AAC 2012 Working Groups



WG1 Laser-Plasma Wakefield Acceleration
Leader Carl Schroeder, LBNL
Co-leader Mike Helle, NRL

Working Group 1 (WG1) will primarily focus on the acceleration of electrons and positrons using laser-plasma interactions. WG1 will also address basic laser-plasma physics, novel radiation sources based on intense laser-plasma interactions, and applications of laser-plasma accelerators such as HEP and particle beam drivers for light sources.

Electron beams accelerated up to and beyond a GeV in energy have been demonstrated in a single stage laser-plasma accelerator. Control over particle injection for improved beam quality and stability is progressing using a variety of methods. Further improvements in beam quality and stability are desirable for applications. Also, improved efficiency and a path to higher energy are required for HEP applications. WG1 will be organized about the following sub-topics and questions:

  1. How can particle injection into the laser-driven plasma wakefields be controlled for stable, reproducible, high-quality beams?
  2. Staging laser-plasma accelerators is required to reach high beam energy for HEP applications. How can staging best be achieved while preserving beam properties?
  3. How can the efficiency of energy transfer from the laser to the beam be improved and/or optimized?
  4. Laser guiding is required to extend the laser-plasma interaction length. Is laser selfguiding sufficient? What methods are available for creation of pre-formed plasma channels and plasma structures? What challenges must be overcome when considering the high repetition rates necessary to reach the luminosity values required for HEP applications?
  5. Can laser-plasma interactions be used to generate radiation for user applications? How can the properties of laser-plasma accelerated electron beams be best exploited for radiation generation?
  6. What novel diagnostic techniques are required to understand the electron beam properties and the laser-plasma interaction.

Contributors are encouraged to address these topics. We will arrange working group discussions around these topics, and joint sessions with other working groups will be arranged based on contributions.

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WG2 Computations for Accelerator Physics
Leader David Bruhwiler, Tech-X Corp.
Co-leader Zhenghai Li, SLAC

The computational working group will review and assess state-of-the-art computational tools for modeling

    1. beam-driven and laser-driven accelerating structures (plasma, dielectric and metal),
    2. other high-gradient rf structures and high brightness sources,
    3. acceleration and cooling of muon beams, as well as high-intensity proton drivers and the associated pion production,
    4. radiation from beams and beam-driven structures,
    5. phase space manipulation of beams, and
    6. diagnostics relevant to any of the these topics.

Verification and validation of models will be an emphasis, especially as it relates to computational support of present and near-term experimental programs, including the simulation of beam, laser and radiation diagnostics. We will discuss recent advances in algorithmic developments, the effective use of parallel computing on conventional and manycore architectures, and long-term computational needs for next-generation accelerators.

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WG3 Laser and High-Gradient Structure-Based Acceleration
Leader Mike Fazio, SLAC
Co-leader Scott Anderson, LLNL

WG 3 will assess current challenges involved in developing an advanced accelerator based on electromagnetic (EM) structures, and survey state-of-the-art methods to address those challenges. A critical challenge for EM structures is gradient limitation imposed by breakdown, pulsed heating, dark current, quench, thermal breakdown and other factors, depending on structure type, pulse width, duty cycle and regime of operation. WG 3 will assess the understanding of gradientlimiting phenomena over the range of frequencies in room temperature, superconducting, THz and optical EM, and dielectric-based structures. This workshop particularly seeks to emphasize sources and approaches at Terahertz frequencies, which is a frequency band that is relatively unexplored in terms of its potential. It will survey the state of the art in RF source and component development and new ideas in material development, surface coating and processing for accelerator applications. WG 3 will also address challenges beyond gradient limitation, including simulation challenges, high order mode characteristics and damping, emittance requirements, power source requirements, wall-plug to beam power efficiency, limitations to luminosity or brightness, and fabrication tolerances.

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WG4 Beam-Driven Acceleration
Leader Patric Muggli, USC/MPI
Co-leader Joel England, SLAC

The use of particle beams to generate intense wakefields and produce high-gradient acceleration has experienced a renewed interest. Experiments using dielectric-lined waveguides and capillaries as confining structures for high-gradient beam-driven Cherenkov wakes are ongoing at ANL and UCLA. And as the experimental plasma wakefield acceleration (PWFA) program at SLAC restarts this year at the FACET user facility, new experiments are being proposed at CERN (using proton drive bunches), DESY, DESY Zeuthen, Frascati, in the UK, in Russia, and possibly elsewhere. Experiments are also continuing at BNL-ATF. New concepts based on selfmodulation of the PWFA drive bunch are also emerging. Working Group 4 will attempt to capture this renewal by examining the latest results, and determining the status and the goals of the various proposed programs. The main issues that should be tested experimentally and studied numerically will be discussed. We will also attempt to determine the various possible concepts for a future lepton collider or for other applications (electron/positron colliders, injectors, etc.).

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WG5 Beam and Radiation Generation, Monitoring, and Control
Leader Pietro Musumeci, UCLA
Co-leader Jeroen van Tilborg, LBNL

WG 5 will address a variety of themes:

  1. Beam sources for modern and future accelerators. In particular we would like the contributors in this section to analyze critically the performances of conventional photoemission and field emission based injectors (DC, RF and superconducting) with respect to the recent progress achieved with all optical laser plasma injection schemes. What are the respective differences and advantages in terms of beam parameters? What are the practical and fundamental limits of performances in terms of high intensity, small emittances, short bunch lengths, and strict synchronization requirements? How are the beam properties maintained during transport (say, for example, to an undulator or a delivery beam line)?
  2. Beam control and manipulation schemes. These include emittance exchange, microbunch train and beam shaping (ramped beams, ellipsoidal distributions), and flat beam transforms. An important question here is the limit of applicability of these schemes for higher intensity beams. How well do we understand and control the space charge effects in the beam dynamics?
  3. Novel frontiers in beam parameters required corresponding progress in advanced beam diagnostics. We will discuss advanced beam diagnostics including time-resolved diagnostics, non-intercepting measurement systems, low beam charge and transverse halo diagnostics. Diagnostics characterizing beams during injection, acceleration or transport are all relevant. In particular the temporal duration of the beam is one parameter that has seen a dramatic order-of magnitude in the last few years. What are the techniques required to study particle beams with sub-10 fs time-resolutions?
  4. Radiation generation. Beam-generated radiation is interesting as it reveals information on the beam and can be used as a powerful beam diagnostic. More importantly beam-based radiation sources form an increasingly important section of advanced accelerator research especially in the cases where the spectrum of the radiated photons is in a region of electromagnetic spectrum where other sources are scarce. These are typically the THz region 0.1-10 THz, and the X-ray and gamma-ray region (below 30 nm). What are the unique characteristics of these radiation sources?

We will accept contributed papers, both theoretical and experimental, in the above areas as well as other related topics. We invite the speakers to take advantage of the new poster section to leave more space for discussion in the working group and make an effort to try to answer the questions posed in these general themes and 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 sections with WG1 on the topic of beam generation and radiation generation will be scheduled.

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WG6 Laser-Plasma Acceleration of Ions
Leader Sergei Tochitsky, UCLA
Co-leader Manuel Hegelich, LANL

Recent demonstration of protons with a cut-off energy >100 MeV and carbon C6+ ions at >1 GeV from laser-plasma interactions with nanofoils and quasi-monoenergetic ~22 MeV protons generated in H2 gas renewed interest to potentially compact and affordable Laser Driven Ion Accelerators (LDIAs) of high-energy proton/ion beams. This WG will review various acceleration mechanisms, target media and configurations, and laser characteristics used in recent experiments and simulations. Paths for achieving monoenergetic beams at and above 200 MeV/u will be explored. Two main approaches to monoenergetic ion source will be studied:

  1. production of high-energy proton/ion beams with a narrow energy spread from plasmas and
  2. selection of monoenergetic beam from a broad energy spectrum. WG 6 will discuss requirements to advanced accelerators for proton/ion radiotherapy, a high-brightness picosecond ion injector and kJ high-energy ion fast igniter for fusion.

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WG7 Muon Colliders and Advanced Concepts
Leader Sergey Nagaitsev, FNAL
Co-leader Scott Berg, BNL

The subject matter of this WG has evolved over the years. The muon collider has become a viable concept for achieving 3-5 TeV center-of-mass energy. WG 7 will address major challenges facing the muon collider community, such as high-gradient acceleration and emittance reduction via cooling. Alternative methods for muon production, acceleration and beam cooling will be explored. Among other advanced concepts, new particle production, storage and acceleration techniques that lie outside the purview of the other WGs, will be explored.

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WG8 Laser Technology for Laser-Plasma Accelerators
Leader Erhard Gaul, UT-Austin Austin and National Energetics, Inc.
Co-leader Csaba Toth, LBNL

This newly created WG harkens back to AAC 1996, which featured a very successful WG entitled “Laser Sources for Particle Acceleration” at a time when multi-terawatt chirped-pulseamplified solid-state laser systems were beginning to heavily influence advanced accelerator research. Today multi-petawatt laser systems are sparking another renaissance in laser-plasma electron and ion acceleration and associated x-ray source development. This WG will bring together researchers from academia and national laboratories and representatives of commercial vendors of high average- and peak-power laser systems to explore needs and possibilities for the next generation of laser-plasma acceleration research. The goal of the WG is to establish as a baseline of what laser systems are available now or in the near future (0-4 years), and identify the trends and requirements in laser development towards higher peak power, higher average power and higher efficiency together with other parameters (pulse duration, wavelength, beam quality, etc…).

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