Endcap Requirements n n Brief overview of SCT
Endcap Requirements n n Brief overview of SCT Endcap Requirements n n CF Structures tendering n n layout, X 0, thermal, positioning, stability Future plans, K 5/KB comments Summary 1 st Nov 2001 Nigel Hessey SCT Endcap Structures FDR 1
Inner Detector Overview 1 st Nov 2001 Nigel Hessey SCT Endcap Structures FDR 2
Disc Layout 1 st Nov 2001 Nigel Hessey SCT Endcap Structures FDR 3
Basic Requirements n Support ~1000 modules + services on 9 discs n n Correct place, stable ~168 kg per Endcap, 7. 5 kg per disc n Safe under normal loads n n n Safe during transport, assembly 4 -hit coverage (with Barrel SCT) to = 2. 5 (9 deg) n n n Self-calibrating with tracks (module overlaps) and FSI Minimise 3 -hit gaps Spread hits evenly in radius n n gravity, cooldown, moisture, N 2 pressure… Haywood, ATL-INDET-2001 -007 Fit in SCT Endcap envelope n 1 st Nov 2001 TB-0049 -158 -01, ATL-IS-ER-0017 (J. Tarrant) Nigel Hessey SCT Endcap Structures FDR 4
Radiation n Minimise X 0 n n Optimise p. T resolution Minimise conversions etc. for calorimeters Yardstick is Silicon wafer/module material Spread material evenly n n Talk from Tim Jones Survive 10 years operation n n Up to 100 k. Grey ionising dose Up to 2 x 1014 /cm 2/a 1 -Me. V equiv. Neutron flux 1 st Nov 2001 Nigel Hessey SCT Endcap Structures FDR 5
Thermal n Remove power of ~1000 modules n n n 7. 5 W Hybrid, 240 micro. W/mm 2 (max) irradiated Si Use C 3 F 8 evaporative cooling Si at ~ -7 deg C n n Minimise radiation damage Avoid thermal runaway n n Endcap thermally neutral: ~-7/+25 deg. C in/outside n n Outer thermal enclosure and wings active Inner bore cools down; Pixels thermally neutral n n n Care with convective heat loads on top modules Active shield unnecessary during normal running Heater still needed during maintenance to prevent condensation Dry nitrogen purge n 1 st Nov 2001 Avoid condensation on coldest pipes (allow for ~-25 deg. C) Nigel Hessey SCT Endcap Structures FDR 6
Positioning n Wafers ordered; position fixed n Overlaps in r and for hermiticity and alignment n n n High/low modules in a ring Respect tolerances, allow for HV Disc edges protect modules n 1 st Nov 2001 Care with tolerances to not overlap edges Nigel Hessey SCT Endcap Structures FDR 7
Physics requirements for Module Positioning n n “Do as well as reasonably possible” Tracking can use software alignment n Trigger can use LUT now n n Relaxes requirements since TDR Discussed in ATL-IS-ER-0027 n Main constraint is overlap for track-alignment n n 67, 100, 290 micron for inner/middle/outer Also mounts of module need care n Avoid deforming modules out-of-plane n 1 st Nov 2001 100 micron disc flatness (machined), 50 micron module mounts Nigel Hessey SCT Endcap Structures FDR 8
Stability n Vibrations n n Maximise fundamental frequencies and damping Keep amplitude well below resolution: n n << 20 micron in-plane; more tolerance in z. Slower movements n Endcap as a whole n Can follow well with tracks and align to Pixels/TRT n n 250 micron per day ok Internal distortions n n n Minimise; 50 micron in-plane on a disc OK? Use FSI and tracks to follow Modules on a disc: 12 micron in r in a day n n 1 st Nov 2001 TDR, from Snow/Weidberg ATL-INDET-97 -160 Allow for 2 deg. C change. Moisture effects very slow. Nigel Hessey SCT Endcap Structures FDR 9
Requirements Highlights n n n Stability: Challenging but important Radiation length: Minimise Positioning: Relatively easy to achieve 1 st Nov 2001 Nigel Hessey SCT Endcap Structures FDR 10
Comments on Disc Order n Discs supplied by industry n n Major expense, main lead-time Order is for plane disc n n n 2 skins on a core and 2 rings, no machining, no holes Largely independent of services and layout Details such as inserts can be changed later (K 5/KB) But thickness, ring-depth (r) may change Procede as far and fast as possible for K 5 assumption 1 st Nov 2001 Nigel Hessey SCT Endcap Structures FDR 11
K 5/KB Implications n If K 5: full-speed ahead n n n Incorporate comments from FDR Finalise tender docs, design, finance January 2002 PRR (Assume K 5) Tender If KB: n We have time to take maximum advantage n n Lot of work n n Thickness, ring dimensions Though in principle, KB fits with current disc design Manpower and money spent…(at least NIKHEF) Likely Delay to programme Need care to check all will work 1 st Nov 2001 Nigel Hessey SCT Endcap Structures FDR 12
Summary n Main FDR emphasis: n Disc, Cylinder, and Wing: CF Support Structure n n n Major expense items and lead times Thermal Shields Does the design meet the requirements Also: Cylinder Services Layout Disc services: n n n May change K 4 layout = Existence proof of a solution Avoid lengthy K 5/KB discussion 1 st Nov 2001 Nigel Hessey SCT Endcap Structures FDR 13
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