Integration of Cavities and Coupling Coil Modules

1. Integration of Cavities and Coupling Coil Modules MICE Collaboration Meeting March 28 – April 1, 2004 Steve Virostek Lawrence Berkeley National Laboratory

2. Summary of Integration Issues • Coupling coil geometry • RF module vacuum system • RF coupler configuration • Cavity mounting scheme • Cavity port connections • Vacuum vessel flange joints • Module assembly scheme • LN2 operation design issues Steve Virostek - LBNL

3. MICE RF Module Layout Steve Virostek - LBNL

4. Coupling Coil Geometry • Latest revision of coil design (per Mike Green) is wider than the previous version • New design does not infringe on vacuum vessel interior space • Flange welds to the coil cryostat have been replaced by a single mid-point weld in the vessel • A more compact RF coupler design is required to accommodate the wider coil Steve Virostek - LBNL

5. RF Module Vacuum System • Cavity pairs are pumped by a single cryo-pump through a vacuum manifold • Annular opening around cavity pump-outs provides pumping for vacuum vessel • Common vacuum on both sides of cavities prevents differential pressure across Be windows • Low conductance path prevents cavity vacuum from being affected by vessel gas loads Steve Virostek - LBNL

6. RF Coupler Configuration • As before, all couplers are to be oriented normal to the vacuum shell • All couplers and cavities are identical • Normal orientation facilitates cavity alignment and installation • Bellows eliminates tolerance issues • Coupler body is based on a standard 4-1/16” transmission line • Current layout shows an SNS style RF window (will be used for prototype) Steve Virostek - LBNL

7. Cavity Mounting Scheme • No interconnection between adjacent cavities • Cavities are mounted to vacuum vessel walls through tuner mechanisms • Cavities are installed individually into vacuum vessel • Cavity center lines do not shift during tuning • Cavities are symmetric to coupling coil • RF coupler connections to cavity can be rigid Steve Virostek - LBNL

8. Cavity Port Connections • All ports are on the cavity equator • Local cavity shape is spherical to facilitate port construction • Ports will be formed using a “pulling” technique • Flange clamp is applied after cavity is installed in vacuum shell • Vacuum sealing is not required • Good RF contact will be achieved by using a canted spring RF seal Steve Virostek - LBNL

9. Vacuum Vessel Flange Joints • Sealing flange slides away from mating flanges to provide a clear gap between vacuum vessels • Flexible connection and oversized bolt holes allows for small misalignments between vessel flanges in all 6 DOF • Flexible connection design will cover vessel mfg tolerance range while having adequate strength to satisfy PV code • Magnet forces carried separately from joints Steve Virostek - LBNL

10. Module Assembly Scheme • Curved beryllium windows are installed on cavities • Tuner mechanisms are applied to cavities • Coupling coil can is assembled to two vacuum vessel halves; vessel joint is welded from inside • Assembled cavities are inserted into vacuum vessel from the ends, one at a time • Tuner mechanisms are connected to vessel wall • RF couplers are installed and flange clamps are applied • Vacuum, cooling and electrical connections are made Steve Virostek - LBNL

11. LN2 Operation Issues • Frequency shift caused by cavity thermal contraction • Solution: • Change RF source frequency to be resonated with cavities • Apply force to permanently deform cavity & lower frequency • Thermal losses to vacuum vessel through cavity connections • Solution: No direct vacuum connection to cavities, coupler bodies are long with thin walls, low thermal conductivity isolator materials used for tuner-to-vessel connections • Mechanical stresses at connections between cavity and vessel (tuner mounts, RF couplers, vacuum, etc.) due to thermal contraction of cavity • Solution: No direct vacuum connection to cavities, bellows in RF couplers, non-redundant cavity mounting scheme Steve Virostek - LBNL