1 Update on Q2 Main linac starting gradient, upgrade gradient, and upgrade path Results of WG5 discussions after feedback from plenary on Tuesday New Option 2 (16 MV/m => 28 MV/m) Enhanced upgrade scenario explorations for options 1 & 2

2 Three Upgrade Options (with New Names) 1 : (same as last time)”Highest acceptable risk”based on 10% margin Build tunnel long enough (41km) for one TeV, but install only 500 GeV worth of cryomodules in first 22 km of tunnel for 500 GeV phase. 35 MV/m installed gradient, 31.5 MV/m operating gradient for 500 GeV (gradient choice rationale discussed earlier). Fill second part of tunnel (19 km) with 36 MV/m cavities (gradient choice discussed earlier), install more RF/refrigeration 2**: …NEW ”Lower risk”…based on 20% margin 500 GeV phase: Build tunnel long enough for one TeV (41 km). Populate 24.4 km of tunnel with cavities (35 MV/m installed gradient ) Operate cavities at 20% margin (i.e. 28 MV/m). Increase gradient to 31.5 MV/m over Phase I lifetime, energy climbs to 560 GeV. Upgrade : Add 36 MV/m cavities in remaining 16.6 km, and add RF and refrigeration for upgrade. 3 : Half-Tunnel (same as last time) Build first half of tunnel for 500 GeV (22km) and fill it with full gradient cavities (35 MV/m installed gradient, 31.5 MV/m operating gradient, discussed later). Build second half of tunnel (19km) and add 36 MV/m cavities and RF/refrigeration for upgrade.

3 Initial cost: best = 3: (half-tunnel); worst = Option 2: (20%margin) –Cryomodules + RF + Refrigeration + 2Tunnel “guiding model” costs –Option 1 = 1.16, Option 2 = (1.6) 1.22, Option 3 = 1.0 –Option 2 is less risky, most flexible for physics through higher initial energy reach Upgrade cost: best = Option 2 (20% margin); worst = Option 3 (half- tunnel). –Option 1 = 0.7, Option 2 = (0.4) 0.63, Option 3 = 0.9 Total cost (initial + upgrade): worst = 3: (20% margin) –. Option 1 = 1.85, Option 2 = (1.97) 1.85, Option 3 = 1.9 Pros/cons of upgrade paths

4 But Option 1 and Option 2 are getting closer ! –Cost Model estimates Option 2 (20%margin) ~1.05 x Option 1 (10% margin) ( Linac + RF + Cryo + 2tunnels) –Cost Model estimates Option 1 ~ 1.16 x Option 3 –Option 3 (Half-tunnel): Upgrade viability may be questionable, physics impact of digging new tunnel in vicinity of machine (this is a higher level discussion topic than WG5) WG5 Preferred Choice still is : Option 1 (10% margin)

5 A More Optimistic Upgrade Scenario Based on Weeding out Scheme (Still under discussion) 1 :..”Highest acceptable risk”..based on 10% margin Build tunnel (41km 38.5 km) for one TeV, but install only 500 GeV worth of cryomodules in first 22 km of tunnel. 35 MV/m installed gradient, 31.5 MV/m operating gradient for 500 GeV (gradient choice rationale discussed earlier). Upgrade : Fill second part of tunnel (19 km 16.5 km) with 36 MV/m cavities (gradient choice discussed later), install more RF/refrigeration. Replace the lowest performing cryomodules during upgrade with new cryomodules so that all Phase I modules perform at 35 MV/m..anticipate replacing 10% of existing cryomodules. Note : total tunnel length shortened by 2.5 km 2: …”Lower risk”…based on 20% margin Build tunnel long enough for one TeV (38.5 km). Populate 24.4 km tunnel with cavities in phase1 (35 MV/m installed gradient ) Operate cavities at 20% margin (at 28 MV/m) in 500 GeV Phase 1. Increase gradient of installed cavities to 31.5 MV/m over Phase I, energy climbs to 563 GeV. Upgrade : Add 36 MV/m cavities in 14.1 km, and add RF and refrigeration for upgrade. Replace the lowest performing cryomodules during upgrade with new cryomodules so that all Phase I modules perform at 35 MV/m..anticipate replacing 10% of existing cryomodules. Note total tunnel length shortened by 2.5 km

6 Estimated Cost Impact Upgrade cost: Option 1 = , Option 2 = , Option 3 = Total cost (initial + upgrade): Option 1 = , Option 2 = , Option 3 = (Includes cost of replacement modules)

7 Attractive Features of Weeding Concept Low gradient cryomodules identified during Phase I running Keep cavity and cryomodule production factory running at low rate to produce 10% replacement modules over lifetime of 500 GeV Phase –About modules ( cavities) Avoids factory production halt and start up problems for upgrade production

8 Requests to Other Groups What is the effect of 10%, 20% margin on reliability? What is the effect of 10% or 20% margin on cost? –Guiding model suggests 10% extra margin has initial project cost penalty of 5% (on linac cost only). –All costs need more detail analysis How attractive is the weeding out scheme in feasibility, cost, and upgradability ?