Guiding and focusing of fast electron beams produced by ultra-intense laser pulse using a double cone funnel target

Abstract

A novel double cone funnel target design aiming at efficiently guiding and focusing fast electron beams produced in high intensity (>1019 W/cm2) laser-solid interactions is investigated via two-dimensional particle-in-cell simulations. The forward-going fast electron beams are shown to be directed and focused to a smaller size in comparison with the incident laser spot size. This plasma funnel attached on the cone target guides and focuses electrons in a manner akin to the control of liquid by a plastic funnel. Such device has the potential to add substantial design flexibility and prevent inefficiencies for important applications such as fast ignition. Two reasons account for the collimation of fast electron beams. First, the sheath electric fields and quasistatic magnetic fields inside the vacuum gap of the double cone provide confinement of the fast electrons in the laser-plasma interaction region. Second, the interface magnetic fields inside the beam collimator further guide and focus the fast electrons during the transport. The application of this technique to cone-guided fast ignition is considered, and it is shown that it can enhance the laser energy deposition in the compressed fuel plasma by a factor of 2 in comparison with the single cone target case.

Fast electrons collimating and focusing by an ultraintense laser interacting with a high density layers

“…Simultaneously, the QMF increases to very high levels with time, effectively working to confine the fast electrons, figure 3(d). The QMF inside the cone gaps and beam collimator at t=1000 fs increases very rapidly to large value, ≈216 MG [21] for the type II. This is because that in the cone gaps and beam collimator with HDL there appear FEC density gradients and temperature gradients close to tip of the cone and on the contact layers of high and low density, which causes an increasing QMF, refer to [21] is the magnetic field, j h is the current density of fast electron.…”

“…We can obtain the surface magnetic field by using a simple one-dimensional model, i.e., only considering the transverse variations. In fact, the magnetic flux acrossing the surface of density jump in different materials in the cone and beam collimator [21] where B 0 denotes the magnetic field amplitude at the contact layers in the target. Subscripts 1 and 2 are for the high and low density layers, respectively, and…”

Generation mechanism of 100 MG magnetic fields in the interaction of ultra-intense laser pulse with nanostructured target

“…Note that n 1 n 2 , d 1 δ pe1 and d δ pe2 in the nanolayered target. In order to get the values of B 0 and B 1 , we integrate Equation (4) across the interfaces of y = −d and y = d. Then, we can obtain the integrated magnetic flux [30,31]…”

Guiding and collimating the fast electrons by using a low-density-core target with buried high density layers

“…This mechanism has a promising application because of the lower resistivity in the low-density plasma channel. However, it is also shown that the fast electrons are accumulated or deflected near the region of laser-plasma interactions by the magnetic field induced by the two stream instability (TSI) [35,36].…”