ETNA (Efficiency Transfer for Nuclide Activity measurement)

Transcription

1 ETNA (Efficiency Transfer for Nuclide Activity measurement) ETNA is a software for computing efficiency transfer and coincidence summing corrections for gamma-ray spectrometry. The software has been developed at the Laboratoire National Henri Becquerel and is available upon request.

2 ETNA Transfer of efficiency Semi-empirical method (from a reference efficiency) Coaxial cylindrical geometry (point. disk. cylinder. Marinelli) Coincidence summing corrections Knowledge of the efficiency (total and full-energy peak) Possibility of efficiency transfer Decay scheme from Nucleide Data management Decay scheme Attenuation coefficients

3 ETNA main window

4 Recent update (04/11/010) Thanks to Dr Aldo FAZIO (ENEA)!

5 Efficiency transfer principle Point source moving along the detector axis ε (E, P 0 ) = ε I(E). Ω(P 0 ) ε (E, P) = ε I(E). Ω(P) ε (E,P) = ε Ω(P) (E,P0). Ω(P 0 )

6 Solid angle for point source Using polar coodinates. the solid angle Ω(P) between point P (r, φ, z s ) and the detector entrance surface (disc) is: Ω(P) = z R D is the detector radius. π S 0 R dϕ 0 D R R R dr r cosϕ + r + z 3/ S The geometrical factor should include: - attenuation in differents absorbing layers (air, window, dead layer. ) : F att m F att = exp µ i= 1 i δ i - absorption in the detector active volume : F abs Fabs = f1+ f f ' = 1 ( µ δ ) f = 1 ( µ δ ) f ' = exp( µ ( + δ )) f1 exp D 1D exp D D D 1D

7 Solid angle for a cylindrical source For a volume source (cylindrical symmetry : radius R S, thickness H S, vertical position Z S ): Fatt and F abs must be included in the integration procedure + ϕ + ϕ Ω = + π S S S D S H Z Z R 0 3/ 0 R 0 S S h r cos r R R R dr d dr r h dh H R 4

8 Solid angle for a cylindrical source If the source diameter is larger than the detector one: Ω = (V1+ V)S1 dω + (V)S dω = Ω 1 + Ω V V1 V1 V H S Ω 1 = R S 4 H S Z + H S Z S S h dh R 0 S r dr π 0 dϕ R D 0 R F att F abs R dr R r cosϕ + r + h 3/ S R S S1 R D Ω = 4 R S H Z + H φ0 r dr dϕ S S S 0 R D s Z S dh R 0 0 Z D R F att F abs ( r cosϕ R ) R r cosϕ + r + h dz D 3/ H D

9 Integration method Integration are numerically performed using the Gauss-Legendre method: b a f (x)dx = ( b a) n i= 1 w i f (x i ) f (x i ) = ( b a) ( b + a) x x i and w i = roots and weights of Legendre polynomials i + Point sources, discs, cylinders and Marinelli (along the detector axis) are considered.

10 Requires Detector parameters Source parameters Container Matrix Input of data Geometry conditions (source-to-detector distance, screen) Reference efficiency Recorded in the «user» database

11 Efficiency transfer window

12 Input of geometry parameters

13 Input of detector parameters

14 Input of source parameters Source : type and characteristics (container and material)

15 Input of calibration efficiencies Manual input Function (APOCOPE or APOLOG) File import

16 Efficiency transfer results

17 Coincidence summing

18 Calculation principle ETNA uses a numerical method, according to Andreev, Mc Callum principle: Z X C 1 = 1 1 P ε 1 T β - γ 1 A Z + 1 Y γ P 1 : probability for emitting γ simultaneaously with γ 1 ε Pi : FEP efficiency for energy E i ε Ti : Total efficiency for energy E i γ 3 C 3 = C = 1 P ε I I γ 1 γ T 1 ε P1 ε ε P3 P P 1

19 Calculation principle () Double coincidences Coincidences with K X-rays (electron capture or internal conversion) are computed Correction for K-X-rays (from gamma or X rays) are computed Beta+ emitting nuclides are considered (modification of the decay scheme) No angular correlation

20 ETNA Input data ETNA requires: 1. Decay scheme (Nucleide database). FEP and total efficiency for at least one source-to-detector geometry («calibration geometry» recorded in the «user» database)

21 ETNA Coincidence tab From Nucleide

22 Calibration geometry window

23 Efficiency calibration

24 Coincidence correction results dimanche février 009 ETNA Version 5.5 Rev 51 Filename :C:\Documents and Settings\ML11836\Bureau\Workshop_ICRM\Presentations\ETNA\test_ETNA dimanche février 009 Processing identification : Coincidence summing correction (simplified computing) Nuclide :Ba133 Daughter nuclide :Cs133 Half-life threshold : s Calibration geometry : G1 SP reference (Source ponctuelle à 10 cm) Calibration source :Source ponctuelle Calibration source - detector distance :100 mm Calibration absorber :None Calibration absorber - detector distance :0 mm Measurement geometry :Calibration geometry Detector :G1 - pièce 6A Results : Error codes : 0 0 X-ray correction : Starting Arrival Energy Gamma-gamma Gamma-X Total level level (kev) correction correction correction : CEA\LNHB BNM

25 Calculation with efficiency transfer

26 Decay scheme data Attenuation coefficients Data update Nucléide: import of updated data (only for LNHB!)

27 Data update Attenuation coefficients Manual input File import (XCOM or ASCII)

28 Import file from XCOM Attenuation coefficients

29 Experimental validation (1) Efficiency transfer: point source from 1 to 5 cm from detector window 137 Cs et 57 Co (with Al screen): no coincidences Reference peak area: 10 cm Source-todetector distance Experiment al peak relative area 137 Cs (66 kev) ETNA Ratio ETNA/Expe rimental Experiment al peak relative area 57 Co (1 kev) Ratio ETNA/Expe ETNA rimental 5 cm 0.06 (1) 0.06 (5) (1) (4) cm (1) (6) (1) 0.86 (6) cm (1) (10) () (11) cm 1.43 (3) 1.40 (36) (5) 1.46 (40) cm.17 (5).18 (7) (7).3 (8) cm.785 (6).8 (9) (10) 3.06 (11) cm (8) 3.75 (14) (13) 4.18 (18) cm (1) 5.1 (4) (19) 6.00 (30) cm (17) 7.73 (43) (9) 9.19 (55) cm 1.40 (3) 1.4 (10) (5) 15.1 (13) Maximum relative standard uncertainties: (parameters uncertainties). % at 15 cm.8 % at 8 cm 3.7 % at 5 cm 5 % at 3 cm % at 1 cm

30 Experimental validation () EUROMET Exercice Comparison of software used to compute transfer efficiency Experimental calibration for 3 volume sources HCl 1N (density=1.016) Silica (d=0.5) Sand-resin mixture (d=1.54) Transfer of Ge detectors efficiency calibration from point source geometry to other geometries M.C. Lépy et al., Rapport CEA R5894 (000)

31 Experimental calibration Energy (kev) Efficiency (%) for liquid Efficiency (%) for silica Efficiency (%) for sand/resin (1.3 %).863 (1.3 %) (1.4 %) (1.3 %) (1.3 %) (1.4 %) (1.1 %) 6.9 (1. %) 4.74 (1.3 %) (1.1 %) 6.01 (1.1 %) (1.3 %) (1.1 %) 5.0 (1.1 %) (1.3 %) (1.1 %) (1.1 %) (1.3 %) (1.1 %).40 (1.1 %) (1.3 %) (1.1 %) (1.1 %) (1.3 %) (1.0 %) 1.13 (1.1 %) (1.3 %) (1.0 %) (1.1 %) (1.3 %) (1.0 %) (1.1 %) 0.79 (1.3 %) (1.0 %) 0.78 (1. %) 0.66 (1.4 %) (1. %) (1.3 %) 0.57 (1.7 %)

32 Calculation for silica ETNA/EXP Silica Rel unc exp silica (%) Silica (kev) ETNA Exp transfer Energy

33 Calculation for sand-resin mixture ETNA/EXP Sand Rel unc exp sand (%) Sand (kev) ETNA Exp transfer Energy

34 Calculation validation T. Vidmar intercomparison (IAEA CRP) Two detectors Simple «school case» geometries Point source Soil Filter Reference geometry: liquid

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