Initialisation

The initialisation is controlled by the user in the subroutine UGINIT who has the responsibility to call the appropriate routines ( [BASE100]). It consists of the following steps, most of them performed through calls to GEANT subroutines:

GINIT

initialise the GEANT common blocks with default values ( [BASE030], [BASE110]);

GFFGO

read free format data records either to modify the default options ( [BASE040], [BASE110]) or to provide information on the current run;

GZINIT

initialise the memory manager, the link areas and the run header bank JRUNG ( [BASE110]);

GDINIT

initialise the drawing package ( [DRAW]), calling this routine without having initialised the graphics package via a call to IGINIT or HPLINT will cause GEANT to abort;

GPART

(or GSPART) fill the data structure JPART with the particle properties ( [CONS]);

GMATE

(or GSMATE) fill the data structure JMATE with the characteristics of the materials used ( [CONS]);

User code

it is the responsibility of the user to:

• define the geometry of the different components of the setup ( [GEOM]), stored in the JROTM and JVOLUM data structures;
• define tracking medium parameters ( [CONS],[TRAK]), stored in the JTMED data structure;
• specify which elements of the geometrical setup should be considered as sensitive detectors, giving a response when hit by a particle ( [HITS]);
• usually all done in a user routine called UGEOM;

GGCLOS

process all the geometrical information provided by the user and prepare for particle transport;

GBHSTA

book standard GEANT histograms if required by the user with the data record HSTA ( [BASE040], [BASE110]);

GPHYSI

compute energy loss and cross-section tables and store them in the data structure JMATE ( [CONS], [PHYS]).