We propose to study the magnetic excitations in the quantum spin liquid candidate `Mg-herbertsmithite', which forms a geometrically perfect and highly frustrated two-dimensional kagome lattice of S=1/2 quantum spins with dominant antiferromagnetic nearest-neighbor interactions. No long-range order is observed down to T=20 mK and recent theoretical work predicts a rich phase diagram with different types of gapless, chiral, and U(1) quantum spin liquids that await experimental confirmation. The measurements aim at determining the high-energy part of the magnetic excitations, which will complement the low-energy measurements already performed on IN5, and hopefully lead to a full picture of this fascinating S=1/2 kagome physics.