Quasi-monoenergetic Proton Beam Research Articles

High-density quasi-monoenergetic proton beam generation from vacuum sandwiched target

An efficient scheme has been proposed for generating a high-density proton beam by enhancing the accelerating field from the interaction of an intense laser with a vacuum sandwiched target. The prime role of the vacuum gap is to reduce the effect of the sudden shock, exerted by the front edge of the intense laser, on the hydrogen layer. It is shown that the accelerated proton beam quality could be significantly enhanced due to the presence of the vacuum gap. We found that the total number of the accelerated protons is about 17.5 (1.7) and the proton beam peak is about 6.5 (3.7) times higher as compared to the single (double) layer target case. The dependence of the proton acceleration on the different layer thickness, density, and laser pulse intensity has also been studied.

High-energy quasi-monoenergetic proton beam from micro-tube targets driven by Laguerre–Gaussian lasers

High-energy proton beams with low energy spread and angular divergence are highly valuable in various applications, such as proton therapy, ultrafast science, and nuclear physics. Laser-driven ion sources are being explored as a more compact and cost-effective alternative to conventional accelerators. However, producing high-quality proton beams using lasers has been a significant challenge. In this study, we propose a novel approach to achieve high-energy quasi-monoenergetic proton beams by utilizing a Laguerre–Gaussian (LG) laser to irradiate a solid hollow tube target. Our three-dimensional particle-in-cell simulations demonstrate that the LG laser efficiently pulls out and accelerates electrons. As these electrons exit the rear side of the tube, a charge-separation electric field for proton acceleration is self-established. Meanwhile, a considerable part of the electrons are confined to the laser axis by the ponderomotive force of the LG laser, generating a longitudinal bunching field and transverse focusing field. As a result, protons are accelerated and focused in these fields, producing a high- quality proton beam with high energy (247 MeV) and low energy spread (∼2%) using an LG laser with an intensity of W cm−2 and a tube target with an electron density of 40nc . In comparison to a standard Gaussian laser, the LG laser exhibits superior performance in terms of proton cut-off energy, energy spread, and angular divergence.

Cascaded solenoid acceleration of vortex laser-driven collimated proton beam

Efficient cascaded proton acceleration driven by an intense Laguerre–Gaussian (LG) laser is realized in combined three-dimensional particle-in-cell simulations and CST STUDIO SUITE (CST) simulations. CST simulations show that there is no divergent force component in the transverse direction in the coil center. Therefore, the collimated proton beam driven by the LG laser in the first stage benefits from the uniform beam acceleration in the second stage. By contrast, the proton beam with larger divergence disperses to the outside of the coil because of the divergent force near the coil wire in the Gaussian laser case. Finally, a quasi-monoenergetic proton beam with a higher flux is generated by the LG laser, which is much better than the Gaussian laser case. The obtained proton beam can potentially be used in some special applications, such as proton radiography, fast ignition of fusion targets, biomedical applications, and production of warm dense matter.

Efficient ion acceleration driven by a Laguerre–Gaussian laser in near-critical-density plasma

Laser-driven ion accelerators have the advantages of compact size, high density, and short bunch duration over conventional accelerators. Nevertheless, it is still challenging to generate ion beams with quasi-monoenergetic peak and low divergence in experiments with the current ultrahigh intensity laser and thin target technologies. Here we propose a scheme that a Laguerre–Gaussian laser irradiates a near-critical-density (NCD) plasma to generate a quasi-monoenergetic and low-divergence proton beam. The Laguerre–Gaussian laser pulse in an NCD plasma excites a moving longitudinal electrostatic field with a large amplitude, and it maintains the inward bowl-shape for dozens of laser durations. This special distribution of the longitudinal electrostatic field can simultaneously accelerate and converge the protons. Our particle-in-cell (PIC) simulation shows that the efficient proton acceleration can be realized with the Laguerre–Gaussian laser intensity ranging from 3.9 × 1021 W⋅cm−2–1.6 × 1022 W⋅cm−2 available in the near future, e.g., a quasi-monoenergetic proton beam with peak energy ∼ 115 MeV and divergence angles less than 5° can be generated by a 5.3 × 1021 W⋅cm−2 pulse. This work could provide a reference for the high-quality ion beam generation with PWclass laser systems available recently.

The Effect of the Laser Light Polarization on the Generation of Proton Ignitor Beam

In this study, the effect of laser light polarization (linear polarization (LP) and circular polarization (CP)) on the shape of the proton energy spectrum and its energy cut-off is explored. The obtained results from 1D3V PIC simulation showed that two different acceleration mechanisms including target normal sheath acceleration (TNSA) and radiation pressure acceleration (RPA) are dominant. It is found that for the amplitude of a = 27 and pulse duration 333 fs when the laser polarization is changed from LP to CP, the electron heating is reduced which caused the generation of the multi-peak quasi-monoenergetic proton beam. Then by applying the 1D3T hydrodynamic code, the potential of the aforementioned proton beam with a high peak energy 510 MeV to irradiation on pre-compressed DT capsule was examined. Finally, the proton ignition energy threshold at a distance of 0.78 cm between the proton source and pre-compressed DT fuel capsule was investigated. (The threshold proton ignition energy is 15.52 kJ)

Electron and ion acceleration from femtosecond laser-plasma peeler scheme

Using three-dimensional particle-in-cell simulations, we further investigate the electron and ion acceleration from femtosecond laser–plasma peeler scheme which was proposed in our recent paper (Shen et al 2021 Phys. Rev. X 11 041002). In addition to the standard setup where a laser pulse impinges on an edge of a single tape target, two new variants of the target, i.e. a parallel tape and a cross tape target, were proposed, where strong surface plasma waves can also be efficiently excited at the front edges of the target. By using a tabletop 200 TW-class laser pulse, we observe generation of high-flux, well-collimated, superponderomotive electrons. More importantly, quasimonoenergetic proton beams can always be obtained in all the three setups, while with the single tape case, the obtained proton beam has the highest peak energy and narrowest spectrum.

Proton acceleration from picosecond-laser interaction with a hydrocarbon target

As an intense picosecond laser pulse irradiates a hydrocarbon target, the protons therein can be accelerated by the radiation pressure as well as the sheath field behind the target. We investigate the effect of the laser and hydrocarbon target parameters on proton acceleration with two/three-dimensional particle-in-cell simulations. It is found that the resulting two-ion species plasma can generate a multiple peaked charge-separation field that accelerates the protons. In particular, a smaller carbon-to-hydrogen ratio, as well as the thinner and/or lower density of the target, leads to a larger sheath field and thus proton beams with a larger cutoff energy and smoother energy spectrum. These results may be useful in achieving high-flux quasi-monoenergetic proton beams by properly designing the hydrocarbon target.

Simulation study of quasi-monoenergetic high-energy proton beam based on multiple laser beams driving

High-energy proton beams have extensive and important applications. Traditional proton accelerators are bulky and costly. The high-power laser pulse technology provides a new proton acceleration scheme based on the interaction between laser and plasma, and has the advantage of miniaturization. Furthermore, comparing with traditional proton accelerators, the proton acceleration gradient by high-power laser pulses can be increased by three orders of magnitude. The proton beams with high brightness, narrow pulse width, and good directionality can be generated in theory within a very small effective size, and they are suitable for fields such as nuclear physics and particle physics, ion beam fast ignition, medical treatment, and proton beam detection. In order to realize laser proton acceleration, a great many of researches of different target configurations and acceleration mechanisms have been reported on proton acceleration driven by ultrashort and high-power lasers. However, owing to the limitation of laser intensity, the energy of proton beam driven by a single-beam laser is difficult to improve to meet the needs of medical applications. In this paper, a new method of driving proton acceleration by multiple ultrashort high-power lasers with grazing incidence on both sides of the microstrip target is proposed. A proton beam with an energy divergence of about 3% and energy of about 165 MeV can be obtained by using the two-beam driving setting. The results of two-dimensional particle-in-cell simulation show that a large number of collimated high-energy electron charges are extracted from both sides of the solid target by laser and injected into the back of the target. A longitudinal bunching field is established on the back of the target, which drives protons to accelerate and bunch to form a quasi-monoenergetic high-energy proton beam. The research also shows that the proton beam with an energy divergence of about 2% and energy of about 250 MeV can be obtained by using four grazing ultrashort high-power lasers on both sides of the microstrip target. The mechanism of multi-laser beams driving proton acceleration provides a new idea for the energy enhancement of the proton beam, and the quasi-monoenergetic high-energy proton beam is expected to be applied to the field of medical treatment.

Bunched Proton Acceleration from a Laser-Irradiated Cone Target

Laser-driven ion acceleration is an attractive technique to generate compact high-energy ion sources. Currently, among various physical and technical issues to be solved, boosting the ion energy and reducing the energy spread represent the key challenges with this technique. Here we present a scheme to tackle these challenges by using a hundred-terawatt-class laser pulse irradiating a cone target. Three-dimensional particle-in-cell simulations show that a large number of electrons are dragged out of the cone walls and accelerated to hundreds of MeV by the laser fields inside the cone. When these energetic dense electron beams pass through the cone target tip into vacuum, a very high bunching acceleration field, up to tens of TV/m, quickly forms. Protons are accelerated and simultaneously bunched by this field, resulting in quasimonoenergetic proton beams with 100 MeV energy and low energy spread of about 2%. Results exploring the scaling of the proton beam energy with laser and target parameters are presented, indicating that the scheme is robust. This opens an efficient route for compact high-energy proton sources for fundamental research and biomedical applications.

Theoretical Study of the Efficient Ion Acceleration Driven by Petawatt-Class Lasers via Stable Radiation Pressure Acceleration

Laser-driven radiation pressure acceleration (RPA) is one of the most promising candidates to achieve quasi-monoenergetic ion beams. In particular, many petawatt systems are under construction or in the planning phase. Here, a stable radiation pressure acceleration (SRPA) scheme is investigated, in which a circularly-polarized (CP) laser pulse illuminates a CH2 thin foil followed by a large-scale near-critical-density (NCD) plasma. In the laser-foil interaction, a longitudinal charge-separated electric field is excited to accelerate ions together with the heating of electrons. The heating can be alleviated by the continuous replenishment of cold electrons of the NCD plasma as the laser pulse and the pre-accelerated ions enter into the NCD plasma. With the relativistically transparent propagation of the pulse in the NCD plasma, the accelerating field with large amplitude is persistent, and its propagating speed becomes relatively low, which further accelerates the pre-accelerated ions. Our particle-in-cell (PIC) simulation shows that the SRPA scheme works efficiently with the laser intensity ranging from 6.85×1021 W cm−2 to 4.38×1023 W cm−2, e.g., a well-collimated quasi-monoenergetic proton beam with peak energy ∼1.2 GeV can be generated by a 2.74 × 1022 W cm−2 pulse, and the energy conversion efficiency from the laser pulse to the proton beam is about 16%. The QED effects have slight influence on this SRPA scheme.

Experimental study on the dynamic compression of materials at XGIII facility by laser proton photography

A new method for material dynamic density measurement based on proton photography is developed at XGIII facility. The protons produced by the picosecond laser of XGIII was used as the proton source to diagnose the density distribution of lattice foam under the compression of the nanosecond beam of XGIII. The density of lattice foam was calculated from the photographic results using Monte Carlo simulation method. Benefitting fromn this newly developed method, the images of the compressed lattice foam and the shock front at 5.2 ns is obtained successfully. The density distribution of the lattice foam was obtained from the images and the density of lattice foam increases about 20 times at the shock front due to the compression of the shock. The velocity of shock wave in lattice foam is also given, about 40 km/s. The density and spatial resolution of the method are further calibrated by using diamond step objects, and experimental results show that they are better than 4% and 12 <i>μ</i>m, respectively. In order to further improve the density and spatial resolution of the proton photography at XGIII facility, a new radiogrphy method utilizing quasimonoenergetic proton beams obtained from an energy selector is proposed in this paper, and the resolution of this method is simulated by Monte Carlo program. The simulation results show that the relative density resolution can be improved to more than 1%. Through the above experimental and the simulation results, we demonstrated that diagnostic capability has been established for fast process (nanosecond scale), high pressure (nearly 100 GPa) conditions at XGIII facility.

High energy implementation of coil-target scheme for guided re-acceleration of laser-driven protons

Developing compact ion accelerators using intense lasers is a very active area of research, motivated by a strong applicative potential in science, industry and healthcare. However, proposed applications in medical therapy, as well as in nuclear and particle physics demand a strict control of ion energy, as well as of the angular and spectral distribution of ion beam, beyond the intrinsic limitations of the several acceleration mechanisms explored so far. Here we report on the production of highly collimated (sim 0.2^{circ } half angle divergence), high-charge (10s of pC) and quasi-monoenergetic proton beams up to sim 50 MeV, using a recently developed method based on helical coil targetry. In this concept, ions accelerated from a laser-irradiated foil are post-accelerated and conditioned in a helical structure positioned at the rear of the foil. The pencil beam of protons was produced by guided post-acceleration at a rate of sim 2 GeV/m, without sacrificing the excellent beam emittance of the laser-driven proton beams. 3D particle tracing simulations indicate the possibility of sustaining high acceleration gradients over extended helical coil lengths, thus maximising the gain from such miniature accelerating modules.

Laser-driven generation of collimated quasi-monoenergetic proton beam using double-layer target with modulated interface

Usage of double-layer targets consisting of heavy and light material with modulated interface between them provides a way for laser-driven generation of collimated ion beams. With extensive 2D3V PIC simulations we show that this configuration may result in a development of a relativistic instability with Rayleigh-Taylor and Richtmyer-Meshkov like features. Initially small perturbations are amplified during the laser-target interaction leading to the formation of low-density plasma regions and high-density bunches between them, which are accelerated by the laser radiation pressure as whole compact structures. That results in collimated quasi-monoenergetic proton beam with high average energy. The properties of this proton beam such as its low emittance (one order of magnitude lower compared to that of conventional accelerators) and divergence are discussed. Results are compared with similar acceleration schemes such as double-layer target without corrugation and single-layer target.

Hybrid graphene-based material promising target in laser matter interaction

Graphene oxide foils implanted with copper ions at low energy and high dose, have been proposed as hybrid graphene-based materials suitable to be laser irradiated in vacuum to produce hot plasmas. The special lattice structure of the graphene oxide foil can improve the propagation of the laser accelerated electrons inside the foil and to enhance the electron density emerging from the rear foil surface. In such conditions the electric field developed in the non-equilibrium plasma increases and consequently in the forward ion acceleration. The foils have been optimized in thickness and they were irradiated with optimized laser parameters in order to produce high energy and quasi-monoenergetic proton beams by the femtosecond laser at the Institute of Plasma Physics and Laser Microfusion in Warsaw, Poland. Gaf chromic film and silicon carbide detectors were used to monitor the plasma properties and to measure the velocity of the emitted protons and carbon ions from plasma.

Proton acceleration in a laser-induced relativistic electron vortex

We show that when a solid plasma foil with a density gradient on the front surface is irradiated by an intense laser pulse at a grazing angle,${\sim}80^{\circ }$, a relativistic electron vortex is excited in the near-critical-density layer after the laser pulse depletion. The vortex structure and dynamics are studied using particle-in-cell simulations. Due to the asymmetry introduced by non-uniform background density, the vortex drifts at a constant velocity, typically$0.2{-}0.3$times the speed of light. The strong magnetic field inside the vortex leads to significant charge separation; in the corresponding electric field initially stationary protons can be captured and accelerated to twice the velocity of the vortex (100–200 MeV). A representative scenario – with laser intensity of$10^{21}~\text{W}~\text{cm}^{-2}$– is discussed: two-dimensional simulations suggest that a quasi-monoenergetic proton beam can be obtained with a mean energy 140 MeV and an energy spread of${\sim}10\,\%$. We derive an analytical estimate for the vortex velocity in terms of laser and plasma parameters, demonstrating that the maximum proton energy can be controlled by the incidence angle of the laser and the plasma density gradient.

Two-stage laser acceleration of high quality protons using a tailored density plasma

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 demonstrates production of high-energy proton beams with few tens of percents energy spread, few degrees divergence and charge of few nC. This scheme indicates the efficient generation of quasi-monoenergetic proton beams with energies up to several hundreds of MeV with PW-class ultrashort lasers.

Tri-stage quasimonoenergetic proton acceleration from a multi-species thick target

We show that quasimonoenergetic proton beams can be generated through a multi-ion thick target irradiated by a circularly polarized laser pulse. After disrupted by the transverse instabilities in the laser pressure acceleration process, heavy ions as majority species can still provide a co-moving electric field. Different from the dynamics using ultrathin foil, protons with small doped rates can experience a full tri-stage quasimonoenergetic acceleration (hole boring, sheath boosting, and free expansion stages) in this scenario. A theoretical model is developed to explain the proton energy evolution in detail and verified by two-dimensional particle-in-cell simulations. The scaling of proton energy with laser intensity indicates that the 200 MeV proton beam with narrow energy spread (3%–10%) and sufficiently large charges (1010–1011) required for medical applications can be obtained using 100s TW class laser systems in near future.

High Energy electron and proton acceleration by circularly polarized laser pulse from near critical density hydrogen gas target

Relativistic electron rings hold the possibility of very high accelerating rates, and hopefully a relatively cheap and compact accelerator/collimator for ultrahigh energy proton source. In this work, we investigate the generation of helical shaped quasi-monoenergetic relativistic electron beam and high-energy proton beam from near critical density plasmas driven by petawatt-circularly polarized-short laser pulses. We numerically observe the efficient proton acceleration from magnetic vortex acceleration mechanism by using the three dimensional particle-in-cell simulations; proton beam with peak energy 350 MeV, charge ~10nC and conversion efficiency more than 6% (which implies 2.4 J proton beam out of the 40 J incident laser energy) is reported. We detailed the microphysics involved in the ion acceleration mechanism, which requires investigating the role of self-generated plasma electric and magnetic fields. The concept of efficient generation of quasi-monoenergetic electron and proton beam from near critical density gas targets may be verified experimentally at advanced high power – high repetition rate laser facilities e.g. ELI-ALPS. Such study should be an important step towards the development of high quality electron and proton beam.

Graphite oxide based targets applied in laser matter interaction

In the present work, we propose the production of a hybrid graphene based material suitable to be laser irradiated with the aim to produce quasi-monoenergetic proton beams using a femtosecond laser system. The unique lattice structure of the irradiated solid thin target can affect the inside electron propagation, their outgoing from the rear side of a thin foil, and subsequently the plasma ion acceleration. The produced targets, have been characterized in composition, roughness and structure and for completeness irradiated. The yield and energy of the ions emitted from the laser-generated plasma have been monitored and the emission of proton stream profile exhibited an acceleration of the order of several MeVs/charge state.

Collimated protons accelerated from an overdense gas jet irradiated by a 1\u2009\xb5m wavelength high-intensity short-pulse laser

We have investigated proton acceleration in the forward direction from a near-critical density hydrogen gas jet target irradiated by a high intensity (1018 W/cm2), short-pulse (5 ps) laser with wavelength of 1.054 μm. We observed the signature of the Collisionless Shock Acceleration mechanism, namely quasi-monoenergetic proton beams with small divergence in addition to the more commonly observed electron-sheath driven proton acceleration. The proton energies we obtained were modest (~MeV), but prospects for improvement are offered through further tailoring the gas jet density profile. Also, we observed that this mechanism is very robust in producing those beams and thus can be considered as a future candidate in laser-driven ion sources driven by the upcoming next generation of multi-PW near-infrared lasers.