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.

Laser-driven ion accelerators (LDIAs) are well-suited for radiobiological research on ultra-high dose rate effects due to their high intensity. For this application, a transport system is required to deliver the desired beam intensity and dose distribution while online dosimetry is required due to the inherent shot-to-shot variability of LDIAs. At the BELLA Center's iP2 beamline, we implemented two compact, permanent magnet-based beam transport configurations for delivering 10 or 30 MeV protons to a biological sample, along with a suite of diagnostics used for dosimetry. These diagnostics include multiple integrating current transformers (ICTs) for indirect online dose measurements and calibrated radiochromic films (RCFs) to measure the dose profile and calibrate the ICT dosimetry. Benchmarked Monte-Carlo (MC) simulations of the beamline allow us to predict the dose received by the sample and correct the linear energy transfer (LET)-dependent response of the RCFs. This work not only further establishes the practicality of utilizing LDIAs for radiobiological research but also highlights the BELLA Center's capacity to accommodate further experiments in this domain.

We discuss a compact, laser-plasma-based scheme for the generation of positron beams suitable to be implemented in an all-optical setup. A laser-plasma-accelerated electron beam hits a solid target producing electron-positron pairs via bremsstrahlung. The back of the target serves as a plasma mirror to in-couple a laser pulse into a plasma stage located right after the mirror where the laser drives a plasma wave (or wakefield). By properly choosing the delay between the laser and the electron beam the positrons produced in the target can be trapped in the wakefield, where they are focused and accelerated during the transport, resulting in a collimated beam. This approach minimizes the ballistic propagation time and enhances the trapping efficiency. The system can be used as an injector of positron beams and has potential applications in the development of a future, compact, plasma-based electron-positron linear collider. After injection, positrons can be accelerated to high energies in a plasma (e.g., using a plasma column) for applications to plasma-based colliders.

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.

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.

Laser-driven ion accelerators (LDIAs) are well-suited for radiobiological research on ultra-high dose rate effects due to their high intensity. For this application, a transport system is required to deliver the desired beam intensity and dose distribution while online dosimetry is required due to the inherent shot-to-shot variability of LDIAs. At the BELLA Center's iP2 beamline, we implemented two compact, permanent magnet-based beam transport configurations for delivering 10 or 30 MeV protons to a biological sample, along with a suite of diagnostics used for dosimetry. These diagnostics include multiple integrating current transformers (ICTs) for indirect online dose measurements and calibrated radiochromic films (RCFs) to measure the dose profile and calibrate the ICT dosimetry. Benchmarked Monte-Carlo (MC) simulations of the beamline allow us to predict the dose received by the sample and correct the linear energy transfer (LET)-dependent response of the RCFs. This work not only further establishes the practicality of utilizing LDIAs for radiobiological research but also highlights the BELLA Center's capacity to accommodate further experiments in this domain.

Ion beams from laser-driven plasma sources can provide ultra-short (10s of fs for 10s of MeV), ultra-low slice emittance (10s of nm), and high-charge (100s of pC) properties. Demonstrated maximum energies for laser-ion sources are just short of those needed for pivotal applications, such as proton tumor therapy. Here, a robust and energy-scalable concept is presented that could boost the energy of an ultra-intense ion bunch through multiple stages to 100s of MeV/u and even towards the relativistic regime, using identical plasma booster stages based on magnetic vortex acceleration. Electromagnetic, full-3D particle-in-cell simulations are used to demonstrate the capability to capture, accelerate, and preserve the quality of a high-charge (200 pC), 20 nm emittance proton bunch, where both source and booster stages could be realized with capabilities of existing laser facilities.

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.