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Preferential enhancement of laser-driven carbon ion acceleration from optimized nanostructured surfaces.

Dalui M, Wang WM, Trivikram TM, Sarkar S, Sarkar S, Tata S, Jha J, Ayyub P, Sheng ZM, Krishnamurthy M - Sci Rep (2015)

Bottom Line: However, particles smaller than 20 nm have an adverse effect on the ion acceleration.Particle-in-cell simulations provide definite pointers regarding the size of nanoparticles necessary for maximizing the ion acceleration.The inherent contrast of the laser pulse is found to play an important role in the species selective ion acceleration.

View Article: PubMed Central - PubMed

Affiliation: Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India.

ABSTRACT
High-intensity ultrashort laser pulses focused on metal targets readily generate hot dense plasmas which accelerate ions efficiently and can pave way to compact table-top accelerators. Laser-driven ion acceleration studies predominantly focus on protons, which experience the maximum acceleration owing to their highest charge-to-mass ratio. The possibility of tailoring such schemes for the preferential acceleration of a particular ion species is very much desired but has hardly been explored. Here, we present an experimental demonstration of how the nanostructuring of a copper target can be optimized for enhanced carbon ion acceleration over protons or Cu-ions. Specifically, a thin (≈ 0.25 μm) layer of 25-30 nm diameter Cu nanoparticles, sputter-deposited on a polished Cu-substrate, enhances the carbon ion energy by about 10-fold at a laser intensity of 1.2 × 10(18)  W/cm(2). However, particles smaller than 20 nm have an adverse effect on the ion acceleration. Particle-in-cell simulations provide definite pointers regarding the size of nanoparticles necessary for maximizing the ion acceleration. The inherent contrast of the laser pulse is found to play an important role in the species selective ion acceleration.

No MeSH data available.


PIC simulation results.Computed ion energy spectra and ion divergence. Only the ions fleeing to the front vacuum and with energy greater than 20 keV are included in the plots.
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f6: PIC simulation results.Computed ion energy spectra and ion divergence. Only the ions fleeing to the front vacuum and with energy greater than 20 keV are included in the plots.

Mentions: We found that some hot electrons start to flee the simulation box boundaries at 133 fs and therefore only the results on or before this time are valid. Figure 6 shows the result after a propagation period of 133 fs. One can see from Fig. 7 that the maximum ion energy is enhanced significantly when the nanoparticle coated surface is taken. With increasing size of the nanoparticles, the angular divergence of the ions grows considerably. The ion energy first climbs sharply from 10 nm to 30 nm, grows slowly to 100 nm and saturates or marginally decreases beyond this size. These results indicate that a nanoparticle coated surface is favorable for ion emission from the surface-front and the size of the coated particles should be optimized. Although, a peak of the maximum accelerating field appears at 100 nm, the ion number increases monotonically as the particle size is increased. It should be kept in mind that the ion divergence will also have a bearing on the ion detection normal to the surface of the target in experiments.


Preferential enhancement of laser-driven carbon ion acceleration from optimized nanostructured surfaces.

Dalui M, Wang WM, Trivikram TM, Sarkar S, Sarkar S, Tata S, Jha J, Ayyub P, Sheng ZM, Krishnamurthy M - Sci Rep (2015)

PIC simulation results.Computed ion energy spectra and ion divergence. Only the ions fleeing to the front vacuum and with energy greater than 20 keV are included in the plots.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495568&req=5

f6: PIC simulation results.Computed ion energy spectra and ion divergence. Only the ions fleeing to the front vacuum and with energy greater than 20 keV are included in the plots.
Mentions: We found that some hot electrons start to flee the simulation box boundaries at 133 fs and therefore only the results on or before this time are valid. Figure 6 shows the result after a propagation period of 133 fs. One can see from Fig. 7 that the maximum ion energy is enhanced significantly when the nanoparticle coated surface is taken. With increasing size of the nanoparticles, the angular divergence of the ions grows considerably. The ion energy first climbs sharply from 10 nm to 30 nm, grows slowly to 100 nm and saturates or marginally decreases beyond this size. These results indicate that a nanoparticle coated surface is favorable for ion emission from the surface-front and the size of the coated particles should be optimized. Although, a peak of the maximum accelerating field appears at 100 nm, the ion number increases monotonically as the particle size is increased. It should be kept in mind that the ion divergence will also have a bearing on the ion detection normal to the surface of the target in experiments.

Bottom Line: However, particles smaller than 20 nm have an adverse effect on the ion acceleration.Particle-in-cell simulations provide definite pointers regarding the size of nanoparticles necessary for maximizing the ion acceleration.The inherent contrast of the laser pulse is found to play an important role in the species selective ion acceleration.

View Article: PubMed Central - PubMed

Affiliation: Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India.

ABSTRACT
High-intensity ultrashort laser pulses focused on metal targets readily generate hot dense plasmas which accelerate ions efficiently and can pave way to compact table-top accelerators. Laser-driven ion acceleration studies predominantly focus on protons, which experience the maximum acceleration owing to their highest charge-to-mass ratio. The possibility of tailoring such schemes for the preferential acceleration of a particular ion species is very much desired but has hardly been explored. Here, we present an experimental demonstration of how the nanostructuring of a copper target can be optimized for enhanced carbon ion acceleration over protons or Cu-ions. Specifically, a thin (≈ 0.25 μm) layer of 25-30 nm diameter Cu nanoparticles, sputter-deposited on a polished Cu-substrate, enhances the carbon ion energy by about 10-fold at a laser intensity of 1.2 × 10(18)  W/cm(2). However, particles smaller than 20 nm have an adverse effect on the ion acceleration. Particle-in-cell simulations provide definite pointers regarding the size of nanoparticles necessary for maximizing the ion acceleration. The inherent contrast of the laser pulse is found to play an important role in the species selective ion acceleration.

No MeSH data available.