the magnetic flux $\Phi $ in accordance with the Newton’s second law $mdv/dt = qE$, where $E = -\nabla  V - dA/dt$ is the electric field, $L _{k} = ml/ q^{2}n_{s}s = (\lambda _{L}^{2}/s) \mu _{0}l$ is the kinetic inductance of the loop with the length $l$, the cross-sectional area $s = wd$ and the density of Cooper pairs $n_{s}$ and $\lambda _{L} = (m/\mu _{0}q^{2}n_{s})^{0.5} $ is the London penetration depth. The magnetic inductance $L_{f}$ of superconducting loop with a small cross-sectional area $s \ll \lambda _{L}^{2}$ is much lower than the kinetic inductance $L_{f}  \approx \mu _{0}l \ll L _{k} = (\lambda _{L}^{2}/s) \mu _{0}l $ at $s \ll \lambda _{L}^{2}$. The magnetic flux $\Delta \Psi _{I} = L_{f}I _{p}$ induced by the persistent current $I _{p}$ and the energy of the magnetic field $L_{f}I _{p}^{2}/2 \ll L_{k}I _{p}^{2}/2$ are small in this case of weak screening.

![\[fig:epsart\] The scheme of an ideal DDCI. The loops located one above the other and therefore the boundaries of the Josephson junctions $J _{a}$ and $J _{b}$ coincide with the points $a _{u}$, $a _{d}$ and $b _{u}$, $b _{d}$. The critical current of such DDCI should not depend directly on 