Laser-driven high-energy proton beam with homogeneous spatial profile from a nanosphere target

Abstract

A high-energy, high-yield proton beam with a good homogeneous profile has been generated from a nanosphere target irradiated by a short (30-fs), intense (7 × 10 20 W=cm 2) laser pulse. A maximum proton energy of 30 MeV has been observed with a high proton number of 7 × 10 10 in the energy range 5-30 MeV. A homogeneous spatial profile with a uniformity (standard deviation from an average value within 85% beam area) of 15% is observed with the nanosphere dielectric target. Particle-in-cell simulations show the enhancement of proton cutoff energy and proton number with the nanosphere target and reveal that the homogeneous beam profile is related with a broadened angular distribution of hot electrons, which is initiated by the nanosphere structure. The homogeneous spatial properties obtained with the nanosphere target will be advantageous in developing laser-driven proton sources for practical applications in which high-quality beams are required.

Table-top laser-based proton acceleration in nanostructured targets

“…The enhanced energy absorption can be obtained also with other structure geometries, such as rectangles [17,21,27] or nanospheres [20,22]. Our model can, in principle, be extended to account for different structure geometries.…”

“…Different approaches such as varying the target thickness [8], nanostructuring the back surface of the target [9,10] or growing a layer of low density foam [11][12][13] have already been studied. Several publications have reported that adding periodic nanostructures on the target front surface enhances drastically the laser energy absorption [13][14][15][16][17][18][19][20][21]. This generates ions with much higher energies than the ones obtained when targets with a flat surface are used [13,[20][21][22][23][24][25][26][27][28][29][30].…”

“…Several publications have reported that adding periodic nanostructures on the target front surface enhances drastically the laser energy absorption [13][14][15][16][17][18][19][20][21]. This generates ions with much higher energies than the ones obtained when targets with a flat surface are used [13,[20][21][22][23][24][25][26][27][28][29][30]. The nature of this enhancement is still a matter of discussion, however it is known that it is strongly dependent on the shape of the structures, as well as on the angle of incidence of the impinging laser [13-15, 17, 18, 21, 22, 26, 27].…”

Relativistic Electron Streaming Instabilities Modulate Proton Beams Accelerated in Laser-Plasma Interactions

“…Spatial modulations of the proton beams have been observed for insulator targets (e.g. plastic, CH) [14][15][16][17] and attributed to an instability of the ionization front that affects the uniformity of the sheath E-field [16].…”

Nanophase‐separated poly(acrylic acid)/poly(ethylene oxide) plasma polymers for the spatially localized attachment of biomolecules

“…We combine the already‐established plasma‐assisted vapor‐phase deposition of PEO with the recently developed deposition of plasma‐polymerized acrylic acid NPs (ppAA NPs) . The advantage of this approach lies in the fact that ppAA NPs are produced in a separate vacuum chamber and are embedded into ppPEO as ready‐made entities. Therefore, the phase separation processes are not governed by the kinetic phenomena of macromolecular diffusion.…”