Checking material with tools in AidaTT and DD4hep

There are several tools (material scans, material checks) in DD4hep, Geant4 and ROOT too check the material. In the context of tracking surfaces and the material averaged and associated to them, the AidaTT package includes additional tools in its examples. You may need to build the examples by doing (in a working, initialized ILCSoft release):

cd build;
make examples;
cd examples

Of particular interest is check_materials which prints all the information of encountered surfaces along a $ (\theta, \phi) $ track. It can be used to compare against the output from materialScan that is available in $PATH when DD4hep is initialized in your ILCSoft release.

Checking orientation of surfaces

First try to understand the output of check_materials:

$AIDATT/build/examples/check_materials $lcgeo_DIR/CLIC/compact/CLIC_o2_v04/CLIC_o2_v04.xml 30 0
The command above will have a long printout including the geometry initialization, the intersection with surfaces, the type of surface, the u,v,n vectors, etc.

Should you want to filter out most of the information and keep say the u,v,n vectors for the endcaps, use grep and awk for example like so:

$AIDATT/build/examples/check_materials $lcgeo_DIR/CLIC/compact/CLIC_o2_v04/CLIC_o2_v04.xml 30 0 2>&1|grep "sensitive\[1\]" -A1|grep "zDisk\[1\]" -A1 |grep normal|awk '{print $1,$3,$4,$5,$6,$7,$23,$25,$26,$27,$28,$29,$45,$47,$48,$49,$50,$51}'
When firing at an angle $ \phi=0 $ ($ zx $ plane) and $ \theta=30 $ in the positive z direction, the u v n vectors in the endcao should be approximately:
u(1,0,0) <-> r (x for this angle)
v(0,1,0) <-> rPhi (y for this angle)
n(0,0,1) <-> z

ALERT! The convention above yields a right-handed coordinate system in the positive z direction in the endcao, with u along the "bad" measurement direction (with the worse resolution typically for strip detectors in the r-direction). We need to make sure that it makes sense and how it looks in the negative z-direction. The barrel is somehow more straightforward: n points outwards, v along z and u is rPhi.

-- NikiforosNikiforou - 2015-12-04

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Topic revision: r2 - 2015-12-04 - NikiforosNikiforou
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