Search for Drive Parameter of Neutron-Optimized Z-Pinches and Dense Plasma Foci

Dense plasma foci and deuterium gas puff Z-pinches are studied as sources of fusion neutrons. To design a neutron-optimized plasma focus, the drive parameter I₀/(a(ρ₀)^1/2) has been discussed in the last 15 years. Here, I₀, a, and ρ₀ represent the peak discharge current, the inner electrode radius, and the initial gas density, respectively. In this paper, similarities between a dense plasma focus and a gas puff Z-pinch are shown. The drive parameter of dense plasma foci seems to be closely related to the I/(m̂)^1/2 parameter of Z-pinches, where I and m̂ stand for the current during stagnation and linear mass, respectively. On the 3-MA Z-pinch generator, it was found that the optimal I/(m̂)^1/2 parameter reached the value of about 230 kA · (cm/μg)^1/2. This optimal value can be explained by a tradeoff between the energy of fast deuterons and the number of fast and target deuterons. Obtained experimental results show that the optimal drive parameter cannot be fully explained without the consideration of ion acceleration mechanisms to fusion energies.