Four stage HELIA experiment

A four stage, 4 MV, 250 kA, 30 ns accelerator to demonstrate the High Energy Linear Induction Accelerator (HELIA) concept is described. HELIA uses modular, water dielectric, pulse forming lines to drive inductively isolated cavities. A cathode stalk extends the length of the accelerator, adds the voltages from the cavities, and delivers the power to a high voltage anode-cathode gap. The cathode stalk constitutes the inner electrode of a coaxial magnetically insulated transmission line (MITL). The outer electrode of the MITL is not ocntinuous but is interrupted at regular intervals by the cavity feeds. The single cavity experiment demonstrated the performance of individual cavities and pulse forming elements. The four cavity experiment demonstrated the key physics issues of the HELIA concept. The design and performance of the pulsed power driver, induction cavities, and measurements of the power delivered by the MITL to an electron beam load are presented.