Testing the quadrature hybrids and making calculations for the inductor and fast phase shifter

1. Testing the quadrature hybrids and making calculations for the inductor and fast phase shifter Adenrele Fapohunda Supervisors: David Wildman Robyn Madrak 08/07/07

2. Vector Modulator • This summer, I tested 20, 75kW peak power quad hybrids and 3, 400kW peak power quad hybrids using a 30 KHz - 6GHz Agilent Network Analyzer. • I also made some calculations for the fast phase shifter (FFS), such that we can achieve optimal uniformity in the field of the solenoid wound on the garnet ferrite of the FFS. Chopper • I also made a combiner, which is needed to combine 2 individual 1200V voltages serially to make a 2400V output voltage. This voltage will be useful in driving the meanders present in the chopper. I made some calculations were made to maximize the voltage in the combiner with respect to the losses in the cable.

3. Introduction • The aim of the High Intensity Neutrino Source (HINS) program at Fermilab is to develop a multi-mission linear accelerator (Linac), which is capable of accelerating H- ions to 8 GeV while providing 2 MW at 30-120 GeV from the Main Injector and 0.5-2 MW at 8 GeV from the Linac. • The base design through 110 MeV requires multiple room temperature and superconducting cavities to be driven by a single 325 MHz klystron. • A single klystron is used to drive all cavities. This requires a Vector Modulator (VM) for each cavity. As a first step in the HINS R&D program, Fermilab aims to construct the front end of the Linac, which will accelerate a beam to 60 MeV.

4. Phase-shifters 1 2 3 4 THE VECTOR MODULATOR • control the phase and amplitude of a microwave signal. • ΔФ = (ΔФ2 -ΔФ3) /2 Ф = (ΔФ2 +ΔФ3)/2 Output power ~ cos2 (ΔФ) Phase Shift ~ Ф +(3π)/2 Input ΔФ2 ΔФ3 Output Quad Hybrid

5. 90o power dividers and combiners equally divide an input signal into two output signals while imparting to one of the outputs a 90° phase shift combine two equal-amplitude, quadrature-phased input signals into a single output signal -3db -3db Δ = 90O -3db - 3db 3 db Quad Hybrid Coupler QUADRATURE HYBRIDS

6. TESTING THE QUADRATURE HYBRIDS • In order to measure the quad hybrids (QH) …. • Calibrate the connecting adapters on ports 1 and 2 • Connect the adapters to the ports • Set up the network analyzer (NA) • Connect QH to NA and observe data

7. Port 3 Port 1 Network Analyzer Quad Hybrid Port 4 Port 2 R2 R2 < < > 50Ω 50Ω

8. NETWORK ANALYZER MEASURMENTS Port 2 Port 3

9. SOLENOID CALCULATIONS FOR THE FAST PHASE SHIFTER Calculate Bend/ Bcen Vs length Bend Bcen Bend ferrite l/2 center conductor

10. First calculate B for one turn dBz dB Ф z r 90- Ф Φ dl

11. rdθ dz θ b r θ

12. The result for a given length l For b = 1.5, Bcen= For b= 0.75, Bcen= For b = 1.5 Bend = For b= 0.75 Bend =

13. Ideally, Bend/ Bcen ~ 1 • But there is a slower phase shifter response as solenoid length increases (higher inductance) • We can choose 9”, where Bend/Bcent ~ 0.95 • Increasing the solenoid length > 9” only gains a few percent in uniformity but increases L by 10-30%.

14. The Chopper ………uhmmm…….not exactly!

15. Purpose of chopper RF Buckets in M.I. • The High Intensity Neutrino Source (HINS) Linac bunches are spaced at 325MHz approximately 3.1ns • The Main Injector supplies an RF frequency of approximately 53MHz. • Because these bunches will not be accelerated, approximately 1 of every 6 bunches must be chopped off. • The Velocity of the pulse traveling along the chopper plates needs to match that of the beam so that the beam is deflected along the entire 50cm length of the chopper

16. Two parallel meander plates • Meander transmit pulses that deflect the beam • The pulses have a maximum width of approximately 5.5ns (including rise and fall time), 53MHz repetition rate, and a burst of 3ms @ 2.5Hz, or 1ms @10 Hz. • Requires two pulsers to drive each 100Ω meander • Combiner is used to combine 2 pulser voltages of 1200V each.

17. Making the combiner……. +

18. combiner To meander Ferrite V150 Ω 50Ω cable 2V1100Ω V150 Ω Ω 50Ω cable Outer conductor Center conductor The use of the combiner

19. THE COMBINER • a 3/8 inch 50Ω superflexible foam dielectric cable (FSJ2-50) • (5) 1 inch thick Ceramic Magnetics MN60, MnZn toroidal ferrites. • I.D 4.5” and O.D 11.5”

20. Inductor calculations for the chopper • Increasing the cable length allows for more turns on the combiner, hence increasing the output signal • But large length also means more losses in the cable

21. t > 0 i1(t) i2(t) R Io

22. ESTIMATING THE LOSS IN THE CABLE

27. CONCLUSION This summer, I was able to: • successfully test 20, 75KW peak power QH and 3, 400 KW peak power hybrids • make 2 combiners using a 3/8 inch 50 superflexible foam dielectric cable (FSJ2-50) wound around 5 Ceramic Magnetics MN60, MnZn toroidal ferrites and achieved about 46 turns on it • calculate the ratio of fields at the ends and center of the solenoid such as to achieve as much uniformity in the solenoid as possible • also calculate the number of turns on the torroid, which would yield the maximum voltage for our combiner with respect to the loss in the cable.

28. ACKNOWLEDGMENTS I would like to thank: • Almighty God • SIST Committee (Elliot McCrory and Dianne Engram) • Dr. David Wildman • Dr. Robyn Madrak • Joe Dey • Dr. Davenport • And last but not the least my parents!

29. “QUESTIONS!!!!”

30. Thank you FNAL!