title: Laser-beam zooming to mitigate crossed-beam energy losses in direct-drive implosions.
abstract: Spherically symmetric direct-drive-ignition designs driven by laser beams with a focal-spot size nearly equal to the target diameter suffer from energy losses due to crossed-beam energy transfer (CBET). Significant reduction of CBET and improvements in implosion hydrodynamic efficiency can be achieved by reducing the beam diameter. Narrow beams increase low-mode perturbations of the targets because of decreased illumination uniformity that degrades implosion performance. Initiating an implosion with nominal beams (equal in size to the target diameter) and reducing the beam diameter by ∼ 30%-40% after developing a sufficiently thick target corona, which smooths the perturbations, mitigate CBET while maintaining low-mode target uniformity in ignition designs with a fusion gain ≫ 1.
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: I V
authors.initials: IV
authors.lastname: Igumenshchev
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: D H
authors.initials: DH
authors.lastname: Froula
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: D H
authors.initials: DH
authors.lastname: Edgell
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA and Department of Mechanical Engineering, University of Rochester, Rochester, New York 14623, USA.
authors.forename: V N
authors.initials: VN
authors.lastname: Goncharov
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Kessler
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: F J
authors.initials: FJ
authors.lastname: Marshall
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA and Department of Mechanical Engineering, University of Rochester, Rochester, New York 14623, USA and Department of Physics and Astronomy, University of Rochester, Rochester, New York 14623, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: McCrory
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: P W
authors.initials: PW
authors.lastname: McKenty
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA and Department of Mechanical Engineering, University of Rochester, Rochester, New York 14623, USA and Department of Physics and Astronomy, University of Rochester, Rochester, New York 14623, USA.
authors.forename: D D
authors.initials: DD
authors.lastname: Meyerhofer
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Michel
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: T C
authors.initials: TC
authors.lastname: Sangster
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: W
authors.initials: W
authors.lastname: Seka
authors.affiliation: Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, New York 14623-1299, USA.
authors.forename: S
authors.initials: S
authors.lastname: Skupsky