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3.3 Physical elements and Entities

GMAD implements almost all the standard MAD elements, but also allows to define arbitrary geometric entities and magnetic field configurations. The geometry description capabilities are extended by using “drivers” to other geometry description formats, which makes interfacing and standardisation easier. The syntax of a physical element declaration is

element_name : element_type, attributes;

for example

qd : quadrupole, l = 0.1*m, k1 = 0.01;

element_type can be of basic type or inherited. Allowed basic types are

All elements except marker, element, ecol, and rcol are by default modeled with an inner cylindrical beampipe and an outer cylindrical volume. (FOR MAD COMPATIBILITY sbend SHOULD BE A TORUS). The beampipe outer radius and thickness are defined by the global beampipeRadius and beampipeThickness options; the beampipe outer radius can be redefined for almost every element with the aper option. The beampipe material is defined by the global beampipeMaterial option (default: “Vacuum”), while the residual gas in the beampipe at the moment cannot be changed by the user and is set to “Vacuum”. The outer volume is represented (with the exception of the drift element) by a cylinder with inner radius equal to the beampipe outer radius and with outer radius given by default by the global boxSize option, which can usually be overridden with the “outR” option.

An already defined element can be used as a new element type. The child element will have the attributes of the parent.

     
     q:quadrupole, l=1*m, k1=0.1;
     qq:q,k1=0.2;