Tracking routines in a Magnetic Field

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| Geant 3.10  |               GEANT User's Guide              | TRAK500  ##
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Author(s) : R.Brun                                     Submitted: 01.10.81
Origin    : GEANT2/3                                     Revised: 20.05.86
                                  

        +--------------------------------------------------------+
        |CALL GUSWIM (CHARGE,STEP,VECT,VOUT*) |
        +--------------------------------------------------------+
                                  

Called by the GEANT tracking routines: GTELEC, GTHADR, GTMUON.

Calls GRKUTA, GHELIX, GHELX3 according to IFIELD =1, 2, 3 respectively.

(IFIELD = -1 reserved for user decision in GUSWIM)

CHARGE

particle charge

STEP

step size

VECT

initial coordinates, direction cosines, momentum

VOUT

output coordinates, direction cosines, momentum.

        +--------------------------------------------------------+
        | CALL GHELX3 (FIELD,STEP,VECT,VOUT*) |
        +--------------------------------------------------------+
                                  

Performs the tracking (one step) of a particle in a magnetic field. The trajectory is assumed to be a helix in a constant field taken at the mid point of the step. The field is along axis 3.

FIELD

field value multiplied by the charge of the particle

STEP

step size

VECT

initial coordinates, direction cosines, momentum

VOUT

output coordinates, direction cosines, momentum.

The call to this routine is selected by the default routine GUSWIM when the parameter IFIELD =3 in the tracking medium definition (see GSTMED). When the routine is called by the GEANT tracking routines the parameter FIELD is taken from the FIELDM parameter for this tracking medium (see GSTMED).

        +--------------------------------------------------------+
        |CALL GHELIX (CHARGE,STEP,VECT,VOUT*) |
        +--------------------------------------------------------+
                                  

Performs the tracking (one step) in a magnetic field. The trajectory is assumed to be a helix in a constant field taken at the mid point of the step.

CHARGE

particle charge

STEP

step size

VECT

initial coordinates, direction cosines, momentum

VOUT

output coordinates, direction cosines, momentum.

The call to this routine is selected by the default routine GUSWIM when the parameter IFIELD =2 in the tracking medium definition (see GSTMED). The following user routine is called

                           CALL GUFLD(VECT,F*)
                                  

where, F is a vector containing the Field components.

        +--------------------------------------------------------+
        |CALL GRKUTA (CHARGE,STEP,VECT,VOUT*) |
        +--------------------------------------------------------+
                                  

Runge-Kutta method for tracking a particle through a magnetic field. Uses Nystroem algorithm (see Handbook NAT.BUR.OF standards, Procedure 25.5.20)

CHARGE

particle charge

STEP

step size

VECT

initial coordinates, direction cosines, momentum

VOUT

output coordinates, direction cosines, momentum.

The call to this routine is selected by the default routine GUSWIM when the parameter IFIELD =1 in the tracking medium definition (see GSTMED). For one step 3 or 4 calls to a user provided routine GUFLD are done.

                           CALL GUFLD(VECT,F*)
                                  

where, F is a vector with elements containing the field components.