Laser-driven ion acceleration from relativistically transparent nanotargets

Abstract

Here we present experimental results on laser-driven ion acceleration from relativistically transparent, overdense plasmas in the break-out afterburner (BOA) regime. Experiments were preformed at the Trident ultra-high contrast laser facility at Los Alamos National Laboratory, and at the Texas Petawatt laser facility, located in the University of Texas at Austin. It is shown that when the target becomes relativistically transparent to the laser, an epoch of dramatic acceleration of ions occurs that lasts until the electron density in the expanding target reduces to the critical density in the non-relativistic limit. For given laser parameters, the optimal target thickness yielding the highest maximum ion energy is one in which this time window for ion acceleration overlaps with the intensity peak of the laser pulse. A simple analytic model of relativistically induced transparency is presented for plasma expansion at the

Ultrashort Pulsed Neutron Source

“…These ions impinged on the Cu and were stopped in the front plate [17,25], as shown in the resulting activation signal. The ion energy distribution was measured using magnetic spectrometers (see supplementary note [21] for details) and found to reach 25 MeV for protons [26,27]. Half-life measurement of the activation signal for these plates verified that the resulting nuclei ( 63 Zn, τ 1/2 = 38 min) were indeed the product of protons interacting with 63 Cu nuclei.…”

Towards Laser Driven Hadron Cancer Radiotherapy: A Review of Progress

“…However recent developments both theoretical and experimental in laser driven ion acceleration have shown considerable promise for increasing the maximum energy efficiency of the acceleration process taking advantage of the so-called transparent overdense regime [13,[36][37][38][39][40]. The transition to this regime occurs when the target is thin enough-typically tens to hundreds of nanometers-and the laser intensity and contrast are high enough, for all of the target electrons to be removed from the material during the laser-target interaction.…”

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“…However, scaling models show higher energies are reachable with increased laser power [36][37][38] and/or new target geometries [39]. Also, several laser particle acceleration mechanisms are under investigation which could be more efficient yet experimentally much more demanding than TNSA, such as laser-piston regime [40], radiation pressure acceleration [41,42] and breakout afterburner regime [43,44], which could provide higher-energy ion beams with potentially better beam quality (i.e., lower-energy spread with better collimation). Nevertheless, with the development of next generation Petawatt (1,000 Terawatt) laser systems, protons with much higher energies are expected to be reached in the near future.…”