Efforts are made to decrease the accelerator size and to increase the energy efficiency. The accelerator features a coaxial water pulse forming line (PEL), with a helical central conductor. This PEL stores nearly twice the energy as the Blumlein type, given the same outer dimensions. Without the helical inner conductor, such energy storage optimized PEL has fixed impedance about 5-6 Ω, which is not necessarily matched to the load and causes energy loss. With appropriate slow wave factor of the helical line, the load can now be matched. So the PEL can achieve the maximum energy storage and the maximum energy transfer to the load simultaneously. The finished PEL has outer diameter 35 cm, and length 120 cm. Total mass of the accelerator is less than 1 ton. During experiments, the PEL is charged by a fast pulse transformer, and drives a MILO as load. Experiment results show that maximum output rating of the pulse transformer reaches 1.1 MV, and 600 kV is delivered to MILO, and e-beam peak power exceeds 30 GW. Design of the PEL, output switch, ceramic diode and experimental results are presented. (4 pages)