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High Power RF Distribution and Control in the HINS

High Power RF Distribution and Control in the HINS. Alfred Moretti, Oct 11 , 2007. Outline. Description of Terms: Qo, Qext, Q L, β Description of 90 Deg Hybrid as a Vector Modulator. Description of the System Remarks Conclusions. Definitions of Qo, Q ext , Q L , β.

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High Power RF Distribution and Control in the HINS

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  1. High Power RF Distribution and Control in the HINS Alfred Moretti, Oct 11 , 2007

  2. Outline • Description of Terms: Qo, Qext, QL, β • Description of 90 Deg Hybrid as a Vector Modulator. • Description of the System • Remarks • Conclusions

  3. Definitions of Qo, Qext, QL, β • Qo = ωE/PL, E=Stored Energy PL= RF power Loss in walls of the cavity ω= 2πf, f is frequency • Qext=ωE/Prad, Prad RF power radiated out the coupling hole and wave guide to RF power source • QL=ωE/(PL + Prad); β= Qo/Qext Qo= QL( 1+ β); τε= QL/ πf Empty Enclosed Cavity E PL E Prad PL

  4. 90 Deg Hybrid as a Vector Modulator. • Scattering Matrix S 0 0 C jC S = 0 0 jC C C jC 0 0 jC C 0 0 b = S a for a 3 dB Hybrid C=0.707 and b2 = Cos ((θ3 – θ4)/2) Phase = (θ3+θ4)/2 a3 a1 b1 b3 a2 a4 b2 b4

  5. Hybrid Output with 60 Degree Section Added to One of the Ferrite Phase Shifters Power output vs Phase. Amplitude vs Phase

  6. Simplified Layout of the RF Fan-out for 8 GeV HINS Linac • This is simplified Layout of the high power RF distribution system • The 325 MHz high power line is as shown except it will have 3 main waveguide power Hybrid splitter and 4 smaller Hybrid splitters for Powering 6 directional coupler Arms as shown below for the cavities and the RFQ. Directional Couplers To Other Hybrids IQM’s Circulators

  7. High RF Power Distribution MesonLinac 1.1 MW RFQ and RT Cavities 1.3 MW to SSR1 and SSR2 Cavities EPS 0.749 MW to SSR2 Cavities 0.547 MW to SSR1 Cavities EPS EPS Equal Power Split Equal Power Split (EPS) EPS 9 Cav 5Cav 4Cav RFQ RT Cavities SSR1 SSR1 SSSR2

  8. Directional Couplers Coupling Factors for each String of Cavities Note that the First 3 Cavities in the RT cavity string are the the 2 debunching Cavities and the first RT accelerating cavity used as a debuncher, SSR2 Cavities No Current Difference SSR1 Cavities No Current Difference RT Cav at 16 ma RT Cav at 10 ma

  9. Coupling Factors to Minimize IQM Requirements Full Beam (18 MA) to No Beam HINS Driven by One Klystron

  10. Beam Loading Effect and Feedback Compensation Beam Induced Voltage Required Acc. Voltage φd Amplitude and Phase Feedback Control φs Beam Induced Cavity Voltage

  11. Typical Chart of the Meson Linac Cavities Beam Time = .6931 τε

  12. Reflected Power with and without beam No Beam Case Pulse Shape Matched Point at beam time 26 ma 26 ma Case

  13. Conclusions • It maybe possible with one set of vector modulator per cavity to commission the HINS linac at low current upto 16 mA with one 2.5 MW, 325 MHz Klystron. • Major Components are out for bids and under study. • Variable (+/- 0.5 dB) Hybrids (Power dividers) Vendor solitications are in progress with promising results. • Need simulation of the Superconducting cavity section of the meson Linac to determine Feedback and Feed forward requirements. The only simulation we have was done by Marcus Huening 3 years ago. His numbers are at best case minmum +/- 8 Deg Phase and +/- 1 dB amplitude. • He consider micro-phonics, Lorentz force detuning, jitter in energy, phase and charge.

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