Past exam of the short options paper shared by Prelims and Parts A and B of the physics course of the University of Oxford / 2016 / S19 / 2 / e / Solution

For the same lattice radiation-integral ratio, natural geometric emittance scales as ${\gamma }^2$. A factor-ten decrease therefore requires $\boxed{E^{\prime }=3/\sqrt{10}\simeq 0.949\mathrm{GeV}}$. Keeping coupling ratio fixed reduces the vertical emittance by the same factor, within that ideal scaling model.