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Guided post-acceleration of laser-driven ions by a miniature modular structure.

Kar S, Ahmed H, Prasad R, Cerchez M, Brauckmann S, Aurand B, Cantono G, Hadjisolomou P, Lewis CL, Macchi A, Nersisyan G, Robinson AP, Schroer AM, Swantusch M, Zepf M, Willi O, Borghesi M - Nat Commun (2016)

Bottom Line: All-optical approaches to particle acceleration are currently attracting a significant research effort internationally.Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously.These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications.

View Article: PubMed Central - PubMed

Affiliation: School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK.

ABSTRACT
All-optical approaches to particle acceleration are currently attracting a significant research effort internationally. Although characterized by exceptional transverse and longitudinal emittance, laser-driven ion beams currently have limitations in terms of peak ion energy, bandwidth of the energy spectrum and beam divergence. Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously. In a proof-of-principle experiment on a university-scale system, we demonstrate post-acceleration of laser-driven protons from a flat foil at a rate of 0.5 GeV m(-1), already beyond what can be sustained by conventional accelerator technologies, with dynamic beam collimation and energy selection. These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications.

No MeSH data available.


Related in: MedlinePlus

Scaling to higher laser intensity and multistage acceleration.(a) Total charge carried by the pulse moving along the wire connected to the laser-irradiated target, plotted against incident laser intensity on target (black solid line). The blue solid line shows the accelerating gradient inside a helical coil of same diameter and pitch as the one used in our experiment. (b) Schematic representation of a double-stage acceleration setup using two helical coils driven by two laser pulses. (c) Comparison between the simulated proton spectra, taken at 50 mm from the proton source over a 2 mm × 2 mm area, obtained for: flat-foil proton source (black-input spectrum in the simulation), single-stage (blue) and double-stage (red) coil re-acceleration. Both coils were of 0.5 mm internal diameter and 10 mm long, with variable pitch suited to their input proton energies (∼40 and ∼70 MeV, respectively, for the first and second stages). The parameters for the charge pulse in both coils were taken as those expected from the interaction of a PW, 30 fs laser (e.g. as available at GIST, Korea33) with a thin target, leading to an acceleration gradient of ∼3 GeV m−1 (discussed in the text). The shaded areas A, B1 and B2 represent, respectively, the proton bunch accelerated from the first coil and the proton bunches accelerated and decelerated by the second coil. The total number of particles in the bunches B1 and B2 is approximately equal to the number of particles in the bunch A. The time of arrival of the charge pulse at the entrance of the second coil was synchronized with the arrival of the ∼70 MeV proton bunch produced by the first coil.
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f5: Scaling to higher laser intensity and multistage acceleration.(a) Total charge carried by the pulse moving along the wire connected to the laser-irradiated target, plotted against incident laser intensity on target (black solid line). The blue solid line shows the accelerating gradient inside a helical coil of same diameter and pitch as the one used in our experiment. (b) Schematic representation of a double-stage acceleration setup using two helical coils driven by two laser pulses. (c) Comparison between the simulated proton spectra, taken at 50 mm from the proton source over a 2 mm × 2 mm area, obtained for: flat-foil proton source (black-input spectrum in the simulation), single-stage (blue) and double-stage (red) coil re-acceleration. Both coils were of 0.5 mm internal diameter and 10 mm long, with variable pitch suited to their input proton energies (∼40 and ∼70 MeV, respectively, for the first and second stages). The parameters for the charge pulse in both coils were taken as those expected from the interaction of a PW, 30 fs laser (e.g. as available at GIST, Korea33) with a thin target, leading to an acceleration gradient of ∼3 GeV m−1 (discussed in the text). The shaded areas A, B1 and B2 represent, respectively, the proton bunch accelerated from the first coil and the proton bunches accelerated and decelerated by the second coil. The total number of particles in the bunches B1 and B2 is approximately equal to the number of particles in the bunch A. The time of arrival of the charge pulse at the entrance of the second coil was synchronized with the arrival of the ∼70 MeV proton bunch produced by the first coil.

Mentions: While the experiment shows a proof-of-principle demonstration employing a university-scale laser system, there is significant scope for further development of the technique using higher-intensity lasers and more refined target arrangements. For a given diameter of the helical coil target, the accelerating field inside the coil structure, as discussed above, is directly proportional to the charge (Q=∫λ(l)dl) contained in the pulse, which is equal to the number of electrons (Nesc) escaping from the laser-irradiated target during the interaction times the electron charge (e). The scaling for eNesc(=Q) with incident laser intensity can be obtained by using the simple phenomenological model described by Kar et al.9Figure 5a shows estimates of Q obtained using this model, for constant laser pulse length (30 fs) and focal spot size on the target (4 μm). A prudent 30% laser-electron conversion efficiency is assumed in this model, which may be an underestimate for intensities above 1020 W cm−2 (refs 22, 29, 30, 31, 32). In any case, as can be seen in this figure, the scaling agrees well not only with our experimental data but also with the experimental data and model reported recently by Poye et al.24 for similar pulse duration and focussing conditions.


Guided post-acceleration of laser-driven ions by a miniature modular structure.

Kar S, Ahmed H, Prasad R, Cerchez M, Brauckmann S, Aurand B, Cantono G, Hadjisolomou P, Lewis CL, Macchi A, Nersisyan G, Robinson AP, Schroer AM, Swantusch M, Zepf M, Willi O, Borghesi M - Nat Commun (2016)

Scaling to higher laser intensity and multistage acceleration.(a) Total charge carried by the pulse moving along the wire connected to the laser-irradiated target, plotted against incident laser intensity on target (black solid line). The blue solid line shows the accelerating gradient inside a helical coil of same diameter and pitch as the one used in our experiment. (b) Schematic representation of a double-stage acceleration setup using two helical coils driven by two laser pulses. (c) Comparison between the simulated proton spectra, taken at 50 mm from the proton source over a 2 mm × 2 mm area, obtained for: flat-foil proton source (black-input spectrum in the simulation), single-stage (blue) and double-stage (red) coil re-acceleration. Both coils were of 0.5 mm internal diameter and 10 mm long, with variable pitch suited to their input proton energies (∼40 and ∼70 MeV, respectively, for the first and second stages). The parameters for the charge pulse in both coils were taken as those expected from the interaction of a PW, 30 fs laser (e.g. as available at GIST, Korea33) with a thin target, leading to an acceleration gradient of ∼3 GeV m−1 (discussed in the text). The shaded areas A, B1 and B2 represent, respectively, the proton bunch accelerated from the first coil and the proton bunches accelerated and decelerated by the second coil. The total number of particles in the bunches B1 and B2 is approximately equal to the number of particles in the bunch A. The time of arrival of the charge pulse at the entrance of the second coil was synchronized with the arrival of the ∼70 MeV proton bunch produced by the first coil.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837447&req=5

f5: Scaling to higher laser intensity and multistage acceleration.(a) Total charge carried by the pulse moving along the wire connected to the laser-irradiated target, plotted against incident laser intensity on target (black solid line). The blue solid line shows the accelerating gradient inside a helical coil of same diameter and pitch as the one used in our experiment. (b) Schematic representation of a double-stage acceleration setup using two helical coils driven by two laser pulses. (c) Comparison between the simulated proton spectra, taken at 50 mm from the proton source over a 2 mm × 2 mm area, obtained for: flat-foil proton source (black-input spectrum in the simulation), single-stage (blue) and double-stage (red) coil re-acceleration. Both coils were of 0.5 mm internal diameter and 10 mm long, with variable pitch suited to their input proton energies (∼40 and ∼70 MeV, respectively, for the first and second stages). The parameters for the charge pulse in both coils were taken as those expected from the interaction of a PW, 30 fs laser (e.g. as available at GIST, Korea33) with a thin target, leading to an acceleration gradient of ∼3 GeV m−1 (discussed in the text). The shaded areas A, B1 and B2 represent, respectively, the proton bunch accelerated from the first coil and the proton bunches accelerated and decelerated by the second coil. The total number of particles in the bunches B1 and B2 is approximately equal to the number of particles in the bunch A. The time of arrival of the charge pulse at the entrance of the second coil was synchronized with the arrival of the ∼70 MeV proton bunch produced by the first coil.
Mentions: While the experiment shows a proof-of-principle demonstration employing a university-scale laser system, there is significant scope for further development of the technique using higher-intensity lasers and more refined target arrangements. For a given diameter of the helical coil target, the accelerating field inside the coil structure, as discussed above, is directly proportional to the charge (Q=∫λ(l)dl) contained in the pulse, which is equal to the number of electrons (Nesc) escaping from the laser-irradiated target during the interaction times the electron charge (e). The scaling for eNesc(=Q) with incident laser intensity can be obtained by using the simple phenomenological model described by Kar et al.9Figure 5a shows estimates of Q obtained using this model, for constant laser pulse length (30 fs) and focal spot size on the target (4 μm). A prudent 30% laser-electron conversion efficiency is assumed in this model, which may be an underestimate for intensities above 1020 W cm−2 (refs 22, 29, 30, 31, 32). In any case, as can be seen in this figure, the scaling agrees well not only with our experimental data but also with the experimental data and model reported recently by Poye et al.24 for similar pulse duration and focussing conditions.

Bottom Line: All-optical approaches to particle acceleration are currently attracting a significant research effort internationally.Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously.These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications.

View Article: PubMed Central - PubMed

Affiliation: School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK.

ABSTRACT
All-optical approaches to particle acceleration are currently attracting a significant research effort internationally. Although characterized by exceptional transverse and longitudinal emittance, laser-driven ion beams currently have limitations in terms of peak ion energy, bandwidth of the energy spectrum and beam divergence. Here we introduce the concept of a versatile, miniature linear accelerating module, which, by employing laser-excited electromagnetic pulses directed along a helical path surrounding the laser-accelerated ion beams, addresses these shortcomings simultaneously. In a proof-of-principle experiment on a university-scale system, we demonstrate post-acceleration of laser-driven protons from a flat foil at a rate of 0.5 GeV m(-1), already beyond what can be sustained by conventional accelerator technologies, with dynamic beam collimation and energy selection. These results open up new opportunities for the development of extremely compact and cost-effective ion accelerators for both established and innovative applications.

No MeSH data available.


Related in: MedlinePlus