ESS RF Group Unit Leader for Spoke Power and RF Distribution FREIA Group Unit Leader 2 ESS Superconducting 5 MW Linac Frequency 35221 MHz Number of spoke resonators 28 Maximum power to beam 240 kW ID: 1030848
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1. High Power AmplifiersR.A. YogiESS RF Group Unit Leader for Spoke Power and RF DistributionFREIA Group Unit Leader
2. 2ESS: Superconducting 5 MW LinacFrequency = 352.21 MHzNumber of spoke resonators = 28Maximum power to beam = 240 kWMaximum generator power = 300 kW
3. 3Power CouplerNew design being developed at IPN OrsayHigh Power Test Stand at UppsalaHigh power testing needed !Two high power RF chains are needed to test two spoke cavities at Uppsala test stand !
4. Baseline Design for ESS RF system4Generation and distribution of the RF power from a single source to a single accelerating cavity
5. The capital and running cost of an accelerator is strongly affected by the RF power amplifiers:Capital cost: cost of the amplifiers gain of the power amplifier (decides number of stages) and hence size and weight of the amplifiers: (decides gallery requirements) Running cost: efficiency determines the electric power required and also amount of cooling needed Life time: replacement, maintenance schedule 5Importance of selection of RF source
6. RF Source RequirementsMaximum RF power for a spoke resonator = 240 kWConsidering LLRF overhead = 15% (Simulink model shows 12.5% power overhead)RF loss in distribution system = 5%,Power of RF source = 288 kW. Aim for 300 kW (4.0% extra, Why ? Will be explained in next slides)Beam pulse width = 2.86 ms, repetition rate = 14 Hz, fill time of the cavity: Natural fill time = tf = 2QL / = 135 µs, (QL = 1.5 x 106 ) RF pulse width = 3.1 ms Duty factor of the amplifier 4.28 %Spoke cavity band-width = 2.34 kHz system band-width 100 times larger than spoke resonator band-width for tuning and regulation delay. 3 dB bandwidth ≥ 250 kHz.
7. 7High Power RF AmplifierSpecifications of RF Amplifier:Frequency = 352.21 MHzPower = 300 kW3dB band-width ≥ 250 kWPulse width = 3.1 msPulse repetition rate = 14 HzNo RF source exists at ESS specifications ! Hence development and prototyping is important !Compared all the possible RF sources like Tetrode, Klystron, IOT, Solid state amplifier and selected Tetrode for the first high power RF chain. Simultaneously high power RF amplifier using solid state technology under development for the second chain.Supported by AIR and TB at ESS
8. Comparison of Tetrodes 8TH781, TH391 and TH595 tetrodes can be used at ESS specifications. Typ. Performance TH781 TH391 TH595Maximum Frequency 250 MHz450 MHz450 MHz Frequency (as per Thales catalogue)200 MHz352 MHZ380 MHz380 MHzPower 200 kW350 kW200 kW200 kWPulse width cw3.5 ms100 s100 sgain12.2 dB13 dB15 dB 15 dB Efficiency 68.9%55 % (predicted)67 % 67 % Cavity (as per Thales catalogue) TH18230B (200 kW, 380 MHz)TH18528 (100 kW peak, 85-115 MHz)Type of anode cooling & anode dissipationWater, 250 kWAir, 12 kWWater, 40 kW TH595 is selected for first high power RF chain.Output power of two tetrodes needs to be combined.
9. 9Foot area:2.5m x 2.5mFoot area:0.6m x 0.6m
10. Schematic for first RF chain10SG: Signal generator, : Phase shifter, A: Attenuator, A1 & A2: Preamplifiers, PA1 & PA2: High power amplifiers.Transmitted power and RF distribution systems are specified on top of schematic.Loss in theconnections are not considered due to the 4% margin on the generator power.
11. 11Amplifier cavity TH 18595ATetrode TH595Tetrode TH595 and cavity Th18595 A at Thales
12. 12Schematic of RF station used at Thales
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15. 15ParametersESS specifications Test results at Thales Frequency352.21 MHz352.21 MHzPower> 320 kW(> 300 kW)> 400 kW3 dB Band-width> 250 kHz 7 MHzEfficiency> 50 %67 %Gain> 10 dB15 dBConclusion for High power RF AmplifierComparison of target ESS specifications and achieved performance of TH595 and cavity Thus TH595 shall be used for first high power amplifier chain.
16. Pre-amplifierAs gain of tetrode decreases due to aging, conservative gain of 13 dB is considered while calculating specifications of solid state amplifier. Thus output power of pre-driver = 8.7 kW. Aim for 10 kW. 16Specifications of Predriver: Frequency = 352.21 MHzOutput power = 10 kWGain = 70 dBTotal efficiency = 55 %Class of operation: AB
17. Selected solid state amplifier after comparing the available technologies. Gain 70 dB Efficiency > 50 - 55% (class AB)Good reliability: Built in redundancy Modular system, easy replacement possibleOff-shelf available system 17RF unit of 700W power RF 5 kW power module
18. ConclusionTH595 with amplifier cavity TH18595A can be used as high power amplifier Solid state amplifier can be used as pre-driver.18Thank you !Comments and suggestions are welcome
19. 10 kW 352MHz Pre-amplifierSolid state amplifier:Gain 73 dB, so only one stageGood Reliability: Built in redundancy Efficiency > 50 - 55% (class AB)Modular system, so easy replacement possibleTriode:Low Gain 10 dB, so consists of three amplifier stages. It requires pre-predriver triode (1 kW), and solid state low power amplifier (10 W)Complex system. 3 amplifier stages, their power supplies, protections, hence low reliability.Efficiency: 70%19
20. Features RF DistributionNo pressurizationUse of Ferrite loadsDistribution at 3 levels Half height WR2300: 350kW 6-1/8 inch, 50 coax: 175 kW 7/8 inch, 50 coax: 10 kW20
21. 21Typical power sources used at 352 MHz are tetrodes, klystrons, IOTs and solid state amplifiers Criteria of comparison:Power distribution schemeLifetimeEfficiencyGainAvailabilityCosts
22. Too big for 350 kW powerSize: 1 m x 1 m, weight: few tonsEfficiency: 60 – 65%Modulator needed for power-supply,100 kVGain: 37 dB Predriver not neededLife time: 40-50 khoursCirculator needed for handling reflection Base line of one RF amplifier per cavity22Klystron
23. 23Solid state amplifier 70 modules of 5 kW each that are combined High reliability due to use of circulators and hybrid couplers.Size: very big 10 m2Efficiency: 65%Few distributed power supply 50 V, 200 A (low voltage, high current)Gain: 37 dB Predriver not neededLife time: 50 khoursRF unit of 700W powerRF 5kW power module