IAEAInternational Atomic Energy Agency

Coincidence summing correctionCoincidence summing correction

methods applied at IAEAmethods applied at IAEA

Alessia Ceccatelli

Terrestrial Environment Laboratory-Chemistry Unit

ICRMGSWG workshop

Coincidence summing comparison on

volume sourcesENEA, CR Casaccia, Rome (Italy)

18-19 October 2010

IAEA

Analytical Method using Canberra Analytical Method using Canberra

LABSOCS softwareLABSOCS software

� Both FEP efficiencies and total efficiencies have been calculated byLABSOCS software, using a non-characterized detector best match with real detector

Type Diameter

(mm)

Length

(mm)

Diameter-

to-length ratio

CEA n, coaxial 49.8 47.8 1.04

LABSOCS n, coaxial 50 (nominal) - 1

IAEA

Analytical Method using Canberra Analytical Method using Canberra

LABSOCS software LABSOCS software with correctionwith correction

� Diameter-to-length of real detector 3 % greater than LABSOCS detector correction applied correction applied

to coincidence summing correction factorto coincidence summing correction factor

(characterization study performed by Canberra)

� In applying this correction, linearity between correction and diameter-to-length ratio was

assumed

� Coincidence summing correction factors are

reduced (about 2 %)

IAEA

If 1/Ci is the correction factor. the equations for calculating

Ci have been written in matrix form by Semkow et al.(1990).

With some modifications (De Felice et al.. 2000), we have:

Ptkm. Ptij = probabilities per decay that the coincidence transitions

k and m, or i and j, occur

Pk. Pm. Pi. Pj = probabilities that in each transition the respective photons

γk, γm, γi, γj will be emitted

εεεεk. εεεεm.. εεεεi = FEP efficiencies for the photons γk, γm, γi

εεεεtj = total efficiency for a generic photon γj

Summing in Summing out

Fast procedureFast procedure -- 1/31/3

Volume effects

not considered

IAEA

Fast procedureFast procedure -- 2/32/3

Ptkm obtained combining the various transition probabilitiescombining the various transition probabilities

Ptij for each nuclear level involved in the coincidence process

εεεεk. εεεεm. εεεεi obtained by efficiency transfer method efficiency transfer method from

experimental data for point geometry 2 cm distance, using Canberra

LABSOCS software

εεεεtj obtained, for each energy value, using just one experimentaljust one experimental

pointpoint (single source of a monoenergetic radionuclide)

IAEA

Rεεεε = peak-to-total efficiency ratio

Rσσσσ = photoelectric-to-total cross section (in

germanium) ratio

A simple proportionality was

observed between R and Eγγγγ

In each measurement geometry the slope K can be calculated the slope K can be calculated

only for one radionuclideonly for one radionuclide (i.e. 137Cs at 662 keV)

De Felice et al. Applied Radiation and Isotopes 52 (2000)

Fast procedureFast procedure -- 3/33/3

IAEA

General criteria appliedGeneral criteria applied

Coincidences considered:

� γ γ γ γ - γγγγ

� γγγγ - Xkαααα (internal conversion)

� γγγγ - Xkαααα (electron capture decay – Sm branch)

Coincidences neglected:

� triple coincidences

� X - X

� X – γγγγ

� γγγγ – annihilation photon at 511 keV

IAEA

Selection criteria appliedSelection criteria applied

Some photon selection criteria were applied at 152Eu

simplified decay schemesimplified decay scheme

If γγγγγγγγii are the photons to which correction must be applied and

γγγγγγγγjj are the photons which contribute to that correction:

�� SummingSumming--out effectout effect: for each γγγγi photon with an emission

probability Iγγγγi. only coincidences with γγγγj having an

emission probability Iγγγγj ≥≥≥≥ 10 % Iγγγγi were considered.

�� SummingSumming--in effectin effect: only couples γγγγk. γγγγm where at least one

of the two photons has Iγγγγ ≥≥≥≥ 10 % Iγγγγi were considered.

IAEA