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 :
O. Sauter and S. Y
Medvedev, "Tokamak Coordinate Conventions: COCOS", Comput. Phys. Commun. 184
(2013) 293. (https://doi.org/10.1016/j.cpc.2012.09.010)
(with
Appendices updated/corrected after published to keep track of tables)
Useful transformations files:
·
COCOS set of tools, ask for a copy from git spc.epfl.ch
"cocos" repository: Code_transfer_COCOS.pdf
·
It contains check of IDS structures in IMAS if they
follow a given COCOS convention
·
Matlab – IMAS: generic transformation
of IDSs: Interface Data Structure used in particular within the ITER Modeling and Analysis Suite
·
Matlab other functions
(others from CHEASE repository): 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 COCOS 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:
