MICE RF Cavity Design and Fabrication Update Steve Virostek Lawrence Berkeley National Laboratory MICE Collaboration Meeting October 27, 2004

RF Cavity Update Steve Virostek - LBNLPage 2 Design Status Summary Prototype cavity fabrication update Current level of completion Remaining tasks Subcomponent design and fabrication RF coupler with RF windows Cavity tuner mechanism Thin beryllium window Test support stand and manual tuner RF/thermal/structural cavity FEA

RF Cavity Update Steve Virostek - LBNLPage 3 Cooling Channel Overview

RF Cavity Update Steve Virostek - LBNLPage 4 RF Module Overview

RF Cavity Update Steve Virostek - LBNLPage 5 Progress on Cavity Fabrication Cavity half shells formed by spinning Stiffener/tuner rings e-beam welded to shells Interior surfaces mechanically smoothed Shell edges machined, nose hole cut Shells e-beam welded together at equator Nose piece rings e-beam welded to cavity openings Four 4” diameter vacuum and RF ports extruded Port flanges e-beam welded to cavity

RF Cavity Update Steve Virostek - LBNLPage 6 Cavity Half-shell Machining Nose hole being machined using a numerically controlled horizontal mill Interlocking shell equator joint being cut with a numerically controlled mill

RF Cavity Update Steve Virostek - LBNLPage 7 Cavity Equator E-beam Weld E-beam welding of cavity equator joint Finished cavity weld

RF Cavity Update Steve Virostek - LBNLPage 8 Nose Fabrication and Weld Nose ring joint welding Nose ring machining Finished nose ring weld joint

RF Cavity Update Steve Virostek - LBNLPage 9 Cavity RF/Vacuum Port Local annealing of ports Finished cavity port Port flange e-beam weld Extruded port Cavity ports being extruded (pulled)

RF Cavity Update Steve Virostek - LBNLPage 10 Remaining Cavity Tasks Brazing of cooling tube to cavity Vacuum leak check of all welds Finish cavity interior buffing Chemical cleaning and high pressure water rinse of cavity interior surfaces Electropolishing of inside surface Low power RF testing (frequency and Q measurement) High power RF conditioning using thick, flat copper windows Cavity tuning sensitivity study

RF Cavity Update Steve Virostek - LBNLPage 11 RF Coupling Loop Design Prototype coupling loop design uses standard off-the-shelf copper co-ax Parts to be joined by torch brazing Coupling loop has integrated cooling Two SNS style RF windows mfg. by Toshiba received (no cost!) Parts for 2 couplers now complete Bellows connection required on MICE for thermal and dimensional reasons Need to integrate with MICE layout

RF Cavity Update Steve Virostek - LBNLPage 12 Cavity Tuning System Six mechanical tuners per cavity needed Tuners push or pull on stiffener rings to deform cavity and adjust frequency ±1 to 2 mm of motion required Current concept incorporates a scissor jack type linkage to gain both mechanical advantage and resolution Actuation forces likely to be hydraulic due to high magnetic fields Detailed design remains to be done

RF Cavity Update Steve Virostek - LBNLPage 13 Beryllium Windows Each cavity will require a pair of 0.38 mm thick, 420 mm dia pre-curved beryllium windows Curved shape prevents buckling caused by RF heating Thermally induced stress and deflection is predictable Window is formed by applying a die at elevated temperature Copper frame is brazed to Be Be is coated with TiN 3 windows currently being fabricated by Brush-Wellman at a cost of $20k each 160 mm 0 Be window for 805 MHz cavity

RF Cavity Update Steve Virostek - LBNLPage 14 Support Stand/Manual Tuner Manual tuner concept consists of thick aluminum plates connected by adjustable struts Tuner allows cavity frequency adjustment while providing support for interior vacuum load Parts for tuner currently being fabricated in U. of Miss. shop Support stand concept attaches to one tuner plate and allows cavity to be placed adjacent to FNAL coil Support design soon to be complete

RF Cavity Update Steve Virostek - LBNLPage 15 Cavity Analysis Summary An FEA analysis has been carried out to characterize the electromagnetic, thermal and structural behavior of cavity using a single ANSYS model Model initially consists of a 1/16 th symmetry representation of the cavity vacuum volume RF solution yields normalized element results in the form of E and H field data A macro converts the H field data at each surface node to heat fluxes based on the known cavity heat dissipation The cavity body thermal model is constructed around the heat flux surface

RF Cavity Update Steve Virostek - LBNLPage 16 Cavity Analysis Summary A convective film coefficient is applied to the cooling tube walls The thermal solution provides the temperature distribution throughout the cavity window and beryllium window The peak temperature occurs at the center of the beryllium window (86 ºC) The lower right hand figure shows the temperature contours with the window removed for better contour resolution

RF Cavity Update Steve Virostek - LBNLPage 17 Cavity Analysis Summary The window temperature contour is shown in the figure to the right The displacements along the beam direction are shown in the figure in the lower right These results are only for a Be window curving out of the cavity Additional modeling for inward curving windows have shown heat fluxes on the window 60% higher than shown here with a correspondingly higher window temperature rise