MCNP Sim of Jack Converter

Simulation inputs

Geometry

Side profile of converter. Distances re in cm. There are thin (0.001 inch) titanium plates on the far left and far right of the model, but they but the are too small to be seen.

Front view of convertor. Distances are in cm.

Materials

Green: Stainless steel

Pink: Titanium

Blue: H2O

Yellow: Tungsten

Assumptions

The beam spot size was given a diameter of 0.5 cm based off of a burn mark on a converter that got hot during irradiation. Electrons are 42 MeV and mono energetic.

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Results

Energy spectrum of neutrons

The plot below shows the energy distribution of neutrons exiting the converter at three different intervals of neutron angle w.r.t. the incident electron beam. The neutron energy spectrum of the neutron-induced fission of U235 is also shown for comparison.

misc

Some of the differences between the resulting neutron energy spectrum and that of U235 may be due to the moderation of the neutrons by H2O. The plot below takes each neutron's energy at the moment of emission.

Below is a plot of the rate of neutron production as the beam traverses through the converter. Zero corresponds to where the beam enters the titanium window.