Yields and Asymmetry for different detectors configurations.

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Follow are some Monte Carlo simulations of 2n correlations. One neutron are from one FF, two neutrons per fission. No accidental neutron was considered, all neutrons are correlated. Total 10M events was simulated. Every neutron was sampled up to 10 MeV. The polarization of gammas are zero.

Below is cos(Theta) of neutrons a and b in LAB frame. No energy cuts was made.

The spectrum is a convolution of the "initial" spectrum which the FF emits, and the kinematic effects due to the fragment recoil

Below is the same spectrum, but made with 2 MeV energy cuts.

Lets do some geometry cuts

Some results of 2n simulations for different cuts.

In the table above are:

• cut1: 2 Mev energy cuts
• cut2: 2 Mev energy cuts. Plus angle cuts for each neutrons [math]|cos(\Theta_{a,b})\lt 0.42|[/math]. That is detectors located in the plane perpendicular to the beam
• cut3: 2 Mev energy cuts. Plus angle cuts for each neutrons [math]|cos(\Theta_{a,b})\gt 0.9|[/math]. That is detectors located in the plane parallel to the beam

• cnts_nn_180: counts with angle between two neutrons are [math]cos(\Theta_{a,b})\lt -0.9[/math]
• cnts_nn_0: counts with angle between two neutrons are [math]cos(\Theta_{a,b})\gt 0.9[/math]

As we can see:

• The best case is of cause [math]4\pi[/math] geometry. The 2n correlation yield is about 2.13 % with 2 MeV energy cuts .
• The next good case is detectors located in the plane perpendicular to the beam. The 2n correlation yield is about 0.92 % with 2 MeV energy cuts.
• The worst case is detectors located in the plane parallel to the beam. The 2n correlation yield is about 0.05 % with 2 MeV energy cuts.

And let see how the 2n correlations looks like for different cuts

• No energy cuts. Total yield is 100 %. Asymmetry yield is about 13 %. Asymmetry of 2n correlations is about 9.

• 2 MeV energy cuts. Total yield is 12 %. Asymmetry yield is about 2 %. Asymmetry of 2n correlations is about 65.

• 2 Mev energy cuts. Plus angle cuts for each neutrons [math]|cos(\Theta_{a,b})\lt 0.42|[/math]. Total yield is 3 %. Asymmetry yield is about 0.9 %. Asymmetry of 2n correlations is about 81.

• 2 MeV energy cuts. Plus angle cuts for each neutrons [math]|cos(\Theta_{a,b})\lt 0.9|[/math]. Total yield is 0.08 %. Asymmetry yield is about 0.05 %. Asymmetry of 2n correlations is about 30.