A One-Mev/Nucleon Sloan and Lawrence Heavy-Ion Linear Accelerator

A description is given of a small heavy-ion linear accelerator based on the use of a twin transmission line as first suggested by Sloan and Lawrence. Ions are accepted if their e/m values are ⅛ or greater (relative to the proton) and are accelerated to a final energy of 1.04 Mev/nucleon. The accelerator has 40 drift tubes fitted with focusing grids, and about 350 kw of pulsed rf are needed for ions of e/m=⅛. The radio frequency is 25 Mc, and the accelerator is pulsed at up to 50 pps with a pulse length of 500 μsec. Injection velocity is 0.007 c, corresponding to a dc acceleration from the ion source through 180 kv for an ion of e/m=⅛. Ions are produced in a pulsed dc arc of the Penning type operating in a magnetic field of 1000 gauss and the dc accelerating voltage is supplied by an electrostatic generator. Typical pulsed meter currents so far obtained are, for He+, input 4 ma, output 150 μa; for N2+, input 3 ma, output 75 μa. The accelerator is the first stage of three which will take the ions to a final energy of 10 Mev/nucleon. The second and third stages, which are under construction, will be cavity resonators of the Alvarez design.