LCLS-II Power Coupler Nikolay Solyak, Ivan Gonin, Andrei Lunin C.Adolphsen - SLAC TTC meeting, March...
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Transcript of LCLS-II Power Coupler Nikolay Solyak, Ivan Gonin, Andrei Lunin C.Adolphsen - SLAC TTC meeting, March...
AWLC2014, FNAL, May 12-16, 2014 1
LCLS-II Power Coupler
Nikolay Solyak, Ivan Gonin, Andrei LuninC.Adolphsen - SLAC
TTC meeting, March 23-27, 2014
AWLC2014, FNAL, May 12-16, 2014 2
Item Spec CommentDesign EuXFEL Coupler 2009 Drawing Package with exceptions noted below
Max Input Power 7 kW CW Assume would run with full reflection
Minimum Qext Foreseen 1e7 Allows 16 MV/m with no beam and 6.6 kW input, and allows 6 MW beams with 33 kW input
Maximum Qext Foreseen 5e7 Match for 0.3 mA beams at 16 MV/m, 26 Hz BW
Reduction in Antenna Length 8.5 mm Maintain 3 mm rounding
Range of Antenna Travel +/- 7.5 mm Range measuredPredicted Qext Min Range Qext Max Range
3.6e6 – 4.7e6 – 7.5e61.0e8 – 1.1e8 – 1.5e8 Assuming +/- 5 mm transverse offsets
Warm Section Outer Cond Plating 10 um +/- 5 um, RRR = 30-80 Nominal EuXFEL
Warm Section Inner Cond Plating 100 um +/- 10 um, RRR = 30-80 Modified – Temp Rise < 150 degC for 14 kWCold Section Outer Cond Plating 10 um +/- 5 um, RRR = 30-80 Nominal EuXFELCenter Conductor HV Bias Optional Use flex copper rings that can be replaced with
existing capacitor rings if HV bias neededWarm and Cold e-Probe ports req No Do not expect multipacting at low power
Warm Light Port Required No Do not expect arcs at low powerMotorized Antenna Yes – max step = 50 um Changes Qext by 1%
RF Processing 7 kW CW with full reflection – vary reflected phase by 180 deg
For initial couplers, use pulse power processing at SLAC
LCLS-II Coupler Technical SpecsPreliminary
AWLC2014, FNAL, May 12-16, 2014 3
Fundamental Power Coupler (FPC)
• XFEL (modified TTF3) coupler is not meet LCLS-II requirements– Tuning range (1.e6-1.e7) not cover required Qext=4.e7– Overheating of the internal bellow in warm section at 7kW CW power at
full reflection (effective power ~14kW)
• Two modifications were proposed to address these problems (R&D program: Four coupler modification test)
– Cut antenna 8.5mm to increase Qext
– Increase copper plating of internal inner conductor of warm section from 30 μm to 100-150 μm to eliminate overheating
TTF-3 design
AWLC2014, FNAL, May 12-16, 2014 4
Inner conductor: Temperature distribution for different thickness of copper coating and different RRR (15kW, TW-regime)
Copper plating at inner part is 100 micronsData is simulated for RRR=10
Conclusion: TTF3 Coupler need to be modified for LCLS-II. 100-150 μm Cu plating inner conductor in warm section of coupler is possible solution.
Tmax limit
AWLC2014, FNAL, May 12-16, 2014 5
Qext ~ 2.4·107
Antenna tip cut by 8.5 mm
Qmin Qnom Qmax
Original coupler 1.106 3.5·106 1.8·107
Tip cut by 7 mm 3.8·106 1.6·107 8.5·107
Tip cut by 8.5mm 5.0·106 2.4·107 12·107
R3
A. Lunin, 12/13/13
Nominal positions
R3
Original XFEL antenna
Qext ~ 4.0·106
LCLS-II Cavity Qext Computation
LCLS-II specs
Q ext– range for ±7.5mm antenna tuning
AWLC2014, FNAL, May 12-16, 2014 6
Conclusion• For LCLS-II coupler the most sensitive parameter is a horizontal antenna shift/tilt. • ± 5 mm shift change Qext by -5%/+50%. Vertical tolerances are relaxed.
Vert. antenna tilt(up and down)
Horiz. antenna tiltalong cavity axis
Qmin Qnom Qmax
Original coupler 0.7·105 (3.0 .. 6.5) ·106 3.0·107
Tip cut by 8.5 mm 5.5·106 (2.3 .. 3.8)*·107 1.2·108
XFEL
LCLS-II
XFEL
Qext sensitivity to antenna displacements (ILC vs. LCLS-II)
A.Lunin
Horizontal
Vertical
Horizontal
AWLC2014, FNAL, May 12-16, 2014 7
TW TW power
2K, W 4K, W 80K, W Tmax K
TTF-III as is 7kW 0.13 1.24 14.2 404
Helium, 1atm 7kW 0.13 1.27 17.3 316
LCLS2 (100µm) 7kW 0.13 1.25 15.5 326
LCLS2; 100/200µm 15kW 0.26 2.28 29.2/30 425/356
Power Losses and max. Temp
I.Gonin (FNAL)
TTF-3 Coupler: Inner coating 30µm, outer coating 10µm.
Helium, P=1atm
Window force 160N
Ivan Gonin, FNAL
Helium cooling of the warm section
7kW TW
TTF3 original coupler 7kW TW
AWLC2014, FNAL, May 12-16, 2014 8
Full reflection: E-field distribution in LCLS-II coupler, Q=4e7, Pin=7kW
AWLC2014, FNAL, May 12-16, 2014 9
L=0 LCLS-II Coupler. Inner coating 100µm. Outer coating 10µm
Maximum Temperature vs. LOn resonance Tmax ~425K
Temperature distribution along surface of inner conductor for TW and SW ( L=0mm & L=65mm )
PEC BC
L
On resonance
Off resonance
Coupler operation at 7kW CW at full reflection
AWLC2014, FNAL, May 12-16, 2014 10
Coupler test in HTS -1
Operational for ~5 yrs (~2 cavity/month throughput)– 1.3 GHz and 3.9 GHz cavities, ~1.5 ms and 9ms RF pulses– Now HTS upgraded for CW operation (commissioning)– Priorities in FY14 (CW regime)
• HOM feedthu’s (XFEL and JLAB designs)• 3 tests of high-Q0 dressed cavity (1 dressed to ILC helium vessel and 2 dressed to LCLS-II vessel)• 2 modified at SLAC Power Couplers• Integrated test of dressed cavity with Slow/Fast tuners, Frequency control and μ-phonics
Active Magnetic shielding
AWLC2014, FNAL, May 12-16, 2014 11
500 mGs
- 500 mGs
Inside 1-layer magnetic shielding Max magnitude < 45mGs
Inside 1-layer magnetic shieldingafter active correction by coilsMax magnitude < 6mG
AWLC2014, FNAL, May 12-16, 2014 12
HTS test preliminary scheduleTest# and goals Start
2014 Cav. type
Helium Vessel
HOM antenna
Couple(cold)
Coupler(warm)
Magn shield
Tuner RF
1:HTS commissioning, HOM feedthru, μ-phon now RI26 ILC XFEL variable None 1L+coil Blade 50W
2: High Q0 cavity #1 June 15 AES11 ILC non variable None 1L+coil None 50W
3: FPC cold modif, μ-phonics study July 1 RI26 or
AES11 ILC XFEL FPCmodif
FPCHe cooled 1L+coil blade IOT
4: FPC modified; μ-phonics study July 25 RI26 or
AES11 ILC JLAB FPCmodif
FPC#1modif 1L+coil blade IOT
5: High-Q cav. #2 FPC#1 Aug 20 HQ#2 LCLS-II XFEL FPC
modifFPC#1modif 1L+coil No
tuner IOT
6:High-Q#3 integrated FPC#2 Sept.20 HQ#3 LCLS-II JLAB FPC
modifFPC#2modif 2-layer Lever
tuner IOT
7: high-Q#2 integrated Tuner reliability Oct.15 HQ#2 LCLS-II XFEL FPC
modifFPC#1modif 2-layer lever
tuner IOT
Assumptions about readiness:• 2 modified “cold” parts of FPC: April (done)• 2 modified “warm” parts of FPC: June
• 4 LCLS-II type of Helium Vessels: end of July• JLAB feedthru: end of June• New lever tuner and 2-layer shielding: Sept.
AWLC2014, FNAL, May 12-16, 2014 13
Conclusion
• XFEL coupler not meet LCLS-II specifications. Problems: Qext range and overheating
• 2 major modification was proposed: shorter antenna (by 8.5mm) and thicker (>100μm) Cu plating of inner conductor in warm section to address these problems:
• Modifications are in progress at SLAC (cold part modification was done, warm sections of couplers will be ready by the end of June 2014, plated at CPI and processed at SLAC).
• HTS tests is essential part of design verification program for LCLS-II.– 3 high Q0 (N2 doped) integrated tests , (HOM feedtru’s, FPC, Helium vessel, Tuner,
magnetic shielding)– two modified FPC assembled on high-Qo cavity.
• Next step: start FPC procurement after HTS tests.– Documentations and review.