This section introduces the various settings used to describe the neutral beams in TRANSP, this includes their geometries, energy fractions and total injected power. All of these settings
are automatically written to the namelist file by the program nblist which executes during the data step. Consequently for clarity these settings are
absent from the template namelist files. Nblist also writes a composite Ufile
( PNBI'shot'.NBI_'seq' ) in the System Data Directory containing the beam powers, voltages and energy fractions in the following format:
PINJ(t) / W) for beams 1 : N EINJ(t) / V) for beams 1 : N FFULL(t)) for beams 1 : N FHALF(t)) for beams 1 : N Use of this file is specified by setting the namelist variable NLBDAT to TRUE and setting PRENB2='PNBI'
and EXTNB2='NBI'.
These variables apply to all PINIs used during the run:
NBSHAP : This sets the shape of the ion source. For JET this should be set to 1 indicating a rectangular source.
BMWIDR : This sets the half-width of the rectangular ion source in cm. For JET it should be set to 9cm.
BMWIDZ : This sets the half-height of the rectangular ion source in cm. For JET it should be set to 22.5cm.
REDGE : This sets the half-width of the rectangular vacuum vessel aperture in cm. For JET it should be set to 17.0cm.
XZEDGE : This sets the half-height of the rectangular vacuum vessel aperture in cm. For JET it should be set to 19.0cm.
FOCLR : This sets the horizontal focal length of the beams in cm. For JET it should be set to 1e-3cm.
FOCLZ : This sets the vertical focal length of the beams in cm. For JET it should be set to 1.4e-3cm.
Beamlets are distributed in angle according to a normal distribution. The following two parameters set the standard deviations of the normal distributions horizontally
and vertically:
DIVR : This sets the horizontal divergence of the beams in radians. For JET it should be set to 1.22e-2cm.
DIVZ : This sets the vertical divergence of the beams in radians. For JET it should be set to 1.22e-3cm.
NBLIST appends a set of the following variables to the end of the namelist file for each active PINI. Each set is given an index to indicate which set it belongs to. Note that
the variables PINJ(i), EINJ(i), FFULL(i) and FHALF(i) are included in the namelist but are all set to zero as these are read in from the Ufile described above.
TBONA(i) : The beam turn on time in seconds.
TBOFFA(i) : The beam turn off time in seconds.
NOTE: It is not clear the above are actually used as NBLIST does not set NLNBTFIX=FALSE and the default is TRUE. In this instance TRANSP will determine
the beam turn-on and turn-off times from the power Ufile data. The default is that the beam will be considered on when the power exceeds 5% of maximum.
RTCENA(i) : The beam tangency radius (the distance to tokamak centerline at closest approach) in cm.
XLBTNA(i) : The distance from the ion source to the point of closest approach to the tokamak center (the beam tangency radius) in cm.
XYBSCA(i) : The elevation of the beam ion source above or below the midplane
NLCO(i) : If set .TRUE. this indicates that the beam is co-injecting with the plasma current.
ABEAMA(i) : The atomic weight of the species in the i'th beam. This should be set to 2.0 for Deuterium beams.
XZBEAMA(i) : The charge of the species in the i'th beam. This should be set to 1.0 for Deuterium beams.
XLBAPA(i) : The distance between the ion source and the vacuum vessel aperture for the i'th beam.
XYBAPA(i) : The elevation of the beam centerline above/below the midplane when it passes through the vacuum vessel aperture.
NOTE : The vessel apertures are considered rectangular by default.
XBZETA(i) : The toroidal angle of the beam source in a right handed (R,zeta,Z) system in degrees.
The various beam geometry parameters are illustrated below: