Proton beam quality enhancement by spectral phase control of a PW-class laser system
T. Ziegler, D. Albach, C. Bernert, S. Bock, F. -E. Brack, T. E. Cowan, N. P. Dover, M. Garten, L. Gaus, R. Gebhardt, I. Goethel, U. Helbig, A. Irman, H. Kiriyam… 展开作者
T. Ziegler, D. Albach, C. Bernert, S. Bock, F. -E. Brack, T. E. Cowan, N. P. Dover, M. Garten, L. Gaus, R. Gebhardt, I. Goethel, U. Helbig, A. Irman, H. Kiriyama, T. Kluge, A. Kon, S. Kraft, F. Kroll, M. Loeser, J. Metzkes-Ng, M. Nishiuchi, L. Obst-Huebl, T. Püschel, M. Rehwald, H. -P. Schlenvoigt, U. Schramm, K. Zeil
We report on experimental investigations of proton acceleration from solid foils irradiated with PW-class laser-pulses, where highest proton cut-off energies were achieved for temporal pulse parameters that varied significantly from those of an ideally Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto-optic programmable dispersive filter enabled us to manipulate the temporal shape of the last picoseconds around the main pulse and to study the effect on proton acceleration from thin foil targets. The results show that applying positive third order dispersion values to short pulses is favourable for proton acceleration and can lead to maximum energies of 70 MeV in target normal direction at 18 J laser energy for thin plastic foils, significantly enhancing the maximum energy compared to ideally compressed FTL pulses. The paper further proves the robustness and applicability of this enhancement effect for the use of different target materials and thicknesses as well as laser energy and temporal intensity contrast settings. We demonstrate that application relevant proton beam quality was reliably achieved over many months of operation with appropriate control of spectral phase and temporal contrast conditions using a state-of-the-art high-repetition rate PW laser system.
We propose a hybrid laser-driven ion acceleration scheme using a combination target of a solid foil and a density-tailored background plasma. In the first stage, a sub-relativistic proton beam can be generated by the radiation pressure acceleration in the intense laser interaction with the solid foil. In the second stage, this sub-relativistic proton beam is further accelerated by the laser wakefield driven by the same laser pulse in a near-critical-density background plasma with a decreasing density profile. The propagating velocity of the laser front and the phase velocity of the excited wak…
A method of generating spin polarized proton beams from a gas jet by using a multi-petawatt laser is put forward. With currently available techniques of producing pre-polarized monatomic gases from photodissociated hydrogen halide molecules and petawatt lasers, proton beams with energy ~ 50 MeV and ~ 80 % polarization are proved to be obtained. Two-stage acceleration and spin dynamics of protons are investigated theoretically and by means of fully self-consistent three dimensional particle-in-cell simulations. Our results predict the dependence of the beam polarization on the intensity of the …
Optimization of laser-driven proton acceleration in a near-critical-density plasma
State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education, CAPT, School of Physics, Peking University（北京大学物理学院，核物理与技术国家重点实验室，教育部高能量密度物理重点实验室，CAPT）；Institute of Theoretical Physics, Chinese Academy of Sciences（中国科学院理论物理研究所）；Institute of Modern Physics, Fudan University（复旦大学现代物理研究所）；Hunan Provincial Key Laboratory of High-Energy Scale Physics and Applications, School of Physics and Electronics, Hunan University（湖南大学物理与电子学院，高能标物理与应用湖南省重点实验室）；Beijing Laser Acceleration Innovation Center（北京激光加速创新中心）
Post-acceleration of protons in helical coil targets driven by intense, ultrashort laser pulses can enhance the ion energy by utilizing the transient current originating from the self-discharging of the targets. The acceleration length of the protons can exceed a few millimeters, and the accelerating gradient is in the order of GeV/m. How to ensure the synchronization of the accelerating electric field with the protons is a crucial problem for an efficient post-acceleration. In this paper, we study how the electric field mismatch induced by the current dispersion affects the synchronous accele…
The interaction of micro- and nano-structured target surfaces with high-power laser pulses is being widely investigated for its unprecedented absorption efficiency. We have developed vertically aligned metallic micro-pillar arrays for laser-driven proton acceleration experiments. We demonstrate that such targets help strengthen interaction mechanisms when irradiated with high-energy-class laser pulses of intensities $\sim$ $10^{17-18}$ W/cm$^2$. In comparison with standard planar targets, we witness strongly enhanced hot-electron production and proton acceleration both in terms of maximum ener…
Laser accelerators can provide proton beams with unique qualities, such as micron size, picosecond pulse duration and high peak current, and have been demonstrated for various applications and for scientific research purposes. The effect of the space charge force in high peak current beams is strong and raises challenges for application after beam transportation. We performed two-dimensional particle-in-cell simulations and studied the influence of electrons that have velocities close to that of the protons after laser acceleration. We employed ellipsoid models with different charge distributi…
We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the PIC simulation code VLPL to make theoretical predictions about the behavior of proton spins in laser-induced plasmas. Simulations of spin-polarized targets show that the polarization is conserved during the acceleration process. For the experimental realization, a polarized HCl gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the…
Proton beams with up to 100 pC bunch charge, 0.48 MeV cut-off energy and divergence as low as a $3^{\circ}$ were generated from solid targets at kHz repetition rate by a few-mJ femtosecond laser under controlled plasma conditions. The beam spatial profile was measured using a small aperture scanning time-of-flight detector. Detailed parametric studies were performed by varying the surface plasma scale length from 8 to 80 nm and the laser pulse duration from 4 fs to 1.5 ps. Numerical simulations are in good agreement with observations and, together with an in-depth theoretical analysis of the a…
We consider the generation of a quasistatic longitudinal electric field by intense laser pulses propagating in a transparent plasma with radiation friction taken into account. For both circular and linear polarization of the driving pulse we develop a 1D analytical model of the process, which is valid in a wide range of laser and plasma parameters. We define the parameter region where radiation friction results in an essential enhancement of the longitudinal field. The amplitude and the period of the generated longitudinal wave are estimated and optimized. Our theoretical predictions are confi…
A cascaded ion acceleration scheme is proposed by use of ultrashort laser-irradiated microtubes. When the electrons of a microtube are blown away by intense laser pulses, strong charge-separation electric fields are formed in the microtube both along the axial and along the radial directions. By controlling the time delay between the laser pulses and a pre-accelerated proton beam injected along the microtube axis, we demonstrate that this proton beam can be further accelerated by the transient axial electric field in the laser-irradiated microtube. Moreover, the collimation of the injected pro…
Relativistically Induced Transparency Acceleration (RITA) of Protons and Light-ions with Ultrashort Laser Interaction with Heavy-ion Plasma Density Gradient
Surface plasmon (SP) excitation in intense laser interaction with solid target can be exploited for enhancing secondary emissions, in particular efficient acceleration of high charge electron bunches. Previous studies have mostly used grating coupling to allow SP excitation, which requires stringent laser contrast conditions to preserve the structural integrity of the target. Here we show via simulations that efficient SP electron acceleration for currently available short pulse lasers can occur in a flat foil irradiated at parallel or grazing incidence ($\sim 5^\circ$ with the target surface)…
We theoretically investigate high energy, collimated proton beam with three dimensional particle in cell simulations of ultrashort petawatt laser interaction with cryogenic hydrogen target of various shapes. Here we show that under appropriate conditions between the laser and target parameters, the protons are accelerated to high energies mainly due to collisionless shock acceleration mechanism combined with TNSA. The dependence of the protonic energy on the laser field, target shape and thickness is reported. It is demonstrated that the irradiation of intense laser (20fs, 2PW) with cryogenic …
We report the experimental results of the commissioning phase in the 10 PW laser beamline of Shanghai Superintense Ultrafast Laser Facility (SULF). The peak power reaches 2.4 PW on target without the last amplifying during the experiment. The laser energy of 72\pm 9 J is directed to a focal spot of ~6 μm diameter (FWHM) in 30 fs pulse duration, yielding a focused peak intensity around 2.0 \times 10^{21} W/cm^2. First laser-proton acceleration experiment is performed using plain copper and plastic targets. High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using co…
We demonstrate in this research the quasi-monoenergetic electron and proton acceleration through three dimensional particle-in-cell simulations of short petawatt circular polarized laser pulse interactions with near critical density hydrogen target. We numerically show that under controlled choice of laser and target parameters, the high energy electrons and protons can be illustrated in experiment at advanced high power laser facilities eg ELI - ALPS. We detailed the microphysics involved in the acceleration mechanism, which required investigating the role of plasma density gradients, plasma …
We propose a scheme to overcome the great challenge of polarization loss in spin-polarized ion acceleration. When a petawatt laser pulse penetrates through a compound plasma target consisting of a double layer slab and prepolarized hydrogen halide gas, a strong forward moving quasistatic longitudinal electric field is constructed by the self-generated laser-driven plasma. This field with a varying drift velocity efficiently boosts the prepolarized protons via a two-stage coherent acceleration process. Its merit is not only achieving a highly energetic beam but also eliminating the undesired po…
A new scheme of proton acceleration from a laser-driven near-critical-density plasma is proposed. Plasma with a tailored density profile allows a two-stage acceleration of protons. The protons are pre-accelerated in the laser-driven wakefields, and are then further accelerated by the collisionless shock, launched from the rear side of the plasma. The shock has a small transverse size, and it generates a strong space-charge field, which defocuses protons in such a way, that only those protons with the highest energies and low energy spread remains collimated. Theoretical and numerical analysis …
Using two-dimensional particle-in-cell simulations, we examine how an externally applied strong magnetic impacts proton acceleration in laser-irradiated solid-density targets. We find that a kT-level external magnetic field can sufficiently inhibit transverse transport of hot electrons in a flat laser-irradiated target. While the electron heating by the laser remains mostly unaffected, the reduced electron transport during proton acceleration leads to an enhancement of maximum proton energies and the overall number of energetic protons. The resulting proton beam is much better collimated compa…
Target shape effects on monoenergetic GeV proton acceleration
圆偏振激光脉冲与薄膜靶相互作用时，可分为预打孔、打孔和光帆加速三个阶段。我们研究了第一阶段的电子和离子动力学，并找到了给定激光强度的最小箔厚度要求。基于此分析，我们建议使用一个形状的箔离子加速，其厚度横向变化，以匹配激光强度。然后，目标演化为三个区域：加速度区域、透明区域和变形区域。在加速区域中，靶可以被均匀地加速，从而产生单能且空间准直的离子束。详细的数值模拟进行检查该计划的可行性和鲁棒性，如形状因子和表面粗糙度的影响。在三维粒子模拟中，当激光脉冲聚焦强度为1022 W = cm ~ 2时，观察到了GeV单能质子束流。激光脉冲到加速质子束的能量转换效率大于23%。在相互作用中还检查了同步辐射和阻尼效应。
The production of polarized proton beams with multi-GeV energies in ultra-intense laser interaction with targets is studied with three-dimensional Particle-In-Cell simulations. A near-critical density plasma target with pre-polarized proton and tritium ions is considered for the proton acceleration. The pre-polarized protons are initially accelerated by laser radiation pressure before injection and further acceleration in a bubble-like wakefield. The temporal dynamics of proton polarization is tracked via the T-BMT equation, and it is found that the proton polarization state can be altered bot…
The use of ultrathin solid foils offers optimal conditions for accelerating protons from laser-matter interactions. When the target is thin enough that relativistic self-induced transparency (RSIT) sets in, all of the target electrons get heated to high energies by the laser, which maximizes the accelerating electric field and therefore the final ion energy. In this work, we first investigate how ion acceleration by ultraintense femtosecond laser pulses in transparent CH$_2$ solid foils is modified when turning from normal to oblique ($45^\circ$) incidence. Due to stronger electron heating, we…
Laser-plasma proton acceleration was investigated in the Target Normal Sheath Acceleration (TNSA) regime using a novel gas-foil target. The target is designed for reaching higher laser intensity at the foil plane owing to relativistic self-focusing and self compression of the pulse in the gas layer. Numerical 3D particle-in-cell (PIC) simulations were used to study pulse propagation in the gas, showing a nearly seven-fold increase in peak intensity. In the experiment, maximum proton energies showed high dependence on the energy transmission of the laser through the gas and a lesser dependence …
We have investigated proton acceleration in the forward direction from a near-critical density hydrogen gas jet target irradiated by a high intensity (10^18 W/cm^2), short-pulse (5 ps) laser with wavelength of 1.054 micron. We observe the signature of shock acceleration driven by the laser pulse, leading to monoenergetic proton beams with small divergence in addition to the commonly used electron-sheath driven proton acceleration. The proton energies we obtained are modest (~MeV), but prospects for improvement are offered through tailoring the gas jet density profile. Also, we observe that thi…
The paper reports the results of two-dimensional particle-in-cell simulations of proton beam acceleration at the interactions of a 130 fs laser pulse of intensity from the range of 10^21-10^23 W/cm^2, predicted for the Extreme Light Infrastructure (ELI) lasers currently built in Europe, with a thin hydrocarbon (CH) target. A special attention is paid to the effect of the laser pulse intensity and polarization (linear-LP, circular-CP) as well as the target thickness on the proton energy spectrum, the proton beam spatial distribution and the proton pulse shape and intensity. It is shown that for…
A continuous cryogenic hydrogen cluster-jet target has been developed for laser-plasma interaction studies, in particular as a source for the acceleration of protons. Major advantages of the cluster-jet target are the compatibility with pulsed high repetition lasers and the absence of debris. The cluster-jet target was characterized using the Mie-scattering technique allowing to determine the cluster size and to compare it with an empirical prediction. In addition, an estimation of the cluster beam density was performed. The system was implemented at the high power laser system ARCTURUS and fi…
The impact of stochasticity effects (SEs) in photon emissions on the proton energy spectra during laser-plasma interaction is theoretically investigated in the quantum radiation-dominated regime, which may facilitate SEs experimental observation. We calculate the photon emissions quantum mechanically and the plasma dynamics semiclassically via two-dimensional particle-in-cell simulations. An ultrarelativistic plasma generated and driven by an ultraintense laser pulse head-on collides with another strong laser pulse, which decelerates the electrons due to radiation-reaction effect and results i…
We present a setup for highly polarized proton beams using two parallel propagating laser pulses that have a carrier envelope phase difference of $π$. This mechanism is examined utilizing particle-in-cell simulations and compared to a single-pulse setup commonly used for magnetic vortex acceleration. We find that the use of the dual-pulse setup allows for peak energies of 124 MeV and good angular spread for two pulses with normalized laser vector potential $a_0 = 100$. Compared to a single pulse, we further observe higher polarization of the accelerated bunch.
Laser ion acceleration from concave targets by subpicosecond pulses
Princeton Plasma Physics Laboratory（普林斯顿等离子体物理实验室）；Focused Energy Inc.（聚焦能源公司）；Department of Astrophysical Sciences, Princeton University（普林顿大学天体科学系）；University of Texas at Austin（德克萨斯大学奥斯汀分校）；University of York（约克大学）
The radiation pressure acceleration (RPA) of charged particles has been considered a challenging task in laser particle acceleration. Laser-driven proton/ion acceleration has attracted considerable interests due to its underlying physics and potential for applications such as high-energy density physics, ultrafast radiography, and cancer therapy. Among critical issues to overcome the biggest challenge is to produce energetic protons using an efficient acceleration mechanism. The proton acceleration by radiation pressure is considerably more efficient than the conventional target normal sheath …
A scheme for controlling the direction of energetic proton beam driven by intense laser pulse is proposed. Simulations show that a precisely directed and collimated proton bunch can be produced by a sub-picosecond laser pulse interacting with a target consisting of a thin solid-density disk foil with a solenoid coil attached to its back at the desired angle. It is found that two partially overlapping sheath fields are induced. As a result, the accelerated protons are directed parallel to the axis of the solenoid, and their spread angle is also reduced by the overlapping sheath fields. The prot…
Understanding the mechanisms of proton energy deposition in matter and subsequent damage formation is fundamental to radiation science. Here we exploit the picosecond (10^-12 s) resolution of laser-driven accelerators to track ultra-fast solvation dynamics for electrons due to proton radiolysis in liquid water (H2O). Comparing these results with modelling that assumes initial conditions similar to those found in photolysis reveals that solvation time due to protons is extended by > 20 ps. Supported by magneto-hydrodynamic theory this indicates a highly dynamic phase in the immediate aftermath …
