RF Power R&D David Wildman May10, 2005 Slides “borrowed” from: G. W. Foster, A. Moretti, D. Sun, I. Terechkine, D.Wildman,& D. Wolff

Fermilab May 10, 2005 wildman - AAC Meeting2 Outline System Overview 325 MHz Klystron Modulator for Klystron I/Q Modulators Phase Shifters (3 Types) Conclusions

325 MHz RF System

Fermilab May 10, 2005 wildman - AAC Meeting4 Tube is designed for particle Accelerators. Tube tunable to 325 MHz: Tube is in production for J-Parc; 17 tubes have recently been delivered to J-Parc. Power Output = 3.0 MW Gain = 50 dB Efficiency = 55 % Duty Factor = 2.6% Toshiba E374A High Power Amplifier Klystron Toshiba factory test at 1.5 ms 4.5 ms test done at Fermilab

Fermilab May 10, 2005 wildman - AAC Meeting5 Klystron Status Negotiations are in the final stages for the purchase of one 325 MHz klystron from Toshiba. Toshiba is quoting a delivery date of March 2006.

Fermilab May 10, 2005 wildman - AAC Meeting6 Proton Driver Modulator Requirements Purpose: Provide the pulsed power needed for Klystron operation Specifications –Pulse width:4.5ms –Pulse Voltage:120kV –Pulse Current:140amps –Repetition rate:2.5Hz –Average Power225kW –Support operation for both MBK and TOSHIBA 325 MHz klystrons –Allow cost effective redeployment to 1.5ms operation

Fermilab May 10, 2005 wildman - AAC Meeting7 Fermi-built TESLA Modulator 3 Modulators built in 1990s Specifications(PD) –Pulse width:1.7ms(4.5) –Pulse Voltage:120kV –Pulse Current:130amps(140) –Repetition rate:10Hz(2.5) –Average Power300kW(225) First modulator has run for 25,000 hours (since 1993) Second and third modulators have run for 18,000 hours each (since 1996)

Fermilab May 10, 2005 wildman - AAC Meeting8 Modifications to Fermi Modulator for PD Changes needed to meet spec –3x larger cap bank –3x larger “Bouncer” Circuit –3x larger pulse transformer Changes to reduce cost –Traction type capacitors Used extensively in Europe and SNS modulators –1.6kV IGBTs replace with 3.3kV units (SLAC collaboration) –Back-up switch plus fast crowbar replaced with redundant, fail- safe switch. –Updated controls

Fermilab May 10, 2005 wildman - AAC Meeting9 4.5 ms Modulator Simplified Diagram

Fermilab May 10, 2005 wildman - AAC Meeting10 Modulator Construction Schedule EE Support is in the process of building 2 modulators for SMTF. Requisitions for capacitors and pulse transformers have been awarded. The first unit should be finished by the end of this year.

Fermilab May 10, 2005 wildman - AAC Meeting11 CAUTION We are now going from one type of modulator to another!

Fermilab May 10, 2005 wildman - AAC Meeting12 I/Q modulator box (stripline structure) Box size: 24” x 20”

Fermilab May 10, 2005 wildman - AAC Meeting MHz I/Q Modulator Specifications Power (peak/average, duty factor 1.5%) –40 kW/ 600 W – kW/ kW –650 kW/9.75 kW (1 feed option for RFQ) Tuning Range –Phase: +/- 45 degree –Amplitude: +/- 1.5 dB Phase Tuner Slew Rate –1 degree/1  sec

Fermilab May 10, 2005 wildman - AAC Meeting MHz I/Q Modulator R&D Program Determine what type of rf structure (stripline, coaxial or waveguide) should be used for each power level. Demonstrate fast tuning capability. Solve potential technical issues: rf breakdown, cooling, and ferrite stability. Simplify assembly and cost reduction. Goal: to be ready when klystron arrives.

Fermilab May 10, 2005 wildman - AAC Meeting MHz I/Q Modulator The Plan –Low power level (40 kW) Use stripline structure to build a joined hybrid and circulator into one box with 4 coaxial ports. Power test this device with coaxial phase shifter at Argonne. –Medium power (150 kW) Power test a coaxial structure –High power level (650 kW) This is a special case. First evaluate the number of rf feeds for RFQ to determine the power level Then choose structure: either waveguide (magic tee) or coax

Fermilab May 10, 2005 wildman - AAC Meeting MHz I/Q Modulator Status –Low power level (40 kW) –Preliminary design of circulator and hybrid (circuit simulation and 3D E-M simulation) is done. –A prototype circulator using available ferrite disks is built and measured: achieved low insertion loss (-0.06 dB) and high isolation (-27 dB) –Received new ferrite disks to adjust the frequency of the circulator.

Fermilab May 10, 2005 wildman - AAC Meeting17 Prototype Circulator

Fermilab May 10, 2005 wildman - AAC Meeting18 Approaching the Phase Shifter 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

Fermilab May 10, 2005 wildman - AAC Meeting19 Amplitude and Phase (IQ) Modulator  = (  1+  2)/2  = (  2-  1)/2 11 22 Yttrium Iron Garnet Ferrite Shifters can be built based on: Coaxial line, Strip-line, Waveguide

Fermilab May 10, 2005 wildman - AAC Meeting20 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

Fermilab May 10, 2005 wildman - AAC Meeting21 Waveguide Phase Shifter Main design issues: High power operation Heat management Tuning range Response time Core Coil

Fermilab May 10, 2005 wildman - AAC Meeting22 Phase Shifter Mockup Low Level RF Measurements Results of the low level RF measurements are in a good agreement with modeling (HFSS)

Fermilab May 10, 2005 wildman - AAC Meeting23 High Power Test A MHz Klystron T = 250 µsec F = 5 Hz Existing A0 interface was used for testing

Fermilab May 10, 2005 wildman - AAC Meeting24 High Power Test at 1300 MHz 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 kW (req. 600 kW) Phase shift - ~ 80° (req. 90° ) SF 6 added

Fermilab May 10, 2005 wildman - AAC Meeting25 Why Choose a Coaxial Design? Usable over a wide frequency range –Unlike waveguide has no cutoff frequency –Same shifter could be used at both 325 MHz and1300 MHz Easy to understand- TEM modes Compact : smaller size is generally good but leads to higher fields Modified 3 1/8” coax line, fully filled with aluminum doped yttrium-iron garnet

Fermilab May 10, 2005 wildman - AAC Meeting26 Phase Shift & Transmission S11 measurement of 10 TCI cores 325 MHzPhase 325 MHz

Fermilab May 10, 2005 wildman - AAC Meeting27 Fast Response of MHz - 5 cores Bias Current 100A/Div Phase Shift ~15 Deg/Div

Fermilab May 10, 2005 wildman - AAC Meeting28 High Power 1300 MHz

Fermilab May 10, 2005 wildman - AAC Meeting29 Phase Shift During 352MHz, 100kW Pulse Phase Shift from mixer Forward Power

Fermilab May 10, 2005 wildman - AAC Meeting30 Coaxial Phase Shifter Coax design is preferred at 325MHz In-house design tested to 660kW at 1300 MHz Tested at 300 kW at Argonne with APS 352MHz Klystron Fast coil and flux return should respond in ~50us

Fermilab May 10, 2005 wildman - AAC Meeting31 Advanced Ferrite Technology GmbH (AFT) Products: High Power Circulators Fast Ferrite Tuner Fast High Power Phase Shifter Hybrid Tuner Systems Ferrite Material Electrical Power Supplies for 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

Fermilab May 10, 2005 wildman - AAC Meeting32 Phase Shifter Conclusions 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 this month. 4.Average power testing, reaction time testing, and IQ modulator modeling should be the next steps of the R&D

Fermilab May 10, 2005 wildman - AAC Meeting33 General Conclusions We’ve made a good start on our R&D program We still have a lot of work to do before the Toshiba klystron arrives next March.