Centroid and Envelope Dynamics of High-Intensity Charged-Particle Beams in an External Focusing Lattice and Oscillating Wobbler

The centroid and envelope dynamics of a high-intensity charged-particle beam are investigated as a beam smoothing technique to achieve uniform illumination over a suitably chosen region of the target for applications to ion-beam-driven high energy density physics and heavy ion fusion. The motion of the beam centroid projected onto the target follows a smooth pattern to achieve the desired illumination, for improved stability properties during the beam-target interaction. The centroid dynamics is controlled by an oscillating “wobbler,” a set of electrically biased plates driven by rf voltage.

Figure 1

Quadrupole focusing lattice and wobbler system. The motion of the centroid projected onto the target follows a smooth pattern in order to achieve uniform illumination over a suitably chosen region of the target.

Figure 2

Final focus and wobbler system for an illustrative heavy ion fusion driver. The vertical scale for ${\kappa }_q$ is ${\mathrm{m}}^{-2}$. The envelope dimensions ($a$, $b$) are normalized by the initial beam envelope dimension $a(0)$. The centroid positions ($\mu$, $\nu$) are normalized by $a(0)/10$ for better illustration.