Conventions

Coordinate convention

Bluemira uses a conventional right-handed Cartesian coordinate convention for all geometry.

Occasionally, for certain modules and calculations, a quasi-toroidal coordinate system and a cylindrical coordinate system are used. Note that to facilitate conversion between the systems, the radial coordinate in the cylindrical coordinate system is denoted with \(x\) and not \(r\).

Fig. 2 The three different coordinate systems used in the bluemira framework: right-handed Cartesian coordinate system (\(x, y, z\), black), quasi-toroidal coordinate system (\(r, \theta, \phi\), red), and cylindrical coordinate system (\(x, \phi, z\), blue).

Tokamaks are largely axisymmetric devices and usually have some form of cyclic symmetry. In bluemira, by convention, tokamak sectors are numbered \(1 .. n\), with the first sector ranging from \(0 .. 360/n_{TF}\) degrees, and subsequent sectors in increasing number, going anti-clockwise as seen from above the machine:

Fig. 3 Indicative sector angles and naming convention (green boxes) in bluemira

Unit conventions

Bluemira uses the International System of Units (SI) convention, with only minor deviations. As a summary, all inputs to the code should be in the following units:

Table 1 Unit conventions in bluemira

Quantity	Unit name	Symbol
time	second	[s]
distance	metre	[m]
mass	kilogram	[kg]
electric current	ampere	[A]
temperature	kelvin	[K]
amount of substance	mol	[mol]
angles	degrees	[°]
density	kilograms per cubic metre	[kg/m^3]
particle density	particles per cubic metre	[1/m^3]
flux density	particles per square metre per second	[1/m^2/s]