  The National Ignition Facility laser focuses 1.8 Mega-joules of ultraviolet
light (wavelength 351 nano-meters) from 192 beams into a
600-micro-meter-diameter volume. Effective use of this output in target
experiments requires that the power output from all the beams match within 8%
over their entire 20-nanosecond waveform. The scope of NIF beam diagnostics
systems necessary to accomplish this task is unprecedented for laser
facilities. Each beam line contains 110 major optical components distributed
over a 510 meter path, and diagnostic tolerances for beam measurement are
demanding. Total laser pulse energy is measured with 2.8% precision, and the
inter-beam temporal variation of pulse power is measured with 4% precision.
These measurement goals are achieved through use of approximately 160 sensor
packages that measure the energy at five locations and power at 3 locations
along each beamline using 335 photodiodes, 215 calorimeters and 36 digitizers.
Successful operation of such a system requires a high level of automation of
the widely distributed sensors. Computer control systems provide the basis for
operating the shot diagnostics with repeatable accuracy, assisted by operators
who oversee system activities and setup, respond to performance exceptions, and
complete calibration and maintenance tasks.
