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In this paper, we have studied the influence of laser polarization on the dynamics of the ionization-injected electron beams, and subsequently, the properties of the emitted betatron radiation in laser wakefield accelerators (LWFAs). While ionizing by strong field laser radiation, the generated photo-electrons carry a residual transverse momentum in excess of the ionization potential via the above threshold ionization (ATI) process. This ATI momentum explicitly depends on the polarization state of the ionizing laser and eventually governs the dynamics of the electron beam trapped inside the wake potential. In order to systematically investigate the effect of the laser polarization, here, we have employed complete three-dimensional particle-in-cell simulations in the nonlinear bubble regime of the LWFAs. We focus, in particular, on the effects the laser polarization has on the ionization injection mechanism, and how these features affect the final beam properties, such as beam charge, energy, energy spread, and transverse emittance. We have also found that as the laser polarization gradually changes from linear to circular, the helicity of the electron trajectory, and hence the angular momentum carried by the beam, increases significantly. Studies have been further extended to reveal the effect of laser polarization on the radiation emitted by the accelerated electrons. The far-field radiation spectra have been calculated for the linear and circular polarization states of the laser. It has been shown that the spatial distributions and the polarization properties (Stokes parameters) of the emitted radiation in the above two cases are substantially different. Therefore, our study provides a facile and efficient alternative to regulate the properties of the accelerated electron beams and x-ray radiation in LWFAs, utilizing ionization injection mechanism. [ABSTRACT FROM AUTHOR]

The laser wakefield acceleration (LWFA) is a highly significant phenomenon within the realm of high-energy physics and the study of interactions between lasers and plasmas. This research is aimed at conducting a thorough comparative analysis of two distinct pulse shapes, namely, Gaussian and sinh-Gaussian, in order to examine their individual effects on the production and propagation of wakefield in plasma. The research utilizes analytical techniques to evaluate the wake potential, wakefield, and electron energy gain that are produced. The research findings demonstrate that the selection of pulse form has a substantial impact on the development of wakefield and their corresponding characteristics. The utilization of a sinh-Gaussian pulse with a greater decentered parameter (b = 2) is deemed highly appropriate for the purpose of wakefield creation and the subsequent augmentation of electron energy. It provides valuable insights for researchers who are interested in fully utilizing laser-driven plasma wakefield for a variety of applications, including high-energy particle accelerators and compact radiation sources. [ABSTRACT FROM AUTHOR]

Ultra-intense laser-plasma wakefield accelerator possess several superior properties compared with the traditional radio-frequency accelerators. These characteristics include femtosecond duration, micro-source size, and ultra-dense beam density, result in highly advantageous for various important applications. In this paper, we reviewed the generation of ultra-intense and high charge electron beam based on laser-plasma acceleration and its nuclear applications in Shanghai Jiao Tong University, including the production of 10 s nC charge beams, the generation of ultra-high flux neutron source on the order of 1019 n/cm2/s, and the excitation of nuclear isomers with the peak efficiency on the order of 1015 particle/s. This laser driving ultra-dense electron source, in conjunction with the plasma environment, presents immense potential in addressing critical problems in astrophysics, and facilitating various nuclear applications. Based on above progress in nuclear astrophysics, a new research plateform about laboratory astrophysics with a 2.5 PW laser will be constructed in TDLI institute.

Laser Wakefield Acceleration (LWFA) has emerged as a groundbreaking approach for generating ultra-high energy electron beams over short distances, revolutionizing the field of particle acceleration. In this paper, we investigate the novel concept of employing sin-Gaussian laser pulse for enhanced LWFA performance. sin-Gaussian pulses combine the advantageous features of both sinusoidal and Gaussian pulse shapes, offering unique opportunities for generating the plasma wakefield and optimizing electron acceleration. We present a comprehensive theoretical analysis of the interaction between a sin-Gaussian laser pulse and an underdense plasma medium, elucidating the intricate dynamics of the wakefield excitation and electron acceleration. Through analytical study, we demonstrate that the sin-Gaussian pulse configuration leads to a significant energy gain (Maximum gain of 2.06 GeV with chosen parameters) for plasma electrons. Furthermore, we explore the effects of varying key parameters such as the laser electric field amplitude and beam waist on the acceleration performance. Our findings reveal the underlying physics governing the interplay between these parameters and the resulting electron energy spectra for LWFA outcomes. [ABSTRACT FROM AUTHOR]

Recently, co-propagating two-color laser pulses have been extensively used to study the attosecond pulse generation, for controlling the electron motion at femtosecond and attosecond time scales, for high harmonic generation in solids and gases, etc. In this paper, we have studied the co-propagational effect of two Gaussian laser pulses of different pulse length and frequency ( ω 1 ≈ 2 ω p and ω 2 ≈ ω p ) through under-dense plasma. Plasma density satisfies the condition of beating to generate maximum wakefield, i.e., the difference of frequency is equal to the frequency of first pulse and equal to plasma frequency (ω 1 - ω 2 ≈ ω p) also. Longitudinal force on electron and laser wakefield developed in plasma are studied analytically. Under the above-stated conditions, approximately 6 times stronger longitudinal force is experienced by the electrons as compared to individual single pulse. An enhanced laser wakefield has also been observed. This study is carried out for optimizing the parameters of lasers and plasma medium to maximize the electron energy gain. [ABSTRACT FROM AUTHOR]

Laser wakefield acceleration is a frequently utilised research methodology for enhancing the energy levels of lighter charged particles, specifically electrons, to relativistic magnitudes. In this investigation, we utilised a linear polarised Gaussian-like laser pulse that propagated along the z-axis through cold collisionless underdense plasma in weakly nonlinear regime. An external planer magnetic wiggler field is applied along the y-axis. The influence of various critical parameters, such as amplitude and propagation constant of wiggler magnetic field, amplitude of laser electric field and laser pulse length on the wakefield and electron energy gain has been studied. A wiggler-assisted laser wakefield accelerator, the electron energy and wakefield evolution can be tuned by the wiggler magnetic field strength. The numerical findings demonstrate that by varying the strength of wiggler magnetic field and laser electric field, the amplitude of the wakefield is affected significantly. Furthermore, the equality of the order of pulse length and plasma wavelength is essential to obtain energy efficient acceleration mechanism. By employing specific parameters, a maximum energy increase of 2.26 GeV is achieved. This research will aid in the development of an energy-efficient electron acceleration technology by choosing suitable laser and plasma parameters. [ABSTRACT FROM AUTHOR]

The laser wakefield acceleration (LWFA) scheme is now a superb and potent instrument for industry, medicine, fusion, and other uses. With the aid of this technique, high-quality electron beams can be generated, which might eventually be employed to create small, portable X-ray sources. Using a linearly polarized Gaussian laser pulse, the present work focuses on examining electron acceleration in an under-dense plasma having a ramp profile with different density-hill widths. Two-dimensional Fourier–Bessel Particle-In-Cell simulation (2D-FBPIC) code shows that optimizing the laser parameters and plasma density profile maximizes the energy gain and minimizes the normalized rms emittance in the x, y directions inside the plasma bubble. For 10 and 90 μ m density-hill widths, respectively, the optimal emittance value is reported to be ϵ x ∼ 3.10 mm.mrad in the x-direction and ϵ y ∼ 2.63 mm.mrad in the y-direction. At a density-hill width of 90 μ m , it is also observed that the charge trapped inside the bubble is 44.91 pC. With this density-hill width and a plasma channel length of 3.84 mm, our simulation findings show an energy gain of 0.38 GeV to the electron-bunch accelerated inside the bubble. [ABSTRACT FROM AUTHOR]

In this paper, the modelling and manufacturing of a two-stage supersonic gas jet nozzle enabling the formation of adaptive plasma concentration profiles for injection and acceleration of electrons using few-cycle laser beams are presented. The stages are modelled using the rhoSimpleFoam algorithm of the OpenFOAM computational fluid dynamics software. The first 200–300 ${\rm \mu}$ m diameter nozzle stage is dedicated to 1 % N2 + He gas jet formation and electron injection. By varying the pressure between the first and second stages of the injectors, the electron injection location could be adjusted, and the maximum acceleration distance could be ensured. By changing the concentration of the nitrogen in the gas mixture, the charge of the accelerated electrons could be controlled. The second nozzle stage is designed for acceleration in fully ionised He or hydrogen gas and forms the optimal plasma concentration for bubble formation depending on the laser pulse energy, duration and focused beam diameter. In order to reduce the diameter of the plasma profile formed by the first nozzle and the concentration drop gap between the two nozzles, a one-side straight section was introduced in the first nozzle. The shock wave reflected from the straight section of the wall propagates parallel to the shock wave of the intersecting supersonic jets and ensures a minimal gap between the jets. The second-stage longitudinal plasma concentration profile could have an increasing gas density gradient to compensate for dephasing between the electron bunch and the plasma wave due to wave shortening with increasing plasma concentration. [ABSTRACT FROM AUTHOR]

Laser wakefield acceleration (LWFA) of electrons is a highly promising and advanced technique within the field of laser plasma physics, which enables the generation of remarkably high-energy electron beams over a comparatively short distance. In this paper, we have used different Gaussian-like laser pulse profiles of the same amplitude of electric field and laser intensity in magnetized plasma. Generated wakefield and energy gain are calculated analytically by using equation of motion and Maxwell's equation. Our results show that generated wakefield and energy gain are greatly affected by the shape of laser electric field profile. Pulse with broader electric field profile produces more effective LWFA under identical conditions of other parameters. Energy gain by electrons increases slightly with increase in the strength of external magnetic field. Results show that for the broadest laser profile, the magnetic field has more influence on wakefield production and electron energy gain. The role of laser pulse length is also analyzed. In this study, we have obtained a maximum of 151.6 MeV energy gain with experimentally feasible parameters. Our findings will assist researchers in selecting the most energy-efficient pulse profile for LWFA. [ABSTRACT FROM AUTHOR]

Laser wakefield acceleration is one of the prominent methods to obtain high energy charge particles. This method can be used to accelerate lighter charged particles like electrons to relativistic energy level. Energy enhancement of electrons depends on the properties of laser pulse as well as plasma. In this study, we have used a circular polarized laser pulse propagating (along z- axis) through under-dense plasma. An external oblique transverse static magnetic field is applied an arbitrary angle (at angle θ with Y-axis in x–y plane). Effect of laser pulse strength (a ), strength of external magnetic field ( B 0 ), and its arbitrary angle (θ ) on generated longitudinal wakefield, wake potential, change in relativistic factor and energy enhancement are calculated theoretically and curves are drawn. Optimized oblique angle for maximum wakefield and potential is calculated for selected parameters. This study is useful for obtaining an energy efficient acceleration technique for electron. [ABSTRACT FROM AUTHOR]

Laser wakefield acceleration (LWFA) is one of the prominent energy efficient techniques to generate high potential gradient (∼ GeV/m) to accelerate electrons. The phenomenon of LWFA depends on several parameters of plasma as well as laser beam like frequency of the laser pulse, the amplitude of the laser electric field, the shape of the laser pulse, density of plasma etc. These parameters can be adjusted to optimize the energy gain of electrons. In the present paper, the wakefield excitation by both positive and negative chirped laser pulse in an under-dense plasma is investigated. Effect of laser pulse length on LWFA is also investigated. For this purpose, the 1D model of laser wakefield acceleration is revisited to obtain analytical expressions for the longitudinal wakefield generated behind the laser pulse. Curves are plotted to compare and discuss the effect of pulse length and chirp (both positive and negative). The results show that the positive chirp enhances while the negative chirp diminishes the LWFA. Also, the wakefield generated by a laser pulse is maximal when the pulse length is close to the plasma wavelength. These results could be very useful as a starting point for optimization studies for a real LWFA experiment which is energy efficient. [ABSTRACT FROM AUTHOR]

We examined electron–positron pair production in solid iron, zinc, tungsten, and lead targets irradiated by a laser-accelerated electron beam generated with a 100 TW laser. These targets were assessed at the target thickness of 0.5, 1.25, and 2.0 radiation lengths for each material. Using a 0.75-T-magnetic spectrometer, we measured the electron and positron yields and spectra, producing 3 × 108 positrons per shot with a peak leptonic density of 4 × 1012 cm−3. These experimental results agree very well with Monte Carlo simulations conducted with the simulation code Geant4. Importantly, our findings show that normalizing the target thickness to each material’s radiation length results in consistent electron and positron yields across the materials, effectively reducing discrepancies due to material differences.

Polarized electron beam production via laser wakefield acceleration in pre-polarized plasma is investigated by particle-in-cell simulations. The evolution of the electron beam polarization is studied based on the Thomas–Bargmann–Michel–Telegdi equation for the transverse and longitudinal self-injection, and the depolarization process is found to be influenced by the injection schemes. In the case of transverse self-injection, as found typically in the bubble regime, the spin precession of the accelerated electrons is mainly influenced by the wakefield. However, in the case of longitudinal injection in the quasi-1D regime (for example, F. Y. Li et al., Phys. Rev. Lett. 110, 135002 (2013)), the direction of electron spin oscillates in the laser field. Since the electrons move around the laser axis, the net influence of the laser field is nearly zero and the contribution of the wakefield can be ignored. Finally, an ultra-short electron beam with polarization of $99\%$ can be obtained using longitudinal self-injection.

Laser-driven electron acceleration in underdense plasma is a promising route towards the realization of reliable sources of relativistic electrons in the 0.1–1 GeV energy range. Generation of such electron bunches at high repetition rates is hindered by the limited energy per pulse, which inevitably results in very short pulse duration and tight focusing. Compressing the laser energy in time and space allows scientists to use higher plasma density to drive wakefieds, which in turn results in enhanced diffraction and dispersion of the broadband laser pulse. These features make difficult to control the acceleration in the plasma wave and to improve the beam quality. Here we propose a mm-long three-stage acceleration scheme, which allows for tunable injection and optimal acceleration of high-quality electron bunches. The full interaction length is modeled by 3D particle-in-cell simulations. [ABSTRACT FROM AUTHOR]

Plasma-based accelerators use the strong electromagnetic fields that can be supported by plasmas to accelerate charged particles to high energies. Accelerating field structures in plasma can be generated by powerful laser pulses or charged particle beams. This research field has recently transitioned from involving a few small-scale efforts to the development of national and international networks of scientists supported by substantial investment in large-scale research infrastructure. In this New Journal of Physics 2020 Plasma Accelerator Roadmap, perspectives from experts in this field provide a summary overview of the field and insights into the research needs and developments for an international audience of scientists, including graduate students and researchers entering the field.

Gas targets hold distinctive significance and advantages in the field of laser-matter interaction. As a major type of gas targets, supersonic gas target is one of the most commonly used targets for laser wakefield acceleration (LWFA). The temporal-spatial resolution study of it could provide valuable data references for the LWFA experiment. In this work, a Nomarski interference system with high spatial-temporal resolution was set up to diagnose the jet process of supersonic gas jet target. The formation process of supersonic gas jet under different jet durations, different injection positions and different gas back pressures was studied. It is beneficial to determine the more optimized time and position of laser injection into target when conducting LWFA experiments. Therefore, the quality of the obtained electron beam and radiation source can be effectively improved.

Supersonic gas jets generated via a conical nozzle are widely applied in the laser wakefield acceleration of electrons. The stability of the gas jet is critical to the electron injection and the reproducibility of the wakefield acceleration. Here we discussed the role of the stilling chamber in a modified converging--diverging nozzle to dissipate the turbulence and to stabilize the gas jets. By the fluid dynamics simulations and the Mach--Zehnder interferometer measurements, the instability originating from the nonlinear turbulence is studied and the mechanism to suppress the instability is proposed. Both the numerical and experimental results prove that the carefully designed nozzle with a stilling chamber is able to reduce the perturbation by more than 10% compared with a simple-conical nozzle. [ABSTRACT FROM AUTHOR]

A single-shot measurement of electron emittance was experimentally accomplished using a focused transfer line with a dipole. The betatron phase of electrons based on laser wakefield acceleration (LWFA) is energy dependent owing to the coupling of the longitudinal acceleration field and the transverse focusing (defocusing) field in the bubble. The phase space presents slice information after phase compensation relative to the center energy. Fitting the transverse size of the electron beam at different energy slices in the energy spectrum measured 0.27 mm mrad in the experiment. The diagnosis of slice emittance facilitates local electron quality manipulation, which is important for the development of LWFA-based free electron lasers. The quasi-3D particle-in-cell simulations matched the experimental results and analysis well. [ABSTRACT FROM AUTHOR]

Laser wakefield acceleration, a highly nonlinear process, can provide high-quality electron beams and betatron radiation. However, it has always been a challenge to optimize the photon number of betatron radiation because X-ray production is the secondary process followed by electron generation and many influential parameters are highly coupled with each other. To balance these parameters and optimize target value, we use a machine-learning algorithm called Bayesian optimization that ignores the complicated middle process and so is suitable to solve this kind of problems. Without designed initialization, we optimize betatron radiation in experiments by changing plasma density and laser focal position. The X-ray photon number doubles compared with initial condition within 10 iterations, which shows the rapidity of this algorithm. PIC simulation also illustrates the complexity of the optimization and reveals the reason why X-ray photon number increases.

Simulations of photoneutron generation are presented for the anticipated experimental campaign at ELI-ALPS using the under-commissioning e-SYLOS beamline. Photoneutron generation is a three-step process starting with the creation of a relativistic electron beam which is converted to gamma radiation, which in turn generates neutrons via the γ , n interaction in high-Z material. Electrons are accelerated to relativistic energies using the laser wakefield acceleration (LWFA) mechanism. The LWFA process is simulated with a three-dimensional particle in cell code to generate an electron bunch of 100s pC charge from a 100 mJ, 9 fs laser interaction with a helium gas jet target. The resultant electron spectrum is transported through a lead sphere with the Monte Carlo N-Particle (MCNP) code to convert electrons to gammas and gammas to neutrons in a single simulation. A neutron yield of 3 × 10 7 per shot over 4 π is achieved, with a corresponding neutron yield per kW of 6 × 10 11 n/s/kW. The paper concludes with a discussion on the attractiveness of LWFA-driven photoneutron generation on high impact, and societal applications. [ABSTRACT FROM AUTHOR]

We consider high-density laser wakefield acceleration (LWFA) in the nonrelativistic regime of the laser. In place of an ultrashort laser pulse, we can excite wakefields via the Laser Beat Wave (BW) that accesses this near-critical density regime. Here, we use 1D Particle-in-Cell (PIC) simulations to study BW acceleration using two co-propagating lasers in a near-critical density material. We show that BW acceleration near the critical density allows for acceleration of electrons to greater than keV energies at far smaller intensities, such as 1014 W/cm2, through the low phase velocity dynamics of wakefields that are excited in this scheme. Near-critical density laser BW acceleration has many potential applications including high-dose radiation therapy. [ABSTRACT FROM AUTHOR]

Plasma-based positron sources are attracting significant attention from the research community, thanks to their rather unique characteristics, which include broad energy tuneability and ultra-short duration, obtainable in a compact and relatively inexpensive setup. Here, we show a detailed numerical study of the positron beam characteristics obtainable at the dedicated user target areas proposed for the EuPRAXIA facility, the first plasma-based particle accelerator to be built as a user facility for applications. It will be shown that MeV-scale positron beams with unique properties for industrial and material science applications can be produced, alongside with GeV-scale positron beams suitable for fundamental science and accelerator physics. [ABSTRACT FROM AUTHOR]

The combination of advanced high-power laser technology, new acceleration methods and achievements in undulator development offers the opportunity to build compact, high-brilliance free electron lasers driven by a laser wakefield accelerator. Here, we present a simulation study outlining the main requirements for the laser–plasma-based extreme ultraviolet free electron laser setup with the aim to reach saturation of the photon pulse energy in a single unit of a commercially available undulator with the deflection parameter K 0 in the range of 1–1.5. A dedicated electron beam transport strategy that allows control of the electron beam slice parameters, including collective effects, required by the self-amplified spontaneous emission regime is proposed. Finally, a set of coherent photon radiation parameters achievable in the undulator section utilizing the best experimentally demonstrated electron beam parameters are analyzed. As a result, we demonstrate that the ultra-short, few-fs-level pulse of the photon radiation with the wavelength in the extreme ultraviolet range can be obtained with the peak brilliance of ∼ 7 × 10 28 photons/pulse/mm 2 /mrad 2 /0.1%bw. [ABSTRACT FROM AUTHOR]

In this paper we investigate the electron laser wakefield acceleration using numerical solution of relativistic Vlasov-Maxwell equations with Semi-Lagrangian method. We found optimum pulse length to excite strong wakefields by investigation of electric fields and density variation, which caused by propagation of intense relativistic laser pulse through underdense plasma as well as average kinetic energy of electrons, for lasers with different pulse lengths.

After the introduction of the ionization-injection scheme in laser wake field acceleration and of related high-quality electron beam generation methods, such as two-color and resonant multi-pulse ionization injection (ReMPI), the theory of thermal emittance has been used to predict the beam normalized emittance obtainable with those schemes. We recast and extend such a theory, including both higher order terms in the polynomial laser field expansion and non-polynomial corrections due to the onset of saturation effects on a single cycle. Also, a very accurate model for predicting the cycle-averaged distribution of the extracted electrons, including saturation and multi-process events, is proposed and tested. We show that our theory is very accurate for the selected processes of ${\mathrm{Kr}}^{8^{+}\to {10}^{+}}$ and ${\mathrm{Ar}}^{8^{+}\to {10}^{+}}$ , resulting in a maximum error below 1%, even in a deep-saturation regime. The accurate prediction of the beam phase-space can be implemented, for example, in laser-envelope or hybrid particle-in-cell (PIC)/fluid codes, to correctly mimic the cycle-averaged momentum distribution without the need for resolving the intra-cycle dynamics. We introduce further spatial averaging, obtaining expressions for the whole-beam emittance fitting with simulations in a saturated regime, too. Finally, a PIC simulation for a laser wakefield acceleration injector in the ReMPI configuration is discussed. [ABSTRACT FROM AUTHOR]

With a circularly polarized (CP) Gaussian laser pulse, we examine theoretically the acceleration of electrons due to a combined effect of laser wakefield (LW) and direct laser (DL) in the plasma bubble regime. The CP laser pulse is ideal for DLA, since it allows for better electron trapping in the plasma bubble regime than a linearly polarized (LP) laser pulse. As a result of a CP laser pulse propagation in z direction, the electrons are accelerated in longitudinal direction by the accelerating field ( W z ) and focused in the transverse direction by the focusing fields ( W x , W y ). The density of plasma medium is about ∼ 1.8 × 10 18 cm - 3 which is from a 99.9 % He / 0.1 % N2 neutral mix, laser pulse duration is 30 f s and wavelength 0.8 μ m . A bubble radius of over 20 μ m is achieved with a CP laser pulse at an intensity on the order of a 0 = 7 ( ∼ 2.14 × 10 20 W / cm 2 ), although the same can be achieved with an LP laser at a significantly higher intensity. The electron energy gain with a CP laser pulse appears to be above 3 GeV at this intensity. CP laser pulse appeared with a lower transverse emittance and a higher energy gain than an LP laser pulse of the same intensity. In comparison to LP laser pulse, CP laser pulse appears to have a more effective acceleration mechanism for LWFA with DLA in the plasma-bubble regime. [ABSTRACT FROM AUTHOR]

A new scheme is proposed to improve the electron beam quality of ionization-induced injection by tailoring gas profile in laser wakefield acceleration. Two-dimensional particle-in-cell simulations show that the ionization-induced injection mainly occurs in high-density stage and automatically truncates in low-density stage due to the decrease of the wakefield potential difference. The beam loading can be compensated by the elongated beam resulting from the density transition stage. The beam quality can be improved by shorter injection distance and beam loading effect. A quasi-monoenergetic electron beam with a central energy of 258 MeV and an energy spread of 5.1% is obtained under certain laserâ€"plasma conditions. [ABSTRACT FROM AUTHOR]

The realization of compact X-ray sources is one of the most intriguing applications of laser-plasma based electron acceleration. These sources based on the oscillation of short micron-sized bunches of relativistic electrons provide femtosecond X-ray pulses that are collimated, bright, and partially coherent. The state-of-the-art laser plasma X-ray sources can provide photon flux of over 1011 photons/shot. The photon flux can further be enhanced with the availability of high repetition rate, high-power lasers, providing capacities complementary to the large scale facilities such as synchrotrons and X-ray free-electron lasers. Even though the optimization of such sources has been underway for the last two decades, their applications in material and biological sciences are still emerging, which entail the necessity of a user-oriented X-ray beamlines. Based on this concept, a high-power-laser-based user-oriented X-ray source is being developed at ELI Beamlines. This article reports on the ELI Gammatron beamline and presents an overview of the research accessible with the ultrashort hard X-ray pulses at the ELI Gammatron beamline.

Simulations of photoneutron generation are presented for the anticipated experimental campaign at ELI-ALPS using the under-commissioning e-SYLOS beamline. Photoneutron generation is a three-step process starting with the creation of a relativistic electron beam which is converted to gamma radiation, which in turn generates neutrons via the γ,n interaction in high-Z material. Electrons are accelerated to relativistic energies using the laser wakefield acceleration (LWFA) mechanism. The LWFA process is simulated with a three-dimensional particle in cell code to generate an electron bunch of 100s pC charge from a 100 mJ, 9 fs laser interaction with a helium gas jet target. The resultant electron spectrum is transported through a lead sphere with the Monte Carlo N-Particle (MCNP) code to convert electrons to gammas and gammas to neutrons in a single simulation. A neutron yield of 3×107 per shot over 4π is achieved, with a corresponding neutron yield per kW of 6×1011 n/s/kW. The paper concludes with a discussion on the attractiveness of LWFA-driven photoneutron generation on high impact, and societal applications.

Featured Application: Compact electron accelerators, Compact synchrotron source, Radiography. Laser wakefield electron acceleration (LWFA) is an emerging technology for the next generation of electron accelerators. As intense laser technology has rapidly developed, LWFA has overcome its limitations and has proven its possibilities to facilitate compact high-energy electron beams. Since high-power lasers reach peak power beyond petawatts (PW), LWFA has a new chance to explore the multi-GeV energy regime. In this article, we review the recent development of multi-GeV electron acceleration with PW lasers and discuss the limitations and perspectives of the LWFA with high-power lasers. [ABSTRACT FROM AUTHOR]

We consider high-density laser wakefield acceleration (LWFA) in the nonrelativistic regime of the laser. In place of an ultrashort laser pulse, we can excite wakefields via the Laser Beat Wave (BW) that accesses this near-critical density regime. Here, we use 1D Particle-in-Cell (PIC) simulations to study BW acceleration using two co-propagating lasers in a near-critical density material. We show that BW acceleration near the critical density allows for acceleration of electrons to greater than keV energies at far smaller intensities, such as 1014 W/cm2, through the low phase velocity dynamics of wakefields that are excited in this scheme. Near-critical density laser BW acceleration has many potential applications including high-dose radiation therapy.