# 2-Neutron Correlation Setup Stuff

## Big Detector Solid Angle Calculations

MCNPX Simulation
• 14 MeV neutron source, emitted isotropically ()
• Detector placed 1m away from source

• face of the detector is 15.24cm x 76.2cm, and 3.6cm deep

The solid angle can be found from the number of particles hitting the detector as:

Results
• Out of 1E9 neutrons generated, 8618287 neutrons hit the detector
• if the detector is placed 70cm away from the source,
• if the detector is placed 65cm away from the source,
• As a test to verify our results
• We change the detector size to 2cm by 2cm and used 1E9 neutrons again
• 32061 neutrons struck the detector
• And, as a second test to verify our results
• We change the detector size to 1cm by 1cm and used 1E9 neutrons again
• 7965 neutrons struck the detector
Now, what neutron singles rate into the detector should correspond to 1 fission per pulse?
• If we have 1 fission per pulse and each fission emits on average 2.3 neutrons, we should expect 2.3 neutrons/pulse
• The number of neutrons hitting the detector per pulse is found as
• @ 1 meter => 0.0198 neutrons hitting the detector per pulse
• @ 70 cm => 0.0379 neutrons hitting the detector per pulse
• Taking into account the efficiency of the detector , the number detected per pulse can be found as
• @ 1 meter from source => () neutrons detected per pulse
• @ 70 cm from source => () neutrons detected per pulse

## Neutron and Photon Flux Through Lead

Using MCNPX, a simulation was done to determine how much of the neutrons and photons from the target will be blocked by various thickness of lead. With a monochromatic pencil beam of incident particles, the following results illustrate how much of the initial beam actually made it through the lead.

## Detector Cross-Talk

Using MCNPX, I am trying to simulated the cross-talk we could expect between the big detectors. I used a fission neutron energy spectrum given in MCNPX, shown below.

These neutrons are incident upon a plastic scintillator and I will look at the neutrons and photons coming out of the scintillator's sides perpendicular to the incident beam. The first case I will look at is where the detectors are placed with only polyethylene between them, as illustrated below.

This results in a neutron and photon energy spectrum as follows.

The next case I will look at is where we put a layer of lead between the polyethylene between the detectors, as shown in the schematic below.

The results for this setup using 1 inch of lead between the detectors is as follows.

And, the results for this setup using 2 inches of lead between the detectors is as follows.