1. Page 1 Cross-sections of Neutron Threshold Reactions studied by activation method Anne Larédo Supervisor: Dr. Vladimír Wagner Nuclear Physics Institute, Academy of Sciences of Czech Republic École des Mines de Nantes (France)

2. Page 2 Plan Introduction Uppsala experiment Spectrum analysis Cross section measurements Incertainty calculation Correction calculation

3. Page 3 Introduction Threshold reactions on Au, Al, Bi, In, Ta, Ni, Zn, Y, I Up to now almost no experimental cross- section data for high energy neutron reaction (E>20MeV) The Uppsala experiment enable new cross- section measurements for high energy neutrons (62 to 93 MeV). My work consists in analysing the gamma spectrum resulting from the experiment to obtain experimental cross-sections.

4. Page 4 Uppsala experiment (1/2) Took place in February 2010 in Uppsala, Sweden Neutron source : quasi-monoenergetic based on reaction 7Li(p,n)7Be energy range  11-175 MeV Proton beam energies : 62, 70, 80, and 93 MeV

5. Page 5 Uppsala experiment (2/2) Threshold reactions on Au, Al, Bi, In, Ta, Ni, Zn, Y, I AlAuBiCoIn Ta Experimental disposition

6. Page 6 Spectrum analysis(1/5) Gamma spectrum peak analysis using DEIMOS32 software

7. Page 7 Spectrum analysis(2/5) Gamma spectrum for different neutron energy and different time MeVFileTreal [s] 62S6RBiP213787 S6RBiP227224 S6RBiP2337749 65S62BiP114207 S62BiP1237288 S62BiP1385038 70S70BiP213869 S70BiP227214 S70BiP2324597 80S80BiP213654 S80BiP227246 S80BiP2321830 93S93BiP213410 S93BiP2223916

8. Page 8 Spectrum analysis(3/5) Possible reactions and isotopes producted by these reaction enable to know what we are looking for.

9. Page 9 Spectrum analysis(4/5) Determination of present isotopes using the result tables from DEIMOS32 compare to data base (decay data search) on gamma radiations...\ANALYSIS\Bi analysis - 4.xlsx energy 609.341 661.331 663.686 670.542 791.292 802.949 820.181 824.982 847.027 880.860 897.180 899.119 910.444 911.707 912.831 918.113 983.846

10. Page 10 Spectrum analysis(5/5) 10 isotopes found from (n,2n) to (n,9n) reactions Isotope 1201Bi 2202Bi 3203Bi 4204Bi 5205Bi 6206Bi 7207Bi 8208Bi 9201Pb 10203Pb

11. Page 11 Cross-section measurement (1/4) Determination of N yield Peak areaSelf-absorption correction Beam correction Dead time correctionDecay during cooling and measurement γline intensity Detector efficiency Correction for coincidences Square-emitter correction Weight normalization Decay during irradiation

12. Page 12 Cross-section measurement (2/4) First approximation of N yield Detector efficiency determination

13. Page 13 Cross-section measurement (3/4) Peak area S p : given by DEIMOS for each peak γline intensity I γ : from decay data search t real : data from experiment t live : data from experiment Decay constant λ : T 1/2 : data from libreries as decay data search t0 = Beam end – start of measurement t irr : time of irradiation

14. Page 14 Cross-section measurement (4/4) N yield : previously calculate N n : number of neutrons in peak (per cm²) For experiment condition and energies MeVNnNn 652,9820E+09 705,3165E+09 806,3691E+09 937,6936E+09 Foil mass m foil (given data from experiment) Foil size S : (2,5)² cm² = 6,25 cm² Relative mass A : 208,98 [g.mol -1 ] Avogadro’s number N A = 6,022.10 23

15. Page 15 Incertainty determination (1/4) First approximation : N yield_average : mean of N yield for a same neutron energy N i : N yield for a neutron energy Precise analysis :

16. Page 16 Incertainty determination (2/4) With : aerr deimos : incertainty on the peak area from the software Deimos32 Then :

17. Page 17 Incertainty determination (3/4) Next step : If: Else :..\ANALYSIS\Bi analysis - 4.xlsx

18. Page 18 Incertainty determination (4/4) Last step : combinaison of the relative uncertainty (from the Deimos data) with the uncertainty from intensity, neutron spectra, detector uncertainty : ΔN yield_average : Deimos uncertainty 10% : Beam intensity uncertainty 10% : neutron spectra uncertainty 3 % : detector efficiency uncertainty Finally:..\Results - Cross-section graphs\XS Bi vysledne srovnani.xls

19. Page 19 Results (1/7) Bi 207 : The results for this isotope are for now out range. Current work : using spectrum from after and before irradiation to soustract the gammas which are not from the irradiation we are interrested in but from previous one.

20. Page 20 Results (2/7) Bi 206 : very small incertainty

21. Page 21 Results (3/7) Bi 205 :

22. Page 22 Results (4/7) Bi 204 :

23. Page 23 Results (5/7) Bi 203 :

24. Page 24 Results (6/7) Bi 202 :

25. Page 25 Results (7/7) Bi 201 :

26. Page 26 Correction calculation COI : correction for coincidences between severals gamma rays of an isotope...\COI\COI calculation.xlsx B a : Beam correction..\beamcorr-Upps2010.xls C S-A : Self absorption correction..\Self-absorption\Self-absorption correction.xlsx Background correction..\ANALYSIS\Bi analysis - 4.xlsx

27. Page 27 Conclusion Now the first result for the cross section are calculated. We compared experimental datas to theorical model. Most importants correction have been added