Report from RF Session (1:30-5:40 PM, 3/30/2004)

1. Report from RF Session (1:30-5:40 PM, 3/30/2004) H. Haseroth and Derun Li Center for Beam Physics Lawrence Berkeley National Laboratory MICE Collaboration Meeting at CERN March 31, 2004

2. MICE RF • Eight 201.25 MHz cavities (4-cavity per module) with curved Be windows (21-cm radius and 0.38 mm thick) • Cavity body, ports, vacuum, probe, cooling channel • RF windows + couplers • Curved Be windows • 8 MW (or more?) peak RF power system + distribution system • Low level RF control (RAL) • Driver amplifiers, amplifiers and PSs • Distribution system (rigid coaxial transmission lines, pressurization with dry N2 or SF6), hybrids vs circulators, phase shifters, … Report from RF Session Derun Li

3. Agenda • Status of the 200 MHz cavity (D. Li) • Status of power amplifiers and drivers at RAL (P. Drumm) • 201 MHz cavity fabrication (R. Rimmer) • Status of power amplifiers and drivers at CERN (H. Haseroth) • Curved Be window designs (S. Yang) • 201 MHz RF system for MICE (hybrids) (Al Moretti) • Controls (Blondel’s table) • Layout • Discussions Report from RF Session Derun Li

4. MICE RF - Power sources and distribution system(PD, HH and AM’s presentations) • RF group at the Daresbury SRS • Mike Dykes (group leader) • Andy Moss (senior RF Engineer) • plus two more • MD & AM are here…

5. Master Oscillator 4 MW Transmitter 2 MW Transmitter 2 MW Transmitter 201 MHz Cavity Module 201 MHz Cavity Module 3 db Hybrid & Load Matched Splitter Circulator & Load Baseline ? Report from RF Session Derun Li

6. R.F. LEVEL SUM R.F.LEVEL PHASE SHIFTER 70db COUPLER CIRCULATOR CAVITY TH116 2.5MW 4616 250kW SOLID STATE DRIVER F R MATCHED POWER SPLITTER LOAD CAVITY PHASE TUNE ERROR PHASE DET 70db COUPLER CIRCULATOR CAVITY F R R.F. LEVEL AND PHASE CONTROL LOAD TUNE ERROR CAVITY PHASE PHASE DET 33kV H.T. R.F. SOURCE 18kV H.T. Split – Circulator - RF Scheme Report from RF Session Derun Li

7. RF Power Baseline Design 8 MW peak RF power: • RF Power Design driven by cost issues (no funds for a new system) • Optimal – one amplifier per cavity • Two amplifiers from LBNL = 4 MW total • One or two amplifiers from CERN = 4 MW total • If 1 amplifier – needs a bigger drive? • Possibly more coaxial components from CERN • Spare TH116 Tubes from ISIS • Low level RF and RF layout (not covered this time) Report from RF Session Derun Li

8. RF Power Amplifiers available at CERN/PS There is one more amplifier from Linac1: It got modified to 88 MHz (foreseen for tests with our 88 MHz cavity for the cooling channel in the CERN scenario. 2 MW (FTH triode tube) driver (LHC type, modified) available If amplifier is modified: 4 MW achievable, but driver must be pushed Of course: to modify to 88 MHz and modify again is not too attractive… Report from RF Session Derun Li

9. RF driver Amplifiers available at CERN/PS 200 MHz: 3 amplifiers 350 (400) kW, one available now, 2 more in the near future (with Siemens tube no longer built). Still several spare tubes in stock. One tube good for up to 15 000 h in 300ms, 1 Hz, not full power regime. Needs power supply for 40 kCHF. Switching via cathode (5 kCHF). GSI (Hutter) says that change to a tube which is still available is not a major issue… Report from RF Session Derun Li

10. RF Power and Distribution (1) • Hybrids versus circulators • Helpful discussions • Issues become clearer • Should come to an agreement soon • RF experience from two communities: (reflection & isolation of RF power – protection of components) Synchrotron/storage ring Linacs Options: circulators hybrids Costs expensive cheaper Reliability + √ Source klystrons triodes Operation mode 99% for users …… • A reasonable choice for MICE: hybrids Report from RF Session Derun Li

11. RF Power and Distribution (2) • Rigid 50 Ω, 4 1/16”- 9 3/16” coaxial transmission lines with pressurized gas • SF6 gives higher P/P’ ratio, but have safety issues • Dry N2 at ~ 2 atm absolute pressure Cost of the Components (by AM): The cost of components assuming 25 feet of 9 3/16 straight and 4 EL-Bows and 25 feet of straight 6 1/8 and 4 EL-Bows 25 feet ST 9 3/16 line $5,600 25 feet ST 6 1/8 line $3,700 4 EL-Bows 9 3/16 $10,300 4 EL-Bows 6 1/8 $6,800 The first Hybrid $8,000 Second Hybrid $4,500 First Hybrid Load $2,022 Second Hybrid Load $1,400 Mech. Phase Shifter $4,300 Several directional C $4,500 Total Cost = $49,722 Report from RF Session Derun Li

12. Power Consumption (HH) Main power consumption and cooling requirements for 1 Hz and 1 ms pulse length: 2  4 MW rf require about 2  10 MW supply. Total: 20 kW with 0.1% duty cycle. Filament needs 2 360 A and 15 V = 2  5 kW = 10 kW. Total for final amplifiers: 30 kW Total for driver amplifiers: 10 kW Grand Total for rf amplifiers: 40 kW 50 % of power estimated to go into the cooling water: requires about 20 l/min water. The rest goes into the air… Available coax lines (9 inch?): 10 cubes for making 90 bends. Report from RF Session Derun Li

13. The 201.25 MHz Cavity with Be windows-Prototype(DL,RR,SY)

14. Status The 201 MHz cavity design and fabrication go smoothly • Spun shells ready for machining after e-beam welding • Nose pieces, stiffener rings and fixture were made • Support structures for the equator welding • Ready for equator welding tomorrow at JLab Engineering design (details) is still continuing • Ports (succeeded in extruding tests and qualified the techniques) • Couplers (done with conceptual design) • Tuners Significant progress on curved window design and fabrication • Succeeded in making S.S. curved windows, curved Be windows for 805 MHz cavity by Brush-Wellman company • Ready for 201 MHz cavity windows The cavity will be ready for test at MTA, Fermilab this fall ! Report from RF Session Derun Li

15. The Cavity Profile update Spherical section at the equator to ease addition of ports (± ~ 6o) Elliptical-like (two circles) nose to reduce peak surface field Stiffener ring 2o tilt angle 6-mm Cu sheet allows for uses of spinning technique and mechanical tuners De-mountable Pre-curved Be windows to terminate RF fields at the iris Report from RF Session Derun Li

16. The Cavity Parameters The cavity design parameters • Frequency: 201.25 MHz • β = 0.87 • Shunt impedance (VT2/P): ~ 22 MΩ/m • Quality factor (Q0): ~ 53,000 • Curved Be window radius and thickness: 21-cm and 0.38-mm Nominal parameters for cooling channels in a muon collider or a neutrino factory and MICE • 16+/8 MV/m peak accelerating field • Peak input RF power ~ 4.6/1 MW per cavity (85% of Q0, 3τ filling) • Average power dissipation per cavity ~ 8.4/1 kW • Average power dissipation per Be window ~ 100/12 watts Report from RF Session Derun Li

17. Recent progress for the welding fmeasured = 200.88 MHz Report from RF Session Derun Li

18. Ready For Equator Welding Report from RF Session Derun Li

19. Extruding tests at JLab Report from RF Session Derun Li

20. RF Coupler Report from RF Session Derun Li

21. Curved Be windows

22. Convex radius R=230.8mm Convex radius = 498.11 mm Intersecting point 770 mm Intersecting point Concave radius= 300 mm Concave radius R = 500mm Earlier window geometry: Concave radius > convex radius Current window geometry Concave radius < convex radius Evolution of the pre-curved window Report from RF Session Derun Li

23. Stress results Displacement: Max bow 2.1 mm 3-D model Max stress 177 MPa Max stress 170 MPa 2-D model Max bow 2.25mm Curved window thickness: 0.38 mm (100 C temperature gradient) Report from RF Session Derun Li

24. Analysis on the prototype window for 805 MHz cavity The new geometry – 16cm diameter window Report from RF Session Derun Li

25. Curved Be windows by BWM Two curved Be windows for 805 MHz cavity: 0.254 mm thick and 16-cm diameter Pre-formed the Be foils first at high temperature, brazed copper frames afterwards. The windows will be Ti nitrided at LBNL for high power test at MTA, Fermilab. Report from RF Session Derun Li

26. 3D meshed ANSYS model Mechanic Resonances The 1st mode: 1695.3 Hz The 1st mode frequency in 3D model is reasonably agree with that of its 2D model’s and also good agreement with ALGOR 3D result (1696 Hz). Solution from ANSYS Report from RF Session Derun Li

27. The 2nd and 3rd mode: 2055 Hz The 4rd and 5th mode: 3494 The 6th mode: 3754 Hz The 7th mode: 3768 Hz The 9th mode: 4560 Hz The 8th mode: 4544 Hz The 10th mode: 4866 Hz Solution from ANSYS Higher Mechanic Resonance Modes Report from RF Session Derun Li

28. Controls

29. Discussions on Blondel’s table ∆E: A few times 10-3 of tolerance for RF voltage and phase • Voltage stability of 10-3 is very difficult (impossible) • Phase stability: 0.5 degree • Measurement on beam Do best to keep the voltage as stable as possible Report from RF Session Derun Li

30. Summary • 8 MW peak RF power sources have been identified, need to see actions (plans) on refurbishing and conditioning various components soon • RF distribution system: hybrids versus circulators • Should reach an agreement for MICE soon • Cavity prototype • Equator welding tomorrow (April 1, 2004) • Ready for ordering curved 201 MHz Be windows • Ready for high power test at MTA, Fermilab this fall • Controls Report from RF Session Derun Li