Proposals for the ITS/ALICE Upgrade CDR: design and technology for the ultra-light mechanics and cooling systems.

We present here the concept of the new design of the Inner Tracking System (ITS/ALICE) that has to meet several extraordinary contradictive requirements related to the further reduction of material budget in the inner sensitive region of the ALICE barrel, providing the operational conditions for the new types of coordinate-sensitive detectors. These requirements are coming from the new physics tasks to be met by the updated ALICE at the LHC. Considerable improvement of the secondary vertexes determination requires both the smaller radius of the first Si-detectors layer and further minimization of the multiple scattering in the ITS detectors and services. Better then 0.5% X/Xo per Si-detector layer of the updated ITS should be provided while preserving the high mechanical stability of all ITS detectors. One has to achieve about 0.5% X/Xo per Si-detector layer, i.e. at least 2 times better then for the ITS at present (of about 1.1 % per layer) that is currently the world record level established for the large area Si-detector trackers. Another tough requirement is the increased heat drain (up to 0.5 W/cm2 in case of application of the monolithic Si-pixel MAPS detectors). These issues are being considered by the ALICE collaboration in the ITS Upgrade Conceptual Design Report (CDR). In our proposals the mentioned problems are met by the new solutions for the efficient cooling system integrated with the extra-light detector support panels using the carbon fiber technology. Both the general design of the ITS structures and the one for the inner detector layers are presented. The conceptual design of “single-side” services ensures a rapid accessibility to the detector ladders in case of replacement or repair. The new air-cooling system is proposed and considered in detail for the Si-pixel Inner Barrel composed of 3 layers of MAPS.. The first numerical estimates of the cooling efficiency and the CAD design of this Si-pixel Inner Barrel are presented. The liquid and efficient evaporative cooling options could be also considered in a similar layout and technology approach. Feasibility of carbon fiber technology, capable to meet all tough requirements, is demonstrated. Solutions proposed are ensuring about 0.94% of grand total X/Xo for 3 innermost layers of the new ITS. The near plans for the R&D are briefly discussed.