Prototype Cavity Fabrication & Test

1. Prototype Cavity Fabrication & Test Presented by Ilan Ben-Zvi, BNL for Michael Cole, AES

2. Outline • Review of Program Approach via DOE SBIRs • SBIR Objectives for Phase 1 and 2 • Engineering Approach • Fabrication Approach • Cavity Treatment • Test Support • Down Select Impact

3. Program Structure and Funding • Program funded via DOE SBIR • Four DOE SBIRs were Submitted: • The Crab Cavity: AES (Cole), BNL, LBL, and SLAC • Couplers for the Crab Cavity including LOM, SOM, HOM, and FP: AES (Cole), BNL, LBL, and SLAC • A Cryostat for use with the Crab Cavity: AES (Holmes) and FNAL • Crab Cavity Tuning Devices: AES (Holmes) and FNAL • Of these we only won the first, the Crab Cavity SBIR.

4. Award Impact • Only have funding for engineering and analysis of Cavity. • Effort on potentially complex coupler structures will have to come from elsewhere. • Same for Cryostat and Tuner development.

5. SBIR Program Format • Phased Program • Phases Awarded Independently • Phase One in negotiation now • 8-9 Months • Limited Program • 500 Hours (13 Man Weeks) • Feasibility Study • Costing Study for Phase Two • Phase Two • Based on successful Phase One, Late Summer 2010 Award. • Phase Two is proposed via Phase One report. • Two year program $750K max, Level Funded • $350K per year, can impact long lead procurement. • Year two technically optional for DOE • Detailed Design, Hardware, and Test phase

6. Prototype Crab Cavity • Collaborators are AES, BNL, LBL, and SLAC • Phase 1 • Preliminary Design of Cavity (3 man months supported by SBIR) • Coordinate transfer of Physics Design • Develop initial mechanical solid model • Perform Initial Thermal and Structural Analysis • Preliminary Mechanical Design and Fabrication Feasibility Study • Phase 2 • Complete mechanical design with supporting thermal/structural analysis. • Generate complete fabrication drawing package for the Crab Cavity. • Fabricate Prototype Crab Cavity • Perform BCP and HPR on Prototype Crab Cavity at AES if our facilities can accommodate it. • We anticipate that we will be able accommodate an 800 MHz elliptical crab cavity. • Support Crab Cavity VTF testing at BNL

7. Crab Cavity Couplers • Focus of the coupler SBIR was to have been the coupler structures. • The boundary between the cavity and couplers is quite blurry for some of the configurations. • It is reasonable to expect that provisions can be made to retrofit couplers at a later date providing the configuration is conducive.

8. Engineering Approach • Will start from the RF geometry developed from the physics and RF engineering efforts. • AES will develop the cavity structure and RF volume solid models in Pro/Engineer. • Design engineering will then develop approaches to cavity manufacturing and assembly. • Will involve the determination of the detailed parts that will be fabricated and the techniques used.

9. Thermal and Structural Analysis • Three dimensional finite element code ANSYS will be used for thermal analysis. • The model meshing will be in sufficient detail to provide accurate results. • The thermal sink is a helium bath at either 2K or 4K. • At 2K helium is a superfluid. • Kapitza resistance formulations will be used. • If at 4K pool boiling of helium will be assumed. • In either case a non-linear function of temperature is required for heat transfer to helium as well as RF losses to walls.

10. Operating Temperature Determination • Highly nonlinear thermal conductivity of niobium from below 2K to 9.2K. • In the past we have set the niobium temperature limit near 7K to allow for sufficient headroom. • If we assume a 4K helium bath, and the results show that the cavity runs above 7K we will consider decreasing the design bath temperature to 2K.

11. Stress and Vibration • With the temperature distribution complete a structural analysis will be done. • From the structural analysis we will obtain both a stress and displacement distribution. • The stress distribution will determine if the structure is within its material yield limit. • Load conditions from operation to loss of beam line vacuum will be considered. • The structural model will also be used to determine structural frequencies. • We will ensure that no mode frequency is too close to the driver frequencies.

12. Displacement and Frequency Shift • The displacement distribution will be used to determine how the cavity resonant frequency will be altered by the temperature distribution. • If needed, Lorentz-detuning can also be evaluated.

13. Fabrication Approach • AES has a fairly broad range of experience in design, analysis and fabrication of SRF structures similar to those envisaged in this proposal. A review of a few of the more relevant follows.

14. Design, Analysis, Tool Design, and Fabrication of Components for Two Triple Spoke Resonators (ANL) • AES performed tool design and fabrication of all niobium and stainless steel cavity components. • AES performed all forming and machining operations • Sciaky performed the EB Welding under ANL supervision. • AES also performed the final cavity tuning for the 2 prototype resonators. Center Conductors, Beam Tubes, and Saddles Completed Triple Spoke Cavity

15. Fabricate Niobium Details and Assemblies for Six Quarter Wave Resonators for the ATLAS Upgrade Cryomodule Center and Outer Conductors Halves Welded Center conductors and Beam Tubes • Division of work between AES, ANL, and Sciaky similar to Triple Spokes Completed Center conductor in fixture Toroidal End Wall

16. Euclid Cavity Fabrication Cavity cells in welder Cavity cells following welding • AES is currently fabrication a set of cavities which require a complex interface between waveguides and single cell cavities. • Cavity cells are formed and welded. • Waveguide sections with cavity apertures are in being welded. This cell goes in here… Waveguide sections fixtured for welding Waveguide sections following welding

17. Cavity Processing • AES and BNL are currently installing a full cleaning facility at AES. • Clean rooms, Extensive HPR, and BCP facilities are installed and being commissioned. • Providing the cavity is compatible (likely) we will do the cavity processing at AES.

18. Test Support • Following cavity processing AES will support cavity testing at BNL. • This will include integration into BNL’s VTF facility. • This could also include assembly of the VTF test string in AES’s clean rooms.

19. Down Select Impact • Most critical issue is to make timely decision (now). • A design which is complex but incorporates elements all of which have been done before may be superior (for fabrication) to a design which appears simpler but includes lots of “first of a kind” elements. • The UK design does look quite elegant as long as we can successfully get the irises in the cavity cells. • The LARP design does have more bits and pieces, but taken separately we have done them all before. • At this point the physics issues should drive the downselect.

20. Conclusion • AES is ready to begin Preliminary Design of Cavity immediately following physics down select. • All capabilities for design and fabrication are in house and ready to go. • Cleaning and processing capabilities are in development and should be ready in time to support this program.