Brainstorming on how to best proceed with LESS Beniamino Di Girolamo, ATS-DO 1 November 2017

Decisions criteria for the carriage How to arrive to a decision on which mechanical carriage design to adopt Baseline design: review outcome not convincing with a hint to go on because it would be otherwise difficult to build something else and meet the schedule, but with reservation on the achievable precision of 7 mm for the translation and the request of heavy instrumentation Alternative design: good review outcome and ability to meet the schedule. Constraints on the optics setup and the change of fibre head, but no showstopper B Di Girolamo, Brainstorming, 01/11/2017

Decisions criteria for the carriage Baseline design: procurement form multiple suppliers for the various components EMS for robotic arms and rotating head CERN subcontractor for body and other complementary pieces for rotating head IGUS for flexible chain (motorised) Integration of the pieces, commissioning and tests demanded to CERN-Dundee-STFC, busy already for the rest of the treatment work Alternative design: fully industrialized approach with carriage delivered already assembled, tested and commissioned. Lower charge on the collaboration B Di Girolamo, Brainstorming, 01/11/2017

Decisions criteria for the carriage Costs (allocated budget ~ 90 kCHF) Baseline: excluding design costs Robotics arms and rotating head: 29000 CHF Motorized chain: 10000 CHF Body: 10000 CHF TOTAL ~ 50 kCHF Design costs: additional ~ 22000 CHF Alternative: excluding design costs First carriage: 47000 CHF Second optional carriage: 18000 CHF Modification of the fibre head: ~ 6000 CHF Design costs absorbed by strategical work done independently of this collaboration B Di Girolamo, Brainstorming, 01/11/2017

Decisions criteria for the carriage Schedule: tight in both cases The collaboration started only ~ 1 year ago Baseline: difficult to assess. Delivery time for the robotics arms and rotating head (including finalization of the design): 22-24 weeks Alternative: carriage built by mid January, commissioned and handed over by January 26 Difficulties to meet the very tight COLDEX schedule constraints (end February), but the alternative design has a chance because the carriage will be delivered as certified tested B Di Girolamo, Brainstorming, 01/11/2017

How to deal with the schedule It is mandatory to have backup scenarios even if the alternative has a chance to meet the COLDEX schedule Plan A: Participation of Stefan to the assembly phase and commissioning and hand-over at the company premises to shorten the learning time Transport to Dundee asap: trying to transfer the carriage even earlier than January 26th Treatment of the pipe: it is mandatory that the pipe is already on the optical bench, ready for treatment in December 2017 The treated pipe is transferred to CERN via plane in a well-protected package (sky bag): we can buy a ticket for it (we did for the ATLAS Pixel Endcap from SFO to GVA) The treated pipe is dressed with capillaries and flanges at CERN with a crash program in high priority at the central workshop: appointment to be taken now. Risks for the time pressure put on workshop B Di Girolamo, Brainstorming, 01/11/2017

How to deal with the schedule Plan B: If the treated pipe is not ready in time for the COLDEX installation: keep an eye on the needs of the Crab Cavities for possible 1-week technical stop at SPS (typical TS at SPS is 24-48 h max) If we see that it is very difficult to use the end of February slot: immediately release the pressure on the mechanical workshop and opt for a more accurate pipe dressing to eliminate the rush program risk If we see we have a chance: keep the rush program and accept the risks B Di Girolamo, Brainstorming, 01/11/2017

Plan C although MANDATORY Plan C and MANDATORY TESTS: The COLDEX plan is not met, then proceed with the treatment of a second 2-m long beam screen as well as a Classical-Round-COLDEX beam screen and few other shorter racetrack beam screens Extract samples from the treated 2-m and shorter racetrack beam screens to study: SEY (and groove depths): Impact of the focus difference between flat section, rounded section and the transition at corner As above all along the beam screens to evaluate the impact of the macro-steps and the uniformity of the treatment For the above complete the measurements with cross-sectional microscopy to asses the depths of the grooves Particulate: type, size and quantity Assess contribution to impedance and possibly measure N.B.: these tests are mandatory as COLDEX would only give us a result in term of heat load, i.e. is there e-cloud or not within the sensitivity limits B Di Girolamo, Brainstorming, 01/11/2017