Measurement of EC/EC process of 106Cd in the experiment TGV II Short review of TGV IDouble electron capture present results of theory and experiments Experimental setup TGV II Methods of background suppresion Preliminary results of measurement with enriched 106CdI.tekl, P.ermk, P.BeneInstitute of Experimental and Applied Physics, CTU in PragueV.B.Brudanin, V.G.Egorov, N.I.Rukhadze, A.Kovalk, Ts.Vylov et al.Joint Institute of Nuclear Research, DubnaCh.BrianconCSNSM Orsay F.imkovicComenius University, BratislavaIDEA meeting, Zaragoza, 7.-8.11.2005

TGV I : 48Ca: ~ 1.35 x 1022 atoms (1.08 g)open cryostatassembled cryostat, PAs

TGV Icryostat surrounded by Cu shielding

TGV I results (48Ca)Published in Nuclear Physics A700(1-2) (2002) 17-24

TGV IIto improve 48Ca result obtained by TGV Ito investigate processes in 106Cd (to focus on 2nEC/EC channel)purpose:2nEC/EC:106Cd:2nbb:48Ca:

Theorethical results for EC/EC mode:

0+ g.s. - T1/2 : 1.5 x 1022 y; 4.4 x 1021 y; 8.7 x 1020 y; 1 x 1020 y; 9 x 1019 y 0+ 1 - T1/2 : 1.1 x 1024 y; 1.0 x 1023 y; 3.4 x 1021 y; (2.2-3.9 x 1021 y)

Experimental results for EC/EC mode:

0+ g.s. T1/2 : > 5.8 x 1017 y; > 1.5 x 1017 y0+ 1 T1/2 : > 6.2 x 1018 y; > 7.3 x 1019 y

Double Beta Spectrometers

General view of TGV II setup

Copper> 20 cmAirtight boxLead> 10 cmPolyethylenefilled withboron 16 cm

Detector part of the TGV II 32 HPGe planar detectors 60 mm x 6 mm with sensitive volume: 20.4 cm2 x 6 mm Total sensitive volume: 400 cm3 Total mass of detectors: 3 kg Total area of samples : 330 cm2 Total mass of sample(s) : 10 25 g Total efficiency : 50 60 % E-resolution : 3 4 keV @ 60Co LE-threshold : 4050 keV (5 6 keV) Double beta emitters - 16 samples of 48Ca (10 g) : 24 g CaF2 + CH2 ( 75 mg / cm2 ) - 12 samples of 106Cd: 10 10 g 106Cd (~ 50 m )

U+Th

TGV IIpedestalopen cryostat

TGV IIassembled cryostat, PAs

Background suppression Passive shielding Construction of the detector TGV II ElectronicsPassive shieldingsModane Underground LaboratoryPb + Cu, airtight box against radon (antiradon system, 15Bq/m3 ~ mBq/m3 , October 04), anti-neutron shielding (made of borated polyethylene)

Background suppression Constructionradiopure materialsminimization of amount of construction materialsElectronicstelescopic construction (double coincidences from neighboring detectors)time information about events (date, time between coinc. events)pulse rise time analysisdouble-shaping selection of low energy events

Data processing 1) Ca setupinterest in a region (2.7 - 4.2) MeVutilization of a technique for a distinguishing between electrons and -rays based on pulse shape analysis

Pulse shape analysis (48Ca)CurrentTime, nsQ2Q1ge10200strobeQ (integrated charge)geAmplitude (energy) 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

Pulse shape analysis (example)E-Q spectrum, sources: 207Bi + 60CoQEelectronsgammasCompton edge

2) Cd setupinterest in low energy region (19 23) keVadditional source of background are microphonic and electronic noise filtering is done using two different shaping times during the processing of the signalData processing

Suppression of microphonic noise12s4sLow frequency(microphonic)

Microphonic noise suppression (example)no selectionstart: March 2002, stop: July 2002; result presented:May-July 2002, duration 1596 hours coincidence + energy window (19-25) keV coincidence with neighboring detectors microphonic noise cut

Summary of finished activities and present status:two different setups (for 106Cd and 48Ca) were tunned detector TGV II is placed in Modane underground laboratorystandard passive methods to suppress the backgroundsuppression of microphonic backgroundpulse-rise time analysis measurements of background were finishedTGV spectrometer is running in Cd setup with enriched 106Cd !!!!Programme of background measurements:without any foilswith foils made of natural Cd (16 foils, Nov. 2004 Jan. 2005, 14.5 gr.)Programme of EC/EC measurements:Three portions of enriched 106Cd two of them included 113mCdLast one is pure 12 foils, total mass = 9.948 gr., enrichment = 80%(inside of TGV II 12 foils of enriched 106Cd, 4 foils of natural Cd, beginning of measurement Febr. 2005)

Sources of natural Cd in the TGV II spectrometer (16 foils; 14.5 gr.; 743+161 hours = 903 hours)Background measurement

Natural Cd (4 foils of natural Cd)+ all kinds of backgr.suppr. 3736 hours (February 2005 - July 2005) Background measurement

Enriched Cd (12 foils), all kinds of backg. suppr. 3736 hours (February 2005- July 2005)Measurement of EC/EC decay

KX(Pd) and KX(Cd) in 106Cd

106Cd, 10 g, 3000 hPdCd

Enriched Cd (12 foils), all kinds of backg.suppr. 3736 hours (February 2005 - July 2005) 19 keV - 22 keV

total weight of natural Cd foils = 3.151 gramms(events for natural Cd were recalculated for the weight of enriched Cd) 2nEC/EC (g.s. -> g.s.) signal on the level 2.5 s

Natural Cd(3.151 g, 3736 h)Enriched Cd(9.948 g, 3736 h)Signal region (19-22 keV)Backg. region (16-19 keV)+(28-31 keV)35 events35 events58 events39 events

Results2EC/EC (0+0+,g.s.) T1/2 5.6 x 1019 y (90%CL)2+EC (0+0+,g.s.) T1/2 4.1 x 1019 y (90%CL)2+EC/512 T1/2 5.8 x 1019 y (90%CL)2EC/EC/512 T1/2 2.1 x 1019 y (90%CL)2+ 5120+ 11382EC/EC/1138 T1/2 5.3 x 1019 y (90%CL)

Summary:

TGV II is nice equipment for measurement of special bb modes

it could be first direct measurement of 2nEC/EC mode (big shift of half-life)

we will continue with 106Cd as minimum one year

TGV II as part of EU project (to construct the second detector; longer time of measurement; to add special isotopes such as 106Cd into bank of EU isotopes production with 116Cd)

Puvodne vychazi 177 ev./year ale kvuli verohodnosti je umele aplikovan faktor potlaceni 4x-5x => cca 45 ev.Zadni=rear, spodni=lowerbased on difference between interaction of e- and g-rays with detector crystal. Gamma interacts with the same mean probability with the whole volume of detector - but electron, on the other hand, is usually absorbed within a thin layer (after entering the detector). So we get: different point of interaction (for e and gammas) => different charge collection time => different pulse shape (especially the front of the pulse) => various integrated charge => E-Q spectrum