Coil Cooling Workshop Summary June 10, 2004.

Electrical Isolation: Cladding is isolated from the T by Kapton. The chill plates electrically connect at the lower end and have an electrical break at the top end (ie, copper is overlapped and bonded by b-stage epoxy/glass). The tubing is electrically isolated from the chill plates by the 3M adhesive. IE- EVERYTHING IS ELECTRICALLY FLOATING!!!

Copper Cladding Design Decisions “T” sections will be mold released. Kapton will be applied to the back sides of the cladding. Will investigate 3 M double stick tape to bond the cladding to the mold released T section good enough to hold the cladding through manufacturing. Copper Cladding: –Buy dead soft copper or, alternatively, anneal after laser/water cutting. –Investigate laser cutting to see if the edge roughness is less. –Will probably need to tumble or grit blast to smooth sharp edges. –Will form the 90 degree bend at the factory and custom form the end terminations in the field.

Copper Chill Plate Decisions Use perforated copper plate; this will help bond the plates to the coil. Need to discuss copper surface prep. With CTD to develop good bond to the coil ground wrap. Investigate making forming dies to pre-form the various curves, shapes, etc. off line. There will need to be a series of basic curve shapes, etc. Basic copper plate forming / installation steps: –Form the 90 degree bend (already done at the factory) –Make the overlap b-stage extension section. (offline pre operation at PPPL) –Custom fit to the coil using the forming dies above to pre-shape the plates. (Station 4)) –Cut ends as required to fit to the cladding. (Station 4) –Fit chill plate ends into end terminations of the cladding and stake both ends. (Station 4)

Tubing Connection Pre-form the serpentine tubing length. –Length TBD – keep to manageable lengths. –Furnace braze the copper tabs onto the tubing along the straight lengths. Tabs will be re-designed to be short in height but wider to help spread heat load). –Pressure leak test the tubing at a pressure = fault pressure (ie, setting of relief valve or burst disc) X 1.5 safety factor. –NOTE: May be able to “bypass” some tight areas and not connect the tubing to chill plates in these areas. Kevin will check? Connecting the tubing to the chill plates: –Bond the tubing tabs onto the chill plates with 3-M adhesive film. Use as thin a film as possible to minimize thermal resistance. This material IS NOT cryo rated – may only temporarily bond the tabs in place until it’s encapsulated during the VPI process. Should test. –Fill the space between the serpentines with felt (maybe felt metal??) or fiberglass. Check if copper tape will help spread out heat. –Overwrap the entire area with 0.010” fiberglass. –Overwrap with self vulcanizing silicon rubber tape. –Apply French toast cast over the entire area. Joints between tubing lengths will be made with the Nibco resistance heater using cryo rated solder or braze material. –Attractive Alternative: don’t put tubing lengths in series - bring ends out of the shell from each segment.

Near Term R&D Compare thermal conductivity of copper strip with and without a b- stage electrical break. –Make strips 7” long (overall) – one with joint, one without. –Dip 1” of strip into nitrogen bath. NEED TO BE SURE the dipped lengths are the same for the test to be accurate. –Record temperature vs. time of the other end. Perform thermal conductivity of the staked joint to a straight strip of copper. –Same technique as above. Perform electrical and thermal tests of the 3-M adhesive tape. –Make a strip similar to above but using the 3-M material. –Test the same as above. –Megger at 100, 500, and 1kV. Make a short mock-up of a straight length of coil with the proposed cooling details.