1. CPA: Decisions, Issues, Next steps Francesco PIETROPAOLO CERN / INFN-Padova Field Cage CPA and Integration/Installation week, BNL, March 11th, 2016

2. Decisions (I) Baseline option for CPA has been chosen: – FR4/G10 panels, coated on both sides with carbon loaded Kapton foils and mounted in vertical FR4/G10 outer frames. – Frames also resistive coated for better El. field uniformity – Preferred panel size: width ~ 1/2 APA (matching the kapton foil width); height ~ 1/3 of APA – HV distribution bus integrated in resistive tubes surrounding the full CPA.

3. Decisions (I) Involved institutions / tentative responsibility sharing: – Chicago Univ. / Princeton design, mechanical construction, assembly for mockup – BNL CPA design, HV bus design/construction – CERN Small scale tests, resistive lamination, CPA assembly – Ash river mechanical mockup Additional institutions (US/EU) having expressed Interests for CPA design/construction in the ProtoDUNE EoI will be contacted

4. Open issues (I) Detailed CPA design: – Finalization of lamination procedure on large area panels – Hanging structure: single point vs double points – Sliding panel-to-panel mechanical connections to compensate for roof deformation – Electrical connections Panel-to-panel, panel-to-HV bus, CPA-to Field cage – Overall planarity of CPA: Supporting bars construction precision Integration of Field cage pivoting structures Temperature transient LAr flow – Finalization of assembly procedure, installation fixtures and methodology for implementation at Ash River mockup.

5. Open issues (II) HV bus design/prototyping – Segmentation and interconnection plugs – Integration in the CPA supporting structure – HV continuity among sliding panels – Connection with HV feed through Definition of testing procedures for CPA’s – Probe of uniformity of resistive coating – Test of connectivity with HV-bus incorporated? – Cold-testing of panels to verify mechanical stability. – Cold-testing of HV bus to verify robustness to thermal contraction. – …

6. Deliverables Mechanical mockup: – Aim: Develop Installation process and tooling – trial of the assembly procedures and integration in TPC 4 CPA panels columns of 1.2m x 6m modules Material: G10 and/or replacing material: wood? Functional prototype: – Aim: for deformation measurement at cryogenic temperature and electrical test In APA test box CPA: 1 columns of 1.2mx6m modules (with resistive laminated kapton foils) and electrical connections ProtoDUNE – 6 columns of 1.2mx6m modules (+ spares) with: resistive laminated kapton foils, HV bus and HV receptacle, hanging system

7. Next Steps Next meetings: – Process to complete/solve outstanding issues – Involvement of additional new groups – Definitions of deliverables and deadlines – Sharing of tasks among presently involved institutions Tasks: – Finalization of detailed design – Resistive foil lamination procedure on large area panels – HV bus design/prototyping – Mechanical mockup – Functional prototype – …