5th clic advisory committee (clic-ace)2-feb-2010
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Drive beam RF: Klystrons, RF structures, efficiency, modulators, stability of RF systems
Erk Jensen, BE-RF
with major contributions from: Alexandra Andersson, Alexey Dubrovskiy,
Gerard McMonagle, Rolf Wegner
5th CLIC Advisory Committee (CLIC-ACE) 2-Feb-2010
2 Feb. 2010 15th CLIC Advisory Committee (CLIC-ACE)
25th CLIC Advisory Committee (CLIC-ACE)
Outline
2 Feb. 2010
Power sources:KlystronsModulatorsEfficiency (2nd look at IOT’s)
Accelerating structures
Stability/StabilisationMeasurements at CTF3Feed-forwardPhase monitorGlobally distributed reference
35th CLIC Advisory Committee (CLIC-ACE)
CLIC Drive Beam RF System – issues:
2 Feb. 2010
Reminder of the main issues for the Drive Beam RF system:◦ Very large total power (≈23 GW peak, 170 MW average)
What power source? Optimum size of individual power source?This was addressed in the last ACE.
◦ Phase stability (jitter <50 fs)◦ Overall efficiency! ◦ Cost!
Summary from last ACE: Trends:◦ MBK 10 MW ... 20 MW
10 MW available today (X-FEL, ILC) “smaller” klystrons make reliability and serviceability easier
... remained to be done:◦ Make group delay of acc. structure = length of delay loop◦ Redesign structures to optimize for beam dynamics requirements
5th CLIC Advisory Committee (CLIC-ACE) 4
Klystrons... not much new, but converging for CDR:
2 Feb. 2010
Reminder: from last year’s ACE
2 Feb. 2010 55th CLIC Advisory Committee (CLIC-ACE)
65th CLIC Advisory Committee (CLIC-ACE)
What’s new about the klystrons?
2 Feb. 2010
Questionnaire prepared and sent to klystron manufacturers (CPI, Thales, L3, E2V, Toshiba, Istok, Chinese industry) asking about the feasibility of a 20 MW klystron (4 different scenarios)
So far, only CPI replied: ◦ Reasonable to start from ILC/X-FEL klystrons◦ 20 MW, 150 μs, 50 Hz, 65 % ... feasible (≈ 8 beams), ◦ design & proto estimate: 2 M$ and 2 years, ◦ series cost estimate 1.1 M$ (55 k$/MW), ◦ delivery schedule: month 12, 14, 16, ... ARO◦ They tend towards slightly higher voltage (150 kV?)
This sounds reasonable for the conceptual design.
5th CLIC Advisory Committee (CLIC-ACE) 7
Modulators ... not much new
2 Feb. 2010
Reminder: from last year’s ACE
2 Feb. 2010 85th CLIC Advisory Committee (CLIC-ACE)
95th CLIC Advisory Committee (CLIC-ACE)
ScandiNova’s K2-SYSTEM for PSI; 351kV / 416A !
2 Feb. 2010
Achieved pulse to pulse stability: ± 4 10-5
5th CLIC Advisory Committee (CLIC-ACE) 10
Efficiency... not for CDR, but for later other possibilities should be considered:
2 Feb. 2010
115th CLIC Advisory Committee (CLIC-ACE)
IOT’s – a second look:
2 Feb. 2010
According to CPI, IOT’s would be a natural choice for highest efficiencies; CPI’s claims:
IOT VHP-8330 reached 930 kW @ 700 MHz. up to 1.5 MW at 1 GHz should be possible, > 80 % efficiency at this power level are possible, IOT’s would be cheaper/MW (!) typical DC voltage range: 35 kV, no modulator necessary → pulses via RF drive!
ηKlystron ηModulator ≈ 60 % would become ηIOT ηpower distribution ≈ 70 %;
this would reduce wall plug power quite significantly! no saturation → power regulation with feedback possible.
gain ≈ 22 dB (needs 10 kW drive for 1.5 MW)
Disadvantages: less gain, no operational experience, more complex power distribution!
5th CLIC Advisory Committee (CLIC-ACE) 12
Multi-beam HOM IOT’s
2 Feb. 2010
left: existing VHP-8330
right: planned VKP-8330B
Conclusion power sources
2 Feb. 2010 135th CLIC Advisory Committee (CLIC-ACE)
For the CDR, MBK’s derived from ILC/X-FEL with 15 to 20 MW are realistic.
Some of the features of IOT’s make them appear interesting – a more detailed analysis is necessary.
At the same time we’re trying to analyze (fellow to start in September 2010) higher η klystrons.
5th CLIC Advisory Committee (CLIC-ACE) 14
Accelerating Structures
2 Feb. 2010
155th CLIC Advisory Committee (CLIC-ACE)
Input power for full beam loading for different cell numbers
2 Feb. 2010
# cells Pin[MW] h length [m] τ [ns] acc [MV] gradient [MV/m] # struct total length [km] Ptot [GW]
15 6.33 98.81% 1.500 142.0 1.49 0.99 1602 2.402 10.13916 7.21 98.73% 1.600 151.4 1.69 1.06 1407 2.251 10.14617 8.14 98.66% 1.700 160.8 1.91 1.12 1247 2.119 10.15418 9.12 98.58% 1.800 170.2 2.14 1.19 1114 2.005 10.16219 10.2 98.51% 1.900 179.5 2.38 1.26 1000 1.900 10.17020 11.3 98.43% 2.000 188.9 2.64 1.32 901 1.802 10.15021 12.4 98.36% 2.100 198.3 2.90 1.38 821 1.724 10.18522 13.6 98.28% 2.200 207.7 3.18 1.45 749 1.647 10.19323 14.9 98.21% 2.300 217.1 3.48 1.51 685 1.575 10.20124 16.2 98.13% 2.399 226.5 3.78 1.57 630 1.512 10.20825 17.6 98.06% 2.499 235.9 4.10 1.64 580 1.450 10.21626 19.1 97.98% 2.599 245.3 4.45 1.71 535 1.391 10.22427 20.6 97.91% 2.699 254.7 4.79 1.77 497 1.342 10.23228 22.1 97.84% 2.799 264.0 5.14 1.84 463 1.296 10.23929 23.7 97.76% 2.899 273.4 5.50 1.90 432 1.253 10.24730 25.4 97.69% 2.999 282.8 5.89 1.96 404 1.212 10.25531 27.1 97.61% 3.099 292.2 6.28 2.03 379 1.175 10.26332 28.9 97.54% 3.199 301.6 6.70 2.09 355 1.136 10.27033 30.8 97.47% 3.299 311.0 7.13 2.16 334 1.102 10.27834 32.7 97.39% 3.399 320.4 7.57 2.23 315 1.071 10.28635 34.6 97.32% 3.499 329.8 8.00 2.29 298 1.043 10.29436 36.6 97.25% 3.599 339.2 8.46 2.35 281 1.011 10.30237 38.7 97.17% 3.699 348.6 8.93 2.41 266 0.984 10.30938 40.8 97.10% 3.799 358.0 9.41 2.48 253 0.961 10.31739 43.0 97.03% 3.899 367.3 9.91 2.54 240 0.936 10.32540 45.3 96.95% 3.999 376.7 10.43 2.61 228 0.912 10.333
≈ 28.3 kW · ncell2
former “nominal”
New interesting region
Redesign of accelerating structure
2 Feb. 2010 165th CLIC Advisory Committee (CLIC-ACE)
Rolf Wegner’s work:
gapn
RBP E0T
Vacc
Ncells
PoutPin
Pb Pb
SICA -- constant aperture
η= ΔPb/Pin
tfill
mode spectrum
New optimum accelerating structure
2 Feb. 2010 175th CLIC Advisory Committee (CLIC-ACE)
185th CLIC Advisory Committee (CLIC-ACE)
Reminder: Why 245 ns group delay?
2 Feb. 2010
5th CLIC Advisory Committee (CLIC-ACE) 19
New structure design (R. Wegner)
2 Feb. 2010
Scaled from 3 GHz:Outer Ø: 522 mm
New design:Outer Ø: < 300 mm
New idea (A. Grudiev): dampers inside the slots!
This new approach has been verified:
acc. mode Q0= 2.2 10∙ 4, Qext= 3.7 10∙ 7
Verification of efficient damping
2 Feb. 2010 205th CLIC Advisory Committee (CLIC-ACE)
Conclusion accelerating structures:
2 Feb. 2010 215th CLIC Advisory Committee (CLIC-ACE)
SICA structures were successfully redesigned and re-optimized for 1 GHz (thanks to Rolf Wegner!).
Design includes:◦Optimum aperture – to be finalized with BD
simulations◦Optimum RF efficiency◦Optimum group delay (≈ 245 ns)◦New idea for dipole mode damping verified◦Moderate outer Ø < 300 mm
◦The coupler design is ongoing.
5th CLIC Advisory Committee (CLIC-ACE) 22
Phase stabilisation
2 Feb. 2010
235th CLIC Advisory Committee (CLIC-ACE)
Alexey Dubrovskiy analyzed phase- and amplitude stability of 4 CTF3 klystrons. Example given here: MKS03
t 0 10 21 31 42 62 73 83 94 104 114 125 135 146 156 166 177 187 198 208 219 ns
μ 60.8 60.9 61.2 61.5 60.5 59.1 58.9 59.1 59.2 59.5 59.3 59.3 59.5 58.8 58.9 58.6 58.1 57.9 57.5 57.4 57.9 deg
σ2 0.015 0.021 0.017 0.022 0.019 0.018 0.016 0.019 0.018 0.012 0.011 0.011 0.012 0.015 0.019 0.014 0.013 0.013 0.011 0.015 0.012 deg2
σ 0.12 0.14 0.13 0.15 0.14 0.13 0. 13 0.14 0.13 0.11 0.10 0.10 0.11 0.12 0.14 0.12 0.11 0. 11 0.10 0.12 0.11 deg
Phase stability measurement at CTF3
2 Feb. 2010
time
sample #
phase in deg.
Result:• W/o special measures, the
pulse-to-pulse phase jitter is 0.1 ... 0.15°.
• This is “only” a factor 5 ... 8 away from our specification of 0.02°!
• Reminder: with feed-forward (see below), we’re probably about OK!
• This is very encouraging!
245th CLIC Advisory Committee (CLIC-ACE)
Phase measurement and correction scheme
2 Feb. 2010
Drive Beam
Main Beam Outgoing
PETS
Accelerating Structure
LO
21km
RF
Phase locked to low frequency refernce to prevent slow drift
A. Andersson: CLIC Workshop 14-Oct-09
255th CLIC Advisory Committee (CLIC-ACE)
The phase monitor
2 Feb. 2010
Requirement: low impedance, 20 fs resolutionStatus: Task 9.5 in the Work-package NCLinac of
the EuCARD FP7 project (in collaboration with PSI and INFN/LNF), making good progress.
Double-mirror concept developed (F. Marcellini)
11.70 11.80 11.90 12.00 12.10 12.20 12.30Freq [GHz]
-80.00
-75.00
-70.00
-65.00
-60.00
-55.00
-50.00
-45.00
-40.00
Y1
Ansoft Corporation HFSSDesign19XY Plot 4
Setup1 : Sw eep1
Setup1 : Sw eep1
s21, s31
5th CLIC Advisory Committee (CLIC-ACE) 26
Global vs. local timing reference
2 Feb. 2010
MBREFRFBB
MBRFBB
71
76
762:scheme Global
2:scheme Local
Highly stable globally distributed REF de-magnifies MB jitter dependence
For a more detailed analysis, including influence of feed-forward, see D. Schulte’s presentation
5th CLIC Advisory Committee (CLIC-ACE) 27
1 10 100 1k 10k 100k 1M 10M-180
-160
-140
-120
-100
-80
-60
-40
offset frequency, [Hz]
nois
e po
wer
, dB
c
Phase Noise LOFiltering by beam pathFiltered noise
• We need an LO with « 23 fs integrated phase jitter.
• The beam path provides some noise filtering below 3 kHz
• The system here seems to come in around ~ 4 fs
O(5k€)
Local Oscillator
2 Feb. 2010
noise
pow
er d
ensit
y dB
c/Hz
285th CLIC Advisory Committee (CLIC-ACE)
Global Optical Phase-stable Timing Distribution?Major developments underway in the field,
primarily for X-FEL type light-sources.Two relevant presentations at the last CLIC
workshop:◦ F. Ömer İlday, Bilkent Üniversitesi: Long-distance
optical stabilization with femtosecond resolution, (http://indico.cern.ch/contributionDisplay.py?contribId=96&sessionId=6&confId=45580)
◦ Matthias Felber, DESY: Femtosecond Optical Synchronization System for FLASH (http://indico.cern.ch/contributionDisplay.py?contribId=100&sessionId=6&confId=45580)
Still requires major work and break throughs in order to work over CLIC distances
2 Feb. 2010
5th CLIC Advisory Committee (CLIC-ACE) 29
Timing-stabilized fiber links
2 Feb. 2010
PZT-based fiber
stretcher
Master Oscillator
fiber link < 5 km
isolator50:50
coupler
optical cross-correlator
coarseRF-lock
OC
<20 fs
ultimately < 1 fs
From Ömer İlday’s talk: Concepts for φ-REF distribution
2 Feb. 2010 5th CLIC Advisory Committee (CLIC-ACE) 30
optic-atomic clockdivide and conquer
Multiple stations with individual master oscillators and mutual links form a chain
Laser frequency combs locked to a precise quantum transition, can be absolutely stable.Position one at each major point, distribute sync signal locally as before. Use long links to keep each clock locked to each other (slow corrections).Distribution of frequencies with 10-14 precision has been demonstrated.
315th CLIC Advisory Committee (CLIC-ACE)
Conclusions phase stabilisation:
• Phase stability measurements at CTF3 gave encouraging values.
• A feed-forward, measuring the phase jitter in the drive beam and correcting for it, can significantly relax the requirements (factor 10).
• The low-impedance, high resolution phase monitor is addressed in FP7/EuCARD and makes correct progress.
• A stable, globally distributed reference can demagnify the dependence on the main beam jitter further by a factor 7.
• For global distribution of ultra-stable phase references, strong synergy with the X-FEL community exists.
2 Feb. 2010
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