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M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

Investigating Neutrinoless Double Beta Decay. Status of the GERDA Experiment. Michael Altmann. Max-Planck-Institut für Physik, Munich. Physics. R&D Detectors. Concept. Schedule, etc. Exp. Setup. Summary. M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005.

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M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

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  1. Investigating Neutrinoless Double Beta Decay Status of the GERDA Experiment Michael Altmann Max-Planck-Institut für Physik, Munich Physics R&D Detectors Concept Schedule, etc. Exp. Setup Summary M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  2. Physics Motivation : Nature of the Neutrino Neutrino masses and lepton flavour mixing established by oscillation experiments  Neutrino mass differences known Still Unknown: • absolute mass values • hierarchy scheme • n= anti-n ?  Neutrinoless Double Beta Decay M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  3. Klapdor-Kleingrothaus positive evidence Phase 1 Phase 2 GERDA Sensitivity Phase-3 Physics Goals and Experimental Requirements For excluding inverted hierarchy:Sensitivity on 10 meV level required  ton-scale @ B < 10-4 / keV kg yr M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  4. Phase-2: Increase mass by adding  20 kg of new enriched Ge-detectorsGoal:100 kg yr statistics at background level B<10-3 / keV kg yr T1/2 > 2 * 1026 yr  mneff < 0.09 – 0.29 eV Phase-3: (Depending on results of phase-2 and possibly other experiments)worldwide collaboration for really big experiment; close contacts and MoU with MAJORANA established GERDA: Germanium Detector Array Array of HP-Germanium Diodes, made from isotopically enriched (86% in Ge-76) material Phase-1: Use existing diodes from Heidelberg-Moscow and IGEX (  15kg)0.01 / keV kg yr intrinsic background expectedGoal: verify concept; probe Klapdor-Kleingrothaus‘ evidence(if no event observed,  1 yr of measuring time needed to disprove at 98% cl) M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  5. Operate Ge diodes in ultraclean environment  cryogenic liquid shield (LN or LAr); graded shielding GERDA‘s Experimental Concept Assumption: External background is dominant • Minimize all impure materials close to Ge diodes • Reject remaining background (internal and external) by exploiting different interaction topology (single-site  multi-site; PSA) Goal: Background index of 0.001 cts / (keV kg y) at Qbb=2039 keV M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  6. GERDA 1400 m ~ 3.800 m.w.e GERDA Location: Gran Sasso National Laboratory (LNGS) Assigned Location for Phases 1 & 2: LNGS Hall A, next to the CRESST and LVD Experiments M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  7. Experimental Setup at LNGS M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  8. GERDA‘s Cleanroom Facility at LNGS: LArGe HD-Moscow‘s KI-detectors were handed over to GERDA M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  9. LArGe‘s Liquid Argon Test Stand M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  10. Detector Arrangement Modular Detector Arrangement : - Detector strings - Hexagonal string arrangement - Low mass, low background crystal holders and suspension - Additional strings can „easily“ be added when new detectors become available, with the vessel remaining cold M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  11. Detector Suspension for Phase-1 - Low mass (bgd index < 10-2 / keV kg y ) - Use only screened materials with known radioimpurities (Cu, PTFE, Si) - Specific ORTEC-type contact (bottom of bore hole) - Mount and test every crystal individually (LArGe Facility at LNGS) M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  12. Ge-76 Procurement for Phase-2 - Enrichment of 37.5 kg of Germanium ongoing(ECP, Krasnoyarsk, Russia) - Delivery procedure tested with natGe: very smooth,no problems encountered (20 day trip Krasnoyarsk  Munich, special shielding container: 10-20 attenuation factor for cosmogenic production of 68Ge and 60Co) - ongoing R&D:  maintaining original purity during enrichment  optimizing yield of chemical purification to 6N metal M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  13. 60Co: 2 photons (l=O(cm))  (multiple) Compton-scattering 2 electrons deposit energy locally (d = O(1 mm)) Phase-2: Segmented Detectors Interaction topology of bb-signal and g-background different  anticoincidence for bgd suppression „pointlike“, single-site vs. „extended“, multi-site M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  14. n-type prototypes:  Naked crystal: available & operated in LN  Naked crystal, 6fx3z segmented, true coax: on order  Naked crystal, true coax: available & operated in LN  Naked crystal, true coax, 6f x 1z segmented: available Detector Development for Phase-2 R&D on two types of detectors: p-type and n-type p-type prototypes:  Naked crystal, true coax, 6f x 3z segmented: on order M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  15. Detector Suspension for Phase-2 18-fold segemented detectors (true-coaxial, 3x6, n-type) Kapton cable bonded contacts Total of 30g mounting material / detector M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  16. Simulation Results on Segmented Detectors - Monte Carlo (MaGe: common Majorana-Gerda simulation framework) :Anticoincidence between segments (18-fold segmentation)  factor 10 increase in 60Co rejection - Further improvement (up to  factor 5): Analysis of pulse shapes and mirror charges (PSA) ( regain signal sitting on segment boundary) (  0.2 cm spatial resolution) - R&D ongoing: Monte Carlo studies and PSA development Laboratory measurements with prototype detectors M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  17. electrode electrode electrode Hit segment:full energy deposit Core signal: full energy deposit core Charge electrode electrode electrode Neighbouring segments:mirror charges Time Pulse Shape Simulation Full simulation of true coaxial 6-fold segmented detector (only 1 segment hit): M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  18. Full Simulation of a True-Coax 18-fold Segmented Detector Signals seen by the segment electrodes  Position Reconstruction (f and z) M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  19. Simulation Results on Segmented Detectors PSA Information on radius and angle: Correlation between ratio of amplitudes of neighbouring segments and angle f of interaction point Clear correlation between time of charge collection and radius of interaction point M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  20. Status & Time Schedule • 2004: • Feb Letter of Intent to LNGS (hep-ex/0404039) • Sep Formation of Collaboration • Oct Funding request approved by MPG; Proposal to LNGS(wwwgerda.mppmu.mpg.de) • 2005: • Feb GERDA approved by LNGS • Mar Technical proposal to LNGS; 30 kg of enriched Ge-76 for phase-2 ordered • May Funding requests approved by INFN • Jun Funding request approved by BMBF • Jul Ge-76 order enlarged to 37.5 kg; safety study for cryostat submitted to LNGS • Aug Expect decision by LNGS on system safety • Sep if OK: tendering for water tank, first orders for cryostat • 2006: • Jun Start of water tank installation at LNGS • ??? Installation of cryostat, clean room and lock, muon veto, ... • 2007: • spring Commissioning, then start of physics run M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  21. The GERDA Collaboration M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

  22. Summary and Conclusions Approved by LNGS with location in hall A substantially funded by BMBF,MPG, INFN and Russia (in kind) construction at LNGS start 6/06 in parallel: substantial R&D for and preparation of phase II start of data taking in 2007 phase-1: verify concept, probe KK-evidence for bb0nphase-2: T1/2 > 2 * 1026 yr  mneff < 0.09 – 0.29 eV phase-3: t.b.d., depending on results; ton-scale experiment in worldwide collaboration M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005

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