The use of a subminiature electron storage ring in the weak-current regime (I b = 0.02 mA) as a source of coherent mm-range synchrotron radiation and a laboratory facility for studying electron scattering in a bunch is studied. The weak-current regime considerably simplifies the construction of a magnetic system and decreases the likelihood of the development of bunch instabilities. To make a more accurate assessment of some basic parameters of a subminiature storage ring, a calculation of the effective accelerating voltage was performed taking account of the transit factor of the rf-system cavity.A particularity of the weak-current regime is the simplicity of its implementation. Before the application of the weak-current regime is discussed, the amplitude of the effective accelerating voltage is calculated taking account of the transit factor of the cavity and methods for calculating the beam lifetime are analyzed.Calculation of the Accelerating Voltage. In a subminiature storage ring [1,2], the orbit of the beam lies inside the cavity of the rf system, while in ordinary storage rings it passes through the rf cavity.The amplitude of the accelerating rf voltage U max and the energy acquired by an equilibrium particle over one revolution ΔE rev are related with one another by the well-known equation