Summary WG8 - Advanced and Novel Accelerators for High Energy Physics Co-leaders: Brigitte Cros (LPGP), Patric Muggli (MPP), Carl Schroeder (LBNL), Chuanxiang Tang (Tsinghua) WG8: Examine key challenges, discuss suitable concepts, and identify topics for future R&D of advanced and novel accelerators for HEP applications.

WG8 Program Tuesday 16:00 Conventional and advanced concepts in the designs of plasma-based colliders SERYI, Andrei (JAI) Energy spread of the beam induced by betatron radiation in PWFA SHPAKOV, Vladimir (INFN) Adiabatic plasma lens experiments at SPARC FILIPPI, Francesco (INFN) Multiple beam acceleration based on proton-driven wakefield in a hollow plasma channel LI, Yangmei (Manchester) Tuesday 18:00 Considerations for Energy Scaling of Dielectric Laser Accelerators ENGLAND, Joel (SLAC) Laser wakefield electron acceleration to multi-GeV energies ANDREEV, Nikolay E. (JIHT-RAS) Matched electron beams in multi stage laser wakefield acceleration PUGACHEVA, Daria (JIHT-RAS) Warp-X: a new exascale computing platform for Beam-Plasma Simulations VAY, Jean-Luc (LBNL)

Energy spread of the beam induced by betatron radiation in PWFA Energy spread of the beam induced by betatron radiation in PWFA SHPAKOV, Vladimir (INFN) No limit to acceleration from betatron radiation Growing energy spread

Adiabatic plasma lens experiments at SPARC FILIPPI, Francesco (INFN) Planned demonstration experiment Adiabatic plasma lens circumvents Oide limit

Multiple beam acceleration based on proton-driven wakefield in a hollow plasma channel -- LI, Yangmei (Manchester) Hollow plasma channel enables the operation of multiple PD-PWFA in the blowout regime channel provides emittance-preserving acceleration Proton bunch Electron bunch hollow radius rc Y. Li, et al. arXiv preprint arXiv:1610.08734 (2016).

Considerations for Energy Scaling of Dielectric Laser Accelerators Considerations for Energy Scaling of Dielectric Laser Accelerators ENGLAND, Joel (SLAC) 2.2 GV/m laser injector concept (with 100 attosecond microbunching) high gradient (0.85 GeV/m) operation and 0.3 MeV energy gain (pulse front tilt demonstration) Use different asynchronous spatial harmonics to provide focusing force Phase control of the laser enables dynamic control of acceleration and focusing. can counteract the resonant defocusing and provide beam confinement now incorporated into structure designs and experimental plans for coming year FAU Erlangen UCLA Pegasus pulse front tilted laser electrons e- E0 k0 Interaction length > 500 um Phase mask Laser LCD programmable phase mask (spatial light modulator) gradient hard-coded phase mask (simulation + fabrication prototype) • Configuration for microbunching and net acceleration in a DLA. • Extended interaction over 1-2 cm with multi-MeV energy gains.

Laser wakefield electron acceleration to multi-GeV energies Laser wakefield electron acceleration to multi-GeV energies ANDREEV, Nikolay E. (JIHT-RAS) Modeling of multi-stage accel. preserving high-quality e-beams for collider Demonstrated laser propagation and wakefield excitation (over many ZR), and GeV beams Beam loading to optimize e-beam parameters (low energy spread)

Matched electron beams in multi stage laser wakefield acceleration Matched electron beams in multi stage laser wakefield acceleration PUGACHEVA, Daria (JIHT-RAS) Matched a beam with focusing forces prevents emittance growth. Smooth exit explored. Polarization preserved in multi-stage LWFA (~0.02% depolarization at 1 TeV)

ECP Project WarpX: Exascale Modeling of Advanced Particle Accelerators Warp-X: a new exascale computing platform for Beam-Plasma Simulations VAY, Jean-Luc (LBNL) ECP Project WarpX: Exascale Modeling of Advanced Particle Accelerators Goal (4 years): Convergence study in 3-D of 10 consecutive multi-GeV stages in linear and bubble regime, for laser- & beam-driven plasma accelerators. How:  Combination of most advanced algorithms Coupling of Warp+BoxLib/AMReX+PICSAR  Port to emerging architectures (Xeon Phi, GPU)   Illustration Team: LBNL ATAP (accelerators) + LBNL CRD (computing science) + SLAC + LLNL Ultimate goal: enable modeling of 100 stages by 2025 for 1 TeV collider design!

Joint WG1-WG8 Session on present & future Facilities Wednesday 18:00 EuPRAXIA@SPARC_LAB: design study towards a new compact FEL facility at LNF FERRARIO, Massimo (INFN) Prospects for Plasma Wakefield Acceleration at the MAX IV Laboratory LUNDH, Olle (Lund Univ.) Lattice design and start-to-end simulations for the ARES linac ZHU, Jun (DESY) FLASHForward - A Future-Oriented Wakefield-Accelerator Research and Development Facility at FLASH OSTERHOFF, Jens (DESY) Layout considerations for a future electron plasma research accelerator facility EuPRAXIA WALKER, Paul Andreas (DESY) Discussion on facilities for collider relevant R&D: Need for positron acceleration R&D (novel laser-based positron generation and cooling)

EuPRAXIA@SPARC_LAB: design study towards a new compact FEL facility at LNF FERRARIO, Massimo (INFN) Candidate LNF to host EuPRAXIA advanced accelerator test facility Integrated with upgraded FLAME high power laser system FEL user facility (1 GeV x-band RF linace producing ~3 nm radiation) Goal: compact 5 GeV accelerator

Prospects for Plasma Wakefield Acceleration at the MAX IV Laboratory Prospects for Plasma Wakefield Acceleration at the MAX IV Laboratory LUNDH, Olle (Lund Univ.) Explored possibility of PWFA experiment with witness beam (6 GeV energy gain) MAX IV (3 GeV) linac well suited for PWFA studies

Lattice design and start-to-end simulations for the ARES linac Lattice design and start-to-end simulations for the ARES linac ZHU, Jun (DESY) Start-to-end simulations identified working points (1-30 pC, 0.5-30 fs rms) at ARES linac (SINBAD project) Aiming for LWFA and LWFA-driven FEL Space-charge effects important (energy upgrade desireable)

FLASHForward - A Future-Oriented Wakefield-Accelerator Research and Development Facility at FLASH -- OSTERHOFF, Jens (DESY) 1.25 GeV, few 100 pC, 100 fs, 3GHz cavity for bunch shaping (triangular); x-band deflector (~1fs resolution); SCRF (<=MHz) Undulators to be added in 2020

Layout considerations for a future electron plasma research accelerator facility EuPRAXIA WALKER, Paul Andreas (DESY) Layout for 5 GeV e-beam accelerator facility Design includes 2 user areas: FEL HOPA: test beams for HEP, detector tests, and other pilot applications (e.g., compact x-ray sources)

Discussions on facilities for HEP-relevant accelerator development Need for positron acceleration R&D (novel laser-based positron generation and cooling) Develop test beams useful for detector development (way to bridge the gap between advanced accelerators and HEP community) Bunch shaping and format tunability highly desirable. Emphasis on reliability Development of high rep rate (kHz and beyond) capabilities important (improved stability via feedback controls, etc.)

General conclusions from WG8 discussions Future linear collider based on ANA must be a global effort Collider subsystems (non-linac components) should be redesigned to take advantage of the properties of the ANA beams. FF/BDS (replace with plasma focusing system?) Damping rings (replace with linear cooling system?) … Accelerator must be integrated with all collider subsystems Communication with conventional accelerator physicists needs to be stronger (not to re-invent) Competition between multiple concepts good (at this R&D phase). Periodic community reviews to identify risks, R&D, and align priorities (this was extremely useful toward development of ILC, CLIC, etc.)

ALEGRO (Advanced LinEar collider study GROup) Provide a framework for international coordination and communication Build on development of R&D roadmaps (in US and Europe) Broaden the community of Advanced Aceelerator R&D towards HEP applications, involving universities, accelerator labs/institutes and including advanced accelerator researchers, conventional accelerator/collider researchers, and high-energy physicists/detector experts. Short-term goal: Report on Advanced Accelerator R&D priorities as input for the European Research Strategy Group for HEP (due end of 2018; first draft June 2018; reviewed by community at AAC in Aug 2018) Regular (yearly) workshops to discuss and prioritize R&D; Workshop being planned for 26-29 March 2018 at Oxford

ALEGRO (Advanced LinEar collider study GROup) Proposed organization (discussed in WG8): 7 Working groups: each with 2 co-Leaders Common topics: Physics Case (Detectors, new developments), Modeling/Simulation, Collider Design (integration of subsystems) Accelerator Concepts: LWFA, PWFA, SWFA, DLA Volunteers welcome (contact Brigitte Cros)