# ITS expected deviations from ideal geometry (mounting + deformations)

References:

• SPD: Adriano Pepato (barrel on cones, half-barrel on barrel, sector on half-barrel), Sandra Moretto (half-stave on sector), Romualdo Santoro (module on half-stave)
• SDD: Ludovic Gaudichet
• SSD: Gert-Jan Nooren, Enrico Fragiacomo

Table last updated: 10th September 2007

 SPD SDD SSD barrel on support cones half-barrel on barrel sector on half-barrel half-stave on sector module on half-stave layer on cone ladder on layer module on ladder layer on cone ladder on layer module on ladder shifts (local x,y,z) 3σ=1mm 3σ=200μm Δ=50,100,100μm Δ=20,100,20μm 3σ=10,50,10μm ? 3σ=5,5,5μm 3σ=45,45,105μm ? 3σ=5,5,5μm (tbc) 3σ=50,50,50μm (tbc) rotations (local ψ,θ,φ) 3σ=500μm at extremes 3σ=100μm at extremes Δ=100,100,50μm at extremes Δ=50,20,50μm at extremes 3σ=0.1mrad ? 0 0 ? 0 (tbc) 0 (tbc)

### Notes:

• Measurements after mounting are done only for:
• few SPD half-staves (just to confirm expected mounting precision)
• SPD ladders on SPD half-staves with precision ∼20μm
• SDD sensors on SDD ladders with precision ∼10μm
• SSD sensors on SSD ladders with precision ∼10μm (measurements + extrapolations from ANSYS simulations)
• SPD: Thermal effects for the ladder-halfstave bonding and hygroscopic effects of the carbon fiber of the sectors are expected to be negligible
• SSD: From measurements of the stiffness of the ladder frame the sag and twist of each ladder according to its position in space can be calculated. The position of the sensors w.r.t. ITS reference points will be also measured with precision better than 10μm
• SSD: Effects of mechanical stress during transport is estimated to stay below 1 μm