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Results of Phase I of the TGV II Experiment. Pavel Cermak. History (TGV I) TGV II Data processing Phase I results Phase II preparation. Histor y (TGV I). (1994 – 2000) designed to study double beta decay of 48 Ca te lescope composed of 16 HPGe planar det ectors - PowerPoint PPT Presentation
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Results of Phase I of the TGV II Experiment
• History (TGV I)History (TGV I)• TGV IITGV II• Data processingData processing• Phase I resultsPhase I results• Phase II preparationPhase II preparation
Pavel Cermak
Pavel Cermak 2June 13, 2006
History (TGV I)
yT 193.33.1
22/1 10)2.4(
)%90(105.1 2102/1 CLyT
afterafter 8700 ho 8700 hoursurs::
sshieldinghielding: 20cm : 20cm of of eleelecctrolytictrolytic copper copper, , airtightairtight box, BPE box, BPE
open cryostat
cryostat, PAs
(1994 – 2000)(1994 – 2000) designed to study double beta decay ofdesigned to study double beta decay of 48Ca tetelescope composed oflescope composed of 16 HPGe 16 HPGe planar planar detdetectorsectors samples: foils of enriched samples: foils of enriched 48Ca (80%),,
total mass 1.08gtotal mass 1.08g
Pavel Cermak 3June 13, 2006
History (TGV I)History (TGV I) TGV IITGV II Data processingData processing Phase I resultsPhase I results Phase II preparationPhase II preparation
Pavel Cermak 4June 13, 2006
TGV II
),(22 10646
10648 raysXPdCde e
(2000 – ...)(2000 – ...) to investigate to investigate processes in processes in 106106Cd (to Cd (to
focus on 2focus on 2EC/EC channel)EC/EC channel)
observables: observables: 2 characteristic X-rays 2 characteristic X-rays from de-excitation of from de-excitation of 106106PdPd shell shell
keVEkeVkeV XECEC 2319:ROI,2778Q /
2EC/EC:
Pavel Cermak 5June 13, 2006
TGV II (predictions, measurements)
T1/2 = 1.0·1020 y (Suhonen)
8.7·1020 y (Hirsch)
4.4·1021 y (Simkovic)
Theoretical predictions:
Experimental results: (mostly to excited states of 106Pd)
T1/2 (g.s → g.s. ) > 5.8·1017 y
T1/2 > 6.2·1018 y (Barabash, HPGe detector + Cd foil,
Modane)T1/2 > 7.3·1019 y (Belli, NaI(Tl), geometry similar to TGV, Gran Sasso)
(Georgadze, measurement with 116CdWO4 scintilators, Solotvina)
Pavel Cermak 6June 13, 2006
TGV IILocation: Modane Underground Laboratory (4800 m.w.e.)
SM
Signal w ires
PA
Cold finger
Pb
Cu
LN Dewar
LN2
N2
Borated Polyethylene
1 m
TG V -2
Copper> 20 cm
Airtight box
Lead >10cm
Boron filled polyethylene
16cm
Pavel Cermak 7June 13, 2006
TGV II (cryostat)
32 HPGe planar detectors ø60 mm x 6 mm (active area 2040mm2)
Total mass of samples: 10 - 25 g E-threshold: ≈ 10 keV Samples: 12x 106Cd foils (~10g)
HPGe
HPGe
Cd
Pavel Cermak 8June 13, 2006
History (TGV I)History (TGV I) TGV IITGV II Data processingData processing Phase I resultsPhase I results Phase II preparationPhase II preparation
Pavel Cermak 9June 13, 2006
Background suppression (1)
besides the passive shielding, additional techniques for background suppression are used:
• No selection (1540663 ev.)• Odd-even coinc. (287778 ev.)• E-window 19-22 keV (4740 ev.)
Data after 8491 hours:
Pavel Cermak 10June 13, 2006
microphonic effect suppression
Matrix + effect of microphonic noise cut
Backgroundsuppression (2)
double shaping technique → scatter plot called ‘matrix’
graphical cut application
Pavel Cermak 11June 13, 2006
History (TGV I)History (TGV I) TGV IITGV II Data processingData processing Phase I resultsPhase I results Phase II preparationPhase II preparation
Pavel Cermak 12June 13, 2006
Phase I result acquisition with 10g
of 106Cd after 8491 hours:
• data• linear background• Cd X-ray multiplet• excluded Pd X-ray events
%)90(100.2)( 20106/22/1 yCdT ECEC
Pavel Cermak 13June 13, 2006
History (TGV I)History (TGV I) TGV IITGV II Data processingData processing Phase I resultsPhase I results Phase II preparationPhase II preparation
Pavel Cermak 14June 13, 2006
Phase II preparation (1)238keV area distributionalong the cryostat:
Pavel Cermak 15June 13, 2006
Phase II preparation (2)
Step 1: internal shielding bricks swapped
→ negative
Background source localization and elimination:
Step 2: detectors with holders swapped
→ negative
Pavel Cermak 16June 13, 2006
weld
Phase II preparation (3)Step 3: endcap central part removal
→ positive
Pavel Cermak 17June 13, 2006
Phase II preparation (4)
test measurement with modified endcap – 1 month acquisition:
Spectrum before and after endcap modification
238keV area reduction:
whole cryostat: 5x
four central detector pairs: 13x
Pavel Cermak 18June 13, 2006
T1/2 = 4.4 · 1021 y (Simkovic)
Conclusions, near-term plans
T1/2 = 8.7 · 1020 y (Hirsch)
more enriched material available (15g)
to continue for at least 3 years
factor 10 of improvement is reasonable
Main source of background inside the cryostat localized and removedMain source of background inside the cryostat localized and removed
Phase II is starting:Phase II is starting:
T1/2 = 1.0 · 1020 y (Suhonen)
T1/2 > 2.0 · 1020 y (TGV II)
Main run (1 year duration) with enriched Main run (1 year duration) with enriched 106106CdCd completed in 2006 completed in 2006
Phase I terminated giving new estimation on Phase I terminated giving new estimation on TT1/21/2 (2 (2EC/EC, g.s.EC/EC, g.s.→g.s.→g.s.) ) of of 106106CdCd
Pavel Cermak 19June 13, 2006
1. PhysicsConceptual design study (MC, theoretical calculations, background study) – a) the possibility to measure 2EC/EC decay with other isotopes (162Er, 156Dy) V.Ceron, J.Hirsch, arXiv:nucl-th/9911021v1b) the study of the posibility to measure 0EC/EC decay (152Gd g.s., 112Sn exc. state– resonance enhancement of the 0EC/EC process if Q – Qr < 1 keV)J.Bernabeu, A. deRujula, C.Jarlskog, Nucl. Phys. B223, 15 (1983)Z.Sujkowski, S.Wycech, Phys. Rev. C70, 052501, 2004signature – X-rays < 100 keV + or e-e+ or Majoron advantage: good value of the rates between 0EC/EC and 2EC/EC processes
Future plans (1)
Pavel Cermak 20June 13, 2006
2. Instrumentation
Future plans (2)
How about to use a pixellated detector for EC/EC measurements?(coincidences, position, X-ray energy)
• Planar pixellated detector (Si, GaAs, CdTe, thickness: 300/700/1000m, Ge ~500m)
• Bump-bonded to Medipix readout chip containing amplifier, double discriminator, and counter in each pixel cell
Medipix2 andTimePixPixels: 256 x 256Pixel size: 55 x 55 m2
Area: 1.5 x 1.5 cm2
Medipix2 QuadPixels: 512 x 512Pixel size: 55 x 55 m2
Area: 3 x 3 cm2