The reader is assumed to be familiar with the way the geometrical setup is described ( [GEOM]), in particular with the concepts of logical and physical volume tree structure.
The user is required to classify into sets all sensitive detectors (defined as those volume defined as detector via GSDET/GSDETV) for which he wants to store hits in the data structure JHITS. The 4-character names which identify the sets are user defined, and the list of sets which the user wants to activate for a given run can be entered through the data record SETS. The user can group together in one or in several sets detectors of the same or different types. For convenience, it is recommended to have at least one set for each main component of the setup, e.g. hadronic calorimeters, electromagnetic calorimeters, vertex chamber, etc.
A volume can be declared as a sensitive detector through the tracking medium parameter ISVOL, and allocated to a set through the subroutine GSDET or GSDETV. Each (logical) sensitive detector is identified by the 4-character name of the corresponding volume. As a given volume may describe several similar detectors in the physical setup, some additional information is needed for associating correctly the hits with the physical detectors.
When using GSDET the user has to enter the (shortest) list of volume names (the vector CHNMSV), which permits unambiguous identification of the path through the physical tree, even in the presence of multiple copies. This identification is obtained by specifying a list of volume numbers (the vector NUMBV), in a one to one correspondence with the list of volume names. This list, after packing, will constitute the identifier of the physical detector.
If GSDETV is used instead of GSDET then the routine GGDETV (called by GGCLOS) constructs the lists CHNMSV automatically and stores them in the structure JSET.