Beam Pipe:
- Inner radius, length of cylindrical section, opening angle of conical section? Driven by decision on magnetic field. To be decided later. Dominik is looking into occupancies for different layouts and two different magnetic field strengths

Vertex Detector:
- Assume 3 double layers as default for barrel and endcap
- 3 (or more) additional disks (single) in very forward region to cover low angle tracks
- Barrel-endcap transition and layer placement -> fast simulation studies by Rosa and Dominik
- Required to first decide on magnetic field strength for final decision on VTX layout
- Support tube required to support vertex detector as well as beam pipe (steel cones and central beryllium section). Most likely placed in between vertex detector and main tracker barrel. Engineering design and therefore the required material budget needs to be investigated.

Main Tracker:
- Outer dimensions fixed by ECAL inner dimensions. Barrel inner radius 1500 mm, endcap front face 2350 mm.
- Layer placement, number of layers -> fast simulation studies by Rosa and Dominik (magnetic field needs to be known)
- Technology choice and heat dissipation -> expert meeting on 24 July (talk by S. Kulis)
- Sufficient material needs to be included in simulation to represent support, electronics and possibly cooling

ECAL:
- Dedicated detector optimisation meeting on 7 August at 10:30.
- Dimensions need to be fixed soon (inner and out radius)

HCAL:
- Keep tungsten absorber in barrel or move to steel absorber?
- Active material thickness of less than 7 mm seems feasible (CALICE/ILD proof of principle done)
- Need to include cassette support material: ~1 mm of steel
- Steel absorber plates can be rolled - less space is required for tolerances compared to tungsten (presently assumed 1mm of air for steel HCAL vs. ~4mm of air per layer for W-HCAL)
- Depending on these assumptions the tungsten version might be only slightly more compact than the steel version (tables in slides by Nikoforos need to be updated)
- Tungsten version still attractive as a technological challenge
- Need to decide on baseline for the default simulation model

QD0 / L*:
- Endcap coils to return the magnetic field are baseline -> yoke endcap thickness reduced to 1.4m
- Two options remain
  - QD0 inside detector -> L* = 4.5m, very forward region can stay like CLIC_ILD, investigate to add HCAL coverage to lower angles, modified support tube/shielding
  - QD0 outside detector -> L* = 6m, full redesign of forward region and opening scenario possible and must be investigated
- Long delay expected until an estimate of the luminosity impact of L* = 6m vs. L* = 4.5m can be obtained (NB. all we ever had was luminosity for L*=3.5m)
- In the meantime, investigate advantages of QD0 outside scenario by studying jet energy resolution with higher HCAL coverage at low polar angles -> use a modified version of CLIC_ILD and di-jet samples including overlay (Nikiforos)

Realism of Simulation Model:
- First iteration should be very similar to CDR models for validation
- Add additional level of realism to all subdetectors: gaps for power, signal, cooling and gas, sufficient material for support and cooling
- Gaps for services should avoid 90deg corners otherwise additional space for bending needs to be foreseen
- Ideal barrel-endcap transition in the calorimeters could be a gap in 45deg direction
- High level of realism significantly more important in inner detector than in yoke or calorimeters

Opening Scenario:
- If QD0 is inside detector scenario can stay like in the CDR
- If QD0 outside a completely new scenario might be necessary/desirable
- A scenario where the detector is opened on the IP (a la CMS) could also be investigated
  - Removes the need of a movable platform and simplifies services for detector
  - QD0 would be outside of the detector, supported from the cavern floor