Bootstrap current calculations

There are several options to calculate the bootstrap current in TRANSP, which are described below.

NLBOOT=.T.
Set this flag to NLBOOT=.T. to enable the bootstrap current calculations based on an aspect ratio approximation. This option is compatible with an anomaly factor XBSTRAP (default value is XBSTRAP=1.0) that may be specified in the namelist.
The following options, in addition to NLBOOT=.T. select more advanced models, which are mutually exclusive.
NLBOOTW=.T.
Use this option to select the boostrap current computed in the fully general geometry NCLASS neoclassical code. This is compatible with the parameter XBSTRAP described above.
The parameter XL1NCJBS can be used to specify a value of the normalized radius (r/a) inside which the NCLASS bootstrap current is not to be believed, but replaced by a smooth extrapolation to zero on axis. The default, XL1NCJBS=0.1, is the minimum, recommended value.
NLBOOT_SAU=.T.
Use this option for full generalized geometry and arbitrary collisionality bootstrap current as in O. Sauter, C. Angioni and Y. R. Lin-Liu, Phys of Plas 6(7), 2834 (1999)
This option is compatible with XBSTRAP described above and with XL1NCJBS. However, the latter correction might not be needed for this model, thus XL1NCJBS=0.0 may be advisable.
Set SAUTER_NC_ADJUST(2) to a value other than 1 to scale the electron collisionality used in the Sauter bootstrap model.
Set SAUTER_NC_ADJUST(3) to a value other than 1 to scale the ion collisionality used in the Sauter bootstrap model.
For these controls the default value is 1.0 and the allowed range is 0.0 to 10.0.
NLBOOTHAGER=.T.
Use this option to select the parametrization by R. Hager [Phys. Plasmas 23, 042503 (2016)], which is a correction to the Sauter model to include higher collisionality regimes, based on calculations run with XGCA.
This option is compatible with XBSTRAP and with XL1NCJBS. However, like for the Sauter model, it might not be needed to use this parameter and XL1NCJBS=0.0 might be advisable.
The additional outputs PLJBSHAGER (SAUTER HAGER bootstrap current J•B), and CURBSHAGER (SAUTER HAGER bootstrap current density A/cm2) are avialable in the TRANSP output.
NLBOOTNEO=.T.
USe this option to select the bootstrap current computed in the gyrokinetic neoclassical model NEO.
This option is compatible with XBSTRAP and with XL1NCJBS, although XL1NCJBS=0.0 may be advisable.
Set NEO_SMOOTH_BOOT=.T. to smooth the bootstrap current calculated by NEO, if needed.
Please cite the following papers if using this option in TRANSP:
  • E. Belli and J. Candy, Plasma Physics and Controlled Fusion, vol. 50, 095010 (2008).
  • E. Belli and J. Candy, Plasma Physics and Controlled Fusion, vol. 51, 075018 (2009).
  • E. Belli and J. Candy, Plasma Physics and Controlled Fusion, vol. 54, 015015 (2012).
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