1. Status of 201 MHz Prototype Cavity and Curved Be Windows Derun Li Center for Beam Physics Lawrence Berkeley National Laboratory MICE Collaboration Meeting at CERN March 28 – April 1, 2004

2. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 2 Collaborators R. MacGill J. Staples, S. Virostek, M. Zisman Lawrence Berkeley National Laboratory, USA R. Rimmer, L. Philips, G. Wu Thomas Jefferson Laboratory, USA W. Lau, S. Yang Dept. of Physics, Oxford University, UK D. Summers, M. Reep Mississippi University, Oxford, MS, USA

3. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 3 The Cavity Design Update Cavity profile design was last updated last summer and with considerations of –Low ratio of acceleration field versus peak surface field (~ 1.04) –Numerical simulations with MAFIA, URMEL, SUPERFISH and ANSYS (RF, thermal and mechanical) codes –Simple (easier) fabrication without losing the performance –Cavity is ready for e-beam welding at JLab now –De-mountable window design allow for other windows and grids >Baseline window design: curved thin(ner) Be windows (S. Yang’s talk) –Four larger (~4”) ports will be extruded: two for loop couplers, one for vacuum and one extra –Two smaller ports for probes –Mechanical tuners similar to the ones used in SCRF cavities, and will be developed very soon The cavity will be ready for high power test this fall

4. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 4 Brief Review: Cavity Concept Spinning of half shells and e-beam welding Water cooling channels Cavity design accommodates different windows Extruding ports

5. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 5 The Cavity Profile update De-mountable Pre-curved Be windows to terminate RF fields at the iris 2 o tilt angle Spherical section at the equator to ease addition of ports (± ~ 6 o ) Elliptical-like (two circles) nose to reduce peak surface field 6-mm Cu sheet allows for uses of spinning technique and mechanical tuners Stiffener ring

6. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 6 The Cavity Profile update (cont’d) RF/Coupling coil module layout Details of the cavity profile Ports for couplers and vacuum Curved Be windows Ports extruding

7. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 7 The Cavity Parameters The cavity design parameters –Frequency: 201.25 MHz – β = 0.87 –Shunt impedance (V T 2 /P): ~ 22 MΩ/m –Quality factor (Q 0 ): ~ 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 Q 0, 3τ filling) –Average power dissipation per cavity ~ 8.4/1 kW – Average power dissipation per Be window ~ 100/12 watts

8. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 8 The 201 MHz Cavity R&D  Pleasant and effective collaboration between national labs and universities, a short summary of activities:  Cavity design and engineered at LBNL  Curved Be window design and engineering at LBNL and Oxford University  Cavity half-shells spun at ACME, a company in Minnesota  Nose pieces, stiffener rings and fixturing made at University of Mississippi and LBNL  E-beam welding, cavity cleaning and ports extruding at JLab  Design and engineering of RF loop couplers at LBNL  SNS RF windows  Weekly video conference with Jlab, daily updates recently while preparing for the equator welding

9. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 9 Spinning @ ACME Spinning a bowl Spinning tools An example of the spinning technique !

10. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 10 A Spun Half Shell @ ACME August 6, 2003 Inner surface scratch was found after chemical cleaning at JLab, and need to be mechanically buffed and electro-polishing. Can be avoided by carefully monitoring and handling during the spinning.

11. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 11 RF and CMM Measurements CMM setup and scans at 0, 45 and 90 degrees, respectively Frequency and Q measurements of half shells; Cu tape for better RF contacts

12. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 12 CMM Profiles 3 CMM scans per half shell conducted at 0 o, 45 o, 90 o, respectively Measured frequency of shell-1: 196.97 MHz (simulated frequency: 197.32 MHz)

13. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 13 Stiffener Rings Two stiffener rings were fabricated at Mississippi University

14. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 14 E-Beam Welding Preparation For The Stiffener Rings

15. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 15 E-Beam Welding of the S. Ring Skip e-beam welding first to hold the stiffener ring in place, then finish the complete welding “Spider” holder Stiffener ring

16. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 16 After Stiffener Ring Welding Mechanical cleaning of the cavity inner surface (right) after e-beam welding of the stiffener ring (above)

17. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 17 Machining at JLab Machining setup Cutting opening for beam iris and nose piece

18. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 18 Recent progress for the welding f measured = 200.88 MHz

19. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 19 Fixturing for the welding

20. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 20 Ready For Equator Welding

21. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 21 Extruding tests at JLab

22. Prototype of Curved Be windows Collaboration with Oxford University Ms. S. Yang will talk on the window designs and FEA modeling

23. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 23 A brief review: Be window R&D Ideal windows – Transparent to muon beams – Perfect electric boundary to RF field – No detuning to cavity frequency Engineering solutions – Pre-stressed flat Be windows – Pre-curved Be windows – Grids A pre-curved Be window: 0.25 mm thick and 21 cm in radius (by Oxford Univ.) Window profile evolutions From flat to curved windows

24. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 24 Curved Be Window Failed in forming Be window at room temperature At that time (last MICE meeting), we believed the curved Be windows can be formed at high temperature (not at LBNL). It can be formed and brazed at Brush-Wellman Company. Purchase order has been placed. We received two curved windows recently.

25. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 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.

26. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 26 201 MHz cavity status Four half shells have been formed by spinning Cu stiffener rings were e-beam welded to two half shells The shells are being mechanically cleaned at JLab Shells are ready for machining prior to e –beam welding of equator joint Equator weld fixturing has been fabricated at LBNL Cavity nose piece rings (Univ. of Mississippi) have been brazed at LBNL Conceptual design of RF loop coupler with SNS RF windows EE-beam welding of equator joint, READY EExtruding four ports, QUALIFIED CChemical cleaning and electro-polishing of the cavity PPre-curved Be windows, QUALIFIED TThe cavity should be ready for test in MTA at Fermilab this fall

27. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 27 Summary 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 Engineering design (details) is still continuing PPorts (succeeded in extruding tests and qualified the techniques) CCouplers (done with conceptual design) TTuners Significant progress on curved window design and fabrication –S–Succeeded in making S.S. curved windows –S–Succeeded in making curved Be windows for 805 MHz cavity by Brush-Wellman company The cavity will be ready for test at MTA, Fermilab this fall !

28. MICE Collaboration Mgt in CERN March 28 – April 1, 2004 Status of 201 MHz Prototype Cavity and Curved Be windows Derun Li Center for Beam Physics LBNL Page 28 Questions ? Thank You!