Allan DeMello Lawrence Berkeley National Lab RFCC Module Design Review October 21, MHz Cavity Fabrication Plan

Page MHz Cavity Fabrication Plan Cavity Assembly Fabrication Steps Q.C. Inspection Steps Analysis E-beam Welding Vendor Visits Summary June RF Cavity Design Review Responses Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 3 Description of the RF Cavity Assembly Page 3Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 4 Half Shell Fabrication by Spinning Page 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 LBNL personnel visited Acme Metal Spinning in Minnesota at the end of September to better understand their process and capabilities A plan was discussed to improve the finish inside the cavity by polishing the raw plate before spinning Two extra shells from the prototype program can be re-spun to our new smaller inside dimensions and used for testing e- beam welding process Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 5 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 the stiffener rings provide for safe handling the half-shells Stiffener 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 Page 5Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 6 Machining the Iris Page 6 Iris is cut with a numerically controlled horizontal mill using the stiffener ring for reference Iris detail includes a 1 mm lip to register the nose piece ring 1mm Lip Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 7 Half Shell Lip is Machined Page 7 CAD model cross section image - the two mating half shells overlap 20 spun shells will be measured using a CMM and sorted into closest matching inner diameter pairs 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 Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 8 Shell Cleaning and Buffing Page 8 Prior to e-beam welding shells must be cleaned Shells are cleaned by rotating them through a chemical bath 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 Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

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 Page 9 Cavity Equator e-beam Welding Page 9Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 10 Q.C. of Cavity RF Measurement Page 10 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 Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 11 Nose Piece Ring Fabrication Page 11 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 Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 12 Nose Piece Ring e-beam Welding Page 12 Cavity is placed in welder chamber horizontally on a rotary table Aluminum fixturing 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 Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 13 Cavity Port Forming & Welding Page 13 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 Structural and vacuum weld is made with a single inside pass MICE cavity will use an all copper flange for RF sealing only Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 14 Cooling Tube TIG Brazing Page 14 Cavity cooling is achieved by TIG brazing a 9.5 mm diameter copper tube to the exterior in an alternating skip pattern 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 TIG brazed copper tubing Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 15 Interior Surface Electro-polish Page 15 (if necessary)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 Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page MHz Beryllium Windows Page 16 Each cavity will require a pair of 0.38 mm thick pre- curved beryllium windows with TiN coating Double-curved shape, developed at Oxford, prevents buckling caused by thermal expansion due to RF heating Thermally induced deflections are predictable A die is applied at high temperature to form window Copper frames are brazed to beryllium windows in a subsequent process The window frame has been redesigned, in cooperation with the vendor, to increase the quality of the braze joint Beryllium windows being ordered – 8 windows needed per module 42 cm 201 MHZ Cavity Fabrication Plan Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008

Page 17 Cavity Analysis Results Page 17 An FEA analysis has been carried out to characterize the electromagnetic, thermal and structural behavior of the cavity using a single ANSYS model Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan The lower figure shows the displacements along the beam direction (1.1 mm outward (red)) 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) Without the window a better resolution of the cavity is shown with a range of 20 ºC - 30 ºC

Page 18Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008 Meyer Tool & Manufacturing, Inc W. Southwest Highway Oak Lawn, Illinois Meyer uses Sciaky’s e-beam welding service at the Sciaky factory close to Meyer Tool (Sciaky is a major e-beam welder manufacturer) Meyer Tool has the machining equipment necessary to fabricate the complete RF cavity (minus spinning) A complete drawing package, specification and request for quote will be presented to Meyer Tool toward the end of 2008 Electron Beam Welding Vendor Visit Sciaky electron beam welding machine 201 MHZ Cavity Fabrication Plan

Page 19Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008 C.F. Roark Welding & Engineering Co, Inc. 136 N. Green St. Brownsburg, IN Roark Welding’s e-beam welder is a Sciaky machine and it is housed in an isolated room with a positive air flow to help maintain cleanliness Roark Welding has the machining equipment necessary to fabricate the complete RF cavity (plus spinning at an outside vendor) A complete drawing package, specification and request for quote will be presented to Roark Welding toward the end of 2008 Electron Beam Welding Vendor Visit Sciaky electron beam welding machine at Roark 201 MHZ Cavity Fabrication Plan

Page 20Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008 Electron Beam Welding Vendor Visit Applied Fusion, Inc Republic Ave. San Leandro, CA Applied Fusion’s e-beam welder is a German made machine Applied Fusion has the machining equipment necessary to fabricate the complete RF cavity (minus spinning) A complete drawing package, specification and request for quote will be presented to Applied Fusion toward the end of 2008 Electron beam welding machine 201 MHZ Cavity Fabrication Plan

Page 21Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008 Cavity Fabrication Process Traveler 201 MHZ Cavity Fabrication Plan Twenty copper sheets will be spun into cavity half shell Out of ten shell pairs eight complete cavities will be fabricated (with two possibly partially complete) Each cavity has sixteen individual parts to assemble Fabrication steps and inspections of each cavity will be followed in a fabrication traveler to confirm that no steps are missed

Page 22Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008 Cavity Fabrication Drawings Stiffener Ring 201 MHZ Cavity Fabrication Plan

Page 23Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008 Cavity Fabrication Drawings Welding of stiffener ring to cavity shell 201 MHZ Cavity Fabrication Plan

Page 24Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008 Cavity Fabrication Drawings Welding in of the nose piece ring 201 MHZ Cavity Fabrication Plan

Page 25Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008 Cavity Fabrication Drawings Welding of strut mounting posts 201 MHZ Cavity Fabrication Plan

Page 26 RF Cavity Fabrication Summary Page 26 The twenty Ø1524 mm copper sheets used in the fabrication of the cavity shells have been purchased and will arrive at LBNL the second or third week of December Quotes from two metal spinning vendors (one local to San Francisco Bay area and the other ACME in Minnesota) have been received A third spinning vendor possibility in Indianapolis has been identified If necessary a process of pre-polishing the copper sheet before spinning will be used to help eliminate scratches on the inside of the spun cavity shell The two spare half shells from the prototype program will be re- spun to the new profile and used for e-beam parameter testing Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 27 RF Cavity Summary RF Cavity Fabrication Summary Page 27 Detail drawings of parts needed to fabricate the cavities are nearly complete Three possible e-beam welding vendors have been identified (one local to San Francisco Bay area and the other two in Illinois and Indiana) Request for quote documents will be sent to fabrication/welding shops before the end of 2008 Lawrence Berkeley Lab has the machining equipment necessary to fabricate the complete RF cavity (minus e-beam welding and spinning) and will be considered depending on cost and schedule priorities 201 MHZ Cavity Fabrication Plan Allan DeMello - Lawrence Berkeley National Lab - October 21, 2008

Page 28 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, 2008 RFCC Group: Derun Li, Mike Green, Steve Virostek, Mike Zisman, Allan DeMello Reviewers: Andy Moss, Andy Nichols, Alan Wheelhouse, Graham Wilks, Steve York. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 29 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, A fall-back supplier for the copper cavity body material should be found if possible. QA assessment of material should be agreed with vendor and C of Cs obtained We have identified a secondary source for the copper sheets, Hussey Copper, and have a quote. The copper ordered is C10100 which is certified and comes with documentation. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 30 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, The QA regime for the spinning and EB welding processes is clearly very important in terms of surface finish/treatment and integrity of the final welded assembly. As part of the dialogue with vendors, a written QA procedure should be formalised and agreed and this should form part of the eventual contract for the cavity assembly. It is desirable that test- pieces that reflect the final design be part of this. We have produced a written QA procedure for the e-beam welding of all of the individual welding steps. Square corner pieces from the sheets the disc blanks are cut from will be shipped along with the order. These will be used to create e-beam welding test pieces which can be destructively tested for welding integrity. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 31 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, Some parts of the cavity rely on torch-brazing. The effect of possible corrosion from flux and joint integrity should be understood. This does not apply to the RF cavity. No torch brazing is performed on the cavity. The cooling lines are TIG brazed to the cavity exterior. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 32 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, It was not clear that the possible effect of LN2 cooling on the design had been understood. However, this should not stop the long-lead items from being ordered. The MICE project should formally state when in the project LN2 cooling might be adopted, so that the RFCC design can adapt early if necessary. This switch to LN is anticipated to occur at the very end of the experiment. This is to prevent any problems from affecting MICE. The design of the water cooling system will be done with an eye toward compatibility with LN cooling in the future. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 33 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, The absence of detail manufacturing drawings made it difficult for the reviewers to assess the requirements for dimensional and geometrical accuracy, related to manufacturing technique. Within manpower limitations, the RFCC group should make the manufacturing drawings of both cavity and vessel as soon as possible. The milestone for this should be the FDR at CM22 in November. We have produced detailed fabrication drawings for all of the RF cavity's parts. These are fully GD&T toleranced drawings. The vacuum vessel detailed drawings will follow the completion of the cavity drawings. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 34 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, The RFCC group should prepare an interface document in conjunction with the WP1 Manager at RAL. Minimally this should include details of: flange mountings, alignment tolerances, lifting arrangements, services quantity and type, mounting feet and footprint, type and manufacturer of co-ax connections, pressurised gas supplies and cryogen supplies. We will compile a list of the interfaces and of the necessary utilities needed for the RFCC module. We will contact the WP1 Manager at RAL during CM22 to start the dialog about interface issues. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 35 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, The vacuum vessel appeared to have some welded ports that intersect with the circumferential welds on the vessel. The possible effect on leaks and reliability should be checked. Allan will research this weld joint and report back the findings to the review group. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 36 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, Steps should be taken to prevent multipactoring if this is indeed a risk at MICE operating levels. Our experience with the prototype indicates that our processing techniques made this a minor issue. 9. There should be an adequate tuning range to allow for predicted external forces on the cavity. The cavity has vacuum on both sides and does not see an unbalanced external load. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 37 RF Cavity Design Review Responses 10.Integrating the cavity, vac-vessel and coupling coil is a complex process, one of the most complex in MICE. The process appears to be well understood, but more detail is needed and tooling and fixture requirements thought through early in case there is an effect on the fundamental design. Integrating of vacuum to coupling coil is done. The proposal was communicated to ICST in Harbin. Allan has already started to compile a list of assembly steps necessary for successful fabrication of the vacuum vessel and for attaching the coupling coil to the vessel. He will start to investigate what types of fixturing will be needed for support of the coupling coil during assembly and the fixturing needed for accurately aligning the vessel and the coil. Allan is also working on the assembly steps that will be needed in order to assemble the complete module. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan MICE RFCC Module Review 4 th June, 2008

Page 38 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, The benchmarks used in the various FEA studies should be more clearly stated and a study of the likely effect of mechanical tuning forces on the beryllium window and frame made. The primary concern here is the stiffness and strength of the cavity and any distortion that may occur during tuning. The stiffness and strength were previously analyzed. A 3-D analysis has been carried out to determine if six tuner locations is sufficient to prevent distortion of the stiffener ring and Be window. A very small distortion of 0.05 mm of the stiffener ring is seen in the FEA analysis. This should not affect the window integrity. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 39 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, Although largely outside the charge of this review, a safety case/risk assessment for the possibility of a broken beryllium window should be made, especially for when the module is at RAL. A break of the window is unlikely but could occur due to a catastrophic vent or due to RF dark currents. Analyses will be performed and a document will be generated which details the risk assessment. Note that the windows are fully contained in the vacuum vessel during operation. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan

Page 40 RF Cavity Design Review Responses MICE RFCC Module Review 4 th June, Local transport of the RFCC to the MICE Hall is likely to present problems, mainly due to the compound slope towards the door and the module’s high C of G. The clearance under the door lintel is tight but adequate. A mock-up will be no bad thing, but the RFCC group should meet with the MICE Hall Manager (Willie Spensley), preferably with drawings and photos to discuss. Discussions with Spensley will take place at CM22 or before. We will provide dimensioned drawings and estimated weights to inform RAL staff of the scope of the task. Allan DeMello - Lawrence Berkeley National Lab - October 21, MHZ Cavity Fabrication Plan