The COCOS
Convention
Coordinate COnvetionS for 3D current and magnetic fields
A current in a ring in a usual
cylindrical coordinate
system yields a magnetic field in the negative direction in a "usual"
coordinate local to
the ring. This helix can appear "right-handed" again by changing the
choice of 
>0 or of 
>0.
This has led to several
different choices in codes related to magnetized plasmas. We have therefore
defined a unique index to specify the COCOS convention as described in :
Useful transformations files:
·
COCOStransform set of tools, ask for a copy from spcsvn COCOStransform repository:
Code_transfer_COCOStransform_generic.pdf
·
matlab: readeqdsk_simple.m,
writeeqdsk.m,
eqdsk_cocos_transform.m,
cocos.m.
In this way you can:
>> eqdsk_in = readeqdsk_simple('EQDSKfilename',cocos_in);
>> [eqdsk_cocosout]=eqdsk_cocos_transform(eqdsk_in,[cocos_in cocos_out]);
>> writeeqdsk(EQDSKfilename_out,eqdsk_cocosout,cocos_out);
·
f90: see COCOStransform
routines/tools (used within CHEASE for
example)
The Appendix of the paper
contains two useful Tables concerning the known COCOS convention for various
codes and tokamaks. They are kept up-to-date here below:
