A simple test to figure out what the material parameters do:

Use Technical proposal benchmark as reference:

Default material is written down in this file: tkgeometry/config/stdinclude/PixelMaterials.cfg

M Si 0 0 0 0.3 mm L ;

pt 1000 Real 2.30948 Ideal 0.53651 Loss 4.3

d 1000 Real 0.00601 Ideal 0.00241 Loss 2.5

z0 1000 Real 0.00696 Ideal 0.00273 Loss 2.5

Changing the following: M Si 0 0 0 3 mm L ;

pt 1000 Real 4.00824 Ideal 0.53651 Loss 7.5

We changed the mass of the modules components (mass of module components ) by doubling it, and we repeated the exercise by leaving the mass of the components as it was and increasing the thickness (sensor thickness) of the sensor in order to get the same increase in mass.

Real
1 GeV	 

Sensor thickness              Mass of module components     
		        				
C	I		C	I	
pT	2.4663  3.80623         3.06497 4.7186
d	0.00651	0.00850		0.00776	0.01019	
z0	0.00747	0.01399	        0.00871	0.01685	
    
Ideal    
1 GeV	   	                TDR				
C	I		C	I	
pT	0.55644 0.086291        0.55644 0.86291
d	0.00255	0.00268		0.00255	0.00268	
z0	0.00277	0.00288	        0.00277	0.00288	 

It is more convenient to use a thicker sensor with respect to using heavier material.