1. GERDA: the Germanium Detector Array at LNGS IDEA meeting, April 14/15, Orsay Stefan Schoenert, MPIK Heidelberg

2. INFN LNGS, Assergi, Italy A.Di Vacri, M. Junker, M. Laubenstein, C. Tomei, L. Pandola JINR Dubna, Russia S. Belogurov,V. Brudanin, V. Egorov, K. Gusev, S. Katulina, A. Klimenko, O. Kochetov, I. Nemchenok, V. Sandukovsky, A. Smolnikov, J. Yurkowski, S. Vasiliev, MPIK, Heidelberg, Germany C. Bauer, O. Chkvorets, W. Hampel, G. Heusser, W. Hofmann, J. Kiko, K.T. Knöpfle, P. Peiffer, S. Schönert, J. Schreiner, B. Schwingenheuer, H. Simgen, G. Zuzel Univ. Köln, Germany J. Eberth, D. Weisshaar Jagiellonian University, Krakow, Poland M.Wojcik Univ. di Milano Bicocca e INFN, Milano, Italy E. Bellotti, C. Cattadori INR, Moscow, Russia I. Barabanov, L. Bezrukov, A. Gangapshev, V. Gurentsov, V. Kusminov, E. Yanovich ITEP Physics, Moscow, Russia V.P. Bolotsky, E. Demidova, I.V. Kirpichnikov, A.A. Vasenko, V.N. Kornoukhov Kurchatov Institute, Moscow, Russia A.M. Bakalyarov, S.T. Belyaev, M.V. Chirchenko, G.Y. Grigoriev, L.V. Inzhechik, V.I. Lebedev, A.V. Tikhomirov, S.V. Zhukov MPP, München, Germany I. Abt, M. Altmann, C. Büttner. A. Caldwell, R. Kotthaus, X. Liu, H.-G. Moser, R.H. Richter Univ. di Padova e INFN, Padova, Italy A. Bettini, E. Farnea, C. Rossi Alvarez, C.A. Ur Univ. Tübingen, Germany M. Bauer, H. Clement, J. Jochum, S. Scholl, K. Rottler GERDA Collaboration 71 physicists / 12 institutions / 4 countries

3. GERDA @ Gran Sasso: experimental concept HP Ge-diodes ( 76 Ge): point-like energy deposition at Q  = 2039 keV Operation of bare Ge diodes in high-purity LN 2 / LAr shield (Heusser, Ann, Rev. Nucl. Part. Sci. 45 (1995) 543); proposals based on this idea: GENIUS (H.V. Klapdor- Kleingrothaus et. al., hep-ph/9910205 (1999)); GEM (Y.G. Zdesenko et al., J. Phys. G27 (2001)) Baseline: LN 2 ; possible upgrade LAr:  =1.4 g/cm 3, active anti- coincidence with scintillation light from LAr Reduction of backgrounds key to sensitivity : –Half-life limit w/o backgrounds: t 1/2  (MT) with backgrounds: t 1/2  (MT) 1/2  Goal: background free!

4. Why Ge-76 ? High resolution (4 keV @ Q  ): no bgd from 2 - mode Huge leap in sensitivity possible … …applying ultra-low background techniques …novel background / 0 -  signal discrimination methods (ie. point-like vs. compton events) Segmentation & pulse shape (with true coaxial detectors) Liquid argon scintillation read out Phased approach: increment of target mass Probably only method to scrutinize 0 -DBD claim on short time scale: test T 1/2, not m ee !

5. GERDA: Baseline design Clean room lock Vacuum insulated copper vessel Water tank / buffer/ muon veto Liquid N/Ar Ge Array

6. Phases and physics reach of GERDA  M·T  (M·T) 1/2 10 -3 / (keV·kg·y) 10 -1 / (keV·kg·y) Phase-I HdM & IGEX 3·10 25 Phase-II +new diodes 2·10 26 KK 20072010

7. Phases and Physics reach of GERDA world-wide collaboration needed for Phase-III; coop. with MAJORANA started Phase-II Phase-III Phase-I 10 -1 /(keV·kg·y) 10 -2 /(keV·kg·y) 10 -3 /(keV·kg·y)

8. Phases and Physics reach of GERDA | m ee | in eV Lightest neutrino (m 1 ) in eV F.Feruglio, A. Strumia, F. Vissani, NPB 659 Phase I: Phase II: Phase III:

9. Backgrounds in GERDA SourceB [10 -3 cts/(keV kg y)] Ext.  from 208 Tl ( 232 Th) <1 Ext. neutrons<0.05 Ext. muons<0.1 Int. 68 Ge (t 1/2 = 270 d)12 Int. 60 Co (t 1/2 = 5.27 y)2.5 222 Rn in LN/LAr<0.2 208 Tl, 238 U in holder<1 Surface contam.<0.6 180 days exposure after enrichment + 180 days underground storage 30 days exposure after crystal growing Assumptions: Target for phase II: B  10 -3 cts/(keV kg y)  additional bgd. reduction techniques derived from measurements and MC simulations

10. Background signature: example Co-60 Multi-site energy deposition inside HP-Ge diode    Co-60 Energy deposition in surrounding medium Ideal detector: 1)Measure energy in surrounding shielding material  LAr calorimeter 2)Measure locations of energy deposition inside the crystal  Segmentation

11. Background reduction techniques Anti-coincidence between detectors Segmentation of readout electrodes (Phase II) Pulse shape analysis (Phase I+II) Waiting (Ge-68, …) Coincidence in decay chain Scintillation light detection (LArGe)

12. Background reduction techniques Anti-coincidence between detectors Segmentation of readout electrodes (Phase II) Pulse shape analysis (Phase I+II) Waiting (Ge-68, …) Coincidence in decay chain Scintillation light detection (LArGe)

13.  2 : 1.332 MeV  : E max = 318 keV  1 : 1.173 MeV T 0 : crystal growing 0.017  Bq/kg per day exposure Test: detector production in 7.4 days Assume 30 days  2.5 ·10 -3 / (keV·kg·y) HdM: ~5·10 -3 / (keV·kg·y) in 2006 T 0 : crystal growing 0.017  Bq/kg per day exposure Test: detector production in 7.4 days Assume 30 days  2.5 ·10 -3 / (keV·kg·y) HdM: ~5·10 -3 / (keV·kg·y) in 2006 Example 60 Co

14. 2 kg 60 Co background spectrum 11 22  1 +  2 Q   MC simulation

15. 2 kg 60 Co: suppression by segmentation Q  MC simulation

16. 2 kg 60 Co: suppression by segmentation ~10 N seg = 1 Q  MC simulation N seg = 3

17. 60 Co: suppression by LAr Ge-anticoinc. ~100 LAr anticoinc. Liquid Argon Q  MC simulation 2 kg

18. 60 Co: segmentation and LAr Ge-anticoinc. ~1000 Liquid Argon N seg = 1 AND LAr anticoinc Q  2 kg MC simulation

19. Experiment: LAr Ge-anticoincidence 54 Mn  -source Liquid Argon  20 cm 0.18 kg

20. Experiment: LAr Ge-anticoincidence Liquid Argon  20 cm Experimental Data ~5 0.18 kg

21. LAr Ge-anticoincidence Liquid Argon  20 cm MC Simulation Suppression factor limited by escape events! ~5

22. LAr Ge-anticoincidence Liquid Argon  100 cm MC Simulation ~60 Suppression factor limited by dead layer 0.18 kg

23. Status of GERDA March 2004: LoI to LNGS Sep. 2004: Proposal to LNGS Sep. 2004: 70% of funding secured Feb. 05: Approval by LNGS Feb. 05: Ge-76 enrichment for Phase II started at ECP Feb. 05: Underground locations frozen (in front of LVD, TIR tunnel Sec. A-B & adjacent to LUNA II) March 05: LArGe facility (i.e. detector laboratory Phase I) under construction March 05: Technical proposal (Vers. 0.1) Autumn 06 (Goal): Detector filling and commissioning

24. Locations of GERDA

25. Infrastructures in HALL A: Super-Structure & Water tank

26. Infrastructures in Hall A: floor plan NB: Sufficient access space for dismounting of LVD

27. Infrastructures in Hall A: Super-insulated cryogenic vessel Cu-cryostat: hanging from neck Cu-cryostat: resting on pads Steel-cryostat: with optimized shielding Two design studies for Cu-cryostat available: Cu-cryostat purchase process commenced with publication in ’Supplememnt of the Official Journal of the European Union’ a ’Prior Information Notice’ - SIMAP-MPI-K 31 Jan’05 ID:2005-002331; 7 companies expressed interest Decision taking Cu vs. steel cryostat: Cu-Steel welding tests and certification

28. Infrastructures in HALL A: Penthouse

29. LArGe Facility Barrack modification close to completion Re-machined shielding system of LArGe underground Underground detector laboratory

30. Testing and modification of enriched detectors November, 2004, in LENS barrack (prior to barrack refurbishment) ANG1ANG2ANG3ANG4ANG5 HdMo Setup 3.03.43.03.53.4 GERDA Lab, Jan.05 3.92.73.02.83.1 NotesWarm Up PA gain ‘jumps ’ Co-60 source - absolute efficiency (done) Ba-133 source - dead layer thickness estimation (done) Check of ANG2 (ongoing) Energy resolution at 2.615 MeV

31. Modification of enriched detectors Design study for a Cu/Si/PTFE-only detector support/contact system Alternative: Silicon support Minimizing mass vs. strength (current design: factor 5 safety)

32. New detectors for Phase II: Procurement of enriched Ge Ge procurement is done in two steps: 1)procurement of 15 kg of natural Ge (‘test run’) 2)subsequently procurement of 30-35 kg of 76Ge (‘real run’) Both samples produced in Siberia / Russian Federation 15 kg ‘test run’ (6N) Ge shipped in same way as enriched sample. Specially designed protective steel container (PSC) which reduces activation by cosmic rays by factor 20 is used for transportation Procurement of natural Ge successfully concluded; sample received at MPI Munich on March 7, 2005

33. New detectors for Phase II Production of 30-35 kg sample of enriched Ge- 76 started in Siberia in February, 2005; Production time: 6 months Increase of purity of enriched Ge-76 to 99.99 % (99.8% originally quoted) R&D on chemical purification technique: yield ≥85%, to be compared to the 70% of the standard procedure Segmented prototype detectors (p-type) ordered and are currently being produced

34. Updated schedule (preliminary)

36. Summary/Outlook GERDA collaboration operational; plans to further grow (Phase II and beyond) Major progress achieved over last 6 months Co-operation with Majorana (MaGe, LArGe) very positive: mutual benefit! Schedule: items on critical path: –Funding for water tank and muon veto (water Cherenkov) –Integration of cryo-vessel, water tank, super-structure, laboratory building and penthouse GERDA well on its way