  The burning plasma performance is limited by the confinement of the
superalfvenic fusion products such as alpha particles and the auxiliary heating
ions capable of exciting the Alfv\'enic eigenmodes (AEs). In this work the
effect of AEs on fast ions is formulated within the quasi-linear (QL) theory
generalized for this problem recently. The generalization involves the
resonance line broadened interaction of energetic particles (EP) with AEs
supplemented by the diffusion coefficients depending on EP position in the
velocity space. A new resonance broadened QL code (or RBQ1D) based on this
formulation allowing for EP diffusion in radial direction is built and
presented in details. We reduce the wave particle interaction (WPI) dynamics to
1D case when the particle kinetic energy is nearly constant. The diffusion
equation for EP distribution evolution is then one dimensional and is solved
simultaneously for all particles with the equation for the evolution of the
wave angular momentum. The evolution of fast ion constants of motion is
governed by the QL diffusion equations which are adapted to find the fast ion
distribution function. We make initial applications of the RBQ1D to DIII-D
plasma with elevated q-profile where the beam ions show stiff transport
properties. AE driven fast ion profile relaxation is studied for validations of
the QL approach in realistic conditions of beam ion driven instabilities in
DIII-D.
