1. Andrew BurrillFall 2011 Project X Collaboration Meeting 650 MHz Developments at JLAB Andrew Burrill for the JLab Team

2. Andrew BurrillFall 2011 Project X Collaboration Meeting Program Overview Jefferson Laboratory has designed a 5 cell, β = 0.61, 650 MHz cavity as an option for Project X. Based on this design two single cell cavities have been fabricated, processed and tested in-house. The cavities were fabricated from 4 mm RRR>250 niobium sheet. The cavities were chemically etched using 1:1:2 BCP to remove ~250 μm of material. Hydrogen degassing at 600 °C for 10 hours Cavity-A had a Qo value >1x10 11 at 1.6 K corresponding to a residual resistance of < 1.5 nΩ. Both cavities have exceeded E acc of 17 MV/m. Additional information may be found in: MOPO007 Proceedings of SRF 2011 MOPC114 Proceedings of IPAC 2011

3. Andrew BurrillFall 2011 Project X Collaboration Meeting Cavity Design 5 cell cavity design based on β=1 high average current cavity shape fabricated & tested at 748.5 MHz & 1497 MHz. –Cavity features flat cell walls Facilitates chemical etching and cleaning Reduces electron impact energy –multipacting –Large iris apertures & flat equator region Should aid in mechanical stability Increased cell to cell coupling Aid in field flatness sensitivity Reduce amount of post-fabrication tuning

4. Andrew BurrillFall 2011 Project X Collaboration Meeting RF Parameters JLab design utilizes a larger beamtube and iris ID Advantages: better cell-to-cell coupling better mechanical stability less field flatness distortion less HOM trapping and field tilts better cleaning Disadvantages trade-off with RF properties (see table)

5. Andrew BurrillFall 2011 Project X Collaboration Meeting 5 cell β=0.61 Multipacting Analysis

6. Andrew BurrillFall 2011 Project X Collaboration Meeting Fabrication & Processing at JLab 2 cavities fabricated from 4 mm RRR>250 sheet material from ATI Wah Chang Beamtubes made from reactor grade sheet Standard deep drawing and surface grinding of half cells Equator butt weld NbTi flanges with AlMg 3 seals Mating flanges are SS 250 µm bulk BCP w and w/o flow diverter Hydrogen degassing : 600C,10 hrs Light, 50 µm, BCP Single pass HPR, 1250 psi with 2 opposed 25 degree nozzles Drying and assembly in Class 10 space

7. Andrew BurrillFall 2011 Project X Collaboration Meeting 650 MHz Cavity A Vertical RF Test

8. Andrew BurrillFall 2011 Project X Collaboration Meeting Cavity Test Results Temperature dependence of the surface resistanceΔf/Δp of 4.4 kHz/mbar unstiffened and 1.7 kHz/mbar Lorentz Force detuning for the unstiffened (Cavity A), and stiffened (Cavity B)

9. Andrew BurrillFall 2011 Project X Collaboration Meeting

12. Current Research Path Finalize the mechanical design for the 5 cell β=0.61 cavity –Pressure calculation –Stiffening ring location optimization –Integration into the Fermi helium vessel Things we would like to do: Build a 5 cell β=0.61 to prove out the design, measure RF performance, compare BCP to EP, etc. Finalize the design & Fabricate a JLab β=0.9 prototype

13. Andrew BurrillFall 2011 Project X Collaboration Meeting Summary Jefferson Laboratory has designed a 5 cell, β = 0.61, 650 MHz cavity as an option for Project X. Based on this design two single cell cavities have been fabricated, processed and tested in-house. Cavity-A had a Qo value >1x10 11 at 1.6 K corresponding to a residual resistance of < 1.5 nΩ. Both cavities have exceeded E acc of 17 MV/m. Things we would like to do: Build a 5 cell β=0.61 to prove out the design, measure RF performance, compare BCP to EP, etc. Finalize the design & Fabricate a JLab β=0.9 prototype

14. Andrew BurrillFall 2011 Project X Collaboration Meeting Acknowledgments Frank Marhauser (RF design, simulations, copper model measurements) Peter Kneisel (Cavity Testing) Bill Clemens, Gary Slack (Cavity Fabrication) Cavity Production technical staff