.. index:: 
   single: Parameters; 1D Top Infl

1D Top Infl
===========

The top or peak position of a FFF field is estimated by fitting a parabola (2nd order polynomial):

.. math:: y = ax^2 + bx + c

over the central :ref:`Top Radius` of the profile peak. The peak position is determined where the tangent to the parabola is zero.

.. math:: x = - \cfrac {b} {2a}

**Protocol invocation name**: 1D Top Infl