Set materials by a Detector construction messenger

Hello I need to set the sample material using a detector construction messenger

Here the DetectorMessenger (3.5 KB)
MGEMIDetectorMessenger.hh (2.8 KB)

then in the DetectorConstruction I called the messenger (line 269)

theMessenger = new MGEMIDetectorMessenger(this);

and I setted the sample material as (line 338)

G4Material* sample_mat = G4Material::GetMaterial(sample_mat_name); (58.9 KB)

In the Detectorconstruction.hh I defined the function (line 81)

void SetSampleMaterial(G4String mat_name){sample_mat_name = mat_name;};

B1DetectorConstruction.hh (13.2 KB)

I don’t get errors during the building and the compiling, but when I run the simulation I get the error

------ EEEE ------- G4Exception-START -------- EEEE -------
*** G4Exception : GeomMgt0002
      issued by : G4Region::ScanVolumeTree()
Logical volume <sample_log>
does not have a valid material pointer.
A logical volume belonging to the (tracking) world volume must have a valid material.Check your geometry construction.

*** Fatal Exception *** core dump ***
 **** Track information is not available at this moment
 **** Step information is not available at this moment

-------- EEEE -------- G4Exception-END --------- EEEE -------

i.e. it doens’t get the material from the messenger


Maybe the problem is the function
void SetSampleMaterial(G4String mat_name){sample_mat_name = "SampleName";};

in the detector construction.hh because even if I wrtite the string (“SampleName”) it doesn’t set sample_mat_name="SampleName".

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