Working Groups

Working Group 1: Laser-plasma acceleration

Working Group Leaders: Kei Nakamura (LBNL); Chaojie Zhang (UCLA)

Working Group 1 (WG1) will focus on the acceleration of electrons and positrons using laser-plasma accelerators (LPAs). Work on developing LPAs are motivated by two major applications: high energy physics (HEP) colliders at the TeV scale and compact light sources. The path from recent results towards achieving high-quality beams required for these applications will be discussed.

Contributors are encouraged to present laser-plasma physics, simulations, and experiments that address the following topics, which will be the organizing themes for arranging working group discussions.

1. Injection: Controlled particle injection into laser-driven plasma wakefields to produce beams that are: stable and reproducible, lower in transverse and longitudinal emittances, and higher in charge. What are promising techniques that can produce high-quality beams needed for applications such as colliders, free-electron lasers, Thomson/Compton sources, etc.?
2. Acceleration: Laser-driven plasma wakefields to accelerate particle beams that are efficient in energy transfer of the laser energy to particle beams, applicable for high repetition rate operations, and energy-scalable for HEP applications. Self- and external-guiding schemes as well as manipulation of spatio-temporal couplings can be utilized to extend the acceleration length. Staging can overcome laser depletion limit. What are challenges, limitations, and solutions for laser-driven acceleration structures for light source, HEP and other applications?
3. Beam manipulation: Compact beam manipulation and transportation techniques are needed alongside acceleration structures to realize applications of LPAs. How can compact radiation cooling, focusing systems, and beam property exchanges be realized?
4. Diagnostics: Diagnostics are key for all elements described above to be developed. This includes radiation sources and other methods as tools to diagnose acceleration structures as well as the accelerated beams.

Joint sessions with other working groups will be arranged based on contributions.

Working Group 2: Computation for Accelerator Physics

Working Group Leaders: Diana Amorim (LBNL), Jorge Vieira (IST)

The recent advances on experiments, which now provide measurements with unprecedented detail and the access to new experimental layouts, in conjunction with greater computing resources, enabling realistic three-dimensional modelling with new physics models, pose new questions to numerical simulations of advanced accelerators. The goal for this working group is to understand the state-of-the art of simulation codes in this context. In particular, in this group we aim to review and discuss the following:

• What are the novel advances on reduced modelling of plasma accelerators enabling substantial reductions in computational requirements with high accuracy? This includes discussions on the accuracy of these models versus their speed, and their suitability to take advantage from exa-scale computing.
• What are the recent developments that enable quantitative benchmarks between numerical simulation results and experiments? This includes the recent efforts to incorporate realistic initial conditions in simulations, together with new improved algorithms leading to greater accuracy and numerical stability.
• How will new algorithms allow accurate modeling of relevant multi-scale physics in plasma accelerators? This topic encompasses new advances on multi-physics models, ranging from ultra-short wavelength radiation generation in simulations, to the long-term dynamics of the plasma, crucial for example to determine and enhance repetition rates towards the capabilities of conventional accelerators.
• What are the recent advances in including multi-physics models (e.g. QED processes, spin physics, ionization), the limitations of those models, and how could their applicability be further expanded?
• What is the role of machine learning in modelling, monitoring and controlling experiments and simulations towards the generation of particle and light beam sources with higher quality?
• What are the recent advances on start to end modelling of advanced accelerator and light source techniques?
• How can we improve performance on new computing architecture — possibly while keeping code portability? Are there new findings in order to improve vectorization, load balancing, parallel scaling, etc.?
• Are there tools that could benefit the community and be shared across teams developing separate codes, e.g., in visualization, post-processing, best software practices, and code validation?

Participants are encouraged to address their recent contributions to these topics in their presentations and, in the spirit of this workshop, to actively participate in the questions and answers that will follow them.

Working Group 3: Laser and High-Gradient Structure-Based Acceleration

Working Group Leaders: Emilio Nanni (SLAC), Jiahang Shao (ANL)

The purpose of Working Group 3 is to discuss recent advances in externally-powered structure-based accelerators, both laser and rf driven. The capability to accelerate particles at higher accelerating gradients and efficiencies is essential for reduction of size and cost of future accelerators for science and industry. This includes the future multi-TeV e⁺e^- collider for High Energy Physics, free-electron lasers (FELs) for Basic Energy Sciences and National Security, industrial accelerators for Energy and Environmental Applications, and accelerators for other applications (direct material investigation, medical field, nanotechnology, etc.).

The working group welcomes presentations on the following topics:

1. Recent developments in novel accelerating structures with new geometries, new materials (dielectric, metamaterial, hybrid, etc.), new fabrication technologies (additive manufacturing, micromachining, etc.), frequencies from microwave to THz and optical spectrum, and operating conditions from normal conducting to cryogenic and superconducting.
2. Recent advances in understanding rf breakdown and quench phenomena at different frequencies and materials, and other physics limitations to the accelerating gradient.
3. Recent advances in improving the accelerating efficiency, such as understanding of sources of microwave dissipation and pathways, development of ultra-low rf loss material, heavy beam-loading compensation.
4. Demonstration of high accelerating gradients and efficiencies.

The group will also try to address specific issues such as novel structure-beam interaction schemes (IFEL, undulator-mediated, etc.), high efficiency electromagnetic power source development, optimizing novel accelerating structures using advanced algorithms, beam dynamics and collective effects associated with reduced beam apertures, optimizing power coupling schemes to the structures, increasing wall-plug-to-beam efficiency, and integrated particle source designs.

Working Group 4: Beam-Driven Acceleration

Working Group Leaders: Manoel Conde (ANL), Philippe Piot (NIU)

This working group examines plasma- and structure-based beam-driven wakefield acceleration. The overarching goal of the WG4 is to provide a platform to discuss recent development on the various topics relevant to beam-driven acceleration (both in the collinear and two-beam configurations). In particular, our group will discuss:

• Beam dynamics associated with drive beam: beam shaping for transformer-ratio improvement, methods to mitigate beam-break-up instabilities.
• Recent developments in the production of plasmas (control of density for emittance preservation) and design of structures.
• Generation of suitable main/witness bunches and challenges associated with their acceleration in a beam-driven accelerator (emittance preservation, beam loading compensation, chirp control, etc.).
• Use of wakefields for beam control (dechirper, microbunch generation, etc.), radiation production, and diagnostics.
• Progress toward the integrated design of beam-driven accelerators for linear-collider applications and future light source concepts.

The working group will include discussions on theoretical and numerical-simulation developments along with experiment results and plans.

Working Group 5: Beam Sources, Monitoring, and Control

Working Group Leaders: Heather Andrews (LANL), Agostino Marinelli (SLAC)

WG 5 will address the three subjects in its title:

1. Beam sources: Advanced accelerator and beam sources require and/or generate beams with unique characteristics, including femtosecond bunch lengths, high peak currents, high bunch charges, correlated and uncorrelated energy spreads, and position, pointing, and timing stability issues. This working group will examine the feasibility of meeting these requirements and beam properties.
2. Monitoring and diagnostics: Advanced accelerators carry a much larger burden in terms of diagnostics than conventional accelerators. The properties of these beams, the behavior of the accelerator structure, and the source driver (e.g., wakefield, RF, etc.) must be characterized. One of the goals in this area is a non-destructive single shot 6-d characterization of the particle beam phase space at various points along the accelerator. We will seek solutions for non-interceptive diagnostics to address some of the challenges of beam diagnostics.
3. Beam control and manipulation: Advanced accelerators are notorious for fluctuations in beam parameters such as energy, charge, pointing stability, bunch shape, etc. The capabilities of diagnostics to measure these beam properties have been continuously advancing, but there is also a great need to be able to use these measurements to improve and manipulate beam parameters, as well as shaping beams for use in a variety of scientific applications. We will examine the present advances and efforts in this quest.

We invite presentations, both theoretical and experimental, in the above areas as well as related subjects. We will discuss the state-of-the-art in these topics and we will try to identify the challenges that need to be addressed to further advance the field. Results of this assessment will be presented during the close out session of the workshop and in the written working group summary. Joint sessions with other WGs on the topics of beam generation, diagnostics and control may be scheduled.

Working Group 6: Laser-Ion Acceleration

Working Group Leaders: Franklin Dollar (UCI), Tammy Ma (LLNL)

Laser-driven ion acceleration has applications in advanced accelerators, nuclear fusion, medicine, radiography, and to drive novel states of high energy density matter. Many of these applications require ion bunches with high energy, narrow spectra, and low emittance, and, in principle, laser-based ion accelerators can achieve these ion beam properties at significantly lower cost and greater compactness than conventional accelerators. In recent years, advances in ultra-high power and high-intensity lasers, modern pulse cleaning techniques, methods for spatially and temporally manipulating short laser pulses, higher repetition rates, novel target fabrication approaches, new computing paradigms, and increasing computing power have enabled major developments in the capabilities of ion beams and the understanding of the underlying acceleration physics. ­

In this working group, we will discuss the highlights of recent experiments and simulations in laser-ion generation showing progress towards increased efficiency, charge, and precision tailoring of the spectrum. We will review the recent results across a number of acceleration schemes, and the challenges that remain to be addressed as we develop these ion beams toward specific applications.

We invite both theoretical and experimental presentations addressing the above areas as well as other related topics.

Working Group 7: Radiation Generation and Advanced Concepts

Working Group Leaders: Marie-Emanuelle Couprie (SOLEIL), Jonathan Jarvis (FNAL)

Accelerator-based light sources have opened new frontiers in radiation brilliance, tunability, power, and wavelength and are among the world’s most productive scientific instruments. As advanced-acceleration techniques mature, it is time to explore the achievable performance for light source applications.

We encourage participants to contribute work on radiation generation with charged-particle beams, particularly when the beam is driven by an advanced-accelerator technique. Areas of interest include betatron radiation emitted by electron beams oscillating in a plasma-ion field, undulator radiation, progresses towards a plasma-based free-electron laser, Compton and Thomson scattering, and Bremsstrahlung. The generation of radiation with unique properties such as ultra-short pulses, polarization control, multi-color radiation, and applications of these radiation sources is also of interest.

Finally, advanced concepts that enable improved beam performance, particularly for radiation applications, are also of interest. These include phase-space manipulation and cooling, advanced beam dynamics, and novel configurations or architectures.

Working Group 8: Advanced Laser and Beam Technology and Facilities

Working Group Leaders: Laura Corner (Liverpool), Emily Link (LLNL)

The primary focus of working group 8 will be the laser and beam technologies required for novel accelerators. Both laser-driven and beam-driven efforts will require orders of magnitude improvement to produce future particle colliders. Advancements in technologies and requirements for these future novel accelerators will be of primary importance. Many new facility and experimental capabilities are emerging for users world-wide. We would like to hear about how new experimental capabilities in these facilities will improve our data quality and understanding of the laser- and beam-driven accelerator physics. This can include new experimental, data acquisition and analysis techniques, new diagnostic and stabilization methods, monitoring of facility performance including feedback and machine learning applications, and lessons learned from facilities developing these new, never-before accessed parameter spaces.

Lasers play an important role in advanced accelerator research and technology, from driving novel accelerators — high peak and average power lasers for LWFA, hybrid plasma acceleration schemes, DLA, ion acceleration, vacuum acceleration — to tools as diagnostics for the specialized charged particle bunches produced by advanced accelerators and sources for the fs-level jitter synchronization that will be needed for future facilities. WG8 welcomes submissions on the technologies required to achieve the required laser parameters for all these goals. All proposed architectures are of interest, including improvements in beam quality, pulse fidelity, efficiency, stability, and robustness. We would like to discuss these advances in laser and beam drivers and the supporting technologies required to achieve them, with a focus on how these new technologies will affect the quality of the particle beams produced.