X. Q. Yan

Publications (46)103.94 Total impact

• Article: Ultrasmall divergence of laser-driven ion beams from nanometer thick foils

  J. H. Bin, W. J. Ma, K. Allinger, H. Y. Wang, D. Kiefer, S. Reinhardt, P. Hilz, K. Khrennikov, S. Karsch, X. Q. Yan, F. Krausz, T. Tajima, D. Habs, J. Schreiber
  [show abstract] [hide abstract]
  ABSTRACT: We report on experimental studies of divergence of proton beams from nanometer thick diamond-like carbon (DLC) foils irradiated by an intense laser with high contrast. Proton beams with extremely small divergence (half angle) of 2 degree are observed in addition with a remarkably well-collimated feature over the whole energy range, showing one order of magnitude reduction of the divergence angle in comparison to the results from micrometer thick targets. We demonstrate that this reduction arises from a steep longitudinal electron density gradient and an exponentially decaying transverse profile at the rear side of the ultrathin foils. Agreements are found both in an analytical model and in particle-in-cell simulations. Those novel features make nm foils an attractive alternative for high flux experiments relevant for fundamental research in nuclear and warm dense matter physics.
  03/2013;
• Article: Stabilizing transverse ablative Rayleigh Taylor like instability by using elliptically polarized laser pulses in the hole-boring radiation pressure acceleration regime

  Dong Wu, C. Y. Zheng, C. T. Zhou, X. Q. Yan, M. Y. Yu, X. T. He
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  ABSTRACT: It is shown that the transverse Rayleigh Taylor like instability can be well stabilized by using elliptically polarized laser in the hole boring radiation pressure acceleration regime. The $\bm{J}\times\bm{B}$ effect of the laser will thermalize the local electrons and support a transverse diffusion mechanism of the ions, resulting in the stabilization of the short wavelength perturbations, which is quite similar to the ablative Rayleigh Taylor instability in the initial confinement fusion research. The proper range of polarization ratio is obtained from a theoretical model for the given laser intensity and plasma density. The stabilization mechanism is well confirmed by two dimensional Particle-in-Cell simulations, and the ion beam driven by the elliptically polarized laser is more concentrated and intense compared with that of the circularly polarized laser.
  12/2012;
• Article: Suppressing longitudinal double-layer oscillations by using elliptically polarized laser pulses in the hole-boring radiation pressure acceleration regime

  Dong Wu, C. Y. Zheng, C. T. Zhou, X. Q. Yan, M. Y. Yu, X. T. He
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  ABSTRACT: It is shown that well collimated mono-energetic ion beams with a large particle number can be generated in the hole-boring radiation pressure acceleration regime by using an elliptically polarized laser pulse with appropriate theoretically determined laser polarization ratio. Due to the $\bm{J}\times\bm{B}$ effect, the double-layer charge separation region is imbued with hot electrons that prevent ion pileup, thus suppressing the double-layer oscillations. The proposed mechanism is well confirmed by Particle-in-Cell simulations, and after suppressing the longitudinal double-layer oscillations, the ion beams driven by the elliptically polarized lasers own much better energy spectrum than those by circularly polarized lasers.
  12/2012;
• Source

  Available from: plasmatechnol.com

  Article: Theory of laser ion acceleration from a foil target of nanometer thickness

  X. Q. Yan, T. Tajima, M. Hegelich, L. Yin, D. Habs
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  ABSTRACT: A theory for ion acceleration by ultrashort laser pulses is presented to evaluate the maximum ion energy in the interaction of ultrahigh contrast (UHC) intense laser pulses with a nanometer-scale foil. In this regime, the ion energy may be directly related to the laser intensity and subsequent electron dynamics. This leads to a simple analytical expression for the ion energy gain under the laser irradiation of thin targets. Significantly higher energies for thin targets than for thicker targets are predicted. The theory is concretized with a view to compare with the results and their details of recent experiments. PACS52.59.-f-52.38.Kd-52.35.Mw
  Applied Physics B 04/2012; 98(4):711-721. · 2.19 Impact Factor
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  Available from: Yuanrong Lu

  Article: Determination of carrier-envelope phase of relativistic few-cycle laser pulses by Thomson backscattering spectroscopy.

  M Wen, L L Jin, H Y Wang, Z Wang, B F Shen, Y R Lu, J E Chen, X Q Yan
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  ABSTRACT: A method is proposed to determine the carrier-envelope phase (CEP) of a relativistic few-cycle laser pulse via the frequency of the Thomson backscattering (TBS) light. We theoretically investigate the generation of a flying mirror when a few-cycle drive pulse with relativistic intensity interacts with a target combined with a thin and a thick foil. The frequency of the TBS light generated from the flying mirror shows a sensitive dependence on the CEP of the drive pulse. The obtained results are verified by one-dimensional particle-in-cell simulations and are explained by an analytical model.
  Physical Review E 03/2012; 85(3 Pt 2):035401. · 2.26 Impact Factor
• Article: Sub-TeV proton beam generation by ultra-intense laser irradiation of foil-and-gas target

  F. L. Zheng, H. Y. Wang, X. Q. Yan, T. Tajima, M. Y. Yu, X. T. He
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  ABSTRACT: A two-phase proton acceleration scheme using an ultra-intense laser pulse irradiating a proton foil with a tenuous heavier-ion plasma behind it is presented. The foil electrons are compressed and pushed out as a thin dense layer by the radiation pressure and propagate in the plasma behind at near the light speed. The protons are in turn accelerated by the resulting space-charge field and also enter the backside plasma, but without the formation of a quasistationary double layer. The electron layer is rapidly weakened by the space-charge field. However, the laser pulse originally behind it now snowplows the backside-plasma electrons and creates an intense electrostatic wakefield. The latter can stably trap and accelerate the pre-accelerated proton layer there for a very long distance and thus to very high energies. The two-phase scheme is verified by particle-in-cell simulations and analytical modeling, which also suggests that a 0.54 TeV proton beam can be obtained with a 1023 W/cm2 laser pulse.
  Physics of Plasmas 02/2012; 19(2):023111-023111-5. · 2.15 Impact Factor
• Article: Laser shaping of a relativistic intense, short Gaussian pulse by a plasma lens.

  H Y Wang, C Lin, Z M Sheng, B Liu, S Zhao, Z Y Guo, Y R Lu, X T He, J E Chen, X Q Yan
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  ABSTRACT: By 3D particle-in-cell simulation and analysis, we propose a plasma lens to make high intensity, high contrast laser pulses with a steep front. When an intense, short Gaussian laser pulse of circular polarization propagates in near-critical plasma, it drives strong currents of relativistic electrons which magnetize the plasma. Three pulse shaping effects are synchronously observed when the laser passes through the plasma lens. The laser intensity is increased by more than 1 order of magnitude while the initial Gaussian profile undergoes self-modulation longitudinally and develops a steep front. Meanwhile, a nonrelativistic prepulse can be absorbed by the overcritical plasma lens, which can improve the laser contrast without affecting laser shaping of the main pulse. If the plasma skin length is properly chosen and kept fixed, the plasma lens can be used for varied laser intensity above 10(19) W/cm(2).
  Physical Review Letters 12/2011; 107(26):265002. · 7.37 Impact Factor
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  Available from: ArXiv

  Article: Laser-driven collimated tens-GeV monoenergetic protons from mass-limited target plus preformed channel

  F. L. Zheng, S. Z. Wu, H. C. Wu, H. B. Cai, M Y Yu, T Tajima, X. Q. Yan, X. T. He
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  ABSTRACT: Proton acceleration by ultra-intense laser pulse irradiating a target with cross-section smaller than the laser spot size and connected to a parabolic density channel is investigated. The target splits the laser into two parallel propagating parts, which snowplow the back-side plasma electrons along their paths, creating two adjacent parallel wakes and an intense return current in the gap between them. The radiation-pressure pre-accelerated target protons trapped in the wake fields now undergo acceleration as well as collimation by the quasistatic wake electrostatic and magnetic fields. Particle-in-cell (PIC) simulation shows that stable long-distance acceleration can be realized, and a 30 fs monoenergetic ion beam of > 10 GeV peak energy and < 2degree divergence can be produced by a 9.8 *10^21 W/cm2 circularly polarized laser pulse.
  12/2011;
• Article: Monoenergetic ion beam generation by driving ion solitary waves with circularly polarized laser light.

  D Jung, L Yin, B J Albright, D C Gautier, R Hörlein, D Kiefer, A Henig, R Johnson, S Letzring, S Palaniyappan, R Shah, T Shimada, X Q Yan, K J Bowers, T Tajima, J C Fernández, D Habs, B M Hegelich
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  ABSTRACT: Experimental data from the Trident Laser facility is presented showing quasimonoenergetic carbon ions from nm-scaled foil targets with an energy spread of as low as ±15% at 35 MeV. These results and high-resolution kinetic simulations show laser acceleration of quasimonoenergetic ion beams by the generation of ion solitons with circularly polarized laser pulses (500 fs, λ=1054  nm). The conversion efficiency into monoenergetic ions is increased by an order of magnitude compared with previous experimental results, representing an important step towards applications such as ion fast ignition.
  Physical Review Letters 09/2011; 107(11):115002. · 7.37 Impact Factor
• Article: An ultra-short and TeV quasi-monoenergetic ion beam generation by laser wakefield accelerator in the snowplow regime

  F. L. Zheng, S. Z. Wu, C. T. Zhou, H. Y. Wang, X. Q. Yan, X. T. He
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  ABSTRACT: A new laser-plasma ion acceleration mechanism, snowplow ion acceleration, is proposed using an ultra-relativistically intense laser pulse irradiating on a combination target. When the thickness of the foil D is less than the length where the double-layer consisting of electron and ion layers is formed, the relativistic ion beam pre-accelerated by radiation pressure acceleration can be trapped and accelerated to the TeV level by the laser plasma wakefield over a long distance in the snowplow regime. Based on the classic wakefield theory, the snowplow structure can control the beam quality in terms of pulse duration, leading to the fact that the heavy-ion beam is theoretically shorter than half of the total wakefield structure, the size of the acceleration region. An analytical model is established, suggesting that ultra-short (70 μm) and ultra-highly energetic (3.2 TeV) carbon ion bunches generated by a centimeter-scale laser wakefield acceleration are expected, driven by a circularly polarized (CP) laser pulse with intensity of 1023 W/cm2 and duration of 66 fs. The particle-in-cell simulations agree well with theoretical results.
  EPL (Europhysics Letters) 08/2011; 95(5):55005. · 2.17 Impact Factor
• Article: Experimental demonstration of particle energy, conversion efficiency and spectral shape required for ion-based fast ignition

  B.M. Hegelich, D. Jung, B.J. Albright, J.C. Fernandez, D.C. Gautier, C. Huang, T.J. Kwan, S. Letzring, S. Palaniyappan, R.C. Shah, [......], L. Yin, A. Henig, R. Hörlein, D. Kiefer, J. Schreiber, X.Q. Yan, T. Tajima, D. Habs, B. Dromey, J.J. Honrubia
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  ABSTRACT: Research on fusion fast ignition (FI) initiated by laser-driven ion beams has made substantial progress in the last years. Compared with electrons, FI based on a beam of quasi-monoenergetic ions has the advantage of a more localized energy deposition, and stiffer particle transport, bringing the required total beam energy close to the theoretical minimum. Due to short pulse laser drive, the ion beam can easily deliver the 200 TW power required to ignite the compressed D–T fuel. In integrated calculations we recently simulated ion-based FI targets with high fusion gain targets and a proof of principle experiment [1]. These simulations identify three key requirements for the success of ion-driven fast ignition (IFI): (1) the generation of a sufficiently high-energetic ion beam (≈400–500 MeV for C), with (2) less than 20% energy spread at (3) more than 10% conversion efficiency of laser to beam energy. Here we present for the first time new experimental results, demonstrating all three parameters in separate experiments. Using diamond nanotargets and ultrahigh contrast laser pulses we were able to demonstrate >500 MeV carbon ions, as well as carbon pulses with ΔE/E < 20%. The first measurements put the total conversion efficiency of laser light into high energy carbon ions on the order of 10%.
  Nuclear Fusion 07/2011; 51(8):083011. · 4.09 Impact Factor
• Source

  Available from: Yuanrong Lu

  Article: High-quality proton bunch from laser interaction with a gas-filled cone target

  H. Y. Wang, F. L. Zheng, Y. R. Lu, Z Y Guo, X. T. He, J. E. Chen, X. Q. Yan
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  ABSTRACT: Generation of high-energy proton bunch from interaction of an intense short circularly polarized(CP) laser pulse with a gas-filled cone target(GCT) is investigated using two-dimensional particle-in-cell simulation. The GCT target consists of a hollow cone filled with near-critical gas-plasma and a thin foil attached to the tip of the cone. It is observed that as the laser pulse propagates in the gas-plasma, the nonlinear focusing will result in an enhancement of the laser pulse intensity. It is shown that a large number of energetic electrons are generated from the gas-plasma and accelerated by the self-focused laser pulse. The energetic electrons then transports through the foil, forming a backside sheath field which is stronger than that produced by a simple planar target. A quasi-monoenergetic proton beam with maximum energy of 181 MeV is produced from this GCT target irradiated by a CP laser pulse at an intensity of $2.6\times10^{20}W/cm^2$, which is nearly three times higher compared to simple planar target(67MeV).
  06/2011;
• Source

  Available from: Yuanrong Lu

  Article: Generating sub-TeV quasi-monoenergetic proton beam by an ultra-relativistically intense laser in the snowplow regime

  F. L. Zheng, H. Y. Wang, X. Q. Yan, J. E. Chen, Y. R. Lu, Z Y Guo, T Tajima, X. T. He
  [show abstract] [hide abstract]
  ABSTRACT: Snowplow ion acceleration is presented, using an ultra-relativistically intense laser pulse irradi- ating on a combination target, where the relativistic proton beam generated by radiation pressure acceleration can be trapped and accelerated by the laser plasma wakefield. The theory suggests that sub-TeV quasi-monoenergetic proton bunches can be generated by a centimeter-scale laser wakefield accelerator, driven by a circularly polarized (CP) laser pulse with the peak intensity of 10^23W/cm^2 and duration of 116fs.
  01/2011;
• Article: Experimental demonstration of particle energy, conversion efficiency and spectral shape required for ion-based fast ignition

  B. M. Hegelich, D. Jung, B. J. Albright, J. C. Fernandez, D. C. Gautier, C. Huang, T. J. Kwan, S. Letzring, S. Palaniyappan, R. C. Shah, [......], L. Yin, A. Henig, R. Horlein, D. Kiefer, J. Schreiber, X. Q. Yan, T. Tajima, D. Habs, B. Dromey, J. J. Honrubia
  [show abstract] [hide abstract]
  ABSTRACT: Research on fusion fast ignition (FI) initiated by laser-driven ion beams has made substantial progress in the last years. Compared with electrons, FI based on a beam of quasi-monoenergetic ions has the advantage of a more localized energy deposition, and stiffer particle transport, bringing the required total beam energy close to the theoretical minimum. Due to short pulse laser drive, the ion beam can easily deliver the 200 TW power required to ignite the compressed D-T fuel. In integrated calculations we recently simulated ion-based FI targets with high fusion gain targets and a proof of principle experiment [1]. These simulations identify three key requirements for the success of ion-driven fast ignition (IFI): (1) the generation of a sufficiently high-energetic ion beam (approximate to 400-500 MeV for C), with (2) less than 20% energy spread at (3) more than 10% conversion efficiency of laser to beam energy. Here we present for the first time new experimental results, demonstrating all three parameters in separate experiments. Using diamond nanotargets and ultrahigh contrast laser pulses we were able to demonstrate >500 MeV carbon ions, as well as carbon pulses with Delta E/E < 20%. The first measurements put the total conversion efficiency of laser light into high energy carbon ions on the order of 10%.
  Nuclear Fusion. 01/2011; 51(8).
• Source

  Available from: Kirk Flippo

  Article: Ultraintense laser interaction with nanoscale targets: a simple model for layer expansion and ion acceleration

  B J Albright, L Yin, B M Hegelich, K J Bowers, C Huang, A Henig, J C Fernández, K A Flippo, S A Gaillard, T J T Kwan, X Q Yan, T Tajima, D Habs
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  ABSTRACT: A simple model has been derived for expansion of a thin (up to 100s of nm thickness) target initially of solid density irradiated by an ultraintense laser. In this regime, ion acceleration mechanisms, such as the Break-Out Afterburner (BOA) [1], emerge with the potential for dramatically improved energy, efficiency, and energy spread. Ion beams have been proposed [2] as drivers for fast ignition inertial confinement fusion [3]. Analysis of kinetic simulations of the BOA shows the period of enhanced acceleration occurs between times t1, when the target becomes relativistically transparent to the laser, and t2, when the target becomes classically underdense and the enhanced acceleration terminates. A simple model for target expansion has been derived that contains early, one-dimensional (1D) expansion of the target and three-dimensional (3D) expansion at late times. The model assumes expansion is slab-like at the instantaneous ion sound speed and requires as input target composition, laser intensity, laser spot area, and the efficiency of laser absorption into electron thermal energy.
  Journal of Physics Conference Series 09/2010; 244(4):042022.
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  Available from: D. Kiefer

  Article: Dynamics of Nanometer-Scale Foil Targets Irradiated with Relativistically Intense Laser Pulses

  R Hörlein, S. Steinke, A. Henig, S. G. Rykovanov, M Schnürer, T Sokollik, D. Kiefer, D Jung, X. Q. Yan, J. M. Michailova, T Tajima, J Schreiber, M Hegelich, P V Nickles, M Zepf, G D Tsakiris, W Sandner, D. Habs
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  ABSTRACT: In this letter we report on an experimental study of high harmonic radiation generated in nanometer-scale foil targets irradiated under normal incidence. The experiments constitute the first unambiguous observation of odd-numbered relativistic harmonics generated by the $\vec{v}\times\vec{B}$ component of the Lorentz force verifying a long predicted property of solid target harmonics. Simultaneously the observed harmonic spectra allow in-situ extraction of the target density in an experimental scenario which is of utmost interest for applications such as ion acceleration by the radiation pressure of an ultraintense laser. Comment: 5 pages, 4 figures
  09/2010;
• Chapter: Laser-driven particle acceleration utilizing nm-thin diamond foils: Improved ion acceleration for cancer therapy, improved electron acceleration and potentially ultra-brilliant X-ray beams for medical diagnostics

  D. Habs, A. Henig, D. Jung, D. Kiefer, R. Hörlein, M. Groß, J. Schreiber, V. Kh. Liechtenstein, B. M. Hegelich, S. Karsch, X. Q. Yan, J. Meyer-ter-Vehn, T. Tajima
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  ABSTRACT: Compared to former laser ion acceleration schemes like target normal sheath acceleration (TNSA) [1], the laser acceleration from ultra-thin diamond-like carbon (DLC) foils is more efficient and for the high-power short-pulse laser ATLAS proton energies up to 100 MeV are expected [2]. Also for the generation of very dense relativistic electron bunches the use of ultra-thin diamond foils leads to much better results [3] than for laser bubble acceleration [4]. By reflection of coherent electromagnetic fields from these relativistic electron bunches it seems possible to generate brilliant, intense X-ray beams [5]. In the longer term we plan to use the laser-driven ion beams for cancer therapy and the X-ray beams in medical diagnostics.We describe the present status and the expected beam properties for the upgraded ATLAS laser at MPQ (Garching) and the setup of our medical beam line. KeywordsLaser acceleration-DLC foils-brilliant X-ray beams-cancer therapy-medical diagnostics
  01/2010: pages 304-307;
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  Available from: D. Kiefer

  Article: Radiation-pressure acceleration of ion beams driven by circularly polarized laser pulses.

  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, D Habs
  [show abstract] [hide abstract]
  ABSTRACT: We present experimental studies on ion acceleration from ultrathin diamondlike carbon foils irradiated by ultrahigh contrast laser pulses of energy 0.7 J focused to peak intensities of 5x10(19) W/cm2. A reduction in electron heating is observed when the laser polarization is changed from linear to circular, leading to a pronounced peak in the fully ionized carbon spectrum at the optimum foil thickness of 5.3 nm. Two-dimensional particle-in-cell simulations reveal that those C6+ ions are for the first time dominantly accelerated in a phase-stable way by the laser radiation pressure.
  Physical Review Letters 12/2009; 103(24):245003. · 7.37 Impact Factor
• Article: Self-organizing GeV, nanocoulomb, collimated proton beam from laser foil interaction at 7 x 10;{21} W/cm;{2}.

  X Q Yan, H C Wu, Z M Sheng, J E Chen, J Meyer-Ter-Vehn
  [show abstract] [hide abstract]
  ABSTRACT: We report on a self-organizing, quasistable regime of laser proton acceleration, producing 1 GeV nanocoulomb proton bunches from laser foil interaction at an intensity of 7 x 10;{21} W/cm;{2}. The results are obtained from 2D particle-in-cell simulations, using a circular polarized laser pulse with Gaussian transverse profile, normally incident on a planar, 500 nm thick hydrogen foil. While foil plasma driven in the wings of the driving pulse is dispersed, a stable central clump with 1-2lambda diameter is forming on the axis. The stabilization is related to laser light having passed the transparent parts of the foil in the wing region and enfolding the central clump that is still opaque. Varying laser parameters, it is shown that the results are stable within certain margins and can be obtained both for protons and heavier ions such as He;{2+}.
  Physical Review Letters 09/2009; 103(13):135001. · 7.37 Impact Factor
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  Available from: arxiv.org

  Article: Self-organizing GeV, nano-Coulomb, collimated proton beam from laser foil interaction at 7 * 10^21 W/cm2

  X. Q. Yan, H. C. Wu, Z M Sheng, J. E. Chen, J. Meyer-ter-Vehn
  [show abstract] [hide abstract]
  ABSTRACT: We report on a self-organizing, quasi-stable regime of laser proton acceleration, producing 1 GeV nano-Coulomb proton bunches from laser foil interaction at an intensity of 7*10^21 W/cm2. The results are obtained from 2D PIC simulations, using circular polarized light normally incident on a planar, 500 nm thick hydrogen foil with Gaussian transverse profile. While foil plasma driven in the wings of the driving pulse is dispersed, a stable central clump with 1 - 2 lamda diameter is forming on the axis. The stabilisation is related to laser light having passed the transparent parts of the foil in the wing region and encompassing the still opaque central clump. This feature is observed consistently in 2D and 3D simulations. It depends on a laser pulse shape with high contrast ratio.
  04/2009;