Project X High Power 325 MHz RF Distribution and Control Alfred Moretti, Nov 12, 2007 Project X Workshop

Fermilab 2 Outline Layout of the Entire 325 MHz System Description of RF coupling Network to the beam Accelerating Cavity. Description of Terms: Qo, Qext, Q L, β Description of 90 Deg Hybrid as a Vector Modulator and Experimental results. Description Distribution System Conclusions

Fermilab 3 Layout of High RF Power 325 MHz, 600 MeV Section of Project X H¯H¯ RFQ 18 RT Cav. 18 SSR1 33 SSR266 TSR ······································ ·········· ············ KLY (5) 2.5 MW Klystrons Power Divider (9) Main Power Dividers 2 Cryo- modules 3 Cryo-modules 11 Cro-modules Project X 600 MeV H¯ Linac: Beam 9 mA for 1.0 ms at 5 Hz 15 mA H¯ sourse 2.5 MeV RFQ;18 Room temperature spoke cavities 117 Superconducting Spoke cavities in 16 Cryo-Modules (5) 2.5 MW 325 MHz Klystrons 137 Power Couplers for the cavities; 2 are used in the RFQ Note: The First Stage of HINS will have one Klystron driving Room temperature and Superconducting Cavities

Fermilab 4 Typical Trunk Line Power Coupling Network for Each String of Cavities 4-Way Power Divider To Other Cavity Strings Klystron Klystron: Toshiba, Modified J-PARC, Frequency & Diode Type RF power source; Toshiba E3740Fermi Klystron Located outside the cave Each klystron Supplies RF power to many cavities. VM Hybrid Directional Coupler Dual Directional Coupler Provides a fixed amount of power to its Vector Modulator Passes remaining power downstream to the other cavities in its string. Variable +/- 0.5dB within Specs (VSWR & Isolation. Shorted Ferrite line Vector Modulator Hybrid with shorted Ferrite stubs with Magnetically modulated Electrical Phase Length Provides Phase and Amplitude control. (VM) Vector Modulator Circulator Load Circulator/Isolator; Power from the vector modulator Output goes to the Circulator and then on the cavity Power reflected from the cavity goes into the Load providing a matched condition to the VM and driver. In OUT Load Cavity Beam

Fermilab 5 Definitions of Qo, Q ext, Q L, β Qo = ωE/P L, E=Stored Energy P L = RF power Loss in walls of the cavity ω = 2π f, f is frequency Q ext =ωE/P rad, P rad RF power radiated out the coupling hole and wave guide to RF power source Q L =ωE/(P L + P rad ); β= Qo/Q ext = Z in /Z 0 Qo= Q L ( 1+ β); τ ε= Q L / π f E PLPL Empty Enclosed Cavity E PLPL P rad Z in

Fermilab 6 90 Deg Hybrid as a Vector Modulator (VM). 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 b 2 = Cos ((θ 3 – θ 4 )/2) Phase = (θ 3 + θ 4 )/ 2 a1a1 a2a2 a3a3 a4a4 b4b4 b1b1 b3b3 b2b2

Fermilab 7 Mapping of VM with 60 Degree Section Added to One of the Ferrite Phase Shifters 0 Amplitude vs. Phase Power output vs. Phase.

Fermilab 8 cavity phase shifters hybridcirculator water load 6kW input flexible coax to cavity Vector Modulator Test with Cavity: 6kW Slide Provided by Robyn Madrak & Dave Wildman

Fermilab 9 Vector Modulator Test with Cavity: 6kW Phase shifters (solenoids) driven independently by 2 supplies Output power ~ cos 2 [(  1 -  2 )/2] Relative levels (range) = 13.6 dB current, solenoid 2 current, solenoid 1 output power: cavity gap monitor current, solenoids 1 and 2 phase detector: cavity gap monitor relative to input Phase shifters (solenoids) driven in series by 1 supply phase ~ (  1 +  2 )/2 phase range ~ 155 degrees Slide Provided by Robyn Madrak & Dave Wildman

Fermilab 10 Output Range: Single Phase Shifter Gyromagnetic resonance (lossy region) H = I(solenoid) * (#turns/cm)*4  /10 Slide Provided by Robyn Madrak & Dave Wildman → Vector Modulators work well to > 75 kW phase ~ (  1 +  2 )/2 Low Power Test High Power Test

Fermilab 11 Layout of the RF Fan-out for a typical section of the 325 MHz Linac Typical Section of the high power RF distribution The 325 MHz high power line is shown supplying RF Power to 8 cavities. It has 7 directional couplers. The last Coupler supplies power to 2 cavities. It has 8 VM’s and 8 circulators with their attached loads. Directional Couplers To Other Hybrids VM’s Circulators Loads

Fermilab 12 Typical High RF Power Distribution 325 MHz Linac 1.0 MW RFQ and RT Cavities 1.1 MW to SSR1 and SSR2 Cavities MW to SSR1 Cavities MW to SSR2 Cavities Equal Power Split (EPS) Equal Power Split (Equal Power split) EPS EPS RFQ RT Cavities SSR1 SSR1 SSSR2 EPS 9 Cav5Cav4Cav Klystron

Fermilab 13 Directional Couplers Coupling Factors for each String of Cavities RT Cav at 9 ma RT Cav at 16 ma SSR1 Cavities No Current Difference SSR2 Cavities No Current Difference Note that the First 3 Cavities in the RT cavity string are the 2 debunching Cavities and the first RT accelerating cavity used as a debuncher,

Fermilab 14 Beam Loading Effect and Feedback Compensation φsφs Beam Induced Voltage Beam Induced Cavity Voltage φdφd Required Acc. Voltage Amplitude and Phase Feedback Control

Fermilab 15 Reflected Power with and without beam Matched Point at beam time 16 ma No Beam Case Pulse Shape 16 ma Case

Fermilab 16 Conclusions It is possible with one vector modulator per cavity to commission the Project X linac at low current upto 10mA with (5) 2.5 MW, 325 MHz Klystron. Major Components are out for bids and under study. Variable (+/- 0.5 dB) Hybrids (Power dividers) Vendor solicitation are in progress with promising results. Vector modulators have been tested and have exceeded design specifications.