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TGV II Experiment

TGV II Experiment. Ivan Štekl. for TGV collaboration: JINR Dubna, Russia IEAP CTU Prague, Czech Republic CSNSM Orsay, France CU Bratislava, Slovakia NPI CAS, Czech Republic. TGV II Phase I results Phase II present status. TGV II. (2000 – ...)

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TGV II Experiment

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  1. TGV II Experiment Ivan Štekl • forTGV collaboration: • JINR Dubna, Russia • IEAP CTU Prague, Czech Republic • CSNSM Orsay, France • CU Bratislava, Slovakia • NPI CAS, Czech Republic TGV II Phase I results Phase II present status

  2. TGV II • (2000 – ...) • to investigate bb processes in 106Cd (to focus on 2nEC/EC channel) • observables: 2 characteristic X-rays from de-excitation of 106Pd shell 2nEC/EC:

  3. TGV II (predictions, measurements) T1/2 = 1.0·1020y(Suhonen) 8.7·1020y(Hirsch) 4.4·1021y(Simkovic) • Theoretical predictions: • Experimental results: (mostly to excited states of106Pd) T1/2>6.2·1018 y (Barabash, HPGe detector + Cd foil, Modane) T1/2>7.3·1019 y (Belli, NaI(Tl), geometrysimilar to TGV, Gran Sasso) T1/2(g.s → g.s.) >5.8·1017 y (Georgadze, measurement with116CdWO4 scintilators,Solotvina)

  4. TGV II Location: Modane Underground Laboratory (4800 m.w.e.) Copper > 20 cm Airtight box Lead >10cm Boron filled polyethylene 16cm Published in: P.Beneš et al.,Nucl. Instr. and Meth. in Phys. Research A 569 (2006) 737-742.

  5. TGV II (cryostat) HPGe Cd HPGe • 32 HPGe planar detectors ø60 mm x 6 mm (active area 2040mm2) • Total mass of samples: 10 - 15 g (maximum) • E-threshold: ≈ 10 keV • Samples: 12x106Cd foils (~10g in Phase 1)

  6. Phase I final result • acquisition with 10g of106Cd after 8491 hours: • data • linear background • Cd X-ray multiplet • excluded Pd X-ray • events

  7. Summary of results from Phase I

  8. 238keV area distribution along the cryostat: Phase II preparation

  9. Phase II preparation Step 3: endcap central part removal →positive weld

  10. Phase II preparation • test measurement with modified endcap – 1 month acquisition: Spectrum before and after endcap modification • whole cryostat: 5x 238keV area reduction: • four central detector pairs: 13x

  11. Conclusions, near-term plans • Main run (1 year duration) with enriched 106Cd completed in 2006 • Phase I terminated giving new estimation on T1/2 (2nEC/EC, g.s.→g.s.) of 106Cd T1/2 = 1.0 · 1020y(Suhonen) T1/2 > 3.0 · 1020y(TGV II) T1/2 = 8.7 · 1020y(Hirsch) T1/2 = 4.4 · 1021y(Simkovic) • Main source of background inside the cryostat localized and removed • Phase II is starting (December 2007): • more enriched material available (15g) • to continue for at least 3 years • factor 10 of improvement is reasonable

  12. Spectrum of single events Phase I and Phase II (after endcap modification) Phase I • Single events = 1 540 663 events • Single events = 741 508 events (renormalized to the same time and mass of Cd) Phase II

  13. Spectrum of coinc. events Phase I and Phase II (after endcap modification) Phase I Coinc. events = 294 338 events Coinc. events = 129 526 events (renormalized to the same time and mass of Cd) Phase II

  14. Future plans: • Continuation of the measurement with enriched 106Cd (2nEC/EC decay on the level 1021 yrs.) • 2. Conceptual design study (MC, theoretical calculations, background study) – • a) the possibility to measure 2nEC/EC decay with other isotopes (162Er, 156Dy) V.Ceron, J.Hirsch, arXiv:nucl-th/9911021v1 • b) the study of the posibility to measure 0nEC/EC decay (152Gd g.s., 112Snexc. state– resonance enhancement of the 0nEC/EC process if Q – Qr < 1 keV) • Z.Sujkowski, S.Wycech, Phys. Rev. C70, 052501, 2004 • J.Bernabeu, A. deRujula, C.Jarlskog, Nucl. Phys. B223, 15 (1983) • signature – X-rays < 100 keV + g or e-e+ or Majoron • advantage: good value of the rates between 0nEC/EC and 2nEC/EC processes • 3. Pixel detectors (Si or Ge) in EC/EC decay – thickness between 300 mm-1 mm (coincidence measurement, position of detection, energy of X-ray)

  15. Running R&D Instrumentation • Planar pixellated detector (Si, GaAs, CdTe, thickness: 300/700/1000mm, Ge ~500mm) • Bump-bonded to Medipix readout chip containing amplifier, double discriminator, and counter or ADC (TimePix) in each pixel cell Medipix2 and TimePix Pixels: 256 x 256 Pixel size: 55 x 55 mm2 Area: 1.5 x 1.5 cm2 Medipix2 Quad Pixels: 512 x 512 Pixel size: 55 x 55 mm2 Area: 3 x 3 cm2 How about to use a pixellated detector for EC/EC measurements? (coincidences, precise position of detection, X-ray energy, particle recognition)

  16. Alpha particle pattern

  17. Energy losses defined by Bragg curve Track of electron

  18. Track of muon

  19. to investigate EC/EC processes in 106Cd (to focus on g.s. to g.s. channel) using Timepix detectors in coincidence mode • observables: 2 characteristic X-rays from de-excitation of 106Pd shell Advantages: • better efficiency comparing with TGV II (factor 2) • information about energy + position of registrated X-ray • track recognition (background vs. signal) • much less material needed (lower background) • measurement under room temperature (easy access) P+ N+ P+ N+ Si Si Cd foil Control unit

  20. Phase II of the TGV experiment Measurement with TGV II detector: • start in Modane December 2007 • planned for 3-4 years • more enriched material (15 gr.) • suppression of background. R&D with Timepix detector: • measurement of background in IEAP CTU lab with 1 Timepix detector • measurement of background in Modane underground lab with 1 Timepix detector • development of coincidence mode with 2 Timepix detectors • measurement of background in Modane underground lab using coincidence mode

  21. Thanks a lot for your attention

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