  The nitrogen-vacancy color center in diamond is one of the most important
systems in the fast-growing field of sensing. This color centers are used in
both high-resolution and high-sensitivity sensors. However, techniques for
quick and efficient formations of this color center are still in the
development stage. In this paper, we present a study on the influence of the
electron irradiation dose on the conversion of substitutional nitrogen into
$\text{N}{{\text{V}}^{-}}$ centers. The study was done on diamonds that were
highly enriched with nitrogen (~100 ppm), which on one hand should maximize the
effect of irradiation, and on another be of interest for high-sensitivity
magnetometers. The maximum achieved conversion efficiency was as high as
${37\pm 3.7}$, with no observed saturation on the electron dose even with the
simplest annealing procedure. The measurements of the corresponding dephasing
time made it possible to estimate for shot-noise limited sensitivity per unit
volume of a stationary field sensor with such a diamond to be ${9\pm 1\times
{{10}^{-14}}\text{T}}/{\sqrt{\text{Hz}\cdot \text{m}{{\text{m}}^{-3}}}}\;$.
