Turning the current experimental laser-plasma accelerator state-of-the-art from a promising technology into mainstream scientific tools depends critically on high-performance, high-fidelity modeling of complex processes that develop over a wide range of space and time scales. While computer simulation tools are already essential to laser-plasma accelerator research, modeling of some of the...
Recent progress on generation and application of the Betatron source at LOA will be shown.
We will first present the production of Betatron radiation using ionization injection. We observed that both the signal and beam profile fluctuations are significantly reduced on this regime. In addition, radiation becomes polarized with a polarization that follows the laser polarization.
In this...
Staging acceleration of plasma accelerators is a critical requirement for compact colliders. The achivements have been made based on two different staging accelerartion schemes (from a LWFA to another LWFA [1] or from a Linac to a PWFA [2]) in recent years, however, the capure efficiency is very low (few percent or even lower). Here we present the first successful demonstration of external...
Plasma wakefield acceleration (PWFA) is a novel acceleration technique with promising prospects for both particle colliders and light sources. However, PWFA research has so far been limited to a few large-scale accelerator facilities worldwide. We present first results on plasma wakefield excitation and acceleration using electron beams generated with the Ti:sapphire lasers ATLAS (LMU, Munich)...
Large energy gain by a witness bunch in a single plasma wakefields stage requires a driver carrying a large amount of energy. Proton bunches produced in large synchrotrons (SPS or LHC at CERN) carry tens to hundreds of kilojoules, but are long, typically 6-12cm. The self-modulation (SM) of the bunch in the plasma [1] transforms the continuous bunch in a train of bunches shorter than, and...
The BELLA petawatt (PW) laser facility at Lawrence Berkeley National Laboratory is pursuing development of 10-GeV-class laser plasma accelerators. In this presentation, we show recent progress toward this goal: guiding of 0.85 PW peak power laser pulses over 200 mm in plasma channels and electron acceleration up to 8 GeV. This was achieved by increasing the focusing strength of a capillary...
We will review our recent research activities on high-repetition rate laser-wakefield acceleration. In a recent series of experiments, we have used millijoule near-single-cycle laser pulses of 3.5 fs duration at kHz repetition rate to accelerate electrons to 5 MeV energies [1]. The single-cycle laser pulses were able to excite nonlinear plasma wakefields and accelerate electrons to MeV...
Controlling the parameters of a laser plasma accelerated electron beam is a topic of intense research with a particular focus placed on controlling the injection phase of electrons into the accelerating structure from the background plasma. An essential prerequisite for high-quality beams is dark-current free acceleration (i.e., no electrons accelerated beyond those deliberately injected). We...
We report on the generation of quasi-monoenergetic electron beams with up to 1.2nC charge, 18 pC/MeV spectral charge density and 1mrad rms divergence using shock-front injection in a 100-TW-class laser wakefield accelerator. These high charge densities result in significant beam loading which affects both the final energy and the spectral shape of the electron beam. We confirm and explain the...
Laser wakefield acceleration (LWFA) is a candidate to build next generation of electron accelerators due to its huge acceleration field in a plasma medium. Progresses of intense laser technologies contributed to developments of multi-GeV [1,2] and high repetition-rate electron beams [3] by LWFA. Recently, we accomplished upgrading one of our PW beamlines to 4 PW peak power [4] and started...
The advent of chirped-pulse-amplified CO2 lasers [1] has yielded picosecond, long-wavelength infrared (λ=10 μm) laser pulses of terawatt (TW) peak power suitable for driving laser wakefield accelerators (LWFAs) with high ponderomotive force (∼Iλ2) in low-density (1016 cm-3 < ne <1018 cm-3) plasma [2]. Such pulses...
Demanding applications like radiation therapy of cancer have pushed the development of laser proton accelerators and defined necessary proton beam properties as well as levels of control and stability.
The presentation will give an overview of the recent experiments for laser driven proton acceleration employing a cryogenic target system which is capable of producing a renewable and debris...
Over-dense gas targets are attractive for ion acceleration since they can provide debris free, high repetition sources of pure ion beams. The spatial profile of gas targets are typically not well suited for laser-plasma energy coupling, however, this can be improved by the addition of an optical prepulse which launches a blast-wave into the plasma. This technique has previously been shown to...
Laser Plasma Acceleration (LPA) enables to generate up to several GeV electron beam with short bunch length and high peak current within centimeters scale. However, the generated beam quality (energy spread, divergence) is not sufficient for numerous applications. In view of a Free Electron Laser application, the energy spread has to be adapted to reach the required small slice value while the...
Target Normal Sheath Acceleration (TNSA) is arguably the most robust and well known laser-driven ion acceleration scheme, nevertheless it has one main issue, namely the low efficiency of laser conversion into energetic ions. In order to overcome this limit, one possibility is to use a double-layer target with a near-critical coating [1]. Nevertheless, the electron critical density for the...
Focusing petawatt-level laser beams to a variety of spot sizes for different applications is expensive in cost, labor and space. In this talk, we present a plasma lens, similar to an adjustable eyepiece in a telescope, to flexibly resize the laser beam by utilizing the laser self-focusing effect. Using a fixed conventional focusing system to focus the laser a short distance in front of the...
Plasma beam dump has been recently proposed to absorb the kinetic energy of the spent beam from particle accelerators. In this presentation a passive beam dump with multiple stage plasma cells are investigated. In this new scheme, the stepped plasma densities are required after the first stage so as to maintain a high decelerating gradient compared to a uniform plasma. Particle-in-cell...
Laser-driven ion acceleration promises to provide a compact solution for demanding applications like particle therapy, proton radiography or inertial confinement research. Controlling the particle beam parameters to achieve these goals is currently pushing the frontier of laser driven particle accelerators.
The performance of the plasma acceleration is strongly dependent on the complex...
Plasma channels represent a well-suited environment for laser-based particle acceleration. The reasons for this are twofold. On one hand, the laser can be self-guided within the channel, which allows for long propagation distances. On the other hand, the channel can affect the particles directly. For example, self-generated electromagnetic fields can assist direct laser acceleration within the...
Laser wakefield accelerators (LWFAs) can sustain accelerating gradients that greatly surpass those of conventional accelerators. Long ($\sim$ps) and intense ($>$TW) laser pulses have been employed in LWFAs to generate bright, hard x-rays which are of interest for imaging and diagnosing warm-dense matter. The CO$_2$ laser at the ATF facility of the Brookhaven National Laboratory is a unique...
During laser solid target interactions, the onset of Weibel instability can generate super strong magnetic field structures (up to several $kT$) on the surface and within the bulk of the solid targets. Weibel magnetic fields can be used to understand several physical events in astrophysics [1] as well as impact laser driven inertial confinement fusion process [2] and gamma-ray generation...
Target normal sheath acceleration (TNSA) of ions from laser-irradiated solid foils is a well-known, robust and widely used method. Numerical simulation of this process using PIC codes is, however, very challenging. Indeed, very small space and time steps are required to resolve the plasma skin depth and plasma period at the solid densities considered, while large spatiotemporal domains are...
The development of next generation laser plasma sources for novel applications in various fields ranging from astro-physics, fusion research to particle acceleration and tumor therapy requires methods to study the plasma dynamics and heating on short spatial (few nanometers) and temporal scales (few femtoseconds). Free electron lasers are identified as a potential new tool to achieve this goal...
In plasma wakefield accelerators, intense laser or particle beams drive strong Langmuir waves with the energy density as high as the rest energy of plasma electrons. A large fraction of this energy remains in the plasma after passage of the accelerated beam and causes rapid expansion of the plasma column boundary. The energy initially stored in coherent electron oscillations first transforms...
The energy density deposited in a highly nonlinear “blowout” regime wake reaches that of the rest energy density of plasma electrons [1]. This energy relaxes through a complex redistribution between e.g. accelerated electrons, undirected hot electrons, ion-channel formation, ionization and excitation of surrounding gas and radiation over ns or longer time scales. These relaxation dynamics...
Laser-wakefield accelerators (LWFA) feature electron bunch durations on a fs-scale. Precise knowledge of the longitudinal profile of such ultra-short electron bunches is essential for the design of future compact X-ray light sources. Resolution limits, as well as the limited reproducibility of electron bunches, pose big challenges for LWFA beam diagnostics.
Spectral measurements of broadband...
Three dimensional Particle in Cell simulations of Laser Wakefield Acceleration require a considerable amount of resources but are necessary to have realistic predictions and to design future experiments. The planned experiments for the CILEX facility also include two stages of plasma acceleration, for a total plasma length of the order of centimiters. In this context, where traditional 3D...
Few-cycle microscopy diagnostic [1] combining femtosecond time resolution and micrometer spatial resolution allows for direct observation of laser-driven plasma waves. By comparing the period of the wave train and the independently measured in-situ plasma density, we find that existing 1D models [2, 3] tend to overestimate the contribution of laser intensity to the non-linear plasma wave...
Particle-in-cell (PIC) simulations play a major role to the development of laser-wakefield acceleration (LWFA). Although PIC simulations provide quantitative predictions, that can be directly compared with experimental results, they are also very computationally intensive. Full scale 3d PIC simulations of LWFA are challenging due to the large-scale disparity between the laser wavelength...
Recent progress in laser wakefield acceleration (LWFA) has demonstrated the generation of high peak current electron beams with improved shot to shot stability [1]. Using high-current electron beams from a LWFA as drivers of a beam-driven plasma wakefield accelerator (PWFA) has been proposed as a beam energy and brightness transformer [2], aiming to fulfill the demanding quality requirements...
Radiation processes in plasmas are extremely relevant for a number of fields, ranging from astrophysics to small scale microscopy. These processes are usually associated with the motion of a large number of electrons, under the action of intense electric and magnetic self-consistent fields and require numerical descriptions in order to be explored. Particle-In-Cell (PIC) codes like OSIRIS are...
To optimize and control GeV-level laser plasma acceleration (LPA), it is important to visualize transient LPA structures in a single shot. In this set of LPA experiments using the Texas Petawatt (~120fs, ~120J) in a plasma of He of density ne < 5 × 1017 cm−3, electrons to (~0.6)GeV were produced in (300pC) bunches. The low repetition-rate and slight fluctuations of the laser motivates...
There is intense international interest in the development of high power laser-driven ion sources due to the unique properties of the ion beam and the potential to make these sources compact for applications. This has motivated research into new ion acceleration mechanisms to increase the maximum energies achieved and to control the spectral and divergence properties of the ion beam. In this...
Despite piquing interest in the intense laser-plasma community during the past several decades, monitoring the spatio-temporal evolution of megagauss magnetic fields continues to provide a window to the dynamics of hot electron transport, pivotal to ion acceleration schemes. Besides, these magnetic fields mirror the plethora of electromagnetic waves and instabilities, coupled with the...
Laser driven ion beams provide a promising alternative to conventional accelerators as, in addition to the compactness and possible cost-effectiveness, they exhibit remarkable properties such as high particle flux, short pulse duration and laminarity [1]. However, some of the inherent shortcomings of ion beams driven by target normal sheath acceleration (TNSA) mechanism, such as large...
Plasma mirrors are produced at the surface of solid targets ionized by intense femtosecond laser pulses [1]. Due to their solid-like density, such plasmas specularly reflect these pulses. The main differences with an ordinary mirror is that the critical surface oscillates between +c and –c at each optical cycle and the coupling with the incident beam occurs within a thin layer, that can be...
Laser-driven electron acceleration in gas media [1] provides extreme accelerating fields around 100 GV/m, however, using vacuum should offer even multi-TV/m values. These fields are much beyond that of conventional RF devices. Furthermore, the electron bunches have durations in the few-femtosecond regime, which is also much shorter than from conventional facilities.
A novel approach for the...
A chromatic focusing system combined with chirped laser pulses was used to create a “flying focus” [1]. This advanced focusing scheme provides unprecedented spatiotemporal control over the laser focal volume by enabling a small-diameter laser focus to propagate over 100 times its Rayleigh length. Furthermore, the flying focus decouples the speed at which the peak intensity propagates from the...
The combination of GeV electron beams and ultra-intense lasers provides a perfect basis for experiments testing high intensity QED effects from vacuum pair production to determining the equation of motion of an electron in an intense laser field including strong radiation reaction.
Initial experiments (for example [1,2]) have shown significant promise and highlighted the remaining challenges....
The stability of Laser Plasma Wakefield Accelerated (LWFA) electron beams and the efficiency of betatron X-ray sources can be controlled using staged gas targets. Implementation of ionization-assisted [1] and density down-ramp [2] electron injection allows to change the energy and charge of accelerated electron beams. The double-jet betatron source with a low-density LWFA region and a...
A novel approach is proposed to demonstrate the two-photon Breit-Wheeler process by using collimated and wide-bandwidth γ-ray pulses driven by 10-PW lasers. Theoretical calculations suggest that more than 3.2×10^8 electron-positron pairs with a divergence angle of 7° can be created per shot, and the signal-to-noise ratio is higher than 10^3. The positron signal, which is roughly 100 times...
Thomson backscatter (TBS) of near-IR (hνL ~ 1eV) laser pulses from laser-plasma-accelerated (LPA) electron bunches (200 < γe < 4000) provides a compact source of bright, tunable, ultrashort x-rays (0.1 < 4γe2hvL < 100 MeV) for radiography and nuclear science [1]. Inserting a plasma mirror (PM) near the LPA exit to retro-reflect spent LPA drive pulses onto trailing electron bunches [2] is an...
Low-emittance ultra-relativistic electron beams delivered for next generation of plasma wakefield acceleration (PWFA) experiments are expected to produce very high wakefields over very large distances when going through a plasma. Assessing electron beam dynamics under such fields will be of key importance to achieve the next milestones of the PWFA concept. Here we report on the use of the...
Laser-accelerated protons have a great potential for innovative experiments in radiation biology and chemistry due to the ultra-high dose rate (109 Gy/s) delivered in nanosecond time scale. However, the broad angular divergence around the propagation axis makes them not optimal for applications with stringent requirements on dose homogeneity and total flux at the target. The simplest solution...
Investigating the energy loss of ions in plasma is a long standing research topic of the plasma physics group at GSI. In particular at low particle velocity, which corresponds to the maximum of the stopping power, the theoretical descriptions based on perturbative approaches fail and models show a discrepancy. This lack of understanding is particularly critical and could be a reason for the...
The interaction of short intense pulses with solid targets is known for the acceleration of ions by the target normal sheath acceleration mechanism. After the ions are accelerated they are assumed to drift in space towards the detector. During this time, the temperature of the plasma is understood to be significantly high such that recombination is prevented and all the ions that are...
Laser-driven proton acceleration, as produced during the interaction of a high-intensity (I>1x10^18 W/cm^2), short pulse (<1 ps) laser with a solid target, is a prosperous field of endeavor for manifold applications in different domains, including astrophysics, biomedicine and materials science. These emerging applications benefit from the unique features of the laser-accelerated particles...
Experiments were conducted using a high:repetition rate (500 Hz) Ti:sapphire laser to measure the scaling of laser wakefield acceleration at low energy (< 20 mJ) and high repetition rate. Electron spectra were measured and the effect of feedback control of the laser pulse phase front and the laser temporal phase were investigated. The development of liquid targets for high rep rate ion and...
We will give an overview of the latest commissioning status of the ATLAS-3000 laser system at CALA, before reviewing the main results from the laser-wakefield related campaigns with the predecessor 100-TW system. Quasi-monoenergetic shock-front accelerated electron bunches with energies up to 300 MeV and charge figures of >250 pC were routinely produced. The scaling of their spectral shape...
I will present an overview the research being undertaken in my group at the Clarendon Laboratory, University of Oxford and with colleagues at the Rutherford Appleton Laboratory. We are particularly interested in exploring how laser energy is absorbed in the laser-QED regime for the 10 PW laser pulses that will shortly be available with the ELI facilities. We have found that there is a regime...
Laser-driven charged particle acceleration mechanisms with relativistically intense pulses of ultrashort duration are reviewed for innovative low-density targets either of near critical or near relativistically critical densities. These targets being optimized over thickness and density for given laser intensity with 3D PIC simulations allow generate electrons with maximum total charge and...
Recent studies on laser wakefield acceleration at SJTU will be introduced. Especially two new schemes based on plasma channel will be discussed in detail.
Multistage coupling of laser-wakefield accelerators with independent driving laser pulses is essential to overcome laser energy depletion for high energy applications such as the TeV level electron-positron collider. Currently a staging...
J.L. Martins, J. Vieira, J. Ferri and T. Fülöp
Recent experiments on the production of lasers with Laguerre-Gaussian modes and their interaction with matter have produced high-intensity laser beams with non-zero angular momentum (e.g. [1]). These developments pave the way for exploring laser-wakefield accelerators with structured laser drivers, which provide the access to new acceleration...
Recent progress in laser wakefield acceleration has led to the emergence of a new generation of electron and X-ray sources that may have considerable benefits for a range of scientific, medical and industrial applications. Betatron oscillations of electrons in the strong transverse fields of a laser wakefield accelerator provide X-ray radiation pulses that have a sub-micron source size, are of...
A new generation of accelerator-based hard X/γ-ray sources driven exclusively by laser light will be discussed. One ultrahigh intense CPA laser pulses will be split into two pulse: first used to accelerate electrons by laser-driven plasma wake-field to hundreds-MeV, and second, to collide on the electron for the generation of X/γ-rays by inverse Compton scattering (ICS).
Such all-laser-driven...
We report here on first observations of spontaneous undulator radiation after a 10-m long transport line using a Laser-plasma acceleration (LPA). The line verses to manipulate the singular properties of the produced electron beams (as energy spread, divergence) before being used for lightsource applications. The COXINEL* transport beam line transport and focus a LPA beam in a 2-m long...
When it comes online later this fall, FACET-II will begin delivering 10 GeV beams with up to 300 kA peak current and bunch lengths less than 1 µm for a broad range of experiments in advanced accelerator R&D and other novel research directions. Such extreme beam intensities will make diagnostics particularly challenging for FACET-II. Key to the plasma wakefield experimental program is the...
A single-shot hyperspectral camera has been built and a single-shot ultrafast videography protocol has been developed. The camera is capable of retrieving three dimensions of information (two spatial dimensions along with a time or spectral dimension) from a two-dimensional signal of a conventional CCD camera. The third dimension is retrieved using a combination of compressed sensing along...
The development of high-intensity short-pulse lasers in the Petawatt regime offers the possibility to design new compact accelerator schemes by utilizing high-density targets for the generation of high energy ion beams. The optimization of the acceleration process demands comprehensive diagnostic of the plasma dynamics involved, for example via spatially and temporally resolved optical...
Subluminal and superluminal light pulses have attracted a considerable attention in the past decades opening perspectives in telecommunications, optical storage, and fundamental physics. Usually achieved in matter, superluminal propagation has also been demonstrated in vacuum with quasi-Bessel beams or Spatio-Temporal Couplings (STCs). While in the first case the propagation was...
Laser wakefield accelerators can provide a very compact source of electron beams, which when combined with intense laser pulses result in a versatile X-ray source. Of particular interest for medical imaging are X-rays in the 50-100 keV energy range, high enough energy to penetrate through human-sized objects. Such beams also form the basis of an all optical Thomson source for X-ray...
We present Traveling-Wave Electron Acceleration (TWEAC), a novel compact electron accelerator scheme based on laser-plasma acceleration. While laser-plasma accelerators provide multi-GeV electron beams today, the acceleration to higher energies is limited. The sub-luminal group-velocity of plasma waves let electrons outrun the accelerating field.
In order to control the speed of the...
High-pressure sprays are widely used in various field of industry such as combustion or rocket engines and paint applications. However, quantitative imaging of atomizing sprays is particularly challenging due to the presence of a variety of irregular liquid structures such as ligaments, liquid blobs, droplets, liquid sheets and a possible liquid core. This is why the only measurements of the...
The capture and acceleration of short electron bunches externally injected into wakefields generated by an intense femtosecond laser pulse in the plasma channel are studied. The injection of low-energy bunches is analyzed, which allows to obtain a substantial longitudinal bunch compression, and also to obtain the bunch energy gain to the GeV range with a small energy spread at an acceleration...
Attosecond extreme-ultraviolet (XUV) pulses from laser-matter interactions have provided a unique tool for controlling and measuring electronic dynamics on the atomic scale [1]. Currently these pulses are typically generated via high harmonic generation (HHG) in gases where the highest pulse energies are limited to the microjoule range due to phase-matching effects and ground-state depletion....
It is generally believed [1] that the matched laser profile provides the optimal regime of electron acceleration. The laser spot size and the pulse duration evolve a little during laser propagation when the laser intensity, the plasma density and the laser profile are matched. The scaling laws predicted the electron energy as a function of the laser-plasma parameters have been formulated for...
We study both experimentally and numerically the emission of energetic electrons during the reflection of a relativistic few-cycle laser pulse ($1.4 \times 10^{19} \mathrm{~W/cm}^2$, 3.5 fs) on an overdense plasma. Two distinct acceleration regimes are identified (see Fig. 1), for which the electron ejection mechanisms are radically different. On the one hand, when the plasma-vacuum interface...
Recent advances in laser technology have enabled the generation of relativistic laser pulses at wavelengths above the near infrared for the first time. We present a series of experiments which examine laser solid plasma interactions and applications utilizing a normalized vector potential of near unity at wavelengths of 1300 and 2100 nm. We present results which highlight the unique benefits...
Experiments were performed to study electron acceleration by intense sub-picosecond laser pulses propagating in sub-mm long plasmas of near critical electron density (NCD). Production of hydrodynamically stable NCD-plasmas remains an important issue for such type of experiments. For these purposes we used low density CHO-foam layers of 300-500 m thickness. In foams, the NCD-plasma was...
During the past decade, the development of intense few-cycle mid-infrared (mid-IR, λ<5 µm) laser sources has made significant progress, which has opened many opportunities for infrared nonlinear optics, high-harmonic generation and pump-probe experiments in the “molecular fingerprint” region. However, even longer carrier wavelength (~10 µm) are needed in many applications. It is one of the...
Generation of high energy electrons using laser plasma interactions have been of immense interest over the past few decades, owing to their application in various fields like ion acceleration and fast ignition for ICF. Till date relativistic electrons (> 1 MeV) are mostly obtained at intensities of 〖10〗^18 W/cm^2 and above. Such high intensities are generally achieved by using either high...
In the past 10 years, the generation of terahertz (THz) radiation by ultrashort
laser pulses has become an active field of research due to many promising
applications in medicine, security, telecommunication and spectroscopy [1].
In gas, two-color near infrared laser pulses with moderate pump intensities
and temporally asymmetric profile trigger transverse currents
through photoionization...
The low transverse emittance of electron bunches from laser wakefield accelerators (LWFAs) makes these advanced accelerators attractive for compact FELs and colliders. Single-shot, direct, non-intercepting diagnostics of this emittance outside the LWFA are, however, needed. Here we present single-shot coherent transition radiation (CTR) imaging and interferometry data from electron bunches...
The concept of particle acceleration using collective field generated by charge separation of ions and electrons in a plasma, predated the now famous Tajima and Dawson paper. The many avatars of this concept had had a modest success, until Dawson proposed using a relativistic plasma wave to accelerate electrons. The initial response to this paper was either total disbelief or skepticism. It...
Plasma-based accelerators that impart energy gain as high as several GeV to electrons or positrons within a few centimeters have engendered a new class of diagnostic techniques very different from those used in connection with conventional radio-frequency (rf) accelerators. The need for new diagnostics stems from the micrometer scale and transient, dynamic structure of plasma accelerators,...
The structure of a laser plasma wakefield accelerator is intricately linked to the energy distribution of the driving laser pulse. During propagation, the spatial and temporal variations in the plasma refractive index causes modifications to the laser spectrum and spatial-temporal profile. This results in non-linear evolution of the laser pulse, which in turn affects the properties of the...
Extreme field gradients intrinsic to relativistic laser-interactions with thin solid targets enable compact multi-MeV proton accelerators with unique bunch characteristics. Protons are accelerated in TV/m fields that are established within the micrometer-scale vicinity of the high-power laser focus. This initial acceleration phase is followed by ballistic proton bunch propagation with...
Laser plasma wakefield acceleration is a promising development path for acceleration technologies. Studying this phenomenon relies heavily on numerical simulations. Generic PIC simulations provide the most detailed description of laser-plasma interaction, but they are computationally demanding. Simplyfing the model, e.g., with quasistatic approximation, yields significant performance gains at...
Utilizing laser-wakefield accelerated (LWFA) electrons to drive a
plasma-wakefield accelerator (PWFA) holds great promise for realizing
centimeter-scale electron accelerators providing ultra-high brightness
beams. Recent experiments at HZDR could demonstrate for the first time
such an electron acceleration in a nonlinear PWFA plasma wakefield. For
driving this compact hybrid accelerator setup,...
The "Advanced Proton Driven Plasma Wakefield Acceleration Experiment" (AWAKE) aims to enable lepton acceleration via proton-driven wakefields. It comprises extensive numerical studies as well as experiments at the CERN laboratory.
The baseline scenario has a simulation domain of 0.81 cm in the x, 0.42 cm in the y, and 10 m in the z direction. The smallest scale in this domain is the plasma...
Here we report on optimization of both energy spread and beam divergence in a laser wakefield accelerator (LWFA) operating in the beam loading regime. The self-truncated ionization injection scheme is employed, enabling a precise control over the amount of injected electrons with charges up to 0.5 nC (FWHM) at a quasi-monoenergetic peak.
By employing the optimal beam loading condition, the...
B. Dromey, M. Coughlan, N. Breslin, H. Donnelly, C. Arthur, S. White, M. Yeung,
School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, United Kingdom
b.dromey@qub.ac.uk
Plasma based electron acceleration is widely considered as a promising concept for a compact electron accelerator with broad range of future applications from high energy particle colliders to photon science. These accelerators can be powered by either ultra-intense laser beams (LWFA) or relativistic high-current particle beams (PWFA).
Here, we report on a novel approach to combine both...
Understanding the effects of ion interactions in condensed matter has been a focus of research for decades. While many of these studies focus on the longer term effects such as cell death or material integrity, typically this is performed using relatively long (>100 ps) proton pulses from radiofrequency accelerators in conjunction with chemical scavenging techniques [1]. As protons traverse a...
AWAKE is a proton-driven plasma wakefield experiment under way at CERN that recently demonstrated the successful acceleration of injected electrons [1]. Underpinning the experiment is the fact that the long proton bunches (~6-12 cm) used to drive the wakefields undergo a self-modulation process, which in practice corresponds to a seeded instability [2]. The resulting train of microbunches...
Invention and application of chirped pulse amplification technique in short pulse laser has been leading to unprecedented ultra high laser peak power[1]. After more than three decade development, a few petawatt class lasers, whose pulse durations vary from a few femtoseconds to several picoseconds, have been built up around the world[2]. The focused laser intensity goes beyond 1021W/cm2. ...
A novel approach for positron injection and acceleration in laser driven plasma wakefield is proposed. A three-staged theoretical model is developed and confirmed through simulations. The proposal using two co-axis propagating beams, a Laguerre-Gaussian beam and a Gaussian beam, to drive wakefields in a preformed plasma volume filled with both electrons and positrons. The bremsstrahlung force...
Nowadays’ research on laser-driven proton acceleration is focusing on the interaction of relativistic-intensity laser pulses with sub-micrometer targets. With such targets, a variety of acceleration mechanisms can be studied, from the robust TNSA to more advanced schemes that predict better performances in particle energy and beam parameters. The ideal conditions for this type of studies are...
The Advanced Wakefield Experiment (AWAKE) recently demonstrated that: 1) a 400 GeV/c proton bunch (with a bunch length 30-100 times longer than the plasma electron wavelength) self-modulates over 10m of plasma; 2) externally injected ~20 MeV electrons can be accelerated to GeV energies in the resonantly excited wakefield. In this contribution, we show the results of an AWAKE experimental...
The interaction of relativistically intense short pulse (~few tens of fs) laser pulse with solid material generates quasi-static electric fields with strengths of > TV/m are produced within a short distance of less than $\mu$m [1]. Thanks to the very strong field gradient, the field can accelerate ions beyond MeV within a micron. Unlike the acceleration of low-Z ions, acceleration of the...
Recently the ELIMAIA (ELI Multidisciplinary Applications of laser-Ion Acceleration) beamline has been installed at ELI-Beamlines in the Czech Republic. The main goal of ELIMAIA is to offer short ion bunches accelerated by lasers with high repetition rate to users from different fields (physics, biology, material science, medicine, chemistry, archaeology) and, at the same time, to demonstrate...
Hollow plasma channels are promising candidates for the acceleration of electron and positron beams, as the transverse forces are nearly vanishing inside the hollow channel, as long as the accelerated bunches are perfectly cylindrically symmetric and injected on the axis of the hollow channel structure. Furthermore, the accelerating fields can also be nearly constant provided that the...
Laser-driven ion sources exhibit unique beam properties that open up application opportunities but also pose challenges. Especially the large source divergence (~ 20° half angle) as well as the broad energy bandwidth (100%) of laser-accelerated ion bunches limit their applicability. Yet, temporal structure (~ps bunch durations) and intensity ($10^{13}$ ions per bunch) have roused interest for...
We present the technological advancements of recent years at the laser-driven ion acceleration experiment at the ATLAS 300 laser in Garching near Munich that enabled a first application oriented experiment. Improvements were made in target positioning, proton transport and diagnostics as well as in specimen handling and their capabilities explored by performing an irradiation experiment with...
A high repetition rate target assembly for laser-plasma acceleration has been built at the Laser Laboratory for Acceleration and Applications (L2A2) of the University of Santiago de Compostela. The target consists on two linear stages combined with a rotational one to ensure the focusing and refreshment of the target material shot-by-shot. A multi-target wheel alow us to install different...
Schemes for generating ultra-low emittance beams have been developed in the last years with applications, for example, in high-energy physics and free-electron laser science. Current methods for the characterization of low emittance beams such as pepperpot measurements or quadrupole scans are limit to about $e_n\approx0.2\pi$ $mm$ $mrad$. Here we propose a novel method for the characterization...
We present the development and experimental testing of a permanent magnet system to detect electron positron pairs on high intensity laser experiments at Astra Gemini. These experiments where designed to measure fundamental QED phenomena, like the Linear Breit-Wheeler effect as an example for $e^+ e^-$-pair production from quantum vacuum, or strong field effects like the Nonlinear...
Beam cooling is a crucial step for the luminosity delivery system in a linear collider or an accelerator based light source to achieve ultra low beam emittance required for high luminosity and high brightness, respectively. Damping rings equipped with wiggler magnets and accelerating cavities were previously proposed for systematic reduction of horizontal phase space area through radiation...
Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. When they randomly bond with each other by van der Waals forces, so-called carbon nanotube foam (CNF) is formed. The average density of CNFs lies in the range of a few mg/cm^3 to tens of mg/cm^3. If fully ionized, such a thin foam can turn to a plasma slab with critical density. Here we report the recent progress on...
We report results on all-optical Thomson scattering within a laser wakefield accelerator. We show that the pulse collision can be detected using transverse shadowgraphy, facilitating alignment and permitting accurate determination of the scattering position. As the electron beam energy is evolving inside the accelerator, the emitted spectrum changes with the scattering position. Such a...
In Laser-Plasma Accelerators (LPA), an ultra-short laser pulse is focused in a plasma to generate a plasma wave. The electromagnetic fields amplitude generated by this plasma wave are 3 orders of magnitudes higher than those created in classical accelerators. However, for reaching higher energies, the electron beam has to experience these fields on large distances. This remains an issue in LPA...
Proton-driven plasma wakefield acceleration has been demonstrated in simulations to be capable of accelerating electrons to the energy frontier in a single plasma stage. However, the achieved beam quality especially the normalized emittance is still far from applications. This is because the transverse plasma wakefield acting on the witness electron bunch is nonlinear to the radius, and it...
Abstract
Many applications of laser matter interaction at relativistic intensities, for e.g., ion acceleration, fast ignition, X-ray and neutron radiography, depend crucially on the laser absorption into hot electrons. Measurement of bremsstrahlung spectra generated by these hot electrons inside the target provides information on the electron energy distribution and their transport inside...
Laser-wakefield acceleration experiments performed at the Hercules laser show a lowering of the self-injection threshold by circular polarized laser pulses, similar to the threshold lowering in wakfields driven in a warm plasma. In addition to the lower injection threshold, a significantly higher charge was observed for CP compared to LP for a wide range of parameters. We performed...
The ESCULAP project aims at studying the capture and acceleration of relativistic electron bunches in a laser plasma wave. A configuration has been proposed where the interaction between the electron bunch and the plasma wave starts few Rayleigh lengths before the laser focal plane. In that configuration, a 100fs 10MeV electron bunch can be compressed up to ~ 4fs during the laser focusing....
Many of the underlying mechanisms for laser-driven ion acceleration exploit the interaction of an ultra-intense laser pulse with sub-micrometer thin foils. These mechanisms rely on well-defined plasma conditions at the time of the maximum laser intensity. These conditions, especially the preplasma scale length, are extremely hard to measure and remain mostly not known, which prevents a...
In 2018 the first Laser Wakefield Acceleration campaign took place at the Helmholtz-Institute Jena with the JETi-200 laser-system. When travelling through the plasma and exciting a plasma wave, the pump pulse can get scattered at plasma structures depending on the pump pulse’s evolution inside the plasma, the pump pulse‘s chirp and the plasma electron‘s density.
This (stimulated) Raman Side...
Spectral signatures of laser-accelerated ion beams are frequently used to characterize underlying acceleration mechanisms. Yet regularly, more than just one ion species are accelerated in experiments, e.g. from hydro-carbon contamination layers, multiple charge states or mixed materials. Such presence of multiple ion species ($q/m$) in the accelerating field leads to characteristic modulations...
We report the status of the LWFA driven X-ray sources at ELI beamlines facility. Gammatron beamline, that covers the X-ray energies from 1-100 keV in betatron scheme, and up to a few MeV in Compton scheme will be implemented in the Experimental hall E2. A state-of-the-art Ti:Sa diode-pumped HAPLS laser system (L3 laser) generating laser pulse of less than 30 fs, with energies of up to 30 Joule...
In the regime of Quantum Electricdynamics (QED), relativistic electrons collide with an ultra-intense laser pulse can generate high-energy gamma-rays by nonlinear Compton scattering. All-optical nonlinear Compton scattering regime have been analysed by using different laser-plasma acceleration schemes in past decades. However, since the process involves electron acceleration, non-linear...
Because the proof of principle of operation of plasma-based accelerators is firmly established, much effort is currently been put in demonstrating the generation of relativistic electron bunches with the required quality for various scientific and technological applications. In addition to high-quality beams, several applications also demand very high repetition rates. Here, the long-term...
We investigate acceleration of ion bunches during relativistically intense laser pulse interactions with plasmas. Relying on coherent acceleration, such laser-driven ion sources feature ion bunch characteristics that can be complementary to those typical of conventional (Wideroe-type) accelerators. Particularly novel intrinsic features include (ultra)short bunch duration, high bunch density,...
We present results from a laser-driven proton acceleration experiment performed at the JETI 40 laser system in Jena, Germany. Here, we investigated the influence of the position of water micro-droplets relative to the laser’s focus along the polarization axis on the maximum kinetic energy of accelerated protons, either for a steep plasma gradient or an additional pre-plasma. The first case was...
Development of novel X-ray sources has a significant impact on the society due to its applications on very different fields such as medicine, biology, chemistry, industry. Laser-plasma X-ray sources provides a new route to high brightness and small source size somewhere in the middle of low cost microfocus X-rays and large-scale synchrotron facilities. We explore one application of this new...
Thin aluminium foils irradiated by ultraintense femtosecond-long laser pulses have been extensively used in the last two decades for MeV-range proton beam generation. In the early stage of the interaction, a dense cloud of electrons is directly accelerated by the laser, pass through the target and ionize its rear surface. Here, an extremely high quasi-static electric field (of the order of...
Hollow plasma has been introduced into the proton-driven plasma wakefield accelerator to overcome the issue of beam quality degradation caused by the nonlinear transverse wakefields varying in radius and in time in uniform plasma. It has been demonstrated that the electrons can be accelerated to the energy frontier with a well-preserved beam quality in a long hollow plasma channel. However,...
Characterizing the plasma density profile in a plasma accelerator is important for predicting the beam dynamics and the electric field gradients produced in the plasma wake structure. In this poster, we present a two fluid model for the time evolution of the plasma and neutral gas density profiles for a laser ionized plasma filament. Our model includes the effects of hydrodynamic expansion and...
As the community prepares for the next generation of laser facilities coming online in the near future, attention will shift towards advanced mechanisms such as the radiation pressure acceleration (RPA) which has been predicted to be the dominant ion acceleration mechanism at intensities >10$^{22}$W/cm2 [1]. Recent studies have shown that current facilities can also enter this regime by...
New probes are continuously investigated to explore the physics of laser-plasma interactions. Charged particle detection systems and optical probing are well established techniques. The investigation of the bremsstrahlung generated in laser plasma remains, however, a relatively uncommon method to study these interactions.
In this talk we will present the developments in gamma calorimetry...
In this contribution, we present the result of an investigation of foam-based targets for laser-driven ion acceleration. The study was performed in collaboration between the Laser-Particle Acceleration group at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the Nanolab group at Politecnico di Milano.
Foam targets used in this experiment are composed of µm-thick solid foils with ultra-low...
Plasma accelerators provide unique opportunities for the generation of high quality, short-pulse electrons beams which are an ideal basis for high quality radiation generation. This provides an exciting way forward to the generation of very high brightness X-ray betatron radiation from an ultra-bright, plasma-injected beam in a plasma. In this contribution, we present initial results from...
Laser-driven ion fast ignition (IFI) of fusion targets requires ultra-intense ion beams with parameters whose approximate values are estimated to be as follows (e. g. [1]): the mean ion energy ~10 – 50 MeV/nucleon, the beam intensity ~10^20
W/cm2, the beam fluence ~1 GJ/cm2, the ion pulse duration ~1 - 10 ps, and a total beam energy of ~10 – 20 kJ. To achieve these parameters, an effective...
Few-cycle shadowgraphy is a common tool to qualitatively investigate the longitudinal and transverse structure of laser generated wakefields. However the measured intensity distribution provides hardly any information about the wake amplitude since the wakefield itself is a pure phase object and the measured intensity distribution is a function of the imaging plane. Commonly this plane is not...
The development of second-generation short-pulse laser-driven radiation sources requires a mature understanding of relativistic laser-plasma processes such as plasma oscillations, heating and transport of relativistic electrons as well as the development of plasma instabilities. These dynamic effects occurring on nanometer scales are very difficult to access experimentally during their...
The non-linear bubble regime of laser-wakefield acceleration (LWFA) is studied for a laser beam with a spatial super-Gaussian profile. Contrarily to the Gaussian beam, the intensity profile of the super-Gaussian beam is flat over almost all the covered area, which alters the bubble shape in a different way. Moreover, diffraction rings are induced during the formation of the super-Gaussian...
A laser wakefield accelerator(LWFA)[1], which can be used to accelerate electrons by interaction between high-intensity laser pulse and plasmas, has the advantage to miniaturize the system size as it can obtain in a narrow region compared with conventional systems. The characteristics of the Very High Energy Electron(VHEE) beam in LWFA has attracted much interest because of its potential...
We report the first observation of large amplitude Langmuir waves in a plasma of nanometer-scale clusters. The shape of these wakefields is captured by a single-shot frequency-domain holography diagnostic at an oblique angle of incidence. The wavefronts are observed to curve backwards, in contrast to the forwards curvature of wakefields in uniform plasma. The first wakefield period is longer...
X-ray photon beams in the keV to MeV energy range are essential to study high energy density (HED) matter and to improve the understanding of inertial confinement fusion and astrophysical systems. HED experiments produce highly transient matter under extreme states of temperatures and pressures and it is essential to develop light sources that are: in the hard x-ray energy range (0.01-1 MeV),...
