Blood contains both positive and negative ions. In a certain patient being tested, the speed of these ions in a large artery is measured at \(0.60 \mathrm{~m} / \mathrm{s}\). The patient is placed in a uniform magnetic field of magnitude \(0.20 \mathrm{~T}\). If a potential difference of \(1.0 \times 10^{-3} \mathrm{~V}\) is measured across the diameter of the artery, what is that diameter?