Cosmogenic induced activity

1. Cosmogenic induced activity IDEA (Integrated Double-beta decay European Activities) Task leaders: Maura Pavan, Susana Cebrián Susana Cebrián scebrian@unizar.es University of Zaragoza (Spain) Paris, 14th-15th April 2005

2. Detailed implementation plan for first 18 months 1 2 3 4 • Outline of the talk • Task 2: final remarks • Task 3: description and results of the activation study for Ge • Task 4: points for discussion • Outlook and summary Poster “Cosmogenic activation of materials” presented at the “Low Radioactivity Techniques 2004” workshop, Sudbury (Canada), December 2004 (available at http://lrt2004.snolab.ca/talks/posters/irastorza-poster.pdf) S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

3. Task 2: Analysis of computational codes for n/p activation • DELIVERABLE: Report summarizing the features and limitations of codes: • Target materials and product isotopes covered • Projectiles allowed • Range of applicable energies • Physical models and/or experimental data sets for cross-sections • Checks with experimental data • “Technical” information: language, code source, support, ... • At IDEA website: http://idea.dipscfm.uninsubria.it/frontend/docs/reports/cosmogenics-task2.pdf S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

4. Conclusions for Task 2 Semiempirical codes +wide coverage of targets and products +short calculation time and simplicity of use - only proton-induced reactions Monte Carlo codes + neutron activation studies possible - very time-consuming (specially for some products) General-purpose MC codes +wide coverage of projectiles, targets and energies in principle + easy availability and support + different models can be used for the hadronic physics - not many comparisons with measurements of activation yields available S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

5. Task 3: Comparison of results for some problems of interest Study using different codes and comparing with data when possible • DELIVERABLE: Report comparing the performances of different codes • Identification of the most reliable codes • Quantification of the uncertainties or spread in the estimates • Identification of weak points of codes for treating our problems • … and preliminary results for open questions in activation for DBD • Problem of activation in Ge • Excitation functions for relevant isotopes in Ge have been obtained • Rates of production by cosmic neutrons have been estimated and compared with previous results S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

6. Excitation functions for 60Co and 68Ge Using the following data: • Experimental data with proton beams: • in natural Ge: • Horiguchi’83 25-64 MeV • Aleksandrov’91 660 MeV • Norman’05 800 MeV • in 70Ge and 76Ge: NUCLEX 1000 MeV • Calculations based on semiempirical Silberberg & Tsao formulas: • YIELDX: p >100 MeV • Calculations based on Monte Carlo codes: • CEM p 100-1700 MeV • ISABEL (by Majorana Collaboration) n <2000 MeV • HMS-ALICE p, n <150 MeV • MENDL-2 (using versions of ALICE) p <200 MeV, n <100 MeV Thanks to S. Mashnik for providing us with his calculations with CEM and HMS-ALICE S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

7. Measurements at 660 and 800 MeV agree very well with YIELDX (~15%) 60Co production in nat Ge Differences at low energies between MENDL and HMS-ALICE calculations below a factor ~3 s for neutrons up to 3 times bigger that s for protons The most contributing energy region to the activation yield is 200-500 MeV, (~40% of the total) S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

8. s in 76Ge are bigger than in 70Ge (from both calculations and measurements) enrichment could be useless or even harmful for 60Co 60Co production in 70Ge and 76Ge Calculations seem to overestimate these measurements, but they reproduce experimental data in nat Ge S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

9. 68Ge production in nat Ge s for protons up to twice bigger that s for neutrons Best agreement with measurements: YIELDX at high energy and HMS-ALICE at low energy The most contributing energy region to the activation yield is up to ~100 MeV S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

10. 68Ge production on Ge isotopes Increasing DA between target and product makes cross sections decrease significantly in all estimates … … except for YIELDX calculations, which however agree well with the experimental measurement S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

11. E>20 MeV: • 4.5 10-3 n/cm2/s Cosmic neutron spectrum f(E) • Parameterization based on measurements: • J. F. Ziegler, IBMJournal of Research and Development 42 (1998) 1. S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

12. Rates of production Production of60Co (kg -1 d-1) enriched Ge (86% 76Ge, 14% 74Ge) natural Ge Maximum deviation: factor 2.6 Enrichment does not reduce significantly 60Co activation S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

13. enriched Ge (86% 76Ge, 14% 74Ge) Production of68Ge (kg -1 d-1) natural Ge Enrichment reduces significantly 68Ge activation, but in different proportions Maximum deviation: factor 5 Rates enhanced in some estimates due to high cross sections at low energies S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

14. but … Conclusions for Task 3 Summary of the activation study in Ge • Excitation functions have been described combining HMS-ALICE and YIELDX results below and above 150 MeV • Activity yields derived are acceptably compatible with other estimates for 60Co but quite bigger discrepancies arise for 68Ge Conclusions regarding codes • ALICE codes seem to be the most reliable at low energies and semiempirical YIELDX at high energies • to what extent are equal s for neutrons and protons at medium-high energies? • good prediction capabilities for proton production s at low energies imply the same for neutron production s? S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

15. Task 4: Preparation of n/p activation tests on targets of interest GOAL: to measure the production cross-sections and/or rates of production with n/p beams on the targets of interest Essential to validate calculations with different codes • Indications from the activation studies • Te: the most uncertain region in the excitation function of 60Co is 1-3 GeV • Irradiation experiment underway at CERN with 1.4 GeV p • Ge: the most interesting irradiation experiment could be with neutrons at low energies to shed light on production of 68Ge. The use of both natural and enriched targets would be highly recommended. S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

16. Design of new irradiation experiments • target sample: natural or enriched? • projectile: n or p? • energy beam: mono-energetic? • facility and time: for irradiation and for gamma-counting • An example of a possible experiment: 68Ge in Ge • AtSvedberg Laboratory (Sweden): • monoenergetic neutrons 25-180 MeV, f~5 105 n/cm2/s • Rate of production of 68Ge in nat Ge (assuming s=100 mb): • R = 1.6 104 s-1 • Activity in 68Ge after 1 h of irradiation: • A = 1.7 Bq = 1.5 105 d-1 • Gamma counting at 1077 keV line (3%): • ~440 counts/d S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

17. Outlook S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

18. Summary • The analysis of computational codes for n/p activation is completed and the report is available • A study of activation in Te and Ge for isotopes relevant in DBD is underway, using available experimental data and different calculations. Preliminary conclusions have been drawn. • The preparation of new activation experiments has just been started up S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005