1 Common_Errors

This document will collect a list of TRANSP fatal error or crash messages
that we have seen more than once, and our best estimate of what they mean.

A caution to any TRANSP users finding this document: it is strictly
"work in progress"...

Authors:  D. McCune, R. Andre -- TRANSP support team

2 SCCF integration inaccurate!

This message indicates the failure of an internal consistency check in
SCCF, a subroutine of the bounce averaged Fokker Planck solver (fppmod)
which is generally used in connection with ICRF heating simulations.

The cause has been traced to a lack of sufficient resolution in the pitch
(vpll/v) grid used by fppmod.

The test is a comparison of the bounce time integration of the most deeply
trapped pitch zone with the asymptotic limit (vpll=0 at the flux surface
Bmin, i.e. held at the "bottom" of the magnetic well).  If there are too
few pitch zones resolving the trapped region of velocity space, then, the
most deeply trapped available pitch zone might not be all that close to 
the asymptotic limit.

==> a future version of the code will allow users to increase the pitch
resolution of the fppmod calculation, although this will be expensive in
cpu time.

==> meanwhile, the error criterion has been relaxed in the axial region,
with its narrow range of pitch space in the trapped region, where the
problem is most likely to occur.  A warning message 

 SCCF integration accuracy warning:
      radial zone  1  relative error = 0.1496468993202034
      the usual cause: insufficient pitch (vpll/v) resolution on axis.

will appear instead.

This note written by D. McCune, 10 Mar 2004