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Low Background Techniques for Deep Underground Sciences

This project aims to identify and measure experimental background components in deep underground sites and develop methods to suppress them. The project includes measurements of environmental gamma rays, radioactivity of rock and concrete, neutrons, Rn monitoring, and muons. The project also focuses on the radiopurity of materials and purification techniques.

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Low Background Techniques for Deep Underground Sciences

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  1. JRA1. LBT-DUSL Low background techniques for deep underground sciences • Reminder of goals • Present status • Work in progress

  2. Key objectives • To identify and measure experimental background components • To design methods and techniques to suppress them Working packages WP1 – Measurement of backgrounds in the EU underground labs WP2 –Development of a library of background simulation codes WP3 –R&D for UL background techniques and facilities in the labs WP4 –R&D on radio-purity of materials and purification techniques Links to: N3 (DMD), N4 (DBD), JRA2 (IDEA)

  3. Activity coordinators Julio Morales/José M. Carmona (LSC) Deputy coordinatorNicola Ferrari (LNGS) WP1. Background measurements in the deep underground sites: Coordinator Nicola Ferrari (LNGS) Deputy coordinators Marisa Sarsa/Gloria Luzón (LSC) WP2. Background simulations: Coordinator Gloria Luzón/Susana Cebrián (LSC) Deputy coordinator Vitaly Kudriavtsev (IUS) WP3. Low background facilities: Coordinator Matthias Laubenstein (LNGS) Deputy coordinator Jean Louis Reyss (LSM) WP4 . Radiopurity of the materials: Coordinator: Pia Loaiza (LSM) Deputy coordinator:Lino Miramonti (LNGS) Management structure of JRA1

  4. Participants

  5. 1st General Meeting: September 10, 2004 (Edinburgh) Set-up of Working Groups Presentation of JRA1 main web page Special session on WP2: Monte Carlo simulation codes Meetings 2nd General Meeting: January 12, 2005 (Modane) • Presentation of the mid-termreport • Coordinators: status of activities and future projects

  6. It contains: A description of the JRA1 activity and general documents News and deadlines JRA1 list of participants Information on next and previous meetings Links to other ILIAS activities closely related to JRA1 Working group pages: participants, documents, databases, reference papers, activities… (under construction) JRA1 main web page http://www.unizar.es/ilias

  7. SUMMARY OF ACTIVITIES

  8. WP1 key objective: To measure the environmental background components in the four underground sites in a coherent and coordinated way. • The background components in the deep underground sites • Environmental gamma rays • Radioactivity of rock, concrete, etc. • Neutrons • Rn monitoring in the air and in the water • Muons

  9. Rate (cps/keV) Gamma from nat. radioactivity n captures (?) Energy (keV) WP1 – Environmental gamma ray background LNGS: measured with NaI, Ge, and BGO detectors LSM: measured with a portable Ge detector Boulby: planning ofGe gamma survey with a TARI project LSC: measured in old lab;plans (HPGe, NaI) for new lab Data especially interesting at E>4 MeV (high energy gammas)

  10. WP1 – Environmental gamma ray background • Next steps: • Coordination for new background measurements in the labs will be discussed in the next JRA1 General Meeting (June 2005) • Data interpretation: perform MC simulations • use data from different detectors • This will allow us to: • Extract absolute emitted gamma ray fluxes • Check the validity of the MC codes • Check the compatibility of the radioactivity of rock and concrete with the observed background Data especially interesting at E>4 MeV (high energy gammas)

  11. WP1 – Radiopurity of rock & concrete in the labs • Existing information collected: • Data of U, Th and K contaminations in rock and concrete collected from the labs • This information will be offered at WP1 web page, linked from JRA1 main web page New project at LNGS (starting next spring): Study of the radioactivity in the rock of the Gran Sasso massive Collab. with geophysicists, partially supported by ILIAS Data especially interesting at E>4 MeV (high energy gammas)

  12. WP1 – Neutron monitoring Existing information collected: LNGS: 0.8 10-6 n cm-2 s-1 LSM: 1.6 10-6 n cm-2 s-1 LSC: 3.8 10-6 n cm-2 s-1 (inferred from IGEX experiment) Boulby: 1.3 10-6 n cm-2 s-1 (indirect measurement; new measurement under way) • However: • Different measurements differ in the shape of the fast neutron spectrum (LNGS) • Original number in LSM had to be revised (corrections to MC) NEW MEASUREMENTS ARE IMPORTANT Data especially interesting at E>4 MeV (high energy gammas)

  13. WP1 – Neutron monitoring • Plans for new measurements: • Gd loaded scintillator detector started in Nov 04 at Boulby • Two liquid scintillator cells at LNGS will be installed nextly • 3He liquid scintillator detector used in the past at Baksan and Finland (offer from INR) • New measurements at LSM and at LSC (when new lab is finished) are also being planned Data especially interesting at E>4 MeV (high energy gammas)

  14. LNGS: continuously monitored; 50-150 Bq/m3 in ventilated areas Boulby: ~ 5 Bq/m3; new measurements planned in 2005 LSM:new system of radon purification by adsorption in charcoal Vol. clean air : 150 m3/h Activity 222Rn = 15 mBq/m3 WP1 – Radon measurements Data especially interesting at E>4 MeV (high energy gammas)

  15. Preliminary measurements at the excavation, without ventilation: ~ 70 Bq/m3 WP1 – Radon measurements LSC: 30-150 Bq/m3 in old laboratory; under active control & monitorization in the new lab Data especially interesting at E>4 MeV (high energy gammas)

  16. Muon WP1 – Muon measurements Existing information collected: LNGS: 1.1 m m-2 h-1 (measured by MACRO, incl. angular distrib.) LSM: 0.17 m m-2 h-1 LSC: 7.2 m m-2 h-1 (will be also measured in the new lab) Boulby: 1.5 m m-2 h-1 (recently measured by ZEPLIN) Data especially interesting at E>4 MeV (high energy gammas)

  17. JRA1-WP2 JRA2(IDEA) WP3-B1 N3-BSNS Study on Cosmogenic Induced Activity Background Simulation, Neutron-Shield and Muon-Vetos WP2 key objective: To produce a reliable Monte Carlo library of simulation codes for the interpretation of data and for planning future experiments.

  18. WP2 – Activities • Main initial activity: existing codes compared and discussed • Gamma background:GEANT4 • Neutrons: SOURCES (production) • FLUKA, MCNP, GEANT4 (propagation) • Muon-induced neutrons: MUSIC, MUSUN, SIAM, FLUKA (prod.) • FLUKA, GEANT4 (propagation) • Tasks: • Compare simulation vs experimental data • Compare one code vs another code Data especially interesting at E>4 MeV (high energy gammas)

  19. Production spectrum from mod. SOURCES Spectrum propagated with GEANT4 Evaluated spectrum from measurements (Modane) WP2 – Neutron production • SOURCES: • Neutron flux and energy spectrum from U/Th contaminations • Problem:no alphas above 6.5 MeV → modifications of the code • Major problem:neutron energy spectrum in the laboratory (after propagation) is softer than the one measured Carson et al. Astropart. Phys. 21 (2004) 667 Data especially interesting at E>4 MeV (high energy gammas)

  20. 5.5 MeV alphas - Mg (natural) 5.0 MeV alphas - Al2O3 WP2 – Neutron production • SOURCES: • Energy spectra of alphas incident on Al and Mg slabs are however in good agreement with experimental data Jacobs and Liskien, Annals of Nuclear Energy, 10 (1983) 541 Are cross-sections, transition probabilities and other features correct? The code was tested against measured spectra from various sources, but need more accurate measurements in underground labs (including neutron spectra). Data especially interesting at E>4 MeV (high energy gammas)

  21. Carson et al. Astropart. Phys. 21 (2004) 667 Wulandari et al. Talk at IDM2004 WP2 – Neutron propagation and detection • MCNP and GEANT4: • Substantial differences, probably (partly) due to the difference in initial neutron spectra and geometry. GEANT4 > 105 suppression after 50 g/cm2 PE MCNP 104 suppression with 50 cm PE Data especially interesting at E>4 MeV (high energy gammas)

  22. WP2 – Neutron propagation and detection • MCNP and GEANT4: • Substantial differences, probably (partly) due to the difference in initial neutron spectra and geometry. Neutron propagation through the shielding with the two codes is needed using the same geometry and the same input neutron spectrum – work in progress Data especially interesting at E>4 MeV (high energy gammas)

  23. WP2 – Muon-induced neutrons • FLUKA and GEANT4: • Comparison: yield, spectrum, lateral distribution, and dependence with material. • Both codes agree within a factor of 2 (or even better). However, there is systematic higher production with FLUKA in most materials GEANT4: Araujo et al., hep-ex/0411026 FLUKA: Kudryavtsev et al. NIMA, 505 (2003) 688 Data especially interesting at E>4 MeV (high energy gammas)

  24. WP2 – Activities • Comparison of codes with experiments: • Published neutron flux measurements at Gran Sasso, Modane, Canfranc, CPL (Korea) and others. • Measurements of muon-induced neutrons at various depths underground: neutron yields, energy spectra, lateral distributions etc.: LVD, KARMEN, LSD etc. • Measurements of muon-induced neutrons using active vetoes for dark matter detectors (existing and planned): Canfranc, Modane, Boulby, Gran Sasso. • Planned background flux measurements at Gran Sasso, Modane, Canfranc, Boulby as proposed in JRA1 (ILIAS). Data especially interesting at E>4 MeV (high energy gammas)

  25. WP2 – Activities • First ‘test’ version of the MC libraries: • It will be ready in February 2005 • It will include: • General information about codes and links to the code web-site • Modifications to codes • Library of examples used by underground groups • A mailing distribution list has been created to optimize exchange of ideas (info: http://webmail.unizar.es/mailman/listinfo/montecarlo) • An FTP repository for codes with access through main JRA1 web page has been created (info: luzon@unizar.es) Data especially interesting at E>4 MeV (high energy gammas)

  26. WP3 key objectives: • Construction and upgrading of ultra low background facilities(ULBF) in the four underground labs forming an EU-coordinated service for applications in rare event physics and other fields of world-wide value. • Implementation of newtechniques to deal with the background: active and passive shielding, veto systems, particle discrimination techniques, fragmentation of calorimeter detectors, control and suppression of radon levels... • Study of the feasibility of fabrication of detectors and materials underground.

  27. GNO Ultra low-level gas counting Ultra low-level HPGe detector @ LNGS WP3 – Low background facilities: LNGS • Strengthening of the ultra low-level background facilities at LNGS: • Extension of the Low Level Laboratory at LNGS • New generation of HP-Ge detectors for ultra low-level applications • Set-up of ultra low-level scintillation counter systems • Ultra low-level gas counting (GNO counting lab) Data especially interesting at E>4 MeV (high energy gammas)

  28. Desk GE 1 AC unit GE 2 7.68m Storage Small Proj Bay 11.96m GE 3 0.8m 0.5T swing crane (in place) 4.28m Desk GE 4 Plan for JIF Low Background Lab (Stub A) Entrance Clean-Off 6.0m 6.0m Storage Storage WP3 – Low background facilities: Boulby New ULBF laboratory at Boulby: Plans to develop the existing Ge facility in the new ULB laboratory Data especially interesting at E>4 MeV (high energy gammas)

  29. WP3 – Low background facilities: LSM • On going-projects: • Improvement of a low-background Ge detector, IRIS (400 cc) • A new planar Ge detector will be acquired • The Rn trapping facility was recently installed • Construction of a Radon precision measuring facility, with a sensitivity of ~ mBq/m3 (Vol. 70 l) Data especially interesting at E>4 MeV (high energy gammas)

  30. WP3 – Low background facilities: LSC Old laboratory: 1 kg Ge prototypedetector, equipped with an overpressure system of gaseous N2 to minimize Rn intrusion New laboratory: two new ULB 2 kg Ge detectors (one of them already acquired) for material testing will be installed in the new LSC Data especially interesting at E>4 MeV (high energy gammas)

  31. WP4 key objectives: • Collect new (and old) data on radioactive contamination and cosmogenic activation of materials used in rare-event physics experiments and ultra-low background instrumentation • Development and test of purificationtechniques to improve the radio-purity of materials.

  32. WP4 – Activities • Ellaboration of a database on radiopurity of materials: • The database is stored in a dedicated server of the Centre de Calcul de Lyon. It is built using MySQL system combined with php scripts which allow to communicate from the web page to the database. • Data has been collected from LSC (ANAIS, CAST & ROSEBUD), LSM (EDELWEISS), from the UKDM site and from publications. • At LRT2004, SNO people proposed to make their measurements available to be included in the database. Systematic comparison of measurements in the different labs: Cross-check with one or more reference samples to compare instrumentation and possible systematic in the analysis method is under discussion Data especially interesting at E>4 MeV (high energy gammas)

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