Target Replenishment in Multipulse Radiography

The second axis of DAHRT accomplishes multipulse radiography by hitting a tantalum target four times with a relativistic electron beam. The forwardly directed x rays created by bremsstrahlung from the beam-target interaction are in turn used for the radiography. An undesirable consequence of the beam-target interaction is that the portion of the target that is hit by the beam vaporizes. It is therefore desirable that an unvaporized portion of the target be moved into the path of the beam before the subsequent electron beam pulse occurs, so that the expected x-ray intensity can be maintained. One method of replenishing the target material is to accelerate the target to the appropriate velocity perpendicular to the beam direction by pushing it with a magnetically driven armature. Estimates of the range of accelerations and magnetic fields required to achieve the desired velocity within the constraint that strength of the armature not be overwhelmed by the acceleration will be presented. MHD simulations of the process will also be presented.