1. Physics-Based Modeling Robert Reedy (UNM), Kyeong Kim (U. Ariz
Physics-Based Modeling Robert Reedy (UNM), Kyeong Kim (U. Ariz.), and Jozef Masarik (Komensky Univ.)
Objective: Calculate the best possible production rates for TCNs using:
computer codes that numerically simulate particle production and transport
Monte Carlo N Particle eXtended (MCNPX) [Reedy and Kim]; GEANT & LAHET Code System [Masarik].
the latest measured or evaluated cross sections
Experimental ones for proton reactions; a few measurements or adjusted fits for neutrons.
6 nuclides: 10Be, 26Al, then 14C, 36Cl, 21Ne, 3He.

2. Numerical Simulation Codes
MCNPX, GEANT, and LCS codes
extensively developed for nuclear physics;
well tested with many benchmarks;
often used by us for extraterrestrial problems.
Some results by us for terrestrial in situ (and atmospheric) terrestrial cosmogenic nuclides
Not perfectly accurate, but represent fairly well the basic processes involved in the production and transport of primary and secondary particles
Need fine tuning for TCNs.

3. Work on Codes Compare codes Fine tune parameters in codes
Neutron fluxes
Rates for making cosmogenic nuclides
Fine tune parameters in codes
Input cosmic ray spectra – deep space and for different locations on Earth
“Physics” packages in codes
Test with various measurements

4. Code Work – Compare fluxes
Neutron fluxes using MCNPX and LCS

5. Code Work, GCR fluxes Test various galactic cosmic ray spectra
Castagnoli & Lal (1980), Webber & Higbie (2003), others in space and at Earth
Compare input spectra for protons only and both protons and alpha particles using latest versions of MCNPX.
Test physics parameters in the codes
Done for 2 sets by Kim & Reedy (2004) for spallogenic nuclides in meteorite – similar

6. Code Work, Input spectra
Work by G. W. McKinney et al. (2006) for neutron densities in the Apollo 17 drill core

7. Code Work, Physics Inputs
Work by G. W. McKinney et al. (2006) for neutron densities in the Apollo 17 drill core

8. Input GCR energy cutoffs
1980 vertical cosmic ray cutoff rigidity data were used to then estimate the primary galactic cosmic ray (GCR) spectrum for various geomagnetic latitudes for our MCNPX calculations. [J. Masarik]

9. Code Work, Terr. GCR Fluxes
Need good GCR spectra for all locations

10. Code Work, Terr. GCR Fluxes
Gordon et al. (2004) and MCNPX Calc. [Kim]

11. Code Work, Terr. GCR Fluxes
Gordon et al. (2004) and other calculations

12. BASICS OF CALCULATIONS OF PRODUCTION RATES
Calculate fluxes (neutrons, protons) in specified target (geometry, composition) and incident cosmic rays.
Calculate production rate at depth d using target composition (i, e.g., SiO2), calculated spectra Φ for particles (k), and cross sections σ for target-element pair (i,j; e.g., O to Be-10, Si to Al-26):
Pj(d) = i Ni k ∫σjik(Ek) Φk(Ek,d) dEk

13. Update Cross Sections
Evaluate measured cross sections for proton-induced reactions
Adjust cross sections for neutron-induced reactions
Use any measured (n,x) cross sections
Adjust using good CN measurements in extraterrestrial and terrestrial samples and artificial targets (natural & accelerators)

14. CROSS SECTIONS FOR PRODUCTION OF 10Be & 26Al ON TARGET ELEMENTS BY PROTONS

15. NEUTRON-INDUCED CROSS SECTIONS
Neutrons dominate (~90-95%) TCN production.
Early work, still used (~20 yrs. ago!):
Use a few measured neutron cross sections (Ne).
Use proton cross sections (Al-26),
Adjust neutron cross sections to fit ET measurements (Be-10, C-14).

16. Test Calculations
For now, use existing extraterrestrial and some terrestrial measurements
Use new CRONUS results
Refine codes, their inputs (physics packages, input spectra), and reaction cross sections

18. Preliminary rates for TCNs
from quartz using LCS and [MCNPX]:
Be-10: 5.7, [5.0]
C-14: 18.7, [22.2]
Al-26: 34.3, [36.4]
Close to old rates from Masarik & Reedy [1995]: 5.97, 18.6, and 36.1

19. Work this year Papers presented at AMS-10 on TCNs
by Kim, Reedy, & Masarik
Papers submitted to Proc. AMS-10
Tests using neutron fluxes and Be-10 measured for many locations in southern hemisphere by I. Graham [Kim et al.]
Calculations for the air/ground interface and effects of snow cover [Masarik et al.] (see next 2 images)

20. Fast and thermal neutron fluxes

21. Changes due to water (snow)

22. Future Work
More tests with GEANT (will probably drop LCS as is incorporated in MCNPX and will not be supported. GEANT is entirely different code from LCS/MCNPX.
Fine tune codes and their inputs
Cross section work
Comparisons to improve calculations
Extraterrestrial and other existing data
Terrestrial, especially using CRONUS data