  Starting from the beginning of their research in the early 2000's, the
ultracold plasmas were considered as a promising tool to achieve considerable
values of the Coulomb coupling parameter for electrons. Unfortunately, this was
found to be precluded by a sharp spontaneous increase of temperature, which was
often attributed to the so-called disorder-induced heating (DIH). It is the aim
of the present paper to quantify the effect of spontaneous heating as function
of the initial ionic disorder and, thereby, to estimate the efficiency of its
mitigation, e.g., by the Rydberg blockade. As a result of the performed
simulations, we found that the dynamics of electrons exhibited a well-expressed
transition from the case of the quasi-regular arrangement of ions to the
disordered one; the magnitude of the effect being about 30%. Thereby, we can
conclude that the two-step formation of ultracold plasmas - involving the
intermediate stage of the blockaded Rydberg gas - can really serve as a tool to
increase the degree of Coulomb coupling, but the efficiency of this method is
moderate.
