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Improvements to description of inactive material in VP modules

Thomas Latham requested to merge tlatham_vp_fixmodulefoot into master

Improve the description of the inactive material in the VP modules


  • Add volumes to account for LV, HV and data cables, plus the LV transition PCB
  • Improve description of module foot, adding LV cable clamp and plugs
  • Add VCR connectors to cooling pipes
  • Fix a few bugs/overlaps in cooling pipes and support hurdle descriptions
  • Tweak material densities to improve agreement between simulated and production masses

The module description has been checked to be free from overlaps using both the ROOT tools and pyg4ometry.

Together with lhcb-conddb/DDDB!122, the DD4hep and DetDesc module descriptions are checked to be identical (up to small expected differences in the cooling pipes due to using improved solids available in DD4hep).

The masses of the various components of the modules agree to good precision with the available measurements of the production components, and the total mass of a module agrees to within 0.5g.

Added a parent volume around each module.

  • Checking the detailed timing with Gauss-on-Gaussino to gauge the impact of this change
  • Have dropped the addition of this parent volume until the timing info is understood

While doing this, we noticed that the RF foil was positioned incorrectly in z, so this has also been fixed.

cc: @mmonk

DD4hep Radiation length scans

Click to expand Below are some scans of the radiation length (as a percent of the material travelled through i.e. radiation length / thickness) of two modules to compare the changes proposed in this MR. The scans were performed in 500 bins between x = -150mm to x = +150mm, 500 bins between y = -80mm to +80mm and from z = 290mm to z = 340mm i.e. modules 38 and 39. The RF foil has been ignored in these scans to make the module differences clearer.



There is also a scan that is the difference between this MR and what is currently in master to show the changes. As well as the obvious change due to the LV harness, you can also see the effects of some of the smaller bug fixes we made such as the fix to the GBTX hybrid density and swapping the coolant delivery pipes so that the slightly larger one is on the correct side.


In addition, we include eta vs phi scans over the full length of the VELO, before and after these changes:



And the difference:


Validated by

  • Core Software
  • RTA
  • Simulation
Edited by Gloria Corti

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