1. VALIDATION OF THE FLUKA MONTE CARLO CODE FOR RESIDUAL PRODUCTION WITH 500 MeV/u AND 950 MeV/u URANIUM BEAM ON COPPER AND STAINLESS STEEL TARGET E. Kozlova 1,2, I. Strasik 1,3, A. Fertman 4, E. Mustafin 1, T.Radon 1, R. Hinca 3, M. Pavlovic 3,G. Fehrenbacher 1, H. Geissel 1,2, A. Golubev 3, H. Iwase 1, D. Schardt 1 1 GSI, Darmstadt, Germany 2 II. Physikalisches Institut, Justus-Liebig Universität Giessen, Germany 3 FEI STU Bratislava, Slovak Republic 4 ITEP,Moscow, Russia SAFERIB, 5-6 May 2008 Vilnius, Lithuania

2. Motivation  Activation of structures and surroundings of new high energy heavy ion accelerators like the Facility for Antiproton and Ion Research (FAIR) is an important issue.  Monte Carlo codes such as FLUKA allow to predict the production of individual radioactive isotopes and the induced radioactivity which is often the main contribution to the radiation exposure of personnel.  The aim of this work is a benchmark study of activation predictions for uranium beams with 500 MeV/u and 950 MeV/u deposited in copper and stainless steel targets.

3. Benchmark experiment Air SEETRAM (beam monitor) 640 mm Vacuum 238 U beam Target Al 100 µm 0.1 – millimeter foils were inserted after each thick disk, which allowed to obtain spatial distribution of activation rates in the target along the range  Gamma-spectrometry measurements are carried out with coaxial High Precision Germanium detector (Canberra, 35 % relative efficiency)  Spectra recording, energy and efficiency calibrations, background measurements have been controlled by the GSA Wingamma software package  Nuclide identification and estimation of activity from the spectra were done by Genie 2000 spectroscopy software from Canberra

4. Target materials and energies of the 238 U beam N Material and configuration Initial energy of 238 U ions / range Target thickness Irradiation time, h / Total dose on the target, ions 1 Stainless steel 302 – set of 35 disks 1 500 MeV/u / 6.28 mm (SRIM) 11.9 mm 16.35 / 2.352*10 11 2Cu – set of 34 disks 2 500 MeV/u / 5.79 mm (SRIM) 11 mm 20.0 / 4.66*10 11 3 Stainless steel 302 – set of 40 disks 1 950 MeV/u / 15.57 mm (SRIM) 138.38 mm 28.08 / 8.679*10 10 4Cu – set of 39 disks 2 950 MeV/u / 14.63 mm (SRIM) 133.093 mm 29.68 / 7.956*10 10 1 stainless steel 302 (ρ = 7.9 g/cm 3, 18% Cr, 9% Ni, 2% Mn), d = 50 mm 2 copper (ρ = 8.93 g/cm3, natural copper), d = 50 mm

5. FLUKA simulations: Residual nuclide production in copper (beam: Uranium, E = 950 MeV/u) Directly after irradiation (T cooling = 0) Target fragments Projectile fragments Production of radio-nuclides:  direct production  via serial decays

6. Example of contribution to activity of radio-nuclides from mother decay during cooling time (950 MeV/u 238 U on the copper target)

7. FLUKA simulation Activity calculation was done in 2 ways: "OFFLINE" (excluding serial decay chains) "ONLINE" (including serial decay chains) 1 step: FLUKA output: production rate (N/p.p.) of radio-nuclides. 2 step: Activity (Bq) calculation with activation formula. 1 step: FLUKA output: activity (Bq) per radionuclide.

8. Ratio of activities including and excluding decay chains (950 MeV/u 238 U on the copper target) Target fragments Projectile fragments

9. Contribution to 146 Eu from 146 Gd-decays during cooling time (950 MeV/u 238 U on the copper target) Lines: fits. Symbols: FLUKA results. This is the dependence which can be applied for correction of the measured activity value. (especially in the cases when the mother nuclide is not identified.)

10. Spatial Distribution of 46 Sc-activity in the copper target after 238 U E 0 =950 MeV/u irradiation (Tcooling = 14 days)

11. Spatial Distribution of the 7 Be-activity in the copper target after 238 U E 0 =950 MeV/u irradiation (Tcooling = 14 days)

12. Spatial Distribution of 56 Co-activity in the Copper target after 238 U E 0 =950 MeV/u irradiation (Tcooling = 14 days)

13. 950 MeV/u 238 U on the copper target Target fragments Projectile fragments The total activity for each radionuclide in the target was done via integration of the activity depth profile over the target depth.

14. 950 MeV/u 238 U on the copper target Target fragments Projectile fragments Measured 14-38d. / FLUKA Measured 81-111d. / FLUKA Tcool=14d Tcool=81d

15. 950 MeV/u 238 U on the stainless steel target Target fragments Projectile fragments Measured 3-23d. / FLUKA Measured 33-73d. / FLUKA Tcool=3d Tcool=33d

16. 500 MeV/u 238 U on the copper target Target fragments Projectile fragments Measured 16d. / FLUKA Measured 56d. / FLUKA Tcool=16d Tcool=56d

17. 500 MeV/u 238 U on the stainless steel target Target fragments Projectile fragments Measured 16d. / FLUKA Measured 59d. / FLUKA Tcool=16d Tcool=59d

18. Conclusion  Contribution of the activity from serial decays is significant for nearly all projectile fragments. The contribution of the activity via decays of mother nuclides was observed only in few cases for target fragments.  The agreement between experiment and FLUKA is better for target fragments. The maximum disagreement in the ratio is 3.5 ( 22 Na).  The maximum ratio for projectile fragments is 10.5 ( 237 U).  The main contribution to the activity comes from target fragments.  For long-lived radionuclides which contribute to 95 % of the total activity the agreement is less than a factor of 2.  This benchmark study shows that FLUKA is a very suitable code for the prediction of induced radioactivity at heavy-ion accelerator facilities (e.g. the Super Fragment Separator at FAIR).