Multi foil targets and pellicle dynamics for X-ray radiography

Summary form only given. The major target issues concerning the multiple-exposure intense electron-beam radiography are: (I) To limit the expansion of the plasma plume from the X-ray converter target. (II) To limit the distance traveled upstream by the ions from the target along the beam. This is because substantial plasma plume expansion can reduce the X-ray output dose and uncontrolled backstreaming ions can cause neutralization of the e-beam and thus the beam may not be tightly focused on the target. We present two target configurations based on LASNEX simulations that address these two target issues. 1. Multi-foil targets: Dividing a solid target into many thin foils over a longer length can lengthen the disintegration time of the target and reduces the expansion of the plasma plume. This improves the production of the X-ray dose. We will present the LASNEX simulations of the target expansion. 2. Pellicle dynamics: Placing a pellicle in front of the target can confine the backstreaming ions to a shorter channel so that the cumulative effect on e-beam focusing is reduced. We will present the simulation for hydrodynamic expansion, caused by e-beam heating, of the pellicles. We have studied pellicles made of various materials. Both single-layered and multilayered pellicles have been investigated. Simulations show that the range (/spl rho/r) of the pellicles along the axis remains essentially constant. Therefore, all the pellicles studied here should be able to stop backstreaming ions.