New ATLAS VI Mechanical Tolerances and Aperture Approvals 1

Mechanical Tolerances for New Layout Gap between supports and IST to allow sliding and thermal expansion Sag of IST and beam pipe when installed IST Beam Pipe Installation survey for global position Survey for straightness of IST Circularity 2

New Mechanical Tolerances Mechanical group Sub-group Radial tolerance (mm) Construction Circularity 0.1 Gap for sliding and thermal expansion 0.45 (0.2 for sliding radial clearance and 0.25 for thermal expansion during bake-out) Installation Alignment of installed IST 1.0 (Ref: EDMS 405557) Sag of IST/beam pipe package when installed 0.4 Construction and Deflection Total 1.95 3

Summary for ATLAS Aperture Tolerances Radial Tolerance Value (mm) Mechanical Tolerances 1.95 mm Survey and alignment case 1 2.6 mm at a 2σ, 95 % confidence level when installed with reference to the low beta magnets [NOTE: this will be checked relative to the old beam position and this precision is actually 1 mm, but take worst case for a factor of safety] Stability 2.5 mm= (1.25 mm x 2 FOS) – [NOTE: this assumes 5 years between realignments with a factor of safety of 2. In reality it has been shown from LEB meeting 4 Feb 2011 that the beam is stable to +-0.1 mm over the year and that the Q1 magnets likely move with the ATLAS cavern] Beam stay clear aperture 15.45 mm Total 22.5 mm 4