Simulation of swift boron clusters traversing amorphous carbon foils

Abstract

We use a simulation code to study the interaction of swift boron clusters ($\mathrm{B}_{n}{}^{+}$, $n=2--6$, 14) with amorphous carbon foils. We analyze different aspects of this interaction, such as the evolution of the cluster structure inside the target, the energy and angle distributions at the detector or the stopping power ratio. Our simulation code follows in detail the motion of the cluster fragments through the target and in the vacuum until reaching a detector, taking into account the following interactions: (i) wake force, (ii) Coulomb repulsion among cluster fragments, (iii) stopping force, and (iv) elastic scattering with the target nuclei. Electron capture and loss by each fragment is also included in the code, affecting the above-mentioned interactions. The clusters size grows inside the foil due mainly to the Coulomb explosion but this increase is less pronounced in the plane transversal to the beam direction because of the alignment effect of the wake forces. We obtain an enhancement of the stopping power ratio that increases with the projectile energy and with the number of molecular constituents. Our results agree very well with the available experimental data for the thicker foils $(\ensuremath{\gtrsim}10\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{g}∕{\mathrm{cm}}^{2})$ and are compatible (within the experimental error bars) for the thinner foils.