Limiters can be defined in TRANSP via a set of circles and infinite straight lines defining a closed contour. At JET this set of curves is automatically written into the namelist file by the nblist program and consequently the user does not need to manually enter it. The controls defining the contours are as follows:
NCIRLM: The number of circular limiters to be used.
CRLMR1(i): The major radius of the centre of circle i (cm).
CRLMY1(i): The elevation of the center of circle i above/below the midplane (cm).
CRLMRD(i): The radius of circle i (cm).
NLINLM: The number of infinite line limiters.
ALNLMR(i): The R coordinate of a point on line i (cm).
ALNLMY(i): The Y coordinate of a point on line i (cm).
ALNLMT(i): The orientation of line i in degrees. 0 degrees points along the midplane towards the center of the tokamak. A line of +45
degrees would be inclined so as to be increasing in elevation towards the centre of the device.
It is also possible to overwrite these settings by providing a 1D Ufile of data specifying the closed limiter boundary in the form Z(R) using the trigraph LIM.
This information can be extracted from EFIT using the program scrunch2.