European Physical Society 19 th Nuclear Physics Divisional Conference New Trends in Nuclear Physics Applications and Technology Pavia (Italy) September 5-9, 2005 EXPERIMENTAL STUDIES AND SIMULATIONS OF SPALLATION NEUTRON PRODUCTION ON A THICK LEAD TARGET Mitja Majerle NPI CAS Řež, The Czech Republic

19th NPDC, Pavia (Italy), September 5-9, 2005 Introduction Generally :  Experiments with high-energy protons on heavy targets (~ADS), spallation neutrons, direct beam  We measure transmutation possibilities, neutron fields, we compare data with model simulations Focus – The PHASOTRON experiment :  Protons, neutron field (threshold detectors)  Transmutation of Iodine (short-lived isotopes)... and the simulations  What and how we calculate  Comparison with the experiment  The influence of the setup parts

19th NPDC, Pavia (Italy), September 5-9, 2005 Neutrons and protons react with detectors: (n,  ), (n,2n), (n,xn), (n,  ), (p,n), (p,  ),... Yields of produced elements are detectable in  -detectors

19th NPDC, Pavia (Italy), September 5-9, 2005

Proton beam – 660 MeV, 10 min The integral measured with two foils (Al,Cu) : 1,58·10 15, accuracy 6% Beam displacement (Al, Au, Bi foils): beam was shifted upwards - few mm Reaction : (p,xn+yp), (p,  ),... Neutron field Al, Au, Bi foils Reactions : (n,xn), (n,  ), (n,  ) Spatial and energetic distribution of spallation neutrons We do not see the whole spectrum !

19th NPDC, Pavia (Italy), September 5-9, 2005 Experimental results B=Number of produced nuclei in 1 g of material per one incident proton

19th NPDC, Pavia (Italy), September 5-9, 2005 How do we get the neutron spectrum from that ? We cannot ! Experimentaly we can get it with other types of detectors. 197 Au(n,  ) 198 Au 197 Au(n,2n) 196 Au 27 Al(n,  ) 24 Na Our results are however important for simulations.

19th NPDC, Pavia (Italy), September 5-9, 2005 Iodine samples 4 samples: 2× 127 I, 2× 129 I 129 I - 90% of 129 I, 10% of 127 I During the experiment ~1/10 11 part of the iodine nuclei transmuted Chart explanation :  130 I produced only in 129 I  Ratios of produced elements are higher in 127 I samples (on graphblue)  120 I lower than expected – two isomers produced with almost the same lines, and only one is detected Stable  =hours, days  =years  =minutes (n,xn) ++ 127 I and 129 I samples at 9 th cm 1E+06 1E+07 1E+08 1E+09 1E+10 I-130I-128I-126I-124I-123I-121I-120I-119I-118 Isotope Number of produced nuclei i7n3 i9n2

19th NPDC, Pavia (Italy), September 5-9, 2005 Simulations, how/what we calculate MCNPX code v (on Linux, parallel computing) Input :  setup geometry  starting conditions Output 1:  neutron distribution Cross-section libraries (Au, Al - ENDF; Bi - experimental; Iodine - ?) Output 2:  masses of produced elements or B-values

19th NPDC, Pavia (Italy), September 5-9, 2005 How do we get the neutron spectrum from that ? We can convolute the calculated neutron spectrum with the cross-section for a given reaction (SSW+HTAPE3X+convolution). 197 Au(n,  ) 198 Au 197 Au(n,2n) 196 Au 27 Al(n,  ) 24 Na Computer can convolute the spectrum with cross-sections and outputs B (F4+FM tally).

19th NPDC, Pavia (Italy), September 5-9, 2005 Calculations vs. experiment B-values for Bi and I were not yet calculated (problem: cross-section libs) Calculated values in comparison with the experiment for 27 Al(n,  ) 24 Na Ratios between calculated and experimental values for 24 Na, 196 Au, 194 Au

19th NPDC, Pavia (Italy), September 5-9, 2005 Influence of the setup parts Concrete walls :  Neutrons are moderated and reflected back

19th NPDC, Pavia (Italy), September 5-9, 2005 Influence of other simplifications Extensive calculation tests on PHASOTRON and EPT setup revealed that :  HTAPE3X and F4 methods results do not always agree.  Beam profile and displacement influence the neutron field (3 mm ~ 5%).  Detectors minimally influence the neutron field.  Metal holders, tables,... have minimal influence. ... and more. The use of parallel processing (PVM) speeds up our calculations significantly.

19th NPDC, Pavia (Italy), September 5-9, 2005 Conclusion We try to imitate an ADS systems with the setup Experimentally : we get new data about transmutation rates (I, (n,xn) reactions, others...) – precious in ADS design Calculations : it seems that we measure right things to test the codes We can describe new, similar systems with the computer with the accuracy (50%) Plans :  to finish analyzing the experimental data,  to improve the accuracy of the calculations,  try to recalculate all this with DCM (Dubna Cascade Model) code,  probably another experiment on Phasotron, different setups... Thank you.

19th NPDC, Pavia (Italy), September 5-9, 2005 Experiment data Intensive beam (2,6·10 13 protons/s) of protons with energy 660 MeV from Phasotron ( Date and time: 14 th of December 2003 at 16:33 Pb target, without box to moderate fast neutrons The irradiation time : 10 minutes After another 10 minutes start of measurements of I samples and foils on detectors ORTEC and CANBERRA