1. Inter-comparison of Medium-Energy Neutron Attenuation in Iron and Concrete (8) H. Hirayama and Attenuation Length Sub-Working Group in Japan

2. From Inter-comparison at SATIF-9  Study the reason for the large difference in the attenuation length and dose between codes.  It is desired to receive improved results from other groups.  Study the reason of the different tendency of C/E values between codes.  It is desired that other groups attend this inter comparisons.

3. Problems for an Inter-comparison (8)  Problems are same with an inter-comparison (7)  Neutron dose, spectrum inside 6m iron or 12m concrete plane for parallel beam of mono-energy neutrons (0.04-100GeV) and  Secondary neutrons produced by protons (0.2- 24GeV)  Comparison with the experimental results of AGS shielding experiments  As the new item to be sent by participants, “ particles treated to obtain the results ” is added.

4. Summary of contributors for Neutron attenuation calculation Name of participants and organization Name of computer code Particles treated T. Koi and D. Wright (SLAC National Accelerator Laboratory) Geant4 v9.3 (2009 Dec. released) All particles (Including recoil nucleus) Y. Uwamino (Riken)HETC-3STEP neutron, proton,   N. Matsuda (JAEA) and K. Niita (RIST) PHITS 2.24all established hadoronic states S. Roesler (CERN)FLUKA 2008.3c.All hadrons which FLUKA can transport N.V. Mokhov and I.L. Rakhno (Fermilab) MARS15(2010)All elementary particles and heavy ions

8. Iron for mono energy neutrons  General tendency of the attenuation length is similar for all results except PHITS with  0 particle.  Differences of dose itself are large.  Difference between Monte Carlo results except PHITS with transport  0 particle is about 10.  The effects of  0 particle in PHITS  The effects can be seen from 3 GeV and maximum at 10 GeV and decrees at 50 and 100 GeV.   0 portion within produced particles except neutrons and protons emitted from 1cm diameter and 1cm iron and concrete by high energy neutrons becomes maximum at 20 GeV and decrease with increase of neutron energy.

11.  0 contribution to neutron attenuation length  Matsuda and Niita estimate the effect of  0 particle to the neutron attenuation length as follows:  The  0 particle is one of the stable baryon, which life time is 2.6x10  10 sec and decayed to nucleon and pion. If the  0 particle is decayed very quickly after its production, as shown in Fig, 5, the additional contribution of  0 is disappeared. Therefore the additional contribution of the  0 particle is realized by the collisions of Lambda on material nucleus.  The mass of the  0 particles is heavier than that of nucleon. Thus much larger energy can be transported by the Lambda particles.  This is a reason, we suppose, that the attenuation through the Lambda particle is much flatter than that of not through the Lambda particle. General tendency of the attenuation length is similar for all results except PHITS with  0 particle.  It is desired to check the contribution of  0 particle to the neutron attenuation by other codes and also to compare various particles production rates from small target..

14. Concrete for mono energy neutron General Tendencies are same with at SATIF-9.  The differences between the attenuation lengths between each code are relatively small at low-energy region and increase with the increase of neutron energy.  The attenuation length have the tendency to increase slightly with increase of neutron energy for 12 m slab.  The dose differences at 8m are about 10 or less between Monte Carlo.

15. Secondary neutrons produced by protons (0.2-24GeV)

17. Comparison with Fe Target  General Tendencies are same with at SATIF-9.  All results show similar tendency to reach an almost constant value above 1 GeV protons.

18. Comparison with Experimental results at AGS

24. Steel shield  The calculated results are smaller than the measured ones in general.  The calculated results for 2.83 GeV protons are agree each other.  The C/E value differences for 24 GeV protons are larger than those for 2.83 GeV.

29. Concrete shield  The results of PHITS, Geant4, FLUKA and MARS relatively agree well each other and with the measured results than for the steel shield.

30. Future Themes   0 effects for iron presented PHITS must be checked by other codes.  It is necessary to compare various produced secondary particles from small target to understand the reason of difference of dose at high energy region.  Study the reason for the large difference in the attenuation length and dose between codes.  Study the reason of difference between measured results and calculated ones by various codes and the reason of the different tendency of C/E values between codes.

31. Appendix

32.  [a] High energy model switched from QGS (Quark Gluon String) to FTF (FriToF) model. Transition energy to the high energy model is lowered.  [b] Calculation only inside concrete for secondary neutrons by 24 GeV protons toward 90 degrees from a Hg target.  [c] Calculation only inside iron for 3-100 GeV neutrons.  [d] PHITS code (JAM [12]: Jet AA Microscopic Transport Model) explicitly treats all established hadoronic states including resonances with explicit spin and isospin as well as their anti-particles. All Hadron-Hadron interactions including lambda hayperon can be simulated up to 200GeV/u.  [e] Calculation only comparison with for the AGS experiments.

38. Attenuation Length for Secondary Neutrons from Hg Target  General Tendencies are same with at SATIF-9.  In the case of iron, all results show similar weak dependence on the emission angle but their values are largely scattered between each other.  In the case of concrete, all results show stronger dependence on the emission angle than in the case of iron and a different dependence between the code used.