NIF
The National Ignition Facility (NIF) Programs Directorate at Lawrence Livermore National Laboratory (LLNL) enables key programs and technologies that support the U.S. Department of Energy's National Nuclear Security Administration Defense Programs and LLNL missions of ensuring that the nation's nuclear weapons remain safe, secure, and reliable.
The charter of the Directorate is to construct and operate the National Ignition Facility, to perform research on ignition and high-energy-density matter in the Inertial Confinement Fusion Program as part of the overall Stockpile Stewardship Program, and to foster the development of associated laser technologies such as those developed in the Photon Science and Applications Program.
The NIF Project in Livermore, California is the largest laser in the world.
For further information see NIF Project Status.
- The facility is very large, the size of a sports stadium
- The target is very small, the size of a pencil eraser
- The laser system is very powerful, equal to 1,000 times the electric generating power of the United States
- Each laser pulse is very short, a few billionths of a second
Experiments in NIF will access high-energy-density and fusion regimes with direct applications to stockpile stewardship, energy research, science, and astrophysics.
The NIF Project draws extensively from expertise from throughout LLNL, including the Engineering, Chemistry and Material Science, and Computation Directorates.
Moho
The
Mohorovi?i? (
IPA: [m?h?'??v?t??t?])
discontinuity, usually referred to as the
Moho, is the boundary between the
Earth's
crust and the
mantle. The Moho serves to separate both
oceanic crust and
continental crust from underlying mantle. The Moho mostly lies entirely within the
lithosphere; only beneath
mid-ocean ridges does the Moho also define the
mesosphere-
asthenosphere boundary. The Mohorovi?i? discontinuity was first identified in 1909 by
Andrija Mohorovi?i?, a
Croatian seismologist, when he observed the abrupt increase in the velocity of
earthquake waves (specifically
P-waves) at this point.
Ophiolites are sections of
oceanic crust and possible mantle rock that have been
obducted into the
continental crust during
plate collisions.
Spermaceti Sound
In smaller odontocetes, the tissues involved in sound production are situated above the bony nares and below the blow hole in front of the brain (Mohl 2001). In Sperm Whales, however, the sound-generating structure, the spermaceti sac, has migrated forward and above the melon structure (junk sac) (Mohl 2001). The spermaceti organ, as a whole, acts as a reverberation and sound-focusing chamber; produces pulsed long range echolocation signals (Schenkkan and Purves 1973, Norris and Harvey 1972).
These acoustic pulses are projected, from sperm whales, into the environment through a series of lenses found in the anterior junk (Cranford 1999). Though these structures have different physiological locations within the head, they are anatomically equivalent to the processes and pathways in delphnoids (Cranford 1999). In the porpoise (Tursiops truncatus) glycerides in external tissue act as an acoustic window; in the Delphid (Stenella), sound velocity measure in melon with heterogeneous lipid concentrations; in the Pilot whale, similar heterogeneous lipid composition (Morris 1975).
The sound produced by a sperm whale is composed of different parts. There is a primary event leads to a train of reflected pulses with long enough intervals for the event to travel back and forth between air sacs (reflectors) (Mohl 2001). Then there is the high pressure air from right post-nasal cavity is drawn into the larynx to produce sonar clicks; the sound is then trasmitted to the bones of the rostrum (Schenkkan and Purves 1973). This pattern is a result of a single acoustic pulse reflected multiple times between two acoustic mirrors in the nasal structure (Norris and Harvey 1997).
Observations were made by Mohl (2001) on a pod of 13 beached whales in Denmark as to their sound generating abilities. During these observations he found that a single excitation at the distal sac produced a multi-pulse pattern similar to ones reported from live sperm whales (Mohl 2001). This same pattern was produced by injecting pulses into the junk (Mohl 2001). This suggests that junk and spermaceti sac form an acoustic continuum (Mohl 2001). Pulses injected dorsally (3m behind tip of snout) did not generate this pattern (Mohl 2001). This would then suggest that the purpose of the junk is to transmit the sound and is in acoustic contact with the spermaceti sac which receives it (Mohl 2001).
