  For many applications of pulsed radiation, the time-history of the radiation
intensity must be optimized to induce a desired time-history of conditions.
This optimization is normally performed using multi-physics simulations of the
system. The pulse shape is parametrized, and multiple simulations are performed
in which the parameters are adjusted until the desired response is induced.
These simulations are often computationally intensive, and the optimization by
iteration of parameters in forward simulations is then expensive and slow. In
many cases, the desired response can be expressed such that an instantaneous
difference between the actual and desired response can be calculated. In
principle, a computer program used to perform the forward simulation could be
modified to adjust the instantaneous radiation drive automaticaly until the
desired instantaneous response is achieved. Unfortunately, such modifications
may be impracticable in a complicated multi-physics program. However, the
computational time increment in such simulations is generally much shorter than
the time scale of changes in the desired response. It is much more practicable
to adjust the radiation source so that the response tends toward the desired
value at later times. This relaxed in-situ optimization method can give an
adequate design for a pulse shape in a single forward simulation, giving a
typical gain in computational efficiency of tens to thousands. This approach
was demonstrated for the design of laser pulse shapes to induce ramp loading to
high pressure in target assemblies incorporating ablators of significantly
different mechanical impedance than the sample, requiring complicated pulse
shaping.
