1. 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 Concept Exp. Setup R&D Detectors Schedule, etc. Summary

2. M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005 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  = anti- ?  Neutrinoless Double Beta Decay

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

4. M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005 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 expected Goal: verify concept; probe Klapdor-Kleingrothaus‘ evidence (if no event observed,  1 yr of measuring time needed to disprove at 98% cl) Phase-2: Increase mass by adding  20 kg of new enriched Ge-detectors Goal: 100 kg yr statistics at background level B 2 * 10 26 yr  m eff < 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

5. M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005 GERDA‘s Experimental Concept Assumption: External background is dominant Minimize all impure materials close to Ge diodes Operate Ge diodes in ultraclean environment  cryogenic liquid shield (LN or LAr); graded shielding 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 Q  =2039 keV

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

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

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

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

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

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

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

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

14. M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005 Detector Development for Phase-2 R&D on two types of detectors: p-type and n-type n-type prototypes:  Naked crystal: available & operated in LN  Naked crystal, 6  x3z segmented, true coax: on order p-type prototypes:  Naked crystal, true coax: available & operated in LN  Naked crystal, true coax, 6  x 1z segmented: available  Naked crystal, true coax, 6  x 3z segmented: on order

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

16. M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005 Simulation Results on Segmented Detectors - Monte Carlo (MaGe: common Majorana-Gerda simulation framework) : Anticoincidence between segments (18-fold segmentation)   factor 10 increase in 60 Co 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

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

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

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

20. M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005 Status & Time Schedule 2004: FebLetter of Intent to LNGS (hep-ex/0404039) SepFormation of Collaboration OctFunding request approved by MPG; Proposal to LNGS (wwwgerda.mppmu.mpg.de) 2005: FebGERDA approved by LNGS MarTechnical proposal to LNGS; 30 kg of enriched Ge-76 for phase-2 ordered MayFunding requests approved by INFN JunFunding request approved by BMBF JulGe-76 order enlarged to 37.5 kg; safety study for cryostat submitted to LNGS AugExpect decision by LNGS on system safety Sepif OK: tendering for water tank, first orders for cryostat 2006: JunStart of water tank installation at LNGS ???Installation of cryostat, clean room and lock, muon veto,... 2007: springCommissioning, then start of physics run

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

22. M.Altmann, GERDA Status Report SNOLAB Workshop IV, 15.-17.8.2005 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  0  phase-2: T 1/2 > 2 * 10 26 yr  m eff < 0.09 – 0.29 eV phase-3: t.b.d., depending on results; ton-scale experiment in worldwide collaboration