fermilab i. terechkine1 rf phase shifter r&d proton driver review march 15, 2005 t. barrak, b....
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I. Terechkine 1Fermilab
RF Phase Shifter R&D
Proton Driver Review
March 15, 2005
T. Barrak, B. Foster, I. Gonin, M. Huening, V. Kashikhin, T. Khabiboulinne, A. Makarov, A. Moretti, P. Prieto, J. Santucci, N. Soliak, D. Sun, J. Volk, D. Wildman,
and
I. Terechkine 2Fermilab
RF Phase Shifter R&D
• Concept of phase & amplitude regulation
• Performance requirements
• Types of phase shifters and known experience
• High power test configuration and results
• Conclusion
I. Terechkine 3Fermilab
PD Linac: RF Power Distribution
One klystron feeds many cavities. For each cavity, fast change of amplitude and phase of input RF power is required.
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Amplitude and Phase (IQ) Modulator
cos0 jeEE
sin0 )2/(jeEE
= (1+2)/2
= (2-1)/2
1 2
Yttrium Iron Garnet
Ferrite Shifters can be built based on:
• Coaxial line,
• Strip-line,
• Waveguide
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Examples of Phase Shifters
L band (1.2 – 1.4 GHz)
350 kW peak power
Field Range 800 – 1500 Oe
Phase shift - 600°
Insertion loss - 0.2 dB
Coaxial Device, 1968
Strip-line-based design, AFT for CERN, ~ 2004
352 MHz
250 kW peak power
25% duty cycle
130º phase shift
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Examples of Phase Shifters
Waveguide-based device, Yoon Kang (ANL) for SNS ~ 2000
805 MHz
500 kW peak power
8% duty cycle
0.15 dB insertion loss
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Phase Control Simulations
Frequency follows that of the cavity
Cavity RF phase close to nominal
Phase Shifter works hard
Detailed simulation (M. Huening, EPAC-2004) shows that 200 sec response time is required.
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Performance Requirements
Frequency: 1300 MHz ± 1 MHz
Phase Change: ± 45°
RF Power Ratings: 550 kW Peak, 1.5 ms, 10 Hz
550 kW Peak, 4.5 ms, 3.3 Hz
Insertion Loss: less than 0.2 dB
Response time: time constant ~ 30 s
Flange: WR-650
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Approaching the Problem
1. Develop and test waveguide-based phase shifter;
2. Test the coaxial phase shifter available at FNAL
3. Work with a vendor to build an I/Q modulator
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Waveguide Phase Shifter
Main design issues:
• High power operation
• Heat management
• Tuning range
• Response time
CoreCoil
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Phase Shifter Mockup Low Level RF Measurements
Results of the low level RF measurements are in a good agreement with modeling (HFSS)
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High Power Test
A0 1300 MHz Klystron
T = 250 µsec
F = 5 Hz
Existing A0 interface was used for testing
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High Power Test
Two methods of phase measurements:
1. Oscilloscope measurements
2. Using available IQ modulator
Available phase zone is limited by sparking that develops near the resonance frequencies
Max Power - 2000 kW (req. 600 kW)
Phase shift - ~ 80° (req. 90° )
SF6 added
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Further Developments
1. Refining RF design
2. Fast phase shifter prototyping
3. IQ modulator prototyping
Anti-Parallel Bias Field
Parallel Bias Field
-2.0
-1.8
-1.6
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
1100 1120 1140 1160 1180 1200 1220 1240 1260 1280 1300 1320 1340 1360 1380 1400 1420 1440 1460 1480 1500F, MHz
20Lo
g(S1
1), d
B
17.5mm 1100 Oe -1110 Oe
17.5mm 1089 Oe -1111 Oe
17.5mm 1100 Oe -1100 Oe shift 1mm both
17.5mm 1080 Oe -1120 Oe shift 1mm both
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Coaxial Phase Shifter
•Coax design is preferred at 325MHz• In-house design tested to 660kW at 1300 MHz• Tested at 250 kW at Argonne with APS 352MHz Klystron • Fast coil and flux return should respond in ~50us
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Advanced Ferrite Technology GmbH (AFT)
Products:
High Power CirculatorsFast Ferrite TunerFast High Power Phase ShifterHybrid Tuner SystemsFerrite MaterialElectrical Power Suppliesfor high power inductive loads
The IQ modulator from AFT is expected in May:
1 Magic Tee; 1 straight waveguide section; 2 waveguide - coax transition; 2 FFT´s directly connecting to the transition; 1 control unit for setting phase and amplitude and feedback loop; 1 dual directional coupler for amplitude control; 1 arc detection system.
Power supply will be provided by FNAL
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Conclusion
1. The prototype of a waveguide-based, 1.3 GHz phase shifter shows excellent maximal power and acceptable phase shift performance.
2. Coaxial phase shifter meets peak power and phase shift requirements both at 1300 MHz and 325 MHz.
3. Commercial prototype of an I/Q modulator due in spring.
4. Average power testing, reaction time testing, and IQ modulator modeling should be the next steps of the R&D
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Phase Shifter Development Line
• Make low level calibration measurements using “as received” YIG blocks and a large gap dipole magnet
• Make steel magnet core and copper waveguide;
• Shape YIG block as modeling requires;
• Make low level RF measurements;
• Make high power measurements;
• Investigate ways to improve performance
• Make a combination “permanent magnet – high frequency winding” bias magnetic system with ferrite core
• Make a waveguide transparent for high frequency magnetic-field
• Make low level a.c. measurements to measure response time
• Work on a full-scale device design and test
DONE
Ongoing R&D
Engineering