mm]: {3.15,2.35} -> {3.6,2.1}
Input,output vg/c [%]: {1.65,0.83} -> {2.25,0.64}
<a>/lambda: 0.11 -> 0.114
N: is the same
Nb: 312 -> 295
0
0
5
10
15
iris number
20
25
Even more tapering: CLIC-P
350
5.0
s
s
200
150
129
2.5
139
100
66
44.8
50
30.3
13.2
0
19.9
tp = 100.0 ns
5
10
15
iris number
20
25
Parameter changes CLIC-G -> CLIC-P:
1st, last iris radii [mm]: {3.15,2.35} -> {4.04,1.94}
Input,output vg/c [%]: {1.65,0.83} -> {2.94,0.53}
<a>/lambda: 0.11 -> 0.1196
N: is the same
Nb: 312 -> 282
300
6.9
304
Pload
= 62.5 MW, P load
= 11.5 MW
in
out
Eff = 24.3 %
tr = 38.9 ns, tf = 61.1 ns, tp = 240.5 ns
250
a
250
258
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
TD26_vg2.9_diskR05
P [MW] (black), E (green), E (red) [MV/m],
300
0
26 regular cells loaded,
N=3.74e9, Nb=282
26 regular cells unloaded
a
2
 T [K] (blue), S c*50 [MW/mm ] (magenta)
P [MW] (black), E (green), E (red) [MV/m],
350
200
3.5
164
152
150
100
78
62.5
59.1
25.7
27.7
50
0
0
5
10
15
iris number
20
25
Summary table for new CLIC structure prototypes
Structure
CLIC-G-CDR
Average loaded accelerating gradient [MV/m]
100
RF phase advance per cell [rad]
2π/3
Average iris radius to wavelength ratio
CLIC-M
CLIC-N
CLIC-O
CLIC-P
0.11
0.1152
0.1116
0.114
0.1196
Input, Output iris radii [mm]
3.15, 2.35
3.41, 2.35
3.34, 2.24
3.6, 2.1
4.04, 1.94
Input, Output iris thickness [mm]
1.67, 1.00
Input, Output group velocity [% of c]
1.65, 0.83
1.99, 0.83
1.89, 0.74
2.25, 0.64
2.94, 0.53
First and last cell Q-factor (Cu)
5536, 5738
First and last cell shunt impedance [MΩ/m]
81, 103
Number of regular cells
26
Structure active length [mm]
230
Bunch spacing [ns]
0.5 ns
Filling time, rise time [ns]
67, 21
62.6, 22.4
57.4, 22.4
62.3, 25.7
62.4, 31.0
61.1, 38.9
Number of bunches in the train
312
312
322
306
295
282
Total pulse length [ns]
243.7
240.5
240.3
240.6
240.4
240.5
3.72
3.72
4.1
3.72
3.74
3.73
3.74
Peak input power [MW]
61.3
60.0
65.2
63.3
60.4
60.7
62.5
RF-to-beam efficiency [%]
28.5
27.9
29.2
27.3
27.3
26.1
24.3
Maximum surface electric field [MV/m]
230
246
243
245
268
304
Max. pulsed surface heating temperature rise [K]
45
45
43
43
48
59
5.4
5.3
5.2
5.1
4.2, 5.6
3.5, 6.9
3.0
3.0
2.9
2.7, 2.0
2.46, 2.27
Bunch population
Maximum Sc
[109]
[MW/mm2]
P/C [MW/mm]
Luminosity per bunch X-ing
Figure of Merit [1025%/m2]
CLIC-G
217
3.0
[1034/m2
]
1.22
1.32
1.22
1.21
1.24
9.15
9.42
8.93
8.46
8.03
Some remarks on the CLIC-G alternatives
•
•
•
CLIC-M (const Sc): More charge in the bunch (higher efficiency and luminosity) for
the same Sc as in CLIC-G
CLIC-N (const Sc): Lower Sc for the same bunch charge as for CLIC-G
CLIC-O (50 % tapering, same as in T18): Same bunch charge as CLIC-G but lower Sc
if loaded with nominal CLIC current
– If P/C is more important then also unloaded gradient will be higher
– Efficiency lower than in CLIC-G due to longer rise time
•
CLIC-P (100% tapering, approximately const loaded Sc): Same bunch charge as
CLIC-G but even lower Sc if loaded with nominal CLIC current
– In my opinion, it can show its potential only in loaded conditions. That means we have to test
CLIC-G in loaded conditions for comparison which is already foreseen in CTF3.
– Needs careful powering/conditioning if there is no/low beam loading in order not to damage
the downstream end
•
Un-damped matching cells to be used to ease the design and to have lower fields
– In case of problems in the TD24_R05 matching cells (or maybe in any case) we should also
build 26 cells long CLIC-G with un-damped matching cells to be a reference for the above
alternatives and also for structures with compact couplers: double feed (TD26_vg1.7_R05_CC)
and single feed (comes later).
Alternative layout of SAS with single feed couplers for CLIC
Image courtesy of A. Samoshkin
Alternative layout:
Baseline layout
Load
AS1
Load
Hybrid
• Off crest kicks set to 0 by design
• On crest Input and Output kicks
are compensated independently
within one SAS = AS1 – AS2
AS2
Load
Advantages:
• No splitters (HOMagic-T)
• 3 loads per SAS instead of 5
• less waveguides
• group delay difference between two AS
can be adjusted to 0
• more space for input/output waveguide
connection to the AS
Input CCSF setup2,
geometry
idw/2
b
idw
ipw/2
idw = 8 mm
b and ipw are matching parameters
4
x 10
4
r = 0 mm
r = 1 mm
r = 2 mm
3
acc
2
1
0
trans
[V/m] @ 2W
0
Effective E
• Dipolar kick for particle on crest is
mostly magnetic (-Z0Hy)
• Hy is needed to let power flow cross
the middle plane: Hy x Ez, that is why it
is in phase with accelerating field Ez
• The kick is proportional to the input
power (fixed) divided by Ez (fixed) and
by the cell radius (more or less fixed
by the cell frequency)
• The sign is given by the direction of
the power flow. It is asymmetric in the
input/output couplers
• There are some ideas how to
minimize this.
Wait for my next
presentation!
E(0) [V/m] @ 2W
Dipolar kick on crest
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
2.5 V
400
-2.5 V
200
0
Ex
-200
-Z0Hy
-400
0
0.01
0.02
0.03
0.04
0.05
z [m]
0.06
Complex mag of Real Poynting vector
E -Z Hy
0.07 x 00.08
jc/w*E (1)
acc
Dipolar kick 90o off crest
4
0
-1
[V/m] @ 2W
-2
trans
r = 0 mm
r = 1 mm
r = 2 mm
1
acc
E(0) [V/m] @ 2W
2
Effective E
• Dipolar kick for particle 90o off crest
is again mostly magnetic (-Z0Hy)
• Hy comes from the offset of the EM
field centre with respect to the beam
axis, that is why it is in phase with Hφ
and 90o out of phase with the
accelerating field Ez
• The kick is proportional to the
accelerating field (fixed) and the offset
between the beam and EM field axis
(can be optimized),
• The sign depends on the sign of the
accelerating field and of the offset. It is
symmetric in input/output couplers
• This kick can be optimized down to
zero if necessary!
x 10
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Ex
0.08
-Z0Hy
Ex -Z0Hy
400
jc/w*E (1)
acc
0.5 V
200
0
-200
0.5 V
-400
0
0.01
0.02
0.03
0.04
0.05
z [m]
0.06
0.07
0.08
For Input coupler Setup1: on crest kick: 2.5 V is already much larger than 90o off
crest kick 0.5 V due to very high degree of symmetry of the EM field. Still can be
fine tuned if necessary.
Dipolar RF kick from Panofsky-Wenzel theorem
and from Lorenz force
Panofsky-Wenzel theorem:
p ( r ,  ) 
je

L
 dz

Eacc (r ,  , z )
0
Gives an expression for
   1 
   ur
 u
;
r
r 
Dipolar kick from accelerating rf field:
p(1) ( ) 
Transverse energy gain from P-W theorem:
L

V(1)  p(1) c / e 
0
jc
L
E

(1)
acc
( z )dz
0
Transverse energy gain direct from Lorenz:
Magnitude of
the RF kick in
input CCSF
( L)

V
L

je 
je 
(1)
(1)
(ur cos( )  u sin(  ))  Eacc
( z )dz  u x  Eacc
( z )dz
 Ex  Z 0 H y
Abs(2.5 + j0.5) V ·(64MW/2W)1/2 = 14.6 kV
To compare with the acceleration per structure of 23 MV => kick ≈ 6.3e-4
It is smaller in the output CCSF since the output power is smaller
by x2 unloaded -- x6 loaded. => (4.5 – 2.6) x e-4

0