Requirements:

• The overlap between adjacent detectors in phi is required to be at least 12 strips.

• The mechanical clearance between rods has to be at least 5 mm

• The difference between the average radii of two consecutive layers has to be at least 8 cm.

Results:

1. rods_1.phi: layers close to minimal overlap, good clearance.
2. rods_2.phi: layers almost perfectly equidistant, larger overlaps, less clearance, more detectors.

Requirements and assumptions:

• The overlap between consecutive modules in z is required to be > 1.5 mm for tracks coming from z=0, and > 0 for tracks coming from |z|=100 mm.

• Rods are required to be identical for the different layers. Therefore, in each case, the smallest and largest radii are considered, and the worst case is taken. The values of R_min = 6a0 mm and R_max = 1080 mm are used.

• R-phi sensors are assumed to be at a radius of +3 -8 mm^[1] wrt to the centre of the rod for DS rods, +3 -3 mm for SS rods.

Results:

Two types of rods are present: having a "high" sensor in z=0 (H) or having a "low" sensor in z=0 (L). In the file rods_1.zpos the z postion of the start of the active area of the six detectors is calculated for four different options:

1. Rods H and L are calculated independently.
2. Rods H and L are adjusted to have the same length.
3. Position of even modules is the same in rods H and L.
4. Positions of all modules is the same in rods H and L.