The NRL Modified Betatron Accelerator*

We have improved the lifetime of the clcctron bcaam from a few microseconds to over 700 11s by adding strong fo-cusing windi:lgs to our original dcviccz. The poloidal bounc< orbit of tile l~eam immediately after injection is always in thr form of an inward spiral, resulting in the t: apping of ihe beam on the minor axis. The t,rapprd hram current is-1 kA and is accelerated t11 an energy in excess of 15 hlr\ ’ from its injcctinn energy of-0.6 Me\‘. Beam energy is inferred from the x-ray signal. Further confirmation is via x-ray attenuation measure-ments and thr dctcction of photonrutrons from the rraction D(?,n)H. The 10s ~ of t,hr clrctrons appwrs to 1) ~ cauwi by t,ht, excitation of cyclotron rcsonanccs