The dimension for electrical charge. Internally, charge q always represents
q/(4 pi epsilon0)^(1/2), so that the force via Coulomb's law is given by q1*q2/r^2.
Internally, charge is a quantity having units of sqrt(force)*length, or mass^(1/2)-length^(3/2)/time,
so the simulation unit for the quantity representing charge is sqrt(D-A^3)/ps.