3v pulse shape (540 TW) 3v near field profile 3v spectrum (90 GHz SBS only)
Theoretical fit
1.2x105
1.0x105 Data
Intensity
8.0x104
6.0x104
4.0x104
2.0x104
10 15 20 0
Time [ns] –150 100 50 0 50 100 150
Frequency shift [GHz]
Performance of an NIF beamline in the ultraviolet (denoted as “3v”) in several areas that are essential for the success of the ignition
campaign. The NIF laser meets all specifications required for ignition experiments.
Power [TW]
600
500
400
300
200
100
0
0 5
Measured shape
Requested shape
N060329-002
3v focal spot (0.145 mm FWHM)
Irradiance [normalized]
1.0
0.8
500
0.5
Y [mm]
0
0.2
–500
0.1
0 –500 0 500
X [mm]
Relative probability
0.06
Fluence [J/cm ]
2
14. 31
0.05 11. 44 100
8.58
0.04
Y [mm]
0
5.72
–100
0.03 2.86
–100 0 100
2xCR
0.02 X [mm]
0
CR= 9.9%
Requirement CR≤15%
25
0.01
0
0 5 10
Fluence [J/cm2]
High-energy petawatt capabilities
at OMEGA and NIF
In the late 1980s, LLE scientists developed chirped pulse
amplification. This revolutionary concept allowed the generation of the ultra-high peak power laser systems. By temporally
stretching a short pulse before the amplification stages and
then using a set of gratings to recompress the pulse to its
original duration, one can produce orders-of-magnitude higher
peak powers than would have been possible by directly amplifying the short pulse. The operators of the Nova Petawatt laser
system used this technique to produce 600-J pulses in 0.5 ps.
This was the first high-energy petawatt (HEPW) laser system.
The OMEGA EP laser system was completed in April 2008.
It is a four-beamline system with an NIF-based architecture.
Each of the four beamlines will deliver 6. 5 kJ to target in
the ultraviolet. Two of the beamlines can also be operated
in HEPW mode, each producing 2. 6 kJ of infrared energy.
The OMEGA EP significantly extends the flexibility of the
OMEGA laser system. (The combined system is referred to
as the OMEGA Laser Facility.) All four beamlines can be
injected into the OMEGA EP target chamber in a variety of
combinations of ultraviolet and HEPW beamlines. The two
HEPW beams can also be injected into the OMEGA target
chamber, significantly extending the flexibility of that system.
NIF’s capabilities will be extended via the installation of a
HEPW system known as the Advanced Radiographic Capability (ARC); this involves the modification of one existing group
of four beams so that it may be operated as a short-pulse CPA
laser system or in normal nanosecond-pulse mode. Because
each beamline can be split into two, NIF will have available
up to eight individually controllable HEPW beamlines with
separate timing and pointing.
Laser pulse widths from 0.75 to 50 ps, and energies of
approximately 3 kJ, can be used for each beamline. These
beamlines can be individually focused onto high-Z targets
adjacent to the main ignition target. Backlit images of the target produced using these X-rays are used to make multi-frame
“movies” of the target during compression and are critical to
diagnosing performance of the ignition target.
Ignition progress and future plans
Achieving ignition on the NIF will provide opportunities for
a wide range of HED physics experiments. The production of
10 14-MeV neutrons and extremely high X-ray fluxes from
19
an igniting target will allow us to study previously unexplored
areas of astrophysical science.
For example, we may gain an understanding of the opacities
and evolution of low-density, radiation-dominated photo-ionized plasmas relevant to the accretion disks of compact
objects (neutron stars, black holes). Nuclear astrophysicists
will use neutron yield to study reactions rates associated with
the C-N-O nuclear fusion cycle in massive stars as well as rare
nuclear fusion reactions that may explain the production of
high-Z materials in supernova explosions.
Ignition and gain
2.0
Total K rRL [g/cm2]
n
NIF point design
1. 5 MJ
1.0
NIF
0.5 MJ
OMEGA
0.5 DT, 22 kJ
2008
OMEGA DT equivalent
0.2
of the NIF point design
OMEGA Hydro equivalent curve
0.1 D , 16 kJ V = const., a = const.
2i
2007 ( 4 x 107 cm/s) ( 2. 5)
0 24 68
K T L [keV]
in
(no alpha deposition)
Circles show progress in direct-drive target performance,
with the ultimate goal of achieving direct-drive ignition on the
NIF with a 1.5-MJ laser pulse (solid blue circle). In 2007, areal
densities of 200 mg/cm were measured with relatively low
2
drive intensities (orange point) and recently with higher implosion velocities and ion temperatures (red point). We expect to
achieve similar areal densities hydrodynamically equivalent to
ignition implosions on the NIF with marginal ignition energy of
0.5 MJ (yellow circle) soon.
