1. Mitja Majerle NPI CAS Řež, The Czech Republic
M&C 2005 Avignon September 12-15, MCNPX STUDIES OF SPALLATION NEUTRON PRODUCTION ON A THICK LEAD TARGET
Mitja Majerle
NPI CAS
Řež, The Czech Republic

2. M&C 2005, Avignon, September 12-15, 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)
... and the simulations
What and how we calculate
Comparison with the experiment
The influence of the setup parts
M&C 2005, Avignon, September 12-15, 2005

3. Yields of produced elements are detectable in g-detectors
Neutrons and protons react with detectors: (n,g), (n,2n), (n,xn), (n,a), (p,n), (p,a), ...
Yields of produced elements are detectable in g-detectors
M&C 2005, Avignon, September 12-15, 2005

4. M&C 2005, Avignon, September 12-15, 2005
Experimental results
B=Number of produced nuclei in 1 g of material per one incident proton
Preliminary results
M&C 2005, Avignon, September 12-15, 2005

5. 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
M&C 2005, Avignon, September 12-15, 2005

6. Neutron spectra + cross-sections
We can convolute the calculated neutron spectrum with the cross-section for a given reaction (SSW+HTAPE3X+convolution).
197Au(n,2n)196Au
27Al(n,a)24Na
197Au(n,g)198Au
Computer can convolute the spectrum with cross-sections and outputs B (F4+FM tally).
M&C 2005, Avignon, September 12-15, 2005

7. Calculations vs. experiment
Calculated values in comparison with the experiment for 27Al(n,a)24Na
Ratios between calculated and
experimental values for 24Na, 196Au, 194Au
M&C 2005, Avignon, September 12-15, 2005

8. Influence of the setup parts
No walls
Concrete walls :
Neutrons are moderated and reflected back
Walls
M&C 2005, Avignon, September 12-15, 2005

9. 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%).
The use of different models (BERTINI, CEM, ISABEL) ~ 10%.
Detectors minimally influence the neutron field.
Metal holders, tables, ... have minimal influence.
...
M&C 2005, Avignon, September 12-15, 2005

10. M&C 2005, Avignon, September 12-15, 2005
Parallel processing
The use of parallel processing (PVM) speeds up our calculations significantly.
M&C 2005, Avignon, September 12-15, 2005

11. M&C 2005, Avignon, September 12-15, 2005
Conclusion
We try to imitate an ADS systems with the setup
We can describe new, similar systems with the computer with the accuracy (50%)
Thank you.
M&C 2005, Avignon, September 12-15, 2005