2NCorr SPDP Introduction - Revision history

Burgjeff: /* Accidentals and trues */

2018-01-24T00:22:55Z

Accidentals and trues

Burgjeff: /* Accidentals and trues */

2018-01-24T00:22:20Z

Accidentals and trues

Burgjeff: /* Accidentals and trues */

2018-01-24T00:21:46Z

Accidentals and trues

Burgjeff: /* Accidentals and trues */

2018-01-24T00:21:22Z

Accidentals and trues

Burgjeff: /* Accidentals and trues */

2018-01-24T00:20:56Z

Accidentals and trues

Burgjeff: /* Accidentals and trues */

2018-01-24T00:20:43Z

Accidentals and trues

Burgjeff: /* Accidentals and trues */

2018-01-24T00:20:27Z

Accidentals and trues

Burgjeff: /* Accidentals and trues */

2018-01-24T00:19:28Z

Accidentals and trues

Burgjeff: /* Accidentals and trues */

2018-01-24T00:18:59Z

Accidentals and trues

Burgjeff at 00:17, 24 January 2018

2018-01-24T00:17:36Z

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 An accidental neutron coincidence, or ''accidental'' for short, is defined here as any pair of neutrons that are uncorrelated despite having been produced during the same pulse. For example, a neutron from a (gamma,n) reaction paired with a neutron from a (gamma, fiss) reaction. As another example, consider a pulse which causes two photofission events, such that one fission releases four and the other two correlated neutrons, creating 4*2=8 possible distinct pairs of uncorrelated neutrons, or in other words, eight accidentals.
-A true neutron coincidence, or ''true'' for short, is defined here as any pair correlated neutrons from the same pulse. For example, a  photofission event that produces 4 correlated neutrons, creates (4*3)/2=6 trues.
+A true neutron coincidence, or ''true'' for short, is defined here as any pair correlated neutrons from the same pulse. For example, a  photofission event that produces 4 correlated neutrons, creates (4*3)/2=6 trues. Throughout the experiment, measured trues/accidentals always occurred as two-neutron coincidences, as there were never three or more neutrons detected in coincidence.
 The detection of accidentals is undesirable, since they are uncorrelated and cannot be told apart from trues. This issue is addressed by using the DP distribution to estimate the accidental distribution, and then subtracting the estimation from the measurement. The two neutrons of an accidental always originate from independent reactions, and so it does not matter whether or not these reactions occurred in the same pulse. Thus, whatever statistical relationship exists between two accidentals in a single pulse, it must be the same for two neutrons taken from separate pulses. It can be shown (see [[Theoretical analysis of 2n accidentals rates|here]]) that the rate of accidentals in SP events is 1/2 of the neutron coincidence rate in DP events. The accidental subtracted, normalized two-neutron opening angle distribution, <math>\Theta_{nn}</math>, is given by:

← Older revision		Revision as of 00:22, 24 January 2018
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	Throughout the experiment, measured trues/accidentals always occurred as two-neutron coincidences, as there were never three or more neutrons detected in coincidence.		Throughout the experiment, measured trues/accidentals always occurred as two-neutron coincidences, as there were never three or more neutrons detected in coincidence.
−

	The detection of accidentals is undesirable, since they are uncorrelated and cannot be told apart from trues. This issue is addressed by using the DP distribution to estimate the accidental distribution, and then subtracting the estimation from the measurement. The two neutrons of an accidental always originate from independent reactions, and so it does not matter whether or not these reactions occurred in the same pulse. Thus, whatever statistical relationship exists between two accidentals in a single pulse, it must be the same for two neutrons taken from separate pulses. It can be shown (see [[Theoretical analysis of 2n accidentals rates\|here]]) that the rate of accidentals in SP events is 1/2 of the neutron coincidence rate in DP events. The accidental subtracted, normalized two-neutron opening angle distribution, <math>\Theta_{nn}</math>, is given by:		The detection of accidentals is undesirable, since they are uncorrelated and cannot be told apart from trues. This issue is addressed by using the DP distribution to estimate the accidental distribution, and then subtracting the estimation from the measurement. The two neutrons of an accidental always originate from independent reactions, and so it does not matter whether or not these reactions occurred in the same pulse. Thus, whatever statistical relationship exists between two accidentals in a single pulse, it must be the same for two neutrons taken from separate pulses. It can be shown (see [[Theoretical analysis of 2n accidentals rates\|here]]) that the rate of accidentals in SP events is 1/2 of the neutron coincidence rate in DP events. The accidental subtracted, normalized two-neutron opening angle distribution, <math>\Theta_{nn}</math>, is given by:

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 ::<math>SP</math> is the measured opening angle distribution from same pulse events, which is the sum of trues, accidentals, and noise.
 ::<math>A</math> is the opening angle distribution of accidentals from same pulse events, which cannot be measured directly.
-::<math>DP</math> is the opening angle distribution from different pulse events.
+::<math>DP</math> is the opening angle distribution taken from different pulse events.
 While the opening angle distribution of accidentals is not known, it can be estimated by <math>A\approx0.5*DP</math>, giving:

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 ::<math>DP</math> is the opening angle distribution from different pulse events.
-While the opening angle distribution of accidentals is not known directly, it can be estimated by <math>A\approx0.5*DP</math>, giving:
+While the opening angle distribution of accidentals is not known, it can be estimated by <math>A\approx0.5*DP</math>, giving:
 :<math>\Theta_{nn} = \frac{SP-\frac{1}{2}DP}{DP}</math>

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 ::<math>DP</math> is the opening angle distribution from different pulse events.
-While the opening angle distribution of accidentals, is not known directly, it can be estimated by <math>A\approx0.5*DP</math>, giving:
+While the opening angle distribution of accidentals is not known directly, it can be estimated by <math>A\approx0.5*DP</math>, giving:
 :<math>\Theta_{nn} = \frac{SP-\frac{1}{2}DP}{DP}</math>

← Older revision		Revision as of 00:18, 24 January 2018
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−	The detection of accidentals is undesirable, since they are uncorrelated and cannot be told apart from trues. This issue is addressed by using the DP distribution to estimate the accidental distribution, and then subtracting the estimation from the measurement. The two neutrons of an accidental always originate from independent reactions, and so it does not matter whether or not these reactions occurred in the same pulse. Thus, whatever statistical relationship exists between two accidentals in a single pulse, it must be the same for two neutrons taken from separate pulses. It can be shown (see [[Theoretical analysis of 2n accidentals rates\|here]]) that the rate of accidentals in SP events is 1/2 of the neutron coincidence rate in DP events. The normalized ~~and corrected~~ two-neutron opening angle distribution, <math>\Theta_{nn}</math>, is given by:	+	The detection of accidentals is undesirable, since they are uncorrelated and cannot be told apart from trues. This issue is addressed by using the DP distribution to estimate the accidental distribution, and then subtracting the estimation from the measurement. The two neutrons of an accidental always originate from independent reactions, and so it does not matter whether or not these reactions occurred in the same pulse. Thus, whatever statistical relationship exists between two accidentals in a single pulse, it must be the same for two neutrons taken from separate pulses. It can be shown (see [[Theoretical analysis of 2n accidentals rates\|here]]) that the rate of accidentals in SP events is 1/2 of the neutron coincidence rate in DP events. The accidental subtracted, normalized two-neutron opening angle distribution, <math>\Theta_{nn}</math>, is given by:

	:<math>\Theta_{nn} = \frac{SP-A}{DP}</math>		:<math>\Theta_{nn} = \frac{SP-A}{DP}</math>

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 [[Production Analysis | go_back ]]
 =The calculation of angular correlation=
 [[File:2N Corr OpeningAngleCf252.png|thumb|300px|right| Unnormalized two-neutron opening angle distribution from the spontaneous fission of Cf252 (E>1.5MeV).]]