Nike KrF Facility Tour HAPL Meeting 31 October 2007 NRL program - - PowerPoint PPT Presentation

Nike KrF Facility Tour

• NRL program became interested in KrF in mid 1980’s
• KrF program begun in 1987
• Nike competed in 1995
• Up to 5 kJ obtained from main amplifier ( ~60% more with modern diode)
• About 600 shots per year for target experiments with ~ 1.5-3 kJ on target
• Complements Electra as half-full scale scale KrF reactor beamline

HAPL Meeting 31 October 2007

Outstanding uniformity: reduces seed for hydro instabilities Shortest wavelength (248 nm) higher absorption, rocket efficiency minimizes risk from laser plasma instability Straight-forward "zooming“ increases absorption & pellet gain

KrF lasers for inertial fusion energy

PHYSICS

NRL ICF physics program is focused on target designs that benefit with KrF

• Conventional direct drive
• Shock ignited direct drive ( may reduce laser energy and increase gain)
• Impact Fast Ignition

We match the electron-beam-pumped amplifier time scale to few ns target time scale via angular multiplexing

Target FRONT END ( few nsec FWHM) LONG PULSE AMPLIFIER (~ 100's nsec) Multiplexer Array (beam splitters) Demultiplexer Array (mirrors) Only three pulses shown for clarity Last Pulse F i r s t P u l s e

Adapted from Rosocha et al, Fusion Technology, May 1987 page 497

A KrF laser train uses Induced Spatial Incoherence (ISI) to produce very uniform target illumination

Target Amplifier 1 (at FT plane) Object aperture Spatially incoherent 3 THz KrF source Amplifier 2 (at FT plane) Intensity profile at target instantaneous averaged Intensity profile at aperture instantaneous averaged

The laser profile at the aperture is imaged through the amplifiers onto the target One can easily achieve focal zooming by passing different temporal portions

• f the pulse through different apertures

Laser beam

high F# optics

Laser spot size follows imploding pellet

Nike laser Chain

Nike laser provides highly uniform target illumination (best by far in the business)

Illuminated aperture imaged

• nto target

Laser profile in target chamber

60-cm aperture amplifier

Nike “propagation” Bay

Optics for angularly multiplexed beams Final turning mirrors and target chamber optics

Nike target chamber

Backlighter array Main Array Optical and x-ray diagnostics Cyro targets

We use Nike is to study laser-accelerated planar targets

MAIN LASER BEAMS QUARTZ CRYSTAL 1.86 keV imaging 2D IMAGE STREAK CAMERA Time Sample RT Data Sample RT Data BACKLIGHTER LASER BEAMS RIPPLED TARGET BACKLIGHTER TARGET Si

• Y. Aglitskiy, et al. , Phys. Rev. Letters, 86, 265001 (2001)

0 to 100 km/sec in <4 ns

Initial Nike laser-plasma experiments show no evidence for parametric instability @ 2-3x1015 W/cm2

12 overlapped 300 ps Nike “backlighter” beams Cryo D2 and plastic foam targets

Two Tour Groups: A-M with Victor Serlin + Y. Chan + Jim Weaver (start with target area) N-Z with David Kehne + Max Karasik + S. Obenschain (start with laser) NRL should be providing bus service (1/4 mile walk)