Soft-X-ray lasing at 32.6 nm in Ne-like Ti ions driven by 40 J of energy from two 650 ps laser pulses

Using only 40 J of driving energy in a 650 ps main pulse, a soft-X-ray lasing on the J = 0 →1, 3p→3s transition in neon-like titanium ions at 32.6 nm is demonstrated. The energy used is an order of magnitude smaller than the driving energy been used previously to drive low-Z neon-like X-ray lasers. A series of experiments are made by using titanium slab targets to study the threshold for lasing in neonlike titanium when the 1.8 cm long targets are illuminated by a low-intensity prepulse 5 ns before the main optical drive pulse of the 1.05 μm Xingguang Nd-glass laser. For a 1% prepulse, the energy threshold is measured to be 40 J, which contrasts with 110 J for a 9% prepulse. In both cases, the 32.6 nm Ti lasing line peaks is 5 mrad off-axis with divergences of 4 and 5 mrad for the 1% and 9% prepulse cases respectively