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For TGV collaboration: JINR Dubna, Russia IEAP CTU Prague, Czech Republic CSNSM Orsay, France

For TGV collaboration: JINR Dubna, Russia IEAP CTU Prague, Czech Republic CSNSM Orsay, France RRC - Kurchatov Institute Moscow, Russia CU Bratislava, Slovakia. Experiment TGV II Multi-detector HPGe telescopic spectrometer for the study of double beta processes of 106 Cd and 48 Ca.

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For TGV collaboration: JINR Dubna, Russia IEAP CTU Prague, Czech Republic CSNSM Orsay, France

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  1. For TGV collaboration: JINR Dubna, Russia IEAP CTU Prague, Czech Republic CSNSM Orsay, France RRC - Kurchatov Institute Moscow, Russia CU Bratislava, Slovakia Experiment TGV IIMulti-detector HPGe telescopic spectrometer for the study of double beta processes of 106Cd and 48Ca P. Čermák Czech Technical University, Prague P. Cermak, Rez near Prague, December 2004

  2. The Aim: To study rare processes - double beta processes of 106Cd and 48Ca (double-beta decay, double electron capture) • TGV I TGV II • Description of TGV II • Background suppression • Data processing, results of background measurements • Conclusion, near future Outline P. Cermak, Rez near Prague, December 2004

  3. TGV • Telescope Germanium Vertical (stack of 32 HPGe • detectors in common cryostat) • aims at the study of double beta processes of 106Cd and 48Ca • (double-beta decay, double electron capture) • started in 2000 • located in Modane Underground Laboratory (France) P. Cermak, Rez near Prague, December 2004

  4. Location • Modane Underground Laboratory • at the French-Italian border • under 1800 m of rock • 4800 m.w.e. P. Cermak, Rez near Prague, December 2004

  5. TGV I 16 HPGe detectors of planar type, diameter 40mm, thickness 6mm Energy resolution (2.6 – 3.3)keV @ 60Co P. Cermak, Rez near Prague, December 2004

  6. TGV I open cryostat assembled cryostat, PAs P. Cermak, Rez near Prague, December 2004

  7. TGV I cryostat surrounded by Cu shielding P. Cermak, Rez near Prague, December 2004

  8. Sources in TGV I spectrometer • 8 foils (48Ca) • 8 foils (Ca natural) 48Ca foil: 80% CaCO3 (enriched 77.8%) + 20% polyvinyl formal • Dimensions: (32.5 x 32.5)mm each • Thickness: 41 mg/cm2 (48Ca) 45 mg/cm2 (Ca natural) • 48Ca: ~ 1.35 x 1022 atoms (1.08 g) P. Cermak, Rez near Prague, December 2004

  9. TGV I results (48Ca) P. Cermak, Rez near Prague, December 2004

  10. purpose: TGV II • to improve 48Ca result obtained by TGV I • to investigate  processes in 106Cd (to focus on EC/EC channel) 106Cd: 2nEC/EC: 48Ca: 2nbb: P. Cermak, Rez near Prague, December 2004

  11. Stack of 32 HPGe planar detectors: Basic parameters diameter 60mm thickness 6mm sensitive area (each detector) ~ 20cm2 total area of samples ~ 330cm2 total mass of samples ~ 10g energy resolution (FWHM) ~ 3keV @ 60Co low energy threshold down to 5keV P. Cermak, Rez near Prague, December 2004

  12. TGV II spectrometer borated polyethylene SM PA Dewar 1m cryostat Pb Cu P. Cermak, Rez near Prague, December 2004

  13. TGV II pedestal open cryostat P. Cermak, Rez near Prague, December 2004

  14. TGV II assembled cryostat, PAs P. Cermak, Rez near Prague, December 2004

  15. Background suppression (1) • Passive shielding • Construction • Electronics • Passive shieldings • Modane Underground Laboratory • Pb + Cu, airtight box against radon (antiradon system, 15Bq/m3 → ~ mBq/m3 , October 04), anti-neutron shielding (made of borated polyethylene) P. Cermak, Rez near Prague, December 2004

  16. Background suppression (2) • Construction • radiopure materials • minimization of amount of construction materials • Electronics • telescopic construction (double coincidences from neighboring detectors) • time information about events (date, time between coinc. events) • pulse rise time analysis • double-shaping selection of low energy events P. Cermak, Rez near Prague, December 2004

  17. Data processing (1) • DAQ program – RT Linux remotely operated and controlled • data are recorded event-by-event, processed offline 1) Ca setup • interest in a region (2.7 - 4.2) MeV • utilization of a technique for a distinguishing between electrons and -rays based on pulse shape analysis P. Cermak, Rez near Prague, December 2004

  18. Pulse shape analysis (principle) Current • based on difference • between interaction • of e- and g-rays with • detector crystal • point of interaction - charge • collection time - pulse shape • - integrated charge => E-Q • spectrum • ability to suppress g-rays • by factor 2-3 Q1 g Q2 e 0 10 Time, ns 20 strobe Q (integrated charge) g e Amplitude (energy) P. Cermak, Rez near Prague, December 2004

  19. Pulse shape analysis (example) Q Compton edge gammas electrons E E-Q spectrum, sources: 207Bi + 60Co P. Cermak, Rez near Prague, December 2004

  20. Data processing (2) 2) Cd setup • interest in low energy region (18.5 – 23.5) keV • additional source of background are microphonic and electronic noise – filtering is done using two different shaping times during the processing of the signal P. Cermak, Rez near Prague, December 2004

  21. ROI Microphonic noise suppression (principle) • events in low energy • region – up to 100keV • utilization of two • amplifiers with different • shaping time • selection by means of • a 'matrix' – Eshort vs. • Elong P. Cermak, Rez near Prague, December 2004

  22. Matrices example

  23. TGV II electronics (Cd setup) • Double – shaping method • Multiplexed channels • MT – Master Trigger block (input register, gate generator, veto generator) • N2 filling flag

  24. Microphonic noise suppression (example) start: March 2002, stop: July 2002; result presented: May-July 2002, duration 1596 hours • no selection • microphonic noise cut • coincidence with neighboring detectors • coincidence + energy window (19-25) keV P. Cermak, Rez near Prague, December 2004

  25. Runs overview (year 2004) • Cd background (December 03 – February 04) • 1363 hours, 14312946 events • no foils

  26. 1768 hours, 16531047 events • 13x 106Cd foil, • 3x Cd-nat. foil • Enriched Cd, type I (March 04 – May 04)

  27. Enriched Cd, type II (May 04 – June 04) • 328 hours, 3515849 events • 12x 106Cd foil, 4x Cd-nat. foil • Enriched Cd, type II (June 04 – October 04) • 2033 hours, 158382662 events • 12x 106Cd foil, 4x Cd-nat. foil • Enriched Cd, type II (November 04 – now) • 16x Cd-nat. foil

  28. Conclusion, near future (1) • both setups were assembled and tested • basic runs needed for background determination (both for 48Ca and 106Cd setup) were performed • background for 48Ca (preliminary – 1 month run): • 45 ev./year in (2.7-4.2)MeV region • expected effect: 35 ev./year P. Cermak, Rez near Prague, December 2004

  29. Conclusion, near future (1) • background for 106Cd (preliminary – 3 months run): • - 44 ev./year in (19-25)keV region • - expected effect: 42 ev./year (T1/2 ~ 1020 y, g.s. → g.s., enriched Cd) • natural Cd • estimation ofT1/2 ~ 1018 y, g.s. → g.s. • estimation ofT1/2 ~ 1019 y, g.s. → 2+1 P. Cermak, Rez near Prague, December 2004

  30. Conclusion, near future (2) • present situation: TGV II is running in Cd setup with Cd-nat. • next steps (2005 – 2006): • enriched Cd purification • Cd-nat. data final procession • measurement with 48Ca P. Cermak, Rez near Prague, December 2004

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