[MID] Add superconducting magnet/cryostat geometry to simulation

[joseesquivel-hub]

Adds the superconducting magnet/cryostat geometry to the MID detector simulation in O2, based on GEANT4 standalone studies by Ian Perez Garcia (ICN-UNAM).

Changes:

• New materials added: Iron (pure Fe), WindingPack (NbTi+Cu+Al composite, Arnaud report v0.2, density 2.96 g/cm3), and Vacuum
• Seven-layer cryostat geometry implemented (inner wall, vacuum gap, winding pack, MLI, support cylinder, vacuum gap, outer wall)
• Two variants supported via MagnetVariant selector: AluminiumWalls (11 cm total) and SteelWalls (10 cm total)
• Magnet positioned at z=-1155 cm, verified with zero geometry overlaps (CheckOverlaps) against the ALICE barrel and MID RPC chambers

Verified with o2-sim: geometry increases from 159 to 167 volumes, 0 illegal overlaps detected.

[lmassacr]

Hi @joseesquivel-hub, with @dstocco we are not aware of this work. Can you tell us more about it?
Is this in the context of ALICE3 simulations?

[joseesquivel-hub]

Hi @lmassacr , this work is part of a study on a potential MID upgrade at ICN-UNAM, in collaboration with (Antonio Ortiz, ICN-UNAM). It consists of porting the superconducting magnet geometry studied by Ian Perez Garcia in GEANT4 standalone into the official O2 framework, to enable fast simulations with realistic ALICE conditions. The context is Run 3 MID, not ALICE 3. Happy to provide more details if needed