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![Page 1: Experiment TGV II Multi-detector HPGe telescopic spectrometer for the study of double beta processes of 106 Cd and 48 Ca For TGV collaboration: JINR Dubna,](https://reader035.fdocuments.us/reader035/viewer/2022062322/5697bfad1a28abf838c9c42a/html5/thumbnails/1.jpg)
Experiment TGV IIMulti-detector HPGe telescopic spectrometer
for the study of double beta processes of 106Cd and 48Ca
For TGV collaboration:
JINR Dubna, RussiaIEAP CTU Prague, Czech Republic
CSNSM Orsay, FranceRRC - Kurchatov Institute Moscow, Russia
CU Bratislava, Slovakia
P. Cermak, Rez near Prague, December 2004
P. ČermákCzech Technical University, Prague
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Outline● TGV I TGV II● Description of TGV II● Background suppression● Data processing, results of
background measurements● Conclusion, near future
The Aim:
To study rare processes - double beta processes of 106Cd and 48Ca (double-beta decay, double electron capture)
P. Cermak, Rez near Prague, December 2004
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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
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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
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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
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TGV I
open cryostat assembled cryostat, PAs
P. Cermak, Rez near Prague, December 2004
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TGV I
cryostat surrounded by Cu shielding
P. Cermak, Rez near Prague, December 2004
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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
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TGV I results (48Ca)
yT 193.33.1
22/1 10)2.4(
)%90(105.1 2102/1 CLyT
yT 193.33.1
22/1 10)2.4(
P. Cermak, Rez near Prague, December 2004
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TGV II• to improve 48Ca result
obtained by TGV I
• to investigate processes in 106Cd (to focus on EC/EC channel)
),(22 10646
10648 raysXPdCde e
purpose:
2EC/EC:
106Cd:
keVEkeVkeV XECEC 5.235.18:ROI,2778Q /
2:
48Ca:
)(2~24822
4820 eTiCa e
MeVEMeVkeV e 2.47.2:ROI,4272Q
P. Cermak, Rez near Prague, December 2004
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Basic parameters
Stack of 32 HPGe planar detectors:
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
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TGV II spectrometer
Dewar
cryostatPbCu
borated polyethylene
PA
SM
1m
P. Cermak, Rez near Prague, December 2004
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TGV II
pedestal open cryostat
P. Cermak, Rez near Prague, December 2004
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TGV II
assembled cryostat, PAs
P. Cermak, Rez near Prague, December 2004
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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
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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
eventsP. Cermak, Rez near Prague, December 2004
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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
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Pulse shape analysis (principle)
Current
Time, ns
Q2
Q1
e10 200
strobe
Q (integrated charge)
e
Amplitude (energy)
• based on difference between interaction of e- and -rays with detector crystal
• point of interaction - charge collection time - pulse shape - integrated charge => E-Q spectrum
• ability to suppress -rays by factor 2-3
P. Cermak, Rez near Prague, December 2004
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Pulse shape analysis (example)
E-Q spectrum, sources: 207Bi + 60Co
Q
E
electrons
gammas
Compton edge
P. Cermak, Rez near Prague, December 2004
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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
Data processing (2)
P. Cermak, Rez near Prague, December 2004
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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
ROI
P. Cermak, Rez near Prague, December 2004
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Matrices example
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TGV II electronics (Cd setup)
• Double – shaping method
• Multiplexed channels
• MT – Master Trigger block (input register, gate generator, veto generator)
• N2 filling flag
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• no selection
start: 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
Microphonic noise suppression (example)
P. Cermak, Rez near Prague, December 2004
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Runs overview (year 2004)
1. Cd background (December 03 – February 04)
• 1363 hours, 14312946 events
• no foils
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2. Enriched Cd, type I (March 04 – May 04)
• 1768 hours, 16531047 events
• 13x 106Cd foil, 3x Cd-nat. foil
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2. Enriched Cd, type II (May 04 – June 04)
• 328 hours, 3515849 events
• 12x 106Cd foil, 4x Cd-nat. foil
3. Enriched Cd, type II (June 04 – October 04)
• 2033 hours, 158382662 events
• 12x 106Cd foil, 4x Cd-nat. foil
4. Enriched Cd, type II (November 04 – now)
• 16x Cd-nat. foil
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Conclusion, near future (1)
• background for 48Ca (preliminary – 1 month run):
– 45 ev./year in (2.7-4.2)MeV region – expected effect: 35 ev./year
• both setups were assembled and tested• basic runs needed for background
determination (both for 48Ca and 106Cd setup) were performed
P. Cermak, Rez near Prague, December 2004
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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 of T1/2 ~ 1018 y, g.s. → g.s.
- estimation of T1/2 ~ 1019 y, g.s. → 2+1
P. Cermak, Rez near Prague, December 2004
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• present situation:
TGV II is running in Cd setup with Cd-nat.
Conclusion, near future (2)
• next steps (2005 – 2006):
• enriched Cd purification
• Cd-nat. data final procession
• measurement with 48Ca
P. Cermak, Rez near Prague, December 2004