1. DUNE APA Overview for SBND Synergy Discussion Lee Greenler University of Wisconsin Physical Sciences Lab September 2, 2015

2. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 2 PSL has fabricated a 40%-of-full-size APA… …and four smaller APAs for the 35T test. APAs

3. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 3 steel cross tube photon detectors electronics plate 2.3m 6.0m The far detector APA frame is fabricated from stainless steel tube: 3”x 4”x 0.120” wall long members and ends 3”x 2”x 0.120” wall cross members The tubes are oriented so the APA frame is 76.2mm (3”) thick. steel side tube APA Structure

4. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 4 The frame is covered with four layers of wires on each side. All the wires start at the top end (right in this picture) of the APA and stop at the bottom. The 1 st and 4 th layers go straight; the 2 nd and 3 rd wrap around the sides. (All layers fill the entire frame area; just partial sections of the layers are shown here.) During fabrication wires are wound around the bottom and the top without break. Wire segments at the top and bottom are snipped out after winding to create individual wires. APA Wire Layers

5. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 5 Active height (not incl. edge and wire boards)5984 mm Active width (not incl. edge boards)2300 mm Side tube length6060.1mm (19’10.6”) U and V angle (deg.)35.71 deg U and V wire to wire pitch4.67 X and G wire to wire pitch4.79 Number and length of top boards10 @ 230 mm U & V wire spacing along top boards5.75 mm Number of U or V wires per top board40 Number of X or G wires per top board48 Number of U, V and X channels per board stack40 + 40 + 48 = 128 Number and length of side boards20 @ 296 mm (end board longer) Side board wire spacing (U & V wires)8.00 mm Layer to layer spacing4.76 mm APA Wire Layers

6. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 6 The four layers of wire on each side are visible here. APA Wire Layers

7. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab Wire boards provide mechanical anchor and electrical connection to wires at head of APA. Edge boards, around sides and bottom end of APA locate the wires, insulate them from the frame and provide rounded edges for guiding them around the corners. Fabrication Overview 7 Wires attach to APA surface at head of APA but to APA edge on other 3 sides. Edge boards and wire boards

8. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 8 This is a close-up of the corner of an APA showing the features in the edge boards that locate the wires. (This image if from one of the 35T APAs so the wire angle is 45 deg. In the current far detector design the wire angle is 35.7 deg.) Edge Boards

9. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 9 These locating teeth were machined into the edges of the boards of the 35T APAs. Where wires cross an opening they are soldered to traces and the segments over the opening clipped away. Edge Boards

10. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab Injection molded strip glued to edges of boards. A likely candidate is 30% glass filled liquid crystal polymer (trade name Vectra) G10 board made by circuit board fabricators All the internal features of the board: traces, holes, countersinks, relief, can be provided accurately and cheaply by circuit board vendors. Molds for injection molding allow complex detail. The ideal plastics candidates for these strips are expensive per kg but this doesn’t matter since so little is needed. 10 An alternate method of producing the edge board teethEdge Boards

11. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 11 We’ve had samples molded. We’ve tested them in LN2 and haven’t seen any weakness in the strip plastic or brittleness in the bond. Edge Boards

12. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab The strip will have to be different for the X and G layers (the longitudinal layers). This design provides accurate location for wires coming in perpendicular to the board. 12 Edge Boards

13. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab Having edge boards held and located by the same screws had drawbacks. The next generation of boards will be located by two pins – one in a close fitting hole and one in a slot. Then the screws only keep the boards on the locating pins. Screws 13 Edge Boards

14. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 14 “Combs” were placed at intermediated positions in one of the long 35T APAs. These toothed strips maintain wire pitch in each layer and maintain layer to layer spacing. Constraining the wires at these intermediate positions greatly improves overall wire and layer spacing uniformity. Combs

15. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab If mesh will be applied then a mesh application setup is a good idea. Clamps and bars are being used here to hold down mesh while it’s tightened. Areas to be glued are masked off. Mesh Application Fixture 15

16. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 16 The 35T frames were made with welded joints… …but a bolted joint has been developed for future APAs that has several advantages. Bolted Frame Joint

17. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 17 Machining of mating surfaces is done after welding – greatly decreasing concerns about weld distortion of the frame. Parts are completely fabricated as long thin members – much easier to handle than full size frames. A defective part can be replaced more easily than in a welded assembly. Thin shims can be inserted during assembly for fine tuning the tube fits if needed. The machining and welding operations required are more ordinary making it easier to subcontract these operations. Bolted Frame Joint

18. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 18 Bolted Frame Joint For the DUNE APA the joints had to be designed with most of the hardware hidden inside so it doesn’t protrude through to the outer surfaces where wires are wound

19. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 19 PSL is developing an automated winder. This is appropriate for the large number of two sided APAs required by DUNE. It would not be appropriate for SBND. Wire Application

20. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab Another wire application concept that we have considered for the DUNE APAs might be ideal for the SBND APAs. Wire are applied to one side of an APA at a time so wires can be applied to a single side of an APA. It is a simple mechanism that uses little or no automation - but more manual labor. This could be just right for the smaller number of APAs required in SBND. The process is still streamlined so wires can be applied at a reasonable rate. 20 Wire Application These sketches show only the critical mechanism without any of the support structure. The key component is a pair of bars, one on each side of the APA, that have a row of pins free to turn in bearings.

21. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 21 Wire Application wires APA frame side tube posts mounted in ball bearings APA frame cross tube These sketches show only the critical mechanism without any of the support structure. The key component is a pair of bars, one on each side of the APA, that have a row of posts free to turn in bearings.

22. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 22 Wire Application a single long APA wire is zig-zagged back and forth between the two rows of posts. The bearings equalize the tension in all the segments of the wire. The mechanism then allows the wires to be “folded” down against the outside edge of the APA keeping a constant wire length (which preserves the tension). wires APA frame side tube pins mounted in ball bearings First Position: Wires are stretched straight between the sets of pins APA frame cross tube

23. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 23 Wire Application Second Position: Links are rotated so the wires bend around APA edge board pins and now extend straight out from the side of the APA. wires APA frame side tube APA frame cross tube

24. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 24 Wire Application Third Position: The bar is swung in a second motion that wraps the wires around the strip on the edge boards – down across the side edge of the APA top APA wire plane bottom APA wire plane edge board mounted on side of APA wires trimmed and soldered to pads

25. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 25 Wire Application top APA wire plane bottom APA wire plane wires from top of APA soldered to pads wires from bottom of APA soldered to pads

26. Lee Greenler, Univ. Wisconsin Phys. Sci. Lab 26 Key points Combs help maintain uniform wire pitch and layer to layer distance If a mesh if being glued down it’s worth developing a good fixture. Consider a bolted frame Synergies The winder concept shown as a possibility for SBND could also serve as good back-up option for DUNE – especially ProtoDUNE. Toothed edge strip design could work well for SBND – research into other plastic material candidates would be welcome. Good bolted joints have been developed – both a corner and a tee joint. These, or a variation of them, might be appropriate for SBND. Key Points and Synergies