1. Cosmogenic induced activity Susana Cebrián scebrian@unizar.esscebrian@unizar.es University of Zaragoza (Spain) IDEA (Integrated Double-beta decay European Activities) Prague, 20 th -21 st April 2006 Task coordinators: Maura Pavan, Susana Cebrián

2.  Implementation plan Outline of the talk Simulation-based work and related report Irradiations tests Outlook and summary S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 WPTask 9.R2 - Table 1 – IDEA - Second 18 months Execution Plan 13 st to 18 th month (1.04.2005-30.09.2005) 19 th to 24 th month (1.10.2005-31.03.2006) 25 th to 30 th month (1.04.2006-30.09.2006) 4B1 Tasks - Up-grade and development of simulation codes - Upgrading of existing codes for n/p activation - Design of further n/p activation tests on Ge and TeO 2 - further n/p activation experiments - Start-up of tests at CERN and other labs on Ge and TeO 2 Milesto nes and Delivera bles - Upgraded codes for n/p activation and related technical report - progress report

3. COLLABORATION WITH JRA1 (WP4 “Radiopurity of materials”): Shared interest in the cosmogenic activation of other targets like Cu and NaI S. Cebrián, Cosmogenic Induced Activity PROCEEDINGS: "Cosmogenic activation of materials" J. Amaré, B. Beltrán, S. Capelli, F. Capozzi, J. M. Carmona, S. Cebrián, O. Cremonesi, E. Garcia, I.G. Irastorza, H. Gómez, G. Luzón, M. Martínez, J. Morales, A. Ortiz de Solorzano, M. Pavan, C. Pobes, J. Puimedon, A. Rodríguez, J. Ruz, M.L. Sarsa, L. Torres, J. A. Villar AIP (American Institute of Physics) Conference Proceedings (Proceedings of the Workshop on Low Radioactive Techniques 2004, Sudbury, Canada, December 2004) Vol. 785 p. 267-271 (September 2005). "Cosmogenic activation in germanium double beta decay experiments" S. Cebrián, J. Amaré, B. Beltrán, J. M. Carmona, E. Garcia, I.G. Irastorza, H. Gómez, G. Luzón, M. Martínez, J. Morales, A. Ortiz de Solorzano, C. Pobes, J. Puimedon, A. Rodríguez, J. Ruz, M.L. Sarsa, L. Torres, J. A. Villar To appear in Journal of Physics: Conference Series, IoP, (Proceedings of the TAUP2005 Conference, Zaragoza, Spain, September 2005).  General issues IDEA meeting, Prague, April 2006

4. S. Cebrián, Cosmogenic Induced Activity Simulation-based work GOAL: Identification of the most reliable codes and of the weak points of computations for treating our problems in order to improve them Studies for relevant activation problems in DBD using different codes and comparing with data when possible: Te, Ge, Cu In the first two years… DELIVERABLE: upgrades in codes and related technical report http://idea.dipscfm.uninsubria.it/frontend/docs/reports/report_upgrade_codes.pdf + answers to open questions about activation problems in DBD IDEA meeting, Prague, April 2006 Remind of activation studies General conclusions on codes Upgrades in codes

5. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 Description of activation studies (I) Te, Ge, and Cu chosen as targets of activation, due to their relevance in DBD experiments Evaluation of cosmogenic activation yields of relevant long-lived products in each of these three targets by nucleons at sea level following a common methodology: 1.To collect available information on isotope production cross sections, from measurements and from calculations (new or from libraries) 2.To choose the best description of the excitation functions of products (calculating deviation factors between measurements and different calculations) 3.To estimate the production rates of relevant products considering a particular cosmic ray spectrum and to compare them with previous estimates and/or measurements

6. S. Cebrián, Cosmogenic Induced Activity J. F. Ziegler, IBM Journal of Research and Development 42 (1998) 1. E>20 MeV: 4.5 10 -3 n/cm 2 /s Cosmic neutron spectrum: parameterization based on measurements IDEA meeting, Prague, April 2006

7. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 Description of activation studies (II) Simulation of some irradiation experiments with beams using both the semiempirical code YIELDX and the Monte Carlo package GEANT4 Details of all these activation studies presented at IDEA meetings: Heidelberg: Te Paris: Ge Zaragoza: Cu and summarized in the delivered report Global analysis of all activation studies (comparing calculations and simulations with all available experimental information) to conclude on codes

8. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 General conclusions on codes (I) From simulation of irradiation experiments… At high energies, in GEANT4 the Bertini model gives the best agreement with measurements At low energies (<100 MeV), in GEANT4 the precompound model underestimates yields in Ge in a factor 3 at least Deviation factors Bertini cascade Binary cascade Te, ~1.8 GeV Ge, 660 MeV ~2 3.2 >10 5.9 Semiempirical YIELDX reproduces well high energy data YIELDX ~3 1.9

9. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 General conclusions on codes (II) From excitation functions … Use of YIELDX is preferred rather than COSMO, since experimental results on Te targets have solved the problem of some found discrepancies Deviation factors (averaged on energy and/or products) evaluated for different calculations range from ~1.5 to ~2.5 HMS-ALICE gives best agreement at low energies YIELDX predictions, very good at high energies, worsen in the medium energy range

10. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 General conclusions on codes (III) Proposed recipe for evaluation of excitation functions: at low energies, calculations specifically developed for neutrons can be used from MENDL or using HMS-ALICE. at medium and high energies, YIELDX calculations, assuming cross sections by neutrons and by protons similar enough Biggest uncertainties from the medium energy range, where there is no neutron measurement to validate calculations From excitation functions … Differences on production cross sections by neutrons or protons are not negligible at low energies for many cases (corroborated by available measurements) important to properly estimate activation yields by neutrons

11. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 General conclusions on codes (IV) From production rates … Most of the cosmogenic yield is usually due to neutrons of some hundreds of MeV. However, for some particular products with small  A, like 68 Ge in natural Ge and 60 Co in Cu, most of the yield seems to come from neutrons below 100 MeV. The use of only semiempirical codes to obtain cross sections can introduce significant deviations for production rates since their applicability at low energies is very limited Our estimates of production rates overestimate in a factor 2-3 rates deduced experimentally in Ge; better agreement is achieved for some nuclides in Cu, although maximum discrepancies in this case are also around a factor 3. A factor of ~3 of uncertainty should be considered when using our recipe Further refinements in cross sections at medium energies could be necessary

12. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 Upgrades in codes (I) Semiempirical codes YIELDX only can calculate the production cross section of a product in a target nucleus at a fixed energy, while COSMO derives activities for selected exposure and decay times, assuming a certain cosmic ray flux. A code is being prepared to compute directly also activities based on the YIELDX routine. Monte Carlo codes: GEANT4 Contact has been established between GEANT4 Collaboration and ILIAS community working on simulations

13. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 Upgrades in codes (II) Monte Carlo codes: GEANT4 “Validation of GEANT4 Bertini Cascade nuclide production using parallel ROOT facility”, A. Heikkinen and T. Linden Computing in High Energy and Nuclear Physics (CHEP2006), India, February 2006 Nuclide production by protons on various targets from 20 MeV to 8 GeV Bertini cascade hybrid model: intranuclear cascade + preequilibrium + fission + evaporation Performance comparable to other codes (HETC, CEM, LAHET, CASCADE) Efforts for validation of hadronic models ongoing within GEANT4 collaboration, including also the problem of isotope production

14. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006

15. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 Upgrades in codes (II) The isotope production capabilities in GEANT4 are being validated and improved by the GEANT4 collaboration Monte Carlo codes: GEANT4 “Validation of GEANT4 Bertini Cascade nuclide production using parallel ROOT facility”, A. Heikkinen and T. Linden Computing in High Energy and Nuclear Physics (CHEP2006), India, February 2006 Nuclide production by protons on various targets from 20 MeV to 8 GeV Bertini cascade hybrid model: intranuclear cascade + preequilibrium + fission + evaporation Performance comparable to other codes (HETC, CEM, LAHET, CASCADE) New models with good isotope production properties are being incorporated in GEANT4 and planned to be released late in 2007 Our report summarizing activation studies in Te, Ge and Cu has been forwarded to GEANT4 people to help in this isotope production validation Efforts for validation of hadronic models ongoing within GEANT4 collaboration, including also the problem of isotope production

16. Proposals for Ge experiments Plans for other targets: Cu, NaI An irradiation experiment in Te has been already carried out at CERN with proton beams S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Zaragoza, November 2005 Irradiation tests GOAL: to measure the production cross-sections and/or rates of production with n/p beams on the targets of interest in dedicated experiments Essential to validate and refine calculations with codes In the first two years …

17. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 Proposals for Ge irradiation with neutrons 68 Ge production seems to be mostly due to low energy neutrons and important discrepancies were found between different estimates irradiation test to check.

18. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 Plans for Ge irradiation with protons By Milano group together with American collaborators Ge samples Proton beams with energies 1.4 and 24 GeV At CERN Irradiation scheduled to take place within next weeks Beam irradiation experiment scheduled Now, the highest energies available in measured production cross sections (p,X) in Ge are 660-800 MeV This experiment will be very useful to validate high energy calculations.

19. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 Plans for Cu By Modane group in JRA1 Cu sample of 2250 g Exposure to cosmic rays at ~2000 m in Modane More than three months of exposure up to now Gamma counting foreseen to determine production rates Natural irradiation experiment underway

20. S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006 Plans for NaI By University of Zaragoza group, in connection with the ANAIS experiment intended to investigate the WIMP annual modulation effect One NaI crystal with a mass of 10.7 kg exposed to cosmic rays in Zaragoza during more than 7 years Natural irradiation experiment underway A rough estimate of the production of some relevant long-lived products has been made, giving some measurable yields ( 125 I, 126 I) A background measurement with this crystal can be made in the Canfranc Underground Laboratory to check these predictions

21. Outlook S. Cebrián, Cosmogenic Induced Activity WPTask 9.R2 - Table 1 – IDEA - Third 18 months Execution Plan 25 th to 30 th month (1.04.2006-30.09.2006) 31 st to 36 th month (1.10.2006-31.03.2007) 37 th to 42 th month (1.04.2007- 30.09.2007) 3B1 Tasks - Upgrade of n/p activation codes: extension to copper - Start of a detailed analysis of the activation experiments and of the consequences on Ge and Te based DBD experiments - Activation tests on Ge - Continuation of activation tests on Te Milestones and Deliverables - Technical report describing the activation experiments - Progress report IDEA meeting, Prague, April 2006

22. Summary A detailed report summarizing the activation studies carried out for Te, Ge and Cu has been delivered, presenting the main conclusions regarding the use of different computational codes for cosmogenic activation in DBD experiments Validation and improvement of isotope production capabilities in GEANT4 are ongoing S. Cebrián, Cosmogenic Induced Activity An irradiation experiment on Ge with protons is scheduled and the neutron proposal must be fixed to be performed in the next future Other irradiation tests in Cu and in NaI are underway in collaboration with people from JRA1 in ILIAS, based on long natural exposures of massive samples to cosmic rays IDEA meeting, Prague, April 2006

24. Sample=detector approach: + higher efficiency for measuring the yield, allowing lower neutron fluxes - irradiation of components other than Ge crystal - not easy continuity for enriched samples Activity ratios: 10000 : 50 : 1 : 0.001 Only X-ray counting possible Very massive samples required S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006

25. 60 Co production in nat Te S. Cebrián, Cosmogenic Induced ActivityIDEA meeting, Prague, April 2006