Difference between revisions of "CrossTalk"
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=Statistics= | =Statistics= | ||
The correlation rate will depend on the number of detectors, <math>N</math>, the mean neutron multiplicity, <math>\nu</math>, and the probability that a given detector registers a hit from a single source neutron , <math>P_{d}</math>. <math>P_{d}</math> is assumed to be the same for all detectors, and is calculated from the simulation as follows: | The correlation rate will depend on the number of detectors, <math>N</math>, the mean neutron multiplicity, <math>\nu</math>, and the probability that a given detector registers a hit from a single source neutron , <math>P_{d}</math>. <math>P_{d}</math> is assumed to be the same for all detectors, and is calculated from the simulation as follows: | ||
| − | <math>\frac{\text{total number of single hits}}{N*(\text{total number of src neutrons})}</math> | + | <math>P_{d}=\frac{\text{total number of single hits}}{N*(\text{total number of src neutrons})}</math> |
| + | The n-n correlation rate can be estimated as follows: | ||
| + | |||
| + | <math>R_{nn}=f\r\nu(\nu-1)*N(N-1)*P_{d}^{2} </math> | ||
| + | |||
| + | The cross talk rate will simply scale proportionally with neutron multiplicity and fission rate. By counting the number of cross talk events directly from the simulation, the estimatet cross talk rate is: | ||
| + | |||
| + | <math>R_{Xtalk}=f\nu\frac{}{}</math> | ||
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Revision as of 00:51, 19 July 2016
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Geometry
An array of 6 detectors are placed radially at a distance of 1 meter from an uncorrelated 252-CF source. The image below shows a top down view of the simulation geometry. The detector setups have a vertical extent of 30".
Detector physics
The detector physics used in the simulation is MCNP-POLIMI's default treatment for plastic organic scintillators. POLIMI uses electron equivalent light output (MeVee) for simulating detector response. Assuming the detectors have a energy deposition threshold of 0.2 MeV, the corresponding threshold, in electron equivalent light output, becomes 0.03 MeVee.
Summary
Neutron energy deposition from collisions with hydrogen and carbon are converted to electron equivalent light output (MeVee) by MCNP-POLIMI. Neutron collisions that all occur within a pulse collection time of 10 ns of each other are converted to MeVee and cumulated. If the cumulative light output exceeds 0.03 MeVee then it is considered a detection. The value 0.03 MeVee was chosen because it corresponds to a mean neutron energy deposit of 0.2 MeV.
Detector response
The electron equivalent (MeVee) conversion functions for neutrons were measured for plastic (BC 420) scintillators as a function of neutron energy deposit, . For deposit on hydrogen the measurements fit the following quadratic function:
and for deposit on carbon:
Statistics
The correlation rate will depend on the number of detectors, , the mean neutron multiplicity, , and the probability that a given detector registers a hit from a single source neutron , . is assumed to be the same for all detectors, and is calculated from the simulation as follows:
The n-n correlation rate can be estimated as follows:
The cross talk rate will simply scale proportionally with neutron multiplicity and fission rate. By counting the number of cross talk events directly from the simulation, the estimatet cross talk rate is:
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