Plasma wakefield acceleration is nowadays very attractive in terms of accelerating gradient, able to overcome conventional accelerators by orders of magnitude. However, this poses very demanding requirements on the accelerator stability to avoid large instabilities on the final beam energy. In this study we analyze the correlation between the driver-witness distance jitter (due to the RF timing jitter) and the witness energy gain in a plasma wakefield accelerator stage. Experimental measurements are reported by using an electro-optical sampling diagnostics with which we correlate the distance between the driver and witness beams prior to the plasma accelerator stage. The results show a clear correlation due to such a distance jitter highlighting the contribution coming from the RF compression.

Laser-plasma accelerators (LPAs) can have high acceleration gradients on the order of 100 GeV/m. The high acceleration gradients of LPAs offer the possibility of powering future colliders at the TeV range and reducing the size of particle accelerators at present energy levels. LPAs need tightly focused, high intensity laser pulses and require guiding structures to maintain the laser focus over the optimum acceleration length. It is necessary to match the parameters of the guiding structure and the laser pulse to couple the maximum laser energy into the guiding structure. Optically field ionized (OFI) plasma channels are a guiding structure capable of matching the parameters of the petawatt (PW) laser facility at the Berkeley Lab Laser Accelerator (BELLA) Center [1, 2]. We will present results on the optimization of laser coupling into OFI plasma channels on BELLA PW. We will also discuss how optimization of laser coupling relates to upcoming staging experiments on BELLA PW.

Using hollow plasma channels is one approach to compact positron acceleration, potentially reducing the cost and footprint of future linear colliders. However, it is prone to transverse instabilities since beams misaligned from the channel axis tend to get deflected into the channel boundary. In contrast, asymmetric electron drive beams can tolerate misalignment and propagate stably after the initial evolution, but this has only been reported for short distances. In this work, we use quasi-static particle-in-cell simulations to demonstrate the instability of asymmetric drivers even after splitting into two beamlets and reaching equilibrium. As the driver decelerates, its particles gradually return into the channel, making the driver susceptible to deflection by the transverse dipole mode. To understand this behavior, the transverse motion of an individual beam particle is modeled. Strategies to mitigate this instability are also proposed.

At the Facility for Advanced Accelerator Experimental Tests (FACET-II) accelerator, a pair of 10 GeV high-current electron beams is used to investigate Plasma Wakefield Acceleration (PWFA) in plasmas of different lengths. While PWFA has achieved astonishingly high accelerating gradients of tens of GeV/m, matching the electron beam into the plasma wake is necessary to achieve a beam quality required for precise tuning of future high energy linear accelerators. The purpose of this study was to explore how start-to-end simulations could be used to optimize two important measures of beam quality, namely maximizing energy gain and minimizing transverse emittance growth in a 2 cm long plasma. These two beam parameters were investigated with an in-depth model of the FACET-II accelerator using numerical optimization. The results presented in the paper demonstrate the importance of utilizing beam-transport simulations in tandem with particle-in-cell simulations and provide insight into optimizing these two important beam parameters without the need to devote significant accelerator physics time tuning the FACET-II accelerator.

The spontaneous emission of radiation from relativistic electrons within a plasma channel is called betatron radiation and has great potential to become a compact x-ray source in the future. We present an analysis of the performance of a broad secondary radiation source based on a high-gradient laser-plasma wakefield electron accelerator. The purpose of this study is to assess the possibility of having a new source for a non-destructive X-ray phase contrast imaging and tomography of heterogeneous materials. We report studies of compact and UV-soft X ray generation via betatron oscillations in plasma channel and in particular measurement of the radiation spectrum emitted from electron beam is analyzed from a grazing incident monochromator at Centro de Laseres Pulsados Ultraintensos (CLPU).

Laser wakefield accelerators (LWFAs) are capable of supporting accelerating and focusing forces on the order of 10–100 GeV/m, about three orders of magnitude greater than conventional RF accelerators. While theoretical solutions for the electromagnetic (EM) focusing fields have been developed, the field structures have yet to be verified experimentally. In this poster, we present simulation results for transverse probing of laser wakefields using ultrarelativistic electrons. We study the behavior of the probing electrons by implementing filtering masks to investigate focusing characteristics of thin electron "bands". The deflection of these bands after propagating through the wakefield is then used to characterize the EM forces. The simulated focusing behavior of these electron bands is in reasonable agreement with a theoretical model developed based on a thin lens model of the wakefield. Simulation results show the focusing of the bands to be an effective experimental diagnostic for verifying the EM field structure. This provides an analytic framework needed for the first direct measurements of focusing forces in an LWFA at the Accelerator Test Facility at Brookhaven National Lab.

Particle beams with asymmetric transverse emittances and profiles have been utilized in facilities for driving wakefields in dielectric waveguides and to drive plasma wakefields in plasma. The asymmetric plasma structures created by the beam produce focusing forces that are transversely asymmetric. We utilize the ellipticity of the plasma ion cavity to model the beam evolution of the flat beam driver.

This paper explores the phenomenon of asymmetric blowout in plasma wakefield acceleration (PWFA), where the transversely asymmetric beam creates a transversely asymmetric blowout cavity in plasma. This deviation from the traditional axisymmetric models leads to unique focusing effects in the transverse plane and accelerating gradient depending on the transverse coordinates. We extend our series of studies on plasma wakefield acceleration (PWFA) by comparing our recently developed analytic model on the blowout cavity shape created by transversely asymmetric long beams, with Particle-in-Cell (PIC) simulations. The analysis focuses on validating the model's ability to predict the behaviors of different beam profiles in this regime.

A beam physics design has been carried out for a 200 MeV-LWFA injector to the AWAKE Run 2 experiment as an alternative to the reference RF injector. It is composed of a laser-plasma acceleration stage and a transport line. In addition to specific environment constraints that impose a dogleg configuration, the electron beam must feature unprecedented performances for a plasma-based accelerator: 100 pC charge, a few mm·mrad emittance, and a few % energy spread. Thanks to an integrated beam physics study assigning specific roles to each section of the accelerator, all the requirements are successfully met in numerical simulations, paving the way for plasma-based accelerators to be competitive with conventional accelerators.

The quest for novel technologies in the ever-evolving landscape of scientific exploration has led to the investigation of plasma lensing as a potential solution for optical matching devices for all kinds of positron sources. This research becomes increasingly significant as the need for higher data output demands innovative concepts to increase positron yield and therefore luminosity. Instabilities were observed during the first test trials. This poster presents the results of high-temporal resolution imaging to analyse the discharge instabilities. Furthermore, the results show not expected but interesting insights and challenges. Overcoming these challenges is pivotal for a future application of plasma lenses as an integral part of high-performance positron sources.

Plasma-wakefield acceleration represents an exciting route towards reducing the footprint of future high-energy electron accelerators by accelerating bunches in fields exceeding 1 GV/m. One such technique employs a double-bunch structure where the trailing bunch is accelerated in the field of a high-amplitude plasma-density wake driven by the leading bunch. A future particle collider or photon science facility incorporating plasma accelerators will be required to accelerate up to millions of bunches per second with high energy efficiency while preserving the brightness of the accelerating bunch. This contribution presents the latest progress towards these goals at FLASHForward (DESY).

This talk summarizes the plans, challenges and key components of the four phases in the AWAKE roadmap. In addition, an overview of the rich measurement program of the second phase, AWAKE Run 2b, during 2023 and 2024 is given. Results from a unique 3-week measurement opportunity with a 10m discharge plasma source prototype are shown, including the effects of different gases, plasma densities, bunch charges and plasma lengths on the proton bunch self-modulation, ion-motion, current filamentation instabilities and plasma light. A new 10 m long rubidium vapor source was installed in the summer of 2023 with the possibility to generate a density step (0-10%) every 50 cm along the first 4 m. First measurement results with this plasma cell are also presented, showing the positive effect of the density step on the plasma light as well as an increased energy gain for externally injected electrons.

The Advanced Wakefield Experiment (AWAKE) aims to accelerate electrons to particle physics relevant energies using self-modulated proton bunches as drivers in a single plasma. AWAKE is now in its Run 2b (2023-2024), where the goal is to stabilise wakefields by using a plasma density step. Experimental demonstrations require probing of the longitudinal wakefields by externally injected electron bunches. To optimise charge capture in the wakefields, the electron beam density should be maximised at the site of injection ze. This is achieved by setting the beam waist at ze. Since no diagnostics are currently available at these locations, waist beam sizes are extrapolated from measurements upstream. The qualitative and quantitative agreement obtained between measured and simulated transverse electron beam sizes, at locations where these can be measured, demonstrates good understanding of the beam line optics and provides confidence in the extrapolated beam sizes at waist locations, where these cannot be measured. This information can then be used in the experiment to maximise the beam density at the site of injection.

Plasma wakefield acceleration is nowadays very attractive in terms of accelerating gradient, able to overcome conventional accelerators by orders of magnitude. However, this poses very demanding requirements on the accelerator stability to avoid large instabilities on the final beam energy. In this study we analyze the correlation between the driver-witness distance jitter (due to the RF timing jitter) and the witness energy gain in a plasma wakefield accelerator stage. Experimental measurements are reported by using an electro-optical sampling diagnostics with which we correlate the distance between the driver and witness beams prior to the plasma accelerator stage. The results show a clear correlation due to such a distance jitter highlighting the contribution coming from the RF compression.

Laser-plasma accelerators (LPAs) are compact accelerators with field gradients that are approximately 3 orders of magnitude higher than RF-based machines, which allows for very compact accelerators. LPAs have matured from proof-of principle experiments to accelerators that can reproducibly generate ultrashort high-brightness electron bunches. Here we will discuss a first combination of LPAs with an electron storage ring, namely an LPA-based injector for the cSTART ring at the Karlsruher Institute of Technology (KIT). The cSTART ring is currently in the final design phase. It will accept electron bunches with an energy of 50 MeV and will have a large energy acceptance to accommodate the comparably large energy spread of LPA-generated electron beams. The LPA will be required to reproducibly and reliably generate 50 MeV electron bunches with few percent energy spread. To that end, different controlled electron injection methods into the plasma accelerating structure, tailored plasma densities are explored and beam transfer lines to tailor the beam properties are designed.

Laser Wakefield Acceleration (LWFA) can generate a high-energetic electron beam in a short accelerating distance of several cm, which is advantageous for the development of an compact accelerator. The LWFA using metal targets is highly influenced by the field ionization process of metal atoms (or ions) due to the high intensity of main laser. Titanium produces a large amount of ionized electrons near the optical axis due to localized peak intensity followed by breaking the wake cavity. However, this nature of ionization process of titanium can apply to the intense ionization injection into the wake cavity formed by the aluminum plasma. Our group suggested a structured metal plasma target using aluminum with a thin titanium layer and investigated the performance of the controlled injection depending on the location and thickness of titanium layer in the aluminum plasma [1]. In this paper, a structured plasma target is designed and optimized using a CFD code to realize the desired profile of metal plasma ablated by a laser. The performance of laser electron acceleration obtained by PIC simulation was presented for different profile of metal plasma targets designed using a CFD code.

Laser wakefield acceleration (LWFA) has been highlighted in the development of table-top accelerators and compact light sources. However, the stability issues on beam quality and pointing remain unsolved problems. Many groups apply the technique of ionization injection for higher charge with the narrower energy spread into a supersonic gas jet target or a capillary discharge system. The LWFA using a laser-ablated metallic plasma target also involves the ionization effects, not only the ionization injection but also ionization diffraction. The ionization injection may increase the bunch charge at the expense of its peak energy. The strong ionization diffraction generally keeps the optical guiding from being steady at long distances, resulting in a decrease in the accelerating length. At a certain condition, it causes the sudden break of the wake cavity, resulting in a nearly zero-accelerating wakefield. In this condition, the electron bunch may keep its property in the steady state, resulting in lower energy spread. In this paper, we present the simulation study to optimize the generation of a near-GeV electron beam using the metal plasma targets.

Plasma-based particle accelerators maintain accelerating fields that are several orders of magnitude higher than conventional accelerators. This allows for more compact accelerator footprints that can deliver particle beams of very high charge (> 100 pC) and large current (> kA) for various applications. Plasma-wakefield accelerators are promising candidates for next-generation TeV-class electron-positron colliders for high-energy physics and secondary light sources. However, to reach the desired TeV energy regime, a staging approach of independent laser-driven plasma accelerators that each preserve low energy spread and beam emittance is required. Maintaining beam emittance over tens and hundreds of stages is a serious challenge but is crucial to achieve a high luminosity in future collider experiments. We present results for the optimization of plasma-stage downramp profiles and inter-stage beam transport in simulations of multi-stage plasma accelerators, carried out with codes from the Beam pLasma & Accelerator Simulation Toolkit (BLAST) and steered by optimas, a Python library for optimization at scale, powered by libEnsemble.

Compact free electron laser (FEL) technology enabled by plasma-based accelerators is rapidly maturing with several milestone demonstrations in the last 2-3 years. Still, critical work is needed to bridge the gap from proof of concept experiments to reliable operation of plasma-based FELs. At the BELLA Center, we have a laser plasma accelerator (LPA) beamline equipped with an electron beam transport section that culminates in a 4m long, strong focusing undulator. This undulator system with 16 embedded FODO cells, represents a comparable proxy to many undulator systems used at XFEL beamlines. Notably, the presence of distributed focusing imposes tight requirements on both transverse matching and alignment of the beam through the undulator in order to enable FEL lasing. Recent efforts have demonstrated quasi matched propagation of the LPA beam in the undulator. Additionally, through control of the launch trajectory into the undulator coherent enhancement of the undulator radiation can be triggered, a strong indication of FEL gain. Recent results and future plans are discussed.

Owing to strong 10-100 GV/m accelerator gradients, Laser Plasma Accelerators (LPAs) have the capability to generate high-brightness and high-energy electron beams in compact facilities. The (sub)PW laser systems that drive LPAs are currently operating at 1-10 Hz repetition rates, while the next generation of multi-kHz technologies are being aggressively pursued at various R&D facilities worldwide. The robustness and stability of LPAs can largely be traced back to the laser performance. Fluctuations in laser pointing and other laser parameters directly translate to variations in electron beam parameters. Here we present results from recent techniques that mitigate laser fluctuations in a two-fold approach: (1) develop on-line and non-perturbative high-power laser diagnostics, both for the high-power laser as well as for a correlated background laser [1], and (2) implementation of active feedback systems to stabilize the high-power laser. Experimental results [2] show that through execution of these efforts at the BELLA Center LPA facilities, we have made significant improvements to the LPA electron beam and light source stability.

Laser-plasma accelerators (LPAs) have potential to enable compact light sources and high-energy linear colliders. At the BErkeley Lab Laser Accelerator (BELLA) PW facility, electron bunches with energy up to 8 GeV have been generated using laser pulses with peak power of 0.85 PW (energy 31 J) and an acceleration length of 20  cm. In order to accelerate over this distance of 15 diffraction lengths, a preformed plasma waveguide based on inverse bremsstrahlung (IB) heating inside a capillary discharge was used [1]. Simulations show the energy gain can be increased to beyond 10 GeV, but with lower density than is feasible with IB heating. The recent addition of a second beamline to BELLA PW has allowed for the use of plasma channels formed by optically field ionization [2-4], which enables optimized density. We will present guiding and acceleration results using this new capability.

Due to their compactness, laser-plasma accelerators are a promising approach to future energy frontier electron accelerators. To reach multi-GeV energies in a single accelerator stage, the high-intensity drive laser pulse must be kept focused over several tens of centimeters through a sufficiently low density plasma. Without an external guiding mechanism, the laser will diffract reducing the laser intensity, which in turn limits acceleration to ~1 cm. Optically generated plasma channels have recently gained attention as a promising method to keep high-intensity laser pulses tightly focused over the meter scale [1,2]. Understanding how the laser pulse evolves in the spatial and temporal domain during propagation is critical for high energy gain, and maintaining high bunch quality. We present experimental results investigating drive laser propagation in optically formed plasma channels at the BELLA PW laser. We demonstrate conditions under which the channel can be tailored to match the drive laser focus at plasma densities suitable for multi-GeV accelerators.

Laser-plasma accelerators (LPAs) can have high acceleration gradients on the order of 100 GeV/m. The high acceleration gradients of LPAs offer the possibility of powering future colliders at the TeV range and reducing the size of particle accelerators at present energy levels. LPAs need tightly focused, high intensity laser pulses and require guiding structures to maintain the laser focus over the optimum acceleration length. It is necessary to match the parameters of the guiding structure and the laser pulse to couple the maximum laser energy into the guiding structure. Optically field ionized (OFI) plasma channels are a guiding structure capable of matching the parameters of the petawatt (PW) laser facility at the Berkeley Lab Laser Accelerator (BELLA) Center [1, 2]. We will present results on the optimization of laser coupling into OFI plasma channels on BELLA PW. We will also discuss how optimization of laser coupling relates to upcoming staging experiments on BELLA PW.

Using hollow plasma channels is one approach to compact positron acceleration, potentially reducing the cost and footprint of future linear colliders. However, it is prone to transverse instabilities since beams misaligned from the channel axis tend to get deflected into the channel boundary. In contrast, asymmetric electron drive beams can tolerate misalignment and propagate stably after the initial evolution, but this has only been reported for short distances. In this work, we use quasi-static particle-in-cell simulations to demonstrate the instability of asymmetric drivers even after splitting into two beamlets and reaching equilibrium. As the driver decelerates, its particles gradually return into the channel, making the driver susceptible to deflection by the transverse dipole mode. To understand this behavior, the transverse motion of an individual beam particle is modeled. Strategies to mitigate this instability are also proposed.

Structured plasma channels are an essential technology for driving high-gradient, plasma-based acceleration and control of electron and positron beams for advanced concepts accelerators. Laser and gas technologies can permit the generation of long plasma columns known as hydrodynamic, optically-field-ionized (HOFI) channels, which feature low on-axis densities and steep walls. By carefully selecting the background gas and laser properties, one can generate narrow, tunable plasma channels for guiding high intensity laser pulses. We present on the development of 1D and 2D simulations of HOFI channels using the FLASH code, a publicly available radiation hydrodynamics code with specific improvements to model plasma channels. We explore sensitivities of the channel evolution to laser profile, intensity, and background gas conditions. We examine efforts to benchmark these simulations against experimental measurements of plasma channels. Lastly, we discuss ongoing work to couple these tools to community PIC models to capture variations in initial conditions and subsequent coupling for laser wakefield accelerator applications.

At the Facility for Advanced Accelerator Experimental Tests (FACET-II) accelerator, a pair of 10 GeV high-current electron beams is used to investigate Plasma Wakefield Acceleration (PWFA) in plasmas of different lengths. While PWFA has achieved astonishingly high accelerating gradients of tens of GeV/m, matching the electron beam into the plasma wake is necessary to achieve a beam quality required for precise tuning of future high energy linear accelerators. The purpose of this study was to explore how start-to-end simulations could be used to optimize two important measures of beam quality, namely maximizing energy gain and minimizing transverse emittance growth in a 2 cm long plasma. These two beam parameters were investigated with an in-depth model of the FACET-II accelerator using numerical optimization. The results presented in the paper demonstrate the importance of utilizing beam-transport simulations in tandem with particle-in-cell simulations and provide insight into optimizing these two important beam parameters without the need to devote significant accelerator physics time tuning the FACET-II accelerator.

The spontaneous emission of radiation from relativistic electrons within a plasma channel is called betatron radiation and has great potential to become a compact x-ray source in the future. We present an analysis of the performance of a broad secondary radiation source based on a high-gradient laser-plasma wakefield electron accelerator. The purpose of this study is to assess the possibility of having a new source for a non-destructive X-ray phase contrast imaging and tomography of heterogeneous materials. We report studies of compact and UV-soft X ray generation via betatron oscillations in plasma channel and in particular measurement of the radiation spectrum emitted from electron beam is analyzed from a grazing incident monochromator at Centro de Laseres Pulsados Ultraintensos (CLPU).

Laser wakefield accelerators (LWFAs) have been experimentally shown to produce sustained gradients of tens of GeV/m over tens of centimeters. While the strength of these fields has been demonstrated, a direct measurement of the field configurations inside an LWFA represents an emerging research topic. Here, we report on the results of transverse probing of the fields inside an LWFA at densities of 1e+15 — 1e+17 1/cm3, corresponding to plasma wavelengths in the range of several hundred microns. The LWFA is driven by BNL Accelerator Test Facility’s unique long-wave-infrared CO2 laser (9.2 μm) pulse, which currently generates 2 ps long pulses at 2-3 TW. The linac-produced electron beam has an energy of 50-60 MeV and about a 200 fs long bunch length. A YAG:Ce scintillator placed on a translation stage records the electron beam density profile at distances of up to 10 cm from the plasma. Particle-In-Cell Simulations using OSIRIS are used to corroborate the results of the experiment.

The plasma accelerator community has made significant progress in advancing particle beams, bringing us closer to realizing the dream of replacing the radio frequency (RF) cavities' MV/m fields with the plasma-sustained GV/m fields for collider applications. The beam requirements for realizing this vision emphasize a collider-quality beam featuring hundreds of pC of charge, energy spread less than 1%, and a normalized emittance in the tens of nanometers range. Achieving the low-energy-spread of the beam during acceleration involves flattening the accelerating field within the wakefield region occupied by the beam, which can be accomplished if the charge per unit length of the injected electron beam to exhibit a trapezoidal profile. In this study, we demonstrate how novel techniques for controlling the spatiotemporal properties of a focusing laser pulse enable the optical injection of an electron bunch inside a plasma wakefield that meets all the beam requirements for collider applications. Quasi-3D particle-in-cell simulations demonstrate the feasibility of this method for producing beams exceeding 200 pC of charge with emittance and energy spread well within collider requirements.

Laser wakefield accelerators (LWFAs) are capable of supporting accelerating and focusing forces on the order of 10–100 GeV/m, about three orders of magnitude greater than conventional RF accelerators. While theoretical solutions for the electromagnetic (EM) focusing fields have been developed, the field structures have yet to be verified experimentally. In this poster, we present simulation results for transverse probing of laser wakefields using ultrarelativistic electrons. We study the behavior of the probing electrons by implementing filtering masks to investigate focusing characteristics of thin electron "bands". The deflection of these bands after propagating through the wakefield is then used to characterize the EM forces. The simulated focusing behavior of these electron bands is in reasonable agreement with a theoretical model developed based on a thin lens model of the wakefield. Simulation results show the focusing of the bands to be an effective experimental diagnostic for verifying the EM field structure. This provides an analytic framework needed for the first direct measurements of focusing forces in an LWFA at the Accelerator Test Facility at Brookhaven National Lab.

This contribution presents the initial findings from the 3.2 Million Euro EuPRAXIA Doctoral Network. European Plasma Research Accelerator with eXcellence In Applications (EuPRAXIA) is at the forefront of advanced particle accelerator research, focusing on the development of plasma-based accelerator technologies. The EuPRAXIA Doctoral Network, a collaborative effort among leading research institutions, is dedicated to exploring and advancing the frontiers of plasma-based particle acceleration. The network’s research involves a wide range of topics, from beam diagnostics and optimization techniques to new applications. Here, we present the innovative approaches and methodologies employed to achieve very high acceleration gradients, improve the energy sharpness and overall beam quality. Some of the early results of this new network are discussed, showcasing the progress made across the network’s three scientific work packages. The contribution also gives an overview of the initial training provided to the network’s Fellows.

Particle beams with asymmetric transverse emittances and profiles have been utilized in facilities for driving wakefields in dielectric waveguides and to drive plasma wakefields in plasma. The asymmetric plasma structures created by the beam produce focusing forces that are transversely asymmetric. We utilize the ellipticity of the plasma ion cavity to model the beam evolution of the flat beam driver.

This paper explores the phenomenon of asymmetric blowout in plasma wakefield acceleration (PWFA), where the transversely asymmetric beam creates a transversely asymmetric blowout cavity in plasma. This deviation from the traditional axisymmetric models leads to unique focusing effects in the transverse plane and accelerating gradient depending on the transverse coordinates. We extend our series of studies on plasma wakefield acceleration (PWFA) by comparing our recently developed analytic model on the blowout cavity shape created by transversely asymmetric long beams, with Particle-in-Cell (PIC) simulations. The analysis focuses on validating the model's ability to predict the behaviors of different beam profiles in this regime.

At UCLA, a plasma source using capillary discharge has been developed and studied for its potential use in plasma wakefield experiments at MITHRA and AWA facilities. This compact, 8-cm long source, has the ability to create plasmas covering a wide range of densities, making it suitable for various experiments involving plasma wakefield acceleration (PWFA). With a 3-mm aperture, it can transmit high-aspect ratio beams, and its adjustable density feature allows for a detailed exploration of the shift from linear to nonlinear PWFA stages. In this paper, we will delve into the construction and evaluation of this capillary discharge plasma source, as well as the utilization of an interferometric diagnostic system for measuring plasma density.

The plasma wakefield accelerator, with acceleration gradients ranging from GeV/m to TeV/m, holds promise for propelling particles to high energies in linear colliders. This results in exceptionally bright beams characterized by intense ion-derived focusing, leading to the collapse of plasma ions. The non-uniform ion density triggers robust nonlinear focusing, potentially resulting in undesirable beam emittance growth. Our study extends prior research focused on electron acceleration by investigating ion-ion collisions, studying different collision models emphasizing the near-equilibrium state post-ion collapse utilizing the OSIRIS PIC code. Notably, our findings reveal that parametric excitations arising from plasma non-uniformity have an insignificant impact on phase space diffusion, a crucial insight for optimizing linear colliders.

FACET-II is the recently completed 10 GeV electron beam facility at SLAC National Accelerator Laboratory. The latest results on the flagship E300 experiment on Plasma Wakefield experiment will be presented.

The viability of next generation, compact, TeV-class electron-positron colliders based on staging of independently-powered plasma-based accelerators relies on the possibility of accelerating high-charge bunches to high energy with high efficiency and high accelerating gradient, while maintaining a small energy spread and emittance. Achieving a small energy spread with high-efficiency requires employing witness bunches with optimally tailored current profiles (optimal beamloading). Such profiles are analytically known in the case of plasma-wakefield accelerators operating in the blowout regime, while in the case of laser-plasma accelerators (LPAs) can only by computed numerically, and their determination requires, among other things, taking into account the laser driver evolution. A small bunch energy spread is a necessary condition to enable staging and minimize emittance degradation from chromaticity when bunches are transported from one plasma accelerator stage to the following one. In this contribution we will discuss examples of LPA stages operating in different regimes, namely a self-guided stage in the nonlinear regime and a quasi-linear stage in a hollow plasma channel, providing high-gradient, high-efficiency, and quality-preserving acceleration of bunches for collider applications. We will present, for each example, the current profile distribution for optimal beamloading, and we will analyze bunch emittance degradation when staging of such LPAs is considered.

Overview on laser plasma accelerators since the dream beam results.