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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 19 — Sep. 23, 2013
  • pp: 22558–22565
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Simultaneous generation of monoenergetic tunable protons and carbon ions from laser-driven nanofoils

T. P. Yu, Y. Yin, D. B. Zou, Z. Y. Ge, X. H. Yang, H. B. Zhuo, Y. Y. Ma, F. Q. Shao, and A. Pukhov  »View Author Affiliations


Optics Express, Vol. 21, Issue 19, pp. 22558-22565 (2013)
http://dx.doi.org/10.1364/OE.21.022558


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Abstract

Simultaneous generation of monoenergetic tunable protons and carbon ions from intense laser multi-component nanofoil interaction is demonstrated by using particle-in-cell simulations. It is shown that, the protons with the largest charge-to-mass ratio are instantly separated from other ion species and are efficiently accelerated in the ”phase stable” way. The carbon ions always ride on the heavier oxygen ion front with an electron-filling gap between the protons and carbon ions. At the cost of widely spread oxygen ions, monoenergetic collimated protons and carbon ions are obtained simultaneously. By modulating the heavier ion densities in the foil, it is capable to control the final beam quality, which is well interpreted by a simple analytical model.

© 2013 OSA

1. Introduction

With a lot of potential applications in oncology [1

1. B. J. Galow, Z. Harman, and C. H. Keitel, “Intense high-quality medical proton beams via laser fields,” Opt. Express 18, 25950–25957 (2010). [CrossRef] [PubMed]

], proton imaging, and inertial confinement fusion [2

2. N. Naumova, T. Schlegel, V. T. Tikhonchuk, C. Labaune, I. V. Sokolov, and G. Mourou, “Hole Boring in a DT Pellet and Fast-Ion Ignition with Ultraintense Laser Pulses,” Phys. Rev. Lett. 102, 025002 (2009). [CrossRef] [PubMed]

], laser-driven ion acceleration has drawn increasing attention these years. Several ion acceleration mechanisms have been proposed, e.g., target normal sheath acceleration (TNSA [3

3. S. C. Wilks, A. B. Langdon, T. E. Cowan, M. Roth, S. Hatchett, M. H. Key, D. Pennington, A. Mackinnon, and R. A. Snavely, “Energetic proton generation in ultra-intense laserCsolid interactions,” Phys. Plasmas 8, 542–549 (2001). [CrossRef]

5

5. S. A. Gaillard, T. Kluge, K. A. Flippo, M. Bussmann, B. Gall, T. Lockard, M. Geissel, D. T. Offermann, M. Schollmeier, Y. Sentoku, and T. E. Cowan, “Increased laser-accelerated proton energies via direct laser-light-pressure acceleration of electrons in microcone targets,” Phys. Plasmas 18, 056710 (2011). [CrossRef]

]), which is one of the best understood laser-driven ion acceleration mechanisms to date. However, the obtained maximum ion energy was limited to 67.5 MeV for protons and 10 MeV/u for heavy ions both with a quasi-thermal distribution [4

4. H. Schwoerer, S. Pfotenhauer, O. Jäckel, K.-U. Amthor, B. Liesfeld, W. Ziegler, R. Sauerbrey, K. W. D. Ledingham, and T. Esirkepov, “Laser-plasma acceleration of quasi-monoenergetic protons from microstructured targets,” Nature (London) 439, 445–448 (2006). [CrossRef]

, 5

5. S. A. Gaillard, T. Kluge, K. A. Flippo, M. Bussmann, B. Gall, T. Lockard, M. Geissel, D. T. Offermann, M. Schollmeier, Y. Sentoku, and T. E. Cowan, “Increased laser-accelerated proton energies via direct laser-light-pressure acceleration of electrons in microcone targets,” Phys. Plasmas 18, 056710 (2011). [CrossRef]

]. In most applications, high quality ion beams are generally desirable [6

6. A. Macchi, M. Borghesi, and M. Passoni, “Ion acceleration by superintense laser-plasma interaction,” Rev. Mod. Phys. 85, 751–793 (2013). [CrossRef]

]. For example, in medical therapy for tumor, we demand a narrow ion energy spread to ensure that the ion energy is deposited over a small distance in the patient’s tissue [1

1. B. J. Galow, Z. Harman, and C. H. Keitel, “Intense high-quality medical proton beams via laser fields,” Opt. Express 18, 25950–25957 (2010). [CrossRef] [PubMed]

]. Meanwhile, a tunable ion peak energy is very beneficial to the therapy of large size tumors. In the concept of fast ignition with laser-driven ions, it is desirable to control the ion energy spectrum as this may lead to a significant reduction of the proton energy required for ignition [2

2. N. Naumova, T. Schlegel, V. T. Tikhonchuk, C. Labaune, I. V. Sokolov, and G. Mourou, “Hole Boring in a DT Pellet and Fast-Ion Ignition with Ultraintense Laser Pulses,” Phys. Rev. Lett. 102, 025002 (2009). [CrossRef] [PubMed]

]. Despite of the relative success of the TNSA in several experiments [4

4. H. Schwoerer, S. Pfotenhauer, O. Jäckel, K.-U. Amthor, B. Liesfeld, W. Ziegler, R. Sauerbrey, K. W. D. Ledingham, and T. Esirkepov, “Laser-plasma acceleration of quasi-monoenergetic protons from microstructured targets,” Nature (London) 439, 445–448 (2006). [CrossRef]

,5

5. S. A. Gaillard, T. Kluge, K. A. Flippo, M. Bussmann, B. Gall, T. Lockard, M. Geissel, D. T. Offermann, M. Schollmeier, Y. Sentoku, and T. E. Cowan, “Increased laser-accelerated proton energies via direct laser-light-pressure acceleration of electrons in microcone targets,” Phys. Plasmas 18, 056710 (2011). [CrossRef]

], the beam quality of the generated protons and heavy ions is much lower than in conventional accelerators, which is insufficient for further applications in practice.

Thanks to the significant increase of the laser peak intensity (up to 1022W/cm2) and the laser contrast (> 10−10), radiation pressure acceleration (RPA) or ”light-sail” regime was proposed, which holds the promise of achieving monoenergetic ion acceleration in laser thin-foil interaction [7

7. T. Esirkepov, M. Borghesi, S. V. Bulanov, G. Mourou, and T. Tajima, “Highly Efficient Relativistic-Ion Generation in the Laser-Piston Regime,” Phys. Rev. Lett. 92, 175003 (2004). [CrossRef] [PubMed]

12

12. V. K. Tripathi, C. S. Liu, X. Shao, B. Eliasson, and R. Z. Sagdeev, “Laser acceleration of monoenergetic protons in a self-organized double layer from thin foil,” Plasma Phys. Control. Fusion 51, 024014 (2009). [CrossRef]

]. The one dimensional (1D) flying mirror model revealed the underlying dynamics and well predicted the final ion energy [7

7. T. Esirkepov, M. Borghesi, S. V. Bulanov, G. Mourou, and T. Tajima, “Highly Efficient Relativistic-Ion Generation in the Laser-Piston Regime,” Phys. Rev. Lett. 92, 175003 (2004). [CrossRef] [PubMed]

]. Particle-in-cell (PIC) simulations showed that GeV monoenergetic collimated proton beams could be produced from a shaped foil [13

13. M. Chen, A. Pukhov, and T. P. Yu, “Enhanced Collimated GeV Monoenergetic Ion Acceleration from a Shaped Foil Target Irradiated by a Circularly Polarized Laser Pulse,” Phys. Rev. Lett. 103, 024801 (2009). [CrossRef] [PubMed]

, 14

14. M. Chen, T. P. Yu, A. Pukhov, and Z. M. Sheng, “Target shape effects on monoenergetic GeV proton acceleration,” New J. Phys. 12, 045004 (2010). [CrossRef]

], a density-modulated foil [15

15. T. P. Yu, M. Chen, and A. Pukhov, “High quality GeV proton beams from a density-modulated foil target,” Laser Part. Beams 27, 611–617 (2009). [CrossRef]

], and a multi-layer foil [16

16. Y. Q. Cui, W. M. Wang, Z. M. Sheng, Y. T. Li, and J. Zhang, “Quasimonoenergetic proton bunches generation from doped foil targets irradiated by intense lasers,” Phys. Plasmas 20, 024502 (2013). [CrossRef]

] at a laser intensity of 1021–22W/cm2. Experimental investigations on RPA have also obtained significant progress these years. By irradiating a diamondlike carbon foil with a circularly polarized laser, 30 MeV carbon ions (C+6) were observed for the first time in experiments [17

17. A. Henig, S. Steinke, M. Schnürer, T. Sokollik, R. Hörlein, D. Kiefer, D. Jung, J. Schreiber, B. M. Hegelich, X. Q. Yan, J. Meyer-ter-Vehn, T. Tajima, P. V. Nickles, W. Sandner, and D. Habs, “Radiation-Pressure Acceleration of Ion Beams Driven by Circularly Polarized Laser Pulses,” Phys. Rev. Lett. 103, 245003 (2009). [CrossRef]

]. The recent ”light-sail” experiment has further demonstrated the quasi-monoenergetic proton generation in this regime [18

18. S. Kar, K. F. Kakolee, B. Qiao, A. Macchi, M. Cerchez, D. Doria, M. Geissler, P. McKenna, D. Neely, J. Osterholz, R. Prasad, K. Quinn, B. Ramakrishna, G. Sarri, O. Willi, X.Y Yuan, M. Zepf, and M. Borghesi, “Ion acceleration in multispecies targets driven by intense laser radiation pressure,” Phys. Rev. Lett. 109, 185006 (2012). [CrossRef] [PubMed]

20

20. B. Aurand, S. Kuschel, O. Jäckel, C. Rödel, H. Y. Zhao, S. Herzer, A. E. Paz, J. Bierbach, J. Polz, B. Elkin, G. G. Paulus, A. Karmakar, P. Gibbon, T. Kuehl, and M. C. Kaluza, “Radiation pressure-assisted acceleration of ions using multi-component foils in high-intensity laserCmatter interactions,” New J. Phys. 15, 033031 (2013). [CrossRef]

]. However, the inevitable transverse instabilities, e.g., Rayleigh-Taylor-like (RT) instability, quickly destroyed the foil acceleration structure and deteriorated the beam quality [21

21. F. Pegoraro and S. V. Bulanov, “Photon Bubbles and Ion Acceleration in a Plasma Dominated by the Radiation Pressure of an Electromagnetic Pulse,” Phys. Rev. Lett. 99, 065002 (2007). [CrossRef] [PubMed]

, 22

22. M. Chen, N. Kumar, A. Pukhov, and T. P. Yu, “Stabilized radiation pressure dominated ion acceleration from surface modulated thin-foil targets,” Phys. Plasmas 18, 073106 (2011). [CrossRef]

]. The stabilization and tunability of ion acceleration are still two critical issues in the RPA regime, which prevent the laser-driven ion beam applications [6

6. A. Macchi, M. Borghesi, and M. Passoni, “Ion acceleration by superintense laser-plasma interaction,” Rev. Mod. Phys. 85, 751–793 (2013). [CrossRef]

]. Recent studies showed that, by using a C-H mixing foil we may obtain stable proton acceleration with respect to the RT-like instability [23

23. T. P. Yu, A. Pukhov, G. Shvets, and M. Chen, “Stable Laser-Driven Proton Beam Acceleration from a Two-Ion-Species Ultrathin Foil,” Phys. Rev. Lett. 105, 065002 (2010). [CrossRef] [PubMed]

,24

24. T. P. Yu, A. Pukhov, G. Shvets, M. Chen, T. H. Ratliff, S. A. Yi, and V. Khudik, “Simulations of stable compact proton beam acceleration from a two-ion-species ultrathin foil,” Phys. Plasmas 18, 043110 (2011). [CrossRef]

]. In this case, carbon ions are immediately separated from the light protons as the laser pressure acts on the foil. Due to their smaller charge-to-mass ratio, the carbon ions move behind the protons and are widely spread in space. Finally, only a high quality proton beam is obtained, whereas stable carbon ion acceleration is still out of the reach in RPA.

In this paper, we demonstrate the simultaneous generation of monoenergetic protons and carbon ions by radiation pressure acceleration of a multi-component nanofoil. It is shown that, the light protons with the largest charge-to-mass ratio moves ahead of the carbon ions and experience a phase stable acceleration. The carbon ion layer always rides at the heavier oxygen ion front with a small electron-filling gap between the protons and carbon ions. The gap plays a key role for proton acceleration because the protons are free from the instability. The oxygen ion layer thermally expands and widely spreads in space which acts as a natural ”buffer” for carbon ion acceleration. Finally, monoenergetic collimated protons and carbon ions are obtained simultaneously. More impressive is that, the peak energy and the energy spread of both protons and carbon ions could be controlled by modulating the initial heavier ion densities in the foil.

2. 3D and 2D PIC simulations and results

We first carry out 3D simulations to demonstrate the feasibility of the scheme by using the PIC code VLPL [25

25. A. Pukhov, “Three-dimensional electromagnetic relativistic particle-in-cell code VLPL (Virtual Laser Plasma Lab),” J. Plasma Phys. 61, 425–433 (1999). [CrossRef]

]. The simulation box is x × y × z = 20λ0 × 20λ0 × 20λ0, which is sampled by 5000×400×400 grid cells. Here, λ0 = cT0 = 1μm is the laser wavelength, c is the light speed, and T0 = 3.3 fs is the laser period. The time step is Δt = 0.0045T0. A circularly polarized laser pulse is incident on the foil from the left boundary at t = 0. The temporal profile of the pulse is trapeziform (linear growth-plateau-linear decrease) and the duration is 12T0 (1T0 + 10T0 + 1T0). The spatial profile is super-Gaussian with the amplitude a=a0exp(r4/σ04) where a0 = 30 is the peak laser intensity and σ0 = 5λ0. A planar foil is initially positioned at x = 5λ0 with a thickness of l = 0.08λ0 (80nm), which is composed of multi-ion-species, e.g., carbon ions (C+6), protons (H+), and oxygen ions (O+6). This is identical to the real chemical composition of the widely employed Formvar film in experiments [19

19. S. Steinke, P. Hilz, M. Schnürer, G. Priebe, J. Bränzel, F. Abicht, D. Kiefer, C. Kreuzer, T. Ostermayr, J. Schreiber, A. A. Andreev, T. P. Yu, A. Pukhov, and W. Sandner, “Stable laser-ion acceleration in the light sail regime,” Phys. Rev. ST Accel. Beams 16, 011303 (2013). [CrossRef]

]. Here, partially ionized oxygen ions are adopted to model the real oxygen ion state in experiments. The ion number density ratio is nC : nH : nO = 1 : 1 : 3 with the corresponding electron density ne = 125nc, where nc=meωo2/4πe2 is the critical plasma density, me is the electron rest mass, and ω0 = 2π/T0 is the laser frequency. Each cell contains 27 numerical macroparticles in the plasma region. Mean-while, a0πnel/ncλ0 is satisfied to make sure of an optimal foil acceleration in RPA [24

24. T. P. Yu, A. Pukhov, G. Shvets, M. Chen, T. H. Ratliff, S. A. Yi, and V. Khudik, “Simulations of stable compact proton beam acceleration from a two-ion-species ultrathin foil,” Phys. Plasmas 18, 043110 (2011). [CrossRef]

].

Figures 1(a)–1(c) show the 3D simulation results of the laser thin-foil interaction at t = 35T0. When radiation pressure dominates the foil acceleration at high laser intensities, electrons move ahead of ions immediately and strong charge separation fields are created. For a thin foil consisting of three ion components with different charge-to-mass ratios, C6+, H+, and O6+, three ion layers are thus formed as illustrated in Fig. 1(a): a compact proton layer (cyan), a thin carbon ion layer (blue), and a thermally expanding oxygen ion layer (purple). The carbon ions ride on the heavier oxygen ion’s front and a small gap forms between the carbon layer and the proton layer. This is significantly different from the two-ion-species case in Ref. [23

23. T. P. Yu, A. Pukhov, G. Shvets, and M. Chen, “Stable Laser-Driven Proton Beam Acceleration from a Two-Ion-Species Ultrathin Foil,” Phys. Rev. Lett. 105, 065002 (2010). [CrossRef] [PubMed]

] where the carbon ion layer is tightly adjacent to the protons and a smooth interface thus forms. Figs. 1(b)–1(c) show the ion energy spectrum and the divergency angle θ = p/px at t = 35T0. We can see a pronounced energy peak for both protons (∼108MeV) and carbon ions (∼43MeV/u). The corresponding peak divergency angle is also very small, ∼ 3.6° for H+ and ∼ 5.4° for C+6. However, the oxygen ions exhibit a thermal-like energy spectrum with a relatively large divergency angle. In accord with the observations above, the carbon ion energy peaks at the cuttoff energy of the oxygen ions and meanwhile, is approximately equal to the adjacent proton’s energy. Such a compact acceleration structure is very stable and can be kept for a long time even after the laser pulse passes away. To our knowledge, it is the first time to simultaneously achieve such a stable monoenergetic proton and carbon ion acceleration in full 3D geometries.

Fig. 1 3D simulations of laser nanofoil interaction at t = 35T0. (a) Multi-panel visualization of density distributions of protons (cyan), carbon ions (blue), and oxygen ions (purple). The circle shows the proton bunch and carbon ion bunch, respectively. (b,c) Energy spectra and divergency angles of protons (black), carbon ions (red), and oxygen ions (blue).

For more insights into the underlying physics, we perform a series of 2D simulations. Because of circularly polarized laser pulses, 2D simulations shall reveal the same observations compared with the 3D ones, but require much less run hours. In the following 2D simulations, we keep the electron and proton densities as in the 3D case above but vary the density ratio of carbon ions to oxygen ions. Here, 4 cases are being considered: nC : nH : nO=1:1:3 (cases 1), 2:1:2 (case 2), 3:1:1 (case 3), and 4:1:0 (case 4). Figs. 2(a)– 2(d) present the axial charge density (niqi) distribution of ions and the corresponding axial electric field Ex at t = 15T0. At that time, the laser-foil interacts for only 5 laser cycles and the RT-like instability is still in a linear stage [21

21. F. Pegoraro and S. V. Bulanov, “Photon Bubbles and Ion Acceleration in a Plasma Dominated by the Radiation Pressure of an Electromagnetic Pulse,” Phys. Rev. Lett. 99, 065002 (2007). [CrossRef] [PubMed]

]. Three different ion regions can be clearly recognized in the Fig. 2 together with an electron-filling gap between the protons and carbon ions. It is also found that the protons in all 4 cases are experiencing a strong linearly-decreasing electric field (Ex,max ∼ 15E0) by which protons are accelerated in a ”phase-stable” way [9

9. X. Q. Yan, C. Lin, Z. M. Sheng, Z. Y. Guo, B. C. Liu, Y. R. Lu, J. X. Fang, and J. E. Chen, “Generating High-Current Monoenergetic Proton Beams by a Circularly Polarized Laser Pulse in the Phase-Stable Acceleration Regime,” Phys. Rev. Lett. 100, 135003 (2008). [CrossRef] [PubMed]

]. Finally, monoenergetic proton beams could be obtained for all 4 cases as seen in Figs. 3(a)– 3(d).

Fig. 2 Axial charge densitiy (niqi) distributions of protons (black), carbon ions (red), and oxygen ions (blue) at t = 15T0. (a) case 1, (b) case 2, (c) case 3, and (d) case 4. The pink shows the corresponding axis electric field Ex.
Fig. 3 Energy spectra of protons (black), carbon ions (red), and oxygen ions (blue) within y = 5 – 15λ0 at t = 15T0. (a) case 1, (b) case 2, (c) case 3, and (d) case 4.

The ion energy spectrum is very sensitive to the initial ion density ratio. With the decrease of the oxygen ion density in the foil, the proton peak energy increases from 122MeV to 162MeV and the energy spread becomes relatively smaller. On the contrary, the heavier ion (C+6, O+6) acceleration is more complicated. First, Coulomb explosion is not very important in this stage as seen from Fig. 2 and the laser pressure dominates the ion acceleration. When the oxygen ion density is lower in the foil, the carbon ions’ acceleration becomes worse. Their peak energy downshifts from 45MeV in the case 1 to 25MeV in the case 3 and then disappears in the case 4. The energy spectrum also becomes broader and approaches a thermal distribution in the case 3. By comparison, in all 4 cases the oxygen ions show a spatially expanding distribution with a thermal-like energy spectrum. We also did one more simulations by substituting C+6 with C+5 but keeping its charge density in the case 1. Stable monoenergetic proton and carbon ion acceleration were reproduced together with an expanding oxygen layer.

3. Analysis and discussions

Actually, the different ion acceleration process depends on the different evolution of the RT-like instability in the foil. We first set up a simple analytical model as shown in Fig. 4 to interpret the underlying physics. Starting from the general formulas of the RT instability in a single-ion layer, we obtain the basic equation of the perturbed pressure p seeded on the vacuum-plasma interface I as [24

24. T. P. Yu, A. Pukhov, G. Shvets, M. Chen, T. H. Ratliff, S. A. Yi, and V. Khudik, “Simulations of stable compact proton beam acceleration from a two-ion-species ultrathin foil,” Phys. Plasmas 18, 043110 (2011). [CrossRef]

]
ρvt=δpδρg,
(1)
where ρ, v, and g are the mass density, the perturbation velocity, and the acceleration [24

24. T. P. Yu, A. Pukhov, G. Shvets, M. Chen, T. H. Ratliff, S. A. Yi, and V. Khudik, “Simulations of stable compact proton beam acceleration from a two-ion-species ultrathin foil,” Phys. Plasmas 18, 043110 (2011). [CrossRef]

]. In the accelerating reference frame of the foil, the above Eq. (1) can be further simplified as 2δp/x2=kRT2δp where kRT is the perturbation wave-number in the direction parallel to the interface [23

23. T. P. Yu, A. Pukhov, G. Shvets, and M. Chen, “Stable Laser-Driven Proton Beam Acceleration from a Two-Ion-Species Ultrathin Foil,” Phys. Rev. Lett. 105, 065002 (2010). [CrossRef] [PubMed]

]. The solution to the equation is δp = AekRTx + BekRTx with A and B being the amplitude coefficients of the perturbation. Then, we find the perturbation amplitude is exponentially decaying away from the first interface by ∼ ekRTLion where Lion is the thickness of the ion layer. That is, the layer father away from the perturbed interface is more stable with respect to the instability. In our case, the typical perturbation growth scales kRT ∼ 1/LC where LC is the thickness of the carbon ion layer. Taking the first three interfaces into account, we find the velocity perturbation at the interface III follows
vIIIvI~exp(LOLC),
(2)
Equation (2) reveals that the velocity perturbation is rapidly decaying at a rate depending on LO/LC. Considering LOLC in our cases, the perturbation amplitude peaks at the first unstable interface, becomes much smaller at the second interface, and finally attenuated at the third interface. The analysis is actually in excellent agreement with that from the linear stability theory of the accelerated foil in the relativistic limit [21

21. F. Pegoraro and S. V. Bulanov, “Photon Bubbles and Ion Acceleration in a Plasma Dominated by the Radiation Pressure of an Electromagnetic Pulse,” Phys. Rev. Lett. 99, 065002 (2007). [CrossRef] [PubMed]

]. That is, the instability evolves much faster for heavy ions than the light ions. Due to the gap between the carbon ions and the protons, the proton layer is free from the instability so that monoenergetic proton acceleration is always achieved in all 4 cases above. When the initial oxygen ion density nO is larger, the oxygen ion layer becomes opaque to the laser. The layer expands and the thickness LO enlarges which is beneficial to the attenuation of the instability according to Eq. (2). On the contrary, when nO is smaller and the foil is transparent to the laser, the oxygen ion layer thickness becomes too thin to attenuate the perturbation. Gradually, the heavier oxygen ion’s ”buffering” role is replaced by C+6 and the carbon ion acceleration is thus deteriorated. In order to obtain stable carbon ion acceleration in experiments, another heavier ion species, e.g., C+5 or F+7 with a lower charge-to-mass ratio, is required so that the perturbation is rapidly exhausted before it approaches the carbon ion layer. This actually offers us an approach to control the beam quality by modulating the heavier ion density in the foil which could be achieved as suggested in Ref. [26

26. K. Ostrikov, “Colloquium: Reactive plasmas as a versatile nanofabrication tool,” Rev. Mod. Phys. 77, 751–793 (2013).

]. In real experiments, due to the prepulse or pedestal of the laser, partially ionized heavier ions are considerably produced so that stable proton and carbon ion acceleration are thus obtained.

Fig. 4 Schematic of the laser multi-component nanofoil interaction and the evolution of the RT-like instability. The top red is protons and the bottom gray is oxygen ions with the middle blue being the carbon ions. Between the carbon ion layer and the proton layer is an electron-filling gap.

The model also provides us with an alternative interpretation for recent observations in Ref. [20

20. B. Aurand, S. Kuschel, O. Jäckel, C. Rödel, H. Y. Zhao, S. Herzer, A. E. Paz, J. Bierbach, J. Polz, B. Elkin, G. G. Paulus, A. Karmakar, P. Gibbon, T. Kuehl, and M. C. Kaluza, “Radiation pressure-assisted acceleration of ions using multi-component foils in high-intensity laserCmatter interactions,” New J. Phys. 15, 033031 (2013). [CrossRef]

], where a C8H8F2 foil was used. In their experiments, a lot of C+4, C+5, and F+5 may be produced because of the prepulse of the laser. According to our model, the observed carbon ion peak (C+6) in the energy spectrum may be attributed to the ”buffer” effect of the heavier fluorin ions (F+5) and partially ionized carbon ions, e.g., C4+ and C5+. Because the material contains only a few heavier ions, very tiny peaks of protons and carbon ions were observed.

4. Conclusion

In conclusion, we study intense laser nanofoil interaction and demonstrate the generation of monoenergetic tunable protons and carbon ions by using PIC simulations. It is shown that, the protons always move ahead of carbon ions with the latter followed by oxygen ions. A small electron-filling gap forms between the protons and carbon ions, which plays a key role for monoenergetic proton acceleration. The oxygen ion layer thermally expands and widely spreads in space, which acts as a natural ”buffer” for carbon ion acceleration. Finally, monoenergetic collimated protons and carbon ions are obtained simultaneously. By modulating the oxygen ion density in the foil, the energy spread and the peak energy of both protons and carbon ions could be controlled, which may have diverse applications in future.

Acknowledgments

This work was supported by NSFC (Grant Nos. 11205243, 91230205, 11375265), RFDP (Contract Nos. 20124307120002), and the Research Projects of NUDT. TR18 is also acknowledged.

References and links

1.

B. J. Galow, Z. Harman, and C. H. Keitel, “Intense high-quality medical proton beams via laser fields,” Opt. Express 18, 25950–25957 (2010). [CrossRef] [PubMed]

2.

N. Naumova, T. Schlegel, V. T. Tikhonchuk, C. Labaune, I. V. Sokolov, and G. Mourou, “Hole Boring in a DT Pellet and Fast-Ion Ignition with Ultraintense Laser Pulses,” Phys. Rev. Lett. 102, 025002 (2009). [CrossRef] [PubMed]

3.

S. C. Wilks, A. B. Langdon, T. E. Cowan, M. Roth, S. Hatchett, M. H. Key, D. Pennington, A. Mackinnon, and R. A. Snavely, “Energetic proton generation in ultra-intense laserCsolid interactions,” Phys. Plasmas 8, 542–549 (2001). [CrossRef]

4.

H. Schwoerer, S. Pfotenhauer, O. Jäckel, K.-U. Amthor, B. Liesfeld, W. Ziegler, R. Sauerbrey, K. W. D. Ledingham, and T. Esirkepov, “Laser-plasma acceleration of quasi-monoenergetic protons from microstructured targets,” Nature (London) 439, 445–448 (2006). [CrossRef]

5.

S. A. Gaillard, T. Kluge, K. A. Flippo, M. Bussmann, B. Gall, T. Lockard, M. Geissel, D. T. Offermann, M. Schollmeier, Y. Sentoku, and T. E. Cowan, “Increased laser-accelerated proton energies via direct laser-light-pressure acceleration of electrons in microcone targets,” Phys. Plasmas 18, 056710 (2011). [CrossRef]

6.

A. Macchi, M. Borghesi, and M. Passoni, “Ion acceleration by superintense laser-plasma interaction,” Rev. Mod. Phys. 85, 751–793 (2013). [CrossRef]

7.

T. Esirkepov, M. Borghesi, S. V. Bulanov, G. Mourou, and T. Tajima, “Highly Efficient Relativistic-Ion Generation in the Laser-Piston Regime,” Phys. Rev. Lett. 92, 175003 (2004). [CrossRef] [PubMed]

8.

A. P. L. Robinson, M. Zepf, S. Kar, and R. G. Evans, “Radiation pressure acceleration of thin foils with circularly polarized laser pulses,” New J. Phys. 10, 013021 (2008). [CrossRef]

9.

X. Q. Yan, C. Lin, Z. M. Sheng, Z. Y. Guo, B. C. Liu, Y. R. Lu, J. X. Fang, and J. E. Chen, “Generating High-Current Monoenergetic Proton Beams by a Circularly Polarized Laser Pulse in the Phase-Stable Acceleration Regime,” Phys. Rev. Lett. 100, 135003 (2008). [CrossRef] [PubMed]

10.

T. P. Yu, A. Pukhov, Z. M. Sheng, F. Liu, and G. Shvets, “Bright Betatronlike X Rays from Radiation Pressure Acceleration of a Mass-Limited Foil Target,” Phys. Rev. Lett. 110, 045001 (2013). [CrossRef]

11.

Q. L. Dong, Z.-M. Sheng, M. Y. Yu, and J. Zhang, “Optimization of ion acceleration in the interaction of intense femtosecond laser pulses with ultrathin foils,” Phys. Rev. E 68, 026408 (2003). [CrossRef]

12.

V. K. Tripathi, C. S. Liu, X. Shao, B. Eliasson, and R. Z. Sagdeev, “Laser acceleration of monoenergetic protons in a self-organized double layer from thin foil,” Plasma Phys. Control. Fusion 51, 024014 (2009). [CrossRef]

13.

M. Chen, A. Pukhov, and T. P. Yu, “Enhanced Collimated GeV Monoenergetic Ion Acceleration from a Shaped Foil Target Irradiated by a Circularly Polarized Laser Pulse,” Phys. Rev. Lett. 103, 024801 (2009). [CrossRef] [PubMed]

14.

M. Chen, T. P. Yu, A. Pukhov, and Z. M. Sheng, “Target shape effects on monoenergetic GeV proton acceleration,” New J. Phys. 12, 045004 (2010). [CrossRef]

15.

T. P. Yu, M. Chen, and A. Pukhov, “High quality GeV proton beams from a density-modulated foil target,” Laser Part. Beams 27, 611–617 (2009). [CrossRef]

16.

Y. Q. Cui, W. M. Wang, Z. M. Sheng, Y. T. Li, and J. Zhang, “Quasimonoenergetic proton bunches generation from doped foil targets irradiated by intense lasers,” Phys. Plasmas 20, 024502 (2013). [CrossRef]

17.

A. Henig, S. Steinke, M. Schnürer, T. Sokollik, R. Hörlein, D. Kiefer, D. Jung, J. Schreiber, B. M. Hegelich, X. Q. Yan, J. Meyer-ter-Vehn, T. Tajima, P. V. Nickles, W. Sandner, and D. Habs, “Radiation-Pressure Acceleration of Ion Beams Driven by Circularly Polarized Laser Pulses,” Phys. Rev. Lett. 103, 245003 (2009). [CrossRef]

18.

S. Kar, K. F. Kakolee, B. Qiao, A. Macchi, M. Cerchez, D. Doria, M. Geissler, P. McKenna, D. Neely, J. Osterholz, R. Prasad, K. Quinn, B. Ramakrishna, G. Sarri, O. Willi, X.Y Yuan, M. Zepf, and M. Borghesi, “Ion acceleration in multispecies targets driven by intense laser radiation pressure,” Phys. Rev. Lett. 109, 185006 (2012). [CrossRef] [PubMed]

19.

S. Steinke, P. Hilz, M. Schnürer, G. Priebe, J. Bränzel, F. Abicht, D. Kiefer, C. Kreuzer, T. Ostermayr, J. Schreiber, A. A. Andreev, T. P. Yu, A. Pukhov, and W. Sandner, “Stable laser-ion acceleration in the light sail regime,” Phys. Rev. ST Accel. Beams 16, 011303 (2013). [CrossRef]

20.

B. Aurand, S. Kuschel, O. Jäckel, C. Rödel, H. Y. Zhao, S. Herzer, A. E. Paz, J. Bierbach, J. Polz, B. Elkin, G. G. Paulus, A. Karmakar, P. Gibbon, T. Kuehl, and M. C. Kaluza, “Radiation pressure-assisted acceleration of ions using multi-component foils in high-intensity laserCmatter interactions,” New J. Phys. 15, 033031 (2013). [CrossRef]

21.

F. Pegoraro and S. V. Bulanov, “Photon Bubbles and Ion Acceleration in a Plasma Dominated by the Radiation Pressure of an Electromagnetic Pulse,” Phys. Rev. Lett. 99, 065002 (2007). [CrossRef] [PubMed]

22.

M. Chen, N. Kumar, A. Pukhov, and T. P. Yu, “Stabilized radiation pressure dominated ion acceleration from surface modulated thin-foil targets,” Phys. Plasmas 18, 073106 (2011). [CrossRef]

23.

T. P. Yu, A. Pukhov, G. Shvets, and M. Chen, “Stable Laser-Driven Proton Beam Acceleration from a Two-Ion-Species Ultrathin Foil,” Phys. Rev. Lett. 105, 065002 (2010). [CrossRef] [PubMed]

24.

T. P. Yu, A. Pukhov, G. Shvets, M. Chen, T. H. Ratliff, S. A. Yi, and V. Khudik, “Simulations of stable compact proton beam acceleration from a two-ion-species ultrathin foil,” Phys. Plasmas 18, 043110 (2011). [CrossRef]

25.

A. Pukhov, “Three-dimensional electromagnetic relativistic particle-in-cell code VLPL (Virtual Laser Plasma Lab),” J. Plasma Phys. 61, 425–433 (1999). [CrossRef]

26.

K. Ostrikov, “Colloquium: Reactive plasmas as a versatile nanofabrication tool,” Rev. Mod. Phys. 77, 751–793 (2013).

OCIS Codes
(320.2250) Ultrafast optics : Femtosecond phenomena
(350.5400) Other areas of optics : Plasmas
(020.2649) Atomic and molecular physics : Strong field laser physics

ToC Category:
Ultrafast Optics

History
Original Manuscript: July 23, 2013
Revised Manuscript: September 8, 2013
Manuscript Accepted: September 9, 2013
Published: September 18, 2013

Citation
T. P. Yu, Y. Yin, D. B. Zou, Z. Y. Ge, X. H. Yang, H. B. Zhuo, Y. Y. Ma, F. Q. Shao, and A. Pukhov, "Simultaneous generation of monoenergetic tunable protons and carbon ions from laser-driven nanofoils," Opt. Express 21, 22558-22565 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-19-22558


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References

  1. B. J. Galow, Z. Harman, and C. H. Keitel, “Intense high-quality medical proton beams via laser fields,” Opt. Express18, 25950–25957 (2010). [CrossRef] [PubMed]
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  3. S. C. Wilks, A. B. Langdon, T. E. Cowan, M. Roth, S. Hatchett, M. H. Key, D. Pennington, A. Mackinnon, and R. A. Snavely, “Energetic proton generation in ultra-intense laserCsolid interactions,” Phys. Plasmas8, 542–549 (2001). [CrossRef]
  4. H. Schwoerer, S. Pfotenhauer, O. Jäckel, K.-U. Amthor, B. Liesfeld, W. Ziegler, R. Sauerbrey, K. W. D. Ledingham, and T. Esirkepov, “Laser-plasma acceleration of quasi-monoenergetic protons from microstructured targets,” Nature (London)439, 445–448 (2006). [CrossRef]
  5. S. A. Gaillard, T. Kluge, K. A. Flippo, M. Bussmann, B. Gall, T. Lockard, M. Geissel, D. T. Offermann, M. Schollmeier, Y. Sentoku, and T. E. Cowan, “Increased laser-accelerated proton energies via direct laser-light-pressure acceleration of electrons in microcone targets,” Phys. Plasmas18, 056710 (2011). [CrossRef]
  6. A. Macchi, M. Borghesi, and M. Passoni, “Ion acceleration by superintense laser-plasma interaction,” Rev. Mod. Phys.85, 751–793 (2013). [CrossRef]
  7. T. Esirkepov, M. Borghesi, S. V. Bulanov, G. Mourou, and T. Tajima, “Highly Efficient Relativistic-Ion Generation in the Laser-Piston Regime,” Phys. Rev. Lett.92, 175003 (2004). [CrossRef] [PubMed]
  8. A. P. L. Robinson, M. Zepf, S. Kar, and R. G. Evans, “Radiation pressure acceleration of thin foils with circularly polarized laser pulses,” New J. Phys.10, 013021 (2008). [CrossRef]
  9. X. Q. Yan, C. Lin, Z. M. Sheng, Z. Y. Guo, B. C. Liu, Y. R. Lu, J. X. Fang, and J. E. Chen, “Generating High-Current Monoenergetic Proton Beams by a Circularly Polarized Laser Pulse in the Phase-Stable Acceleration Regime,” Phys. Rev. Lett.100, 135003 (2008). [CrossRef] [PubMed]
  10. T. P. Yu, A. Pukhov, Z. M. Sheng, F. Liu, and G. Shvets, “Bright Betatronlike X Rays from Radiation Pressure Acceleration of a Mass-Limited Foil Target,” Phys. Rev. Lett.110, 045001 (2013). [CrossRef]
  11. Q. L. Dong, Z.-M. Sheng, M. Y. Yu, and J. Zhang, “Optimization of ion acceleration in the interaction of intense femtosecond laser pulses with ultrathin foils,” Phys. Rev. E68, 026408 (2003). [CrossRef]
  12. V. K. Tripathi, C. S. Liu, X. Shao, B. Eliasson, and R. Z. Sagdeev, “Laser acceleration of monoenergetic protons in a self-organized double layer from thin foil,” Plasma Phys. Control. Fusion51, 024014 (2009). [CrossRef]
  13. M. Chen, A. Pukhov, and T. P. Yu, “Enhanced Collimated GeV Monoenergetic Ion Acceleration from a Shaped Foil Target Irradiated by a Circularly Polarized Laser Pulse,” Phys. Rev. Lett.103, 024801 (2009). [CrossRef] [PubMed]
  14. M. Chen, T. P. Yu, A. Pukhov, and Z. M. Sheng, “Target shape effects on monoenergetic GeV proton acceleration,” New J. Phys.12, 045004 (2010). [CrossRef]
  15. T. P. Yu, M. Chen, and A. Pukhov, “High quality GeV proton beams from a density-modulated foil target,” Laser Part. Beams27, 611–617 (2009). [CrossRef]
  16. Y. Q. Cui, W. M. Wang, Z. M. Sheng, Y. T. Li, and J. Zhang, “Quasimonoenergetic proton bunches generation from doped foil targets irradiated by intense lasers,” Phys. Plasmas20, 024502 (2013). [CrossRef]
  17. A. Henig, S. Steinke, M. Schnürer, T. Sokollik, R. Hörlein, D. Kiefer, D. Jung, J. Schreiber, B. M. Hegelich, X. Q. Yan, J. Meyer-ter-Vehn, T. Tajima, P. V. Nickles, W. Sandner, and D. Habs, “Radiation-Pressure Acceleration of Ion Beams Driven by Circularly Polarized Laser Pulses,” Phys. Rev. Lett.103, 245003 (2009). [CrossRef]
  18. S. Kar, K. F. Kakolee, B. Qiao, A. Macchi, M. Cerchez, D. Doria, M. Geissler, P. McKenna, D. Neely, J. Osterholz, R. Prasad, K. Quinn, B. Ramakrishna, G. Sarri, O. Willi, X.Y Yuan, M. Zepf, and M. Borghesi, “Ion acceleration in multispecies targets driven by intense laser radiation pressure,” Phys. Rev. Lett.109, 185006 (2012). [CrossRef] [PubMed]
  19. S. Steinke, P. Hilz, M. Schnürer, G. Priebe, J. Bränzel, F. Abicht, D. Kiefer, C. Kreuzer, T. Ostermayr, J. Schreiber, A. A. Andreev, T. P. Yu, A. Pukhov, and W. Sandner, “Stable laser-ion acceleration in the light sail regime,” Phys. Rev. ST Accel. Beams16, 011303 (2013). [CrossRef]
  20. B. Aurand, S. Kuschel, O. Jäckel, C. Rödel, H. Y. Zhao, S. Herzer, A. E. Paz, J. Bierbach, J. Polz, B. Elkin, G. G. Paulus, A. Karmakar, P. Gibbon, T. Kuehl, and M. C. Kaluza, “Radiation pressure-assisted acceleration of ions using multi-component foils in high-intensity laserCmatter interactions,” New J. Phys.15, 033031 (2013). [CrossRef]
  21. F. Pegoraro and S. V. Bulanov, “Photon Bubbles and Ion Acceleration in a Plasma Dominated by the Radiation Pressure of an Electromagnetic Pulse,” Phys. Rev. Lett.99, 065002 (2007). [CrossRef] [PubMed]
  22. M. Chen, N. Kumar, A. Pukhov, and T. P. Yu, “Stabilized radiation pressure dominated ion acceleration from surface modulated thin-foil targets,” Phys. Plasmas18, 073106 (2011). [CrossRef]
  23. T. P. Yu, A. Pukhov, G. Shvets, and M. Chen, “Stable Laser-Driven Proton Beam Acceleration from a Two-Ion-Species Ultrathin Foil,” Phys. Rev. Lett.105, 065002 (2010). [CrossRef] [PubMed]
  24. T. P. Yu, A. Pukhov, G. Shvets, M. Chen, T. H. Ratliff, S. A. Yi, and V. Khudik, “Simulations of stable compact proton beam acceleration from a two-ion-species ultrathin foil,” Phys. Plasmas18, 043110 (2011). [CrossRef]
  25. A. Pukhov, “Three-dimensional electromagnetic relativistic particle-in-cell code VLPL (Virtual Laser Plasma Lab),” J. Plasma Phys.61, 425–433 (1999). [CrossRef]
  26. K. Ostrikov, “Colloquium: Reactive plasmas as a versatile nanofabrication tool,” Rev. Mod. Phys.77, 751–793 (2013).

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