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Scripts to generate simulated visar data from a generic velocity profile
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Simulate Line-VISAR data

Building simulated data from a velocity profile.

Simple Example

target = Target(velocity_equation="step")
ray = Ray(pulse_length=10)
ray = target.reflect_off_target(ray)
etalon = Etalon(1, 1.5195)
etalon.set_VPF(2., lambda0=.532)
interferometer = Interferometer(etalon=etalon)
sweep = interferometer.output(ray, target)

plt.imshow(sweep, aspect='auto', cmap="gray", extent=(0, 10, -2, 2))
plt.xlabel("Time [ns]")

Target class

The target class defines the velocity profile that will be recorded by the visar system (i.e. the shock front moving / interface velocity of a target of interest).

This velocity profile is loaded during the initialization of the target instance. Two built-in profiles are available for testing.

  • step : a discontinuous velocity jump
  • sigmoid : a sigmoid-shaped velocity jump
  • stationary : 0 velocity change, used in generating reference images

To help visualize the velocity profile, a helper plotting function is available, and can be called via the following command:


This generates two plots: a 3D plot of the velocity profile, and a 2D color plot. The 2D should be identical to what the "Visar analysis" script would return for the velocity map, if this simulated data were to be analyzed.

Loading a generic velocity profile

User-defined velocity profiles can be loaded. An example of how this is done is demonstrated in the functions

  • sin_step
  • spatial_var_step

In this case, a callable function is defined, which must except a time value, and a spatial location. If the user defined function requires more arguments, this can be simplified with use of a lambda function. e.g.

velocity_equation = lambda t, y : sin_step(20, .5, t, y, max_velocity=1)

the function is then loaded into the target during the initialization of the target instance.

target = Target(velocity_equation=velocity_equation)

Ray class

The ray instance defines the duration, as well as the spatial location over which the velocity profile will be recorded.

The values must be less than target._t and target._y, currently these are hard-coded into the Target.__init__, feel free to change them.

Etalon class

The etalon instance sets the VPF of the generated visar data, determined by twice the thickness (two passes through the etalon for a Mach-Zehnder interferometer) and the index of refraction:

etalon = Etalon(thickness=1, n=1.5195)

If you would like to explicitly set the VPF instead, this can be done with the helper function set_VPF, this then chanced the etalon thickness:

etalon.set_VPF(2, labda0=.532)

Similarly, this can be done with the etalon tau (temporal delay, in ns), set_tau

Interferometer class

The interferometer instance will carry out the mechanics of generating the fringe-comb pattern.

Initilization of the interferometer instance requires 2 arguments.

  • etalon An Etalon instance, used in determining the VPF of the generated data
  • tau the slit opening on the streak camera, this sets the temporal resolution.

Generation of the desired data is then accomplished by calling the output class method.

sweep = interferometer.output(ray, target, noise=False)

output excepts a Ray argument and a Target argument, and optional boolean argument to add noise to the generated data is also available; however, this method is still in development.

Reference Shot

A helper function is included to quickly generate a reference shot. This just generates the output from a stationary target.


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