1. Neutron Capture Cross Sections from 1 MeV to 2 MeV by Activation Measurements Korea Institutes of Geoscience and Mineral Resource G.D.Kim, T.K.Yang, Y.S.Kim, H.J.Woo, H.W.Choi, and W. Hong Korea Atomic Energy Research Institutes J.H.Chang

2. Introduction Activation method : Historically first means of measurement of NCCS in MeV range relatively simple to carry out completely selective for a given nuclide in a mixture of target isotopes Energies : 1 MeV to 2 MeV fusion reactor material research Material : 63 Cu and 186 W Mono-energetic fast neutrons source : 3 T(p,n) 3 He reaction. In KIGAM NCCS are being measured by activation method In KIGAM neutron facility Proton energy stability of the used accelerator : within 1keV Producible maximum neutron energy : 2.6 MeV

3. Target Analysis RBS ERD T : 4.6 x 10 18 atoms/cm 2, Ti : 1.4 x 10 19 atoms/cm 2 TiT target

4. Neutron Energy Spread  measured 2 =  resonance 2 +  tithick 2, : NES 1.3 % at 2.1 MeV NES 1.7 % at 1.67 MeV

5. Neutron Pulse Shape and Height Spectrum

6. KIGAM neutron facility detector sample beam Cooling system monitor Target chamber

7. D = N o  act (1-ee1-e R  d - t 1 - t 3 )( D   gamma counts per unit time, N o : areal density of sample  : neutron flux,  act : neutron captured cross section : decay constant of activated sample t 1 : neutron irradiation time t 2 : elapsed time from irradiation to measurement t 3 : measured time of gamma ray, R : transition probability  d : absolute gamma ray efficiency - t 2 ) Neutron Captured Cross Section

8. f(t) ;time dependence factor, subscript “ o ” refers to standard reaction D o = N o  o  o R o  o f o / o …… (1) D = N   R  f/  …… (2) (1)/(2)  = D o N  R  f o D N o  o R o  o f o oo =0.693/t ½,   /  = (ph o /t o )/(ph/t), t :neutron irradiation time  = D o N (ph) t o R  f t 1/2,0 D N o (ph) o t R o  o f o t 1/2 oo

9. Characteristics of Sample Purity(%)Weight(g)diameterThickness (cm) Density (g/cm 3 ) Molecular weight (g) Areal Density (10 22 ions/cm 2 ) Au-199.99117.345.0900.31019.282196.971.7633 Au-299.99122.845.1150.31519.282196.971.8280 Cu99.99111.855.0500.604 8.9263.5465.3800 W99.95223.545.0150.59519.35183.853.7299 Abundance : 63 Cu = 69.2 %of Cu, 186 W=28.6 % of W

10. Absolute Efficiency of HPGe detector speciesGamma energy [keV] Thickness [mm] Calculated efficiency Au4113.1 or 3.15 0.0285 or 0.0280 Cu5116.040.0290 W6865.950.0183 By MCNP code and standard mixed source

11. Transition Probability transitionGamma energy [keV] Transition probility 198 Au- 198 Hg(  - ) 4110.9503 64 Cu- 64 Ni(  + ) 5110.1750 187 W- 187 Re(  - ) 6860.1499 By Table of Isotopes

12. Gamma Spectrum of 198 Au 411 keV

13. Gamma Spectrum of 64 Cu 511 keV

14. Gamma Spectrum of 187 W and Background 686 479

15. Neutron energy(MeV)Irradiation time(hr) Elapsed time from irradiation to measurement (hr) Neutron fluxGamma counts (n,  )cross section (mb) Statis- tical Error (%) 2.015 197 Au0.9820.0409,542,3795,05753.4 63 Cu0.7920.1449,578,8931,811 5.442.91 1.813 197 Au0.5840.0719,793,8965,31559.6 63 Cu0.4130.3749,720,6481,760 5.492.93 1.611 197 Au0.5490.1288,319,2124,66366.5 63 Cu0.6250.0508,460,9251,814 7.212.91 1.409 197 Au0.6820.2436,444,7514,47969.4 63 Cu0.8690.0316,014,7621,630 7.673.10 Measured Data Table

16. Neutron Captured Cross Sections of 63 Cu

17. Neutron Captured Cross Sections of 186 W

18.  t  ln IoIo I () NoNo I : neutron counts in sample – in I o : neutron counts in sample-out N o : areal density of sample In scattering correction factor D  t = (  /4) (DL/L 1 L 2 ) 2  n (0 o )  n (0 o )= (kR +1) 4 /4k 2 : diffraction theory based on a continuum model R = 1.33 A 1/3 10 -13 cm, D is diameter of detector L is distance from target to detector, L 1 is distance from target to sample L 2 is distance from detector to sample Total Cross Section

19. Total Cross Sections of Cu

20. Total Cross Sections of W

21. Results Neutron capture cross sections of 63 Cu and 186 W Total scattering cross section of Cu and W Geometric Efficiency of HP Ge detector