Implementation of focal zooming on the Nike KrF laser

Journal Article · Tue Jan 15 00:00:00 EST 2013 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4789313· OSTI ID:22105360

Kehne, D. M.; Karasik, M.; Weaver, J. L.; Chan, Y.; Obenschain, S. P. ^[1]; Aglitsky, Y. ^[2]; Smyth, Z.; Lehmberg, R. H. ^[3]; Terrell, S. ^[4]

---

1. Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)
2. Science Applications International, McLean, Virginia 22150 (United States)
3. Research Support Instruments, Inc., Lanham, Maryland 20706 (United States)
4. Commonwealth Technologies, Inc., Alexandria, Virginia 22315 (United States)

In direct drive inertial confinement laser fusion, a pellet containing D-T fuel is imploded by ablation arising from absorption of laser energy at its outer surface. For optimal coupling, the focal spot of the laser would continuously decrease to match the reduction in the pellet's diameter, thereby minimizing wasted energy. A krypton-fluoride laser ({lambda}= 248 nm) that incorporates beam smoothing by induced spatial incoherence has the ability to produce a high quality focal profile whose diameter varies with time, a property known as focal zooming. A two-stage focal zoom has been demonstrated on the Nike laser at the Naval Research Laboratory. In the experiment, a 4.4 ns laser pulse was created in which the on-target focal spot diameter was 1.3 mm (full width at half maximum) for the first 2.4 ns and 0.28 mm for the final 2 ns. These two diameters appear in time-integrated focal plane equivalent images taken at several locations in the amplification chain. Eight of the zoomed output beams were overlapped on a 60 {mu}m thick planar polystyrene target. Time resolved images of self-emission from the rear of the target show the separate shocks launched by the two corresponding laser focal diameters.

• OSTI ID: 22105360
• Journal Information: Review of Scientific Instruments, Vol. 84, Issue 1; Other Information: (c) 2013 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BEAMS
IMPLEMENTATION
INERTIAL CONFINEMENT
KRYPTON FLUORIDE LASERS
NAVAL RESEARCH LABORATORY
POLYSTYRENE
TIME RESOLUTION