1 / 22

MICE RF Cavity Mechanical Design and Analysis

MICE RF Cavity Mechanical Design and Analysis. RFCC Module Preliminary Design Review June 4, 2008. Allan DeMello Lawrence Berkeley National Lab. MICE RF Cavity. Cavity Assembly Fabrication Steps Q.C. Inspection Analysis Plan Moving Forward. Description of the RF Cavity Assembly.

wes
Download Presentation

MICE RF Cavity Mechanical Design and Analysis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. MICE RF Cavity Mechanical Design and Analysis RFCC Module Preliminary Design Review June 4, 2008 Allan DeMello Lawrence Berkeley National Lab

  2. MICE RF Cavity • Cavity Assembly • Fabrication Steps • Q.C. Inspection • Analysis • Plan Moving Forward Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008

  3. Description of the RF Cavity Assembly MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 3

  4. RF Cavity Fabrication Overview The same fabrication techniques used to successfully fabricate a prototype cavity will be used to fabricate the MICE RF cavities Engineering CAD Model of the RF Cavity • Cavity half-shells will be formed using a metal spinning technique • Precision computer controlled milling of large parts (1.2 m diameter) • Precision turning of mid-sized parts (0.6 m diameter) • Precision manufacture of smaller parts • CMM measurements throughout the process • To limit any annealing and maintain cavity strength e-beam welding will be used for all cavity welding • e-beam welding: cavity equator, stiffener rings, nose rings, port annealing and port flanges • Cavity inside surfaces are finished by electro-polishing Prototype RF Cavity MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 4

  5. Half Shell Fabrication by Spinning • 1524 mm diameter x 6.35 mm thick discs of OFHC copper (ASTM B152 C10100) are spun against a pre-machined form to generate half-shells • Shell outer edges will be trimmed as specified after spinning MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 5

  6. Shell CMM & RF Measurement • Half-shell profiles are measured using a portable CMM • Various cross-sections are measured to check symmetry • Half-shell is placed on a copper sheet and frequency will be measured using low power RF • Comparisons will be made between RF analysis of measured shape and frequency check MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 6

  7. Shell Cleaning and Buffing • Prior to e-beam welding shells must be cleaned • Shells are cleaned by rotating them through a chemical bath • Some scratches and dents may be created on the inside surfaces of the shells during spinning • Cavity surfaces will be smoothed out mechanically with an abrasive buffing wheel if necessary • Scratches will be minimized by working closely with vendor prior to the spinning process MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 7

  8. Cavity Stiffener Ring Welding Hard copper stiffener ring is e-beam welded to the outside of the cavity shell Rings are turned on a lathe after being welded on to provide an accurate reference for subsequent operations During fabrication rings provide for safe handling the half-shells Rings provide an interface for tuner mechanisms (talked about later) Load tests on sample welds indicate the e-beam weld strength is much higher than required for tuning MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 8

  9. Half Shell Lip is Machined CAD model cross section image - the two mating half shells overlap • A close fitting aluminum disc will be used to support the lip during machining • Lip detail includes a chamfered step that mates with the opposing shell • The step locks the shell edges together and prevents slipping prior to and during e-beam welding MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 9

  10. Machining the Iris • Iris is cut with a numerically controlled horizontal mill using the stiffener ring for reference • Special aluminum fixturing designed for prototype will be used to hold the half shells during machining • Iris detail includes a 1 mm lip to register the nose piece ring 1mm Lip MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 10

  11. Nose Piece Ring Fabrication • Nose piece ring material is OFHC copper • Fixturing holds the ring for machining on a lathe • Outer edge detail includes a 1 mm lip to register with the cavity iris MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 11

  12. Cavity Equator e-beam Welding • Cavity and fixture system is mounted and assembled on a plate and placed on the welder sliding table • External structural weld is near full penetration and is achieved in three offset passes • A final cosmetic/vacuum weld is performed on the inside of the joint with the cavity mounted on a horizontal rotary table • Weld parameters to be developed by the vendor MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 12

  13. Nose Piece Ring e-beam Welding • Cavity is placed in welder chamber horizontally on a rotary table • Aluminumfixturing holds nose piece ring securely in place • Weld is similar to equator: 3 offset external welds and one inside cosmetic/vacuum pass • Inside equator and nose welds are smoothed using an abrasive wheel • Weld blow through is also removed • Vendor will develop weld parameters MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 13

  14. Cavity Port Forming & Welding • Local annealing only (to preserve cavity overall strength) is achieved by repeatedly passing a diffuse e-beam around port • Port pulling tool is used in a horizontal orientation, and a weld prep is machined into the port lip using an NC mill after extrusions are complete • Cavity is held vertically in welder chamber on a fixture that facilitates 90 degree rotations • Structural and vacuum weld is made with a single inside pass • MICE cavity will use an all copper flange for RF sealing only MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 14

  15. Cooling Tube Brazing • Cavity cooling is achieved by TIG brazing a 9.5 mm diameter copper tube to the exterior in an alternating skip pattern • Four turns (1 circuit) per cavity side step inward near to the stiffener ring OD and then step back out to the equator • Cooling tube spacing is approximately 10 cm • Cooling system allows up to 11.4 L/min (3 gpm) per circuit with an expected 3.8 L/min (1gpm) in normal use • Possibility of LN cooling will be discussed in a later talk on the overall RFCC module TIG brazed copper tubing MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 15

  16. Q.C. of Cavity RF Measurement • Cavity frequency is measured at various points in the fabrication sequence using low-power RF • In photo at right, aluminum plates are placed over the stiffener rings (after equator weld and before nose weld) to close cavity for frequency measurement • The cavity’s frequency measurements will be compared, from one cavity to the next, for consistency • Physical dimensions and vacuum out-gassing will be measured for each cavity MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 16

  17. Interior Surface Electro-polish • Interior buffing of cavity (if necessary) is performed to ensure the surfaces are ready for electro-polishing • The goal is for a scratch depth shallow enough for EP removal • After buffing the cavity undergoes a chemical cleaning process • Cavity is rotated with a U-shaped electrode fixed in place • EP is a successful process for removing scratches in high field regions • Final process is a high pressure water rinse of cavity surface MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 17

  18. Cavity FEA Analysis • 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 1/16th 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 • A convective film coefficient is applied to the cooling tube walls MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 18

  19. Cavity Analysis Results • The thermal solution provides the temperature distribution throughout the cavity window and beryllium window • Water temperature of 20 ºC is used for analysis (dark blue in both figures) • The peak temperature occurs at the center of the inwardly curved beryllium window (86 ºC) using “Nominal Neutrino Factory” parameters (MICE is 4 times lower) • The lower right hand figure shows the temperature contours with the window removed for better contour resolution (the red color represents 30 °C) MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 19

  20. Cavity Analysis Results (cont.) • The window temperature contour is shown in the figure to the right (30 °C (dark blue) to 86 °C (red)) • The displacements along the beam direction are shown in the figure in the lower right (1.1 mm outward (red)) • 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 • A slight reduction in the cavity diameter, to raise the frequency, has been designed into the MICE cavity (this FEA analysis will be redone with the new geometry to confirm the results) MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 20

  21. Current Plan Moving Forward • A copper supplier for the large sheets used in the fabrication of the cavity shells has been identified and procurement has been initiated (16-18 week lead time) • A metal spinning vendor (local to San Francisco Bay area) has been identified and a visit to assess their capabilities will take place after this review • All machine work on the cavities (within our shop’s capabilities) will take place at Berkeley Lab • The search for a local e-beam welding vendor has started • 3D engineering model has been updated and refined • Detail drawings of parts needed immediately have been started MICE RF and Coupling Coil Module PDR - RF Cavity Mechanical Design and Analysis Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008 Page 21

  22. RF Cavity Summary • Fabrication of the prototype cavity was successful • A slight reduction to the cavity diameter, to raise the frequency, has been specified and a complete FEA analysis of the new geometry will be undertaken (no surprises are expected) • The fabrication techniques used to produce the prototype will be used to fabricate the MICE RF cavities • A detailed WBS schedule for the design and fabrication of the MICE RF cavities has been developed Allan DeMello - Lawrence Berkeley National Lab - June 4, 2008

More Related