The acceleration of hydrogen ions up to 35 MeV is observed in the z-pinch experiments on the GIT-12 generator at a 3 MA current and 0.6 MV driving voltage. High ion energies are obtained with a novel configuration of a deuterium gas-puff z-pinch. In this configuration, a hollow cylindrical plasma shell is injected around an inner deuterium gas puff to form a homogeneous, uniformly conducting layer between electrodes at the initial phase of z-pinch implosion. The stable implosion at the velocity up to 650 km s−1 is important to deliver more current onto the z-pinch axis. Magnetohydrodynamic instabilities become apparent first at stagnation. After the disruptive development of m = 0 instabilities, ∼20 ns pulses of high-energy photons, neutrons, electrons, and ions are observed. The average neutron yield is 2 × 1012. The ion emission is characterized by various diagnostic techniques including those based on the usage of neutron-producing samples. When a large neutron-producing sample is placed onto the axis below a cathode mesh, the neutron yield is increased up to (1.1 ± 0.3) × 1013. Considering a ∼130 kJ energy input into z-pinch plasmas and magnetic field, this implies the neutron production efficiency of ∼108 neutrons per one Joule of the z-pinch energy.