Collective ion acceleration during the decay of a high-current Z-pinch

A study is made of the Z-pinch plasma expansion after the current is switched off. Measurements were carried out in experiments on the implosion of tungsten wire arrays in the Angara-5-1 facility. It is found experimentally that, at a distance of 2 m from the pinch, the ion velocity in the expanding Z-pinch plasma is about (2.5–4.0) × 107 cm/s, which substantially exceeds the thermal velocity of tungsten ions. A model describing the plasma expansion process is proposed that is based on the ambipolar acceleration mechanism. The results of numerical simulations are compared with the experimental data.