  In order to predict and analyze turbulent transport in tokamaks, it is
important to model transport that arises from microinstabilities. For this
task, quasilinear codes have been developed that seek to calculate particle,
angular momentum, and heat fluxes both quickly and accurately. In this
tutorial, we present a derivation of one such code known as QuaLiKiz, a
quasilinear gyrokinetic transport code. The goal of this derivation is to
provide a self-contained and complete description of the underlying physics and
mathematics of QuaLiKiz from first principles. This work serves both as a
comprehensive overview of QuaLiKiz specifically as well as an illustration for
deriving quasilinear models in general.
