INFN Frascati contributions to CTF3-002: Monitors and Kickers for
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Transcript of INFN Frascati contributions to CTF3-002: Monitors and Kickers for
INFN Frascati contributions to CTF3-002:
Monitors and Kickers forDrive Beam Phase Feed-forward
F.Marcellini, D.Alesini, A.Ghigo
CLIC working meeting 3th November 2011
In the two beam acceleration scheme is important to synchronize precisely the Main Beam with respect to the RF power produced by the Drive Beam.Timing errors lead to energy variations in the Main Linac and would have an impact on the collider performance (luminosity reduction).
Control of the drive beam phase errors within about 0.1° (23fs @ 12GHz). Feedback and/or feed-forward systems needed.
Phase error control
Overall CLIC layout and the placement of the detectors (green cylinders) in the turnarounds.
Phase monitor main requirementsResolution of the order of 20 fs. Very low coupling impedance due to the high beam current. Rejection, by means of proper designed filters, of RF noise and weak fields in
the beam pipe that otherwise could affect the measurements.Detection is done at 12 GHz.tf monitor ≈ 10ns=2Q/ω →Q ≈380, BW ≈30MHz.
Pick-up designA prototype could be tested in the CTF3 and installed in the chicane region,
before the Delay Loop, where the vacuum pipe diameter is 40mm. At 12 GHz, 6 modes can propagate in a Ø=40mm pipe, A smaller pipe cross section would be useful to reduce the no. of modes.Reducing the pipe diameter at Ø=23mm, only 2 modes have a cut-off
frequency lower than 12 Ghz.
DRIVE BEAM LINAC
CLEXCLIC Experimental Area
DELAY LOOP
COMBINERRING
10 m
4 A – 1.2 ms150 Mev
32 A – 140 ns150 Mev
Phase monitorKicker
Drive Beam phase measurement and correction in CLIC turn around
Feed-forward experiment in CLIC Test Facility CTF3
RF noise RF noise
reflectedreflected
12 GHznotch filter
12 Ghznotch filter
Beam signal pick-up
Beam induced signal
beam
Beam induced field in the volume between the notch filters.
12 GHz component of beam generated field after the first filter could be reflected back by the second filter and detected again.
Unless the distance between the filters is chosen to define a volume resonating at 12 GHz. The pick-up is positioned in correspondence of zero crossing standing wave field. RF noise has to be filtered at both the pick-up sides.
12 GHz resonating volume
How the pick-up works
11.50 12.00 12.50Freq [GHz]
0.00
0.05
0.10
mag
(S(W
aveP
ort1
,Wav
ePor
t1))
Ansoft Corporation HFSSDesign3XY Plot 2 delta='10.85mm'
The beam induced signal is coupled out of the beam pipe through a rectangular slot in a double ridged waveguideThe thickness of the slot defines the coupling levelThe ridged waveguide has a transition to 50 Ω coaxial where a commercial vacuum feedthrough (MSSI part #853872) is placed
Transition design
Reflection coefficient at the input port
d
Cut view of the waveguide pick-ups
Pick-up design
11.80 11.85 11.90 11.95 12.00 12.05 12.10 12.15 12.20Freq [GHz]
-0.008
-0.007
-0.006
-0.005
-0.004
-0.003
-0.002
-0.001
0.000
dB(S
(Wav
ePor
t5,W
aveP
ort5
))
Ansoft Corporation tm01finalXY Plot 1Setup1 : Sw eep1
TM01Resonating volume tuning @12 GHz
Notch for the TM01 Notch for the TE11No coupling with the waveguide
TE11Resonating volume tuning @12 GHz
11.70 11.80 11.90 12.00 12.10 12.20 12.30Freq [GHz]
-0.000010
-0.000009
-0.000008
-0.000007
-0.000006
-0.000005
-0.000004
-0.000003
-0.000002
-0.000001
0.000000
dB(S
(Wav
ePor
t1,W
aveP
ort1
))
Ansoft Corporation te11finalXY Plot 1dB(S(WavePort1,WavePort1))
Setup1 : Sw eep1
Pick-up elettromagnetic design
CTF3 phase pick-up prototype
Beam pipe F=23mm
Tuned pick-up Q=41fres=fRF=12 [GHz]
Detuned pick-up to decrease the voltage Q=42fres=≠fRF=12.22 [GHz]
Waveguides designed to increase coupling and decrease Q -> faster rise time
11.80 11.90 12.00 12.10 12.20 12.30 12.40 12.50Freq [GHz]
-90.00
-70.00
-50.00
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dB(S
(6,5
))
XY Plot 5
ANSOFT
Setup1 : Sweep1
notch frequency
fres=monitor resonance
Qb=2.33e-9 [C] (bunch charge)fRF=12 [GHz]Bunch separation: 1/fRF
I=28 [A]Vout=710 V 0 100 200 300 400 500
-800
-600
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bunch #
Vou
t [V]
0 100 200 300 400 500-40
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bunch #
Vou
t [V]
Qb=2.33e-9 [C] (bunch charge)fRF=12[GHz]Bunch separation: 1/fRF
I=28 [A]Vout=28 V
Tuned version fres=12 GHz
Detuned version fres=12.2 GHz
Time response signal, in bunch number, of the monitor precisely tuned at the bunch frequency
same pick-up with the notch filter with slightly different distance that gives the detuned
The response time is approximately 50 bunches on 2100 bunches of the train
Phase jump (π/6)
Rejection of RF noise and beam generated wake fields, in the detection frequency range, is done by notch filters.The notch filter is realized as a bump in the beam pipe. The dimensions of this bump are chosen to reject the 12GHz frequency component of the noise.
Transmission response of stop-band filter for the TM01 mode
S21[dB]
Installation of the monitor prototype is foreseen before the CTF3 Delay Loop. The pipe radius has been reduced down to 11.5 mm, to limit to only 2 modes (TE11 and TM01) propagation at 12 GHz.
1
4
3
2
V1+V2+V3+V4≠ 0, TM01
= 0 , TE11
This property can be used as a primary mean to reject TE11
Rejection of RF noise and wakefield
TE11 TM01
Pick-up mechanical design
Stripline lenght=0.4m Vin = 3. 9 kV 1mrad @ 150MeV
Stripline lenght=1.0m Vin = 1.35kV 1mrad @ 150MeV
Vin
-Vin
Phase-forward system kicker
0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00Freq [GHz]
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mag
(S(1
,1))
full_struct1000mmXY Plot 1 ANSOFTmag(S(1,...Stripline lenght = 1m Reflection coefficient from stripline input port
0 0.5 1 1.5 2 2.5 3 3.50
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Longitudinal coupling impedanceZ [Ω]
f [GHZ]
The striplines ends are tapered in order to reduce the beam coupling impedance and to have good 50 W matching to the amplifiers
Simulations of the kickerwith stripline 80 cm long + 2x10 cm tapers
Proposed layout of the CTF3 line
CURRENT PROPOSEDSX+Q 84 41.7 QuadDift 16 17.1 BPIQ 41.7 41.7 Quad
BPI 17.1 120 KICKER
Q + Corr 64.8 20 TaperVPI 23.6 6.7 Drift
247.2 247.2 cm
Kicker mechanical design
Lstrip=960mm
LTOT=1100mm
Strip-line Internal Diameter=40mm
WP CTF3-002 INFN Contribution