Electron-orbit control using a postdiode magnetic-field structure
Plasma Science(2013)
Abstract
For many applications, control and manipulation of the electron orbits in a high-current electron beam is desirable. This is especially true when a weakly-self-pinched, multi-MV electron-beam is used to make bremsstrahlung radiation. In this case, the radiation pattern is highly peaked along the direction that the electron beam makes when it strikes the x-ray target. Therefore, to maximize the number of photons in the forward direction, it is desirable that the electrons strike the x-ray target as close to normal with as little spread in the beam angles as possible. In this paper, a method for controlling the macroscopic angle of a high-power electron beam using a post-diode magnetic-field structure is presented. The idea is to extract the electron beam into a vacuum cavity through a thin, low-mass foil where a portion of the return-current flows through a central post. The amount of current that flows through the central post and therefore the amount of beam straightening is controlled by inductively splitting the return current so that a portion of it returns through the central post and a portion returns outside the beam. By adjusting the balance between these two currents one can alter the electron orbits and achieve a wide range of angles that the electron beam makes with the target without the need for plasma or an external pulser.1 Particle-in-cell simulations have been performed to determine the parameters required to straighten an 8-MV, 200-kA, 23-cm-diameter hollow electron beam with an inward 20° macroscopic (average) angle so that it approaches the x-ray target at normal incidence. The simulations show an increase in the forward photon spectrum by up to a factor of 3. Experiments with similar beam parameters using the Mercury Inductive-Voltage Adder at the Naval Research Laboratory have shown an increase of a factor of two in the forward dose using this technique and are in good qualitative agreement with the simulations. Additional s- mulations and experiments are planned to optimize the forward dose and will be reported on during this talk.
MoreTranslated text
Key words
bremsstrahlung,electron beams,plasma diodes,plasma flow,plasma simulation,mercury inductive-voltage adder,naval research laboratory,x- ray target,bremsstrahlung radiation,electron orbits,electron-beam,electron-orbit control,external pulser,high-current electron beam,high-power electron beam,low-mass foil,macroscopic angle,particle-in-cell simulations,photon spectrum,post-diode magnetic-field structure,radiation pattern,return- current flows,vacuum cavity,photonics,solid modeling,electron beam,plasmas
AI Read Science
Must-Reading Tree
Example
![](https://originalfileserver.aminer.cn/sys/aminer/pubs/mrt_preview.jpeg)
Generate MRT to find the research sequence of this paper
Chat Paper
Summary is being generated by the instructions you defined