Stefano Pirro, IDEA Meeting –Milano November 10 2006

Status of the scintillating bolometer program

• Scintillating Bolometers

• Background rejection capabilities

• Interesting Compounds

• Future Prospects

• First tests

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Some remarks

The activity of this task was initially dedicated to the development of Nd based bolometers.

Unfortunately the results obtained in the first 2 years were not encouraging

Therefore the activity of the task was re-planned (since April 2006) but keeping the spirit of the task: the use of the bolometric technique in order to study promising candidates for neutrinoless double beta decay with high Q-value (as 150Nd), such as 116Cd and 100Mo

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Principles of operation

Thanks to the different Quenching Factor ,/, and neutrons can be easily identified

=C/GT=E/C

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Environmental “underground” Background

Background rejection capabilities I

CUORICINO Background

130Te76Ge

100Mo

116Cd

(External Contaminations)

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Background rejection capabilities II(Internal Contaminations)

Thanks to Bi-Po’s and Beatles internal contaminations do not play a significant role

BI-Po

Bi-TlBEATLE

Does not hold for 234Pa (Q=2195 keV)

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Our Setup - I

3x3x2 cm3 CdWO4

(140g)

6.3 cm dia 1 mm thick Ge

Q(116Cd)=2802 keV

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Our Setup - II

17 g CaMoO4

3.2 cm diam 3 cm height CaF2

3x3x2 cm3 CdWO4

Light detector

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Calibration results on CdWO4

0.2% FWHM @ 2615 keV2.9 % FWHM @ 2615 keV

232Th + 56Co Calibration

HeatScitillation

2.9% FWHM is the best result ever achieved with CdWO4 as scintillator

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Background measurement on CdWO4

During last year a long Bg measurement was performed with the RAD detector

The measure was optimized for the TeO2 crystals

440 h live time measurement

Stefano Pirro, IDEA Meeting –Milano November 10 2006

CdWO4- some considerations

Stefano Pirro, IDEA Meeting –Milano November 10 2006

CdWO4- some considerations II

E-rotated

Erotaded=Heat cos + Light sin

FWHM @ 2615 improves by ~ 40 % !!!!!

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Lig

ht S

igna

l [a

u]

CaMoO4 -17.4 g sample

147Sm (ext)

238U226Ra

210Po

222Rn 224Ra

214Bi-214Po (+/)

218Po

-

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Contaminations

Both series of 238U and 232Th are observed, but both of them are broken at Radium

238U series238U 7.6 0.8 mBq/kg (0.61 0.06) 10-9 g/g

226Ra 107 3 mBq/kg (0.86 0.02) 10-8 g/g **(broken series)

232Th series232Th 0.17 0.12 mBq/kg (4.2 3) 10-11 g/g

228Ra 4.6 0.6 mBq/kg (1.13 0.14) 10-9 g/g**

(broken series)

**(equivalent to parent in case of secular equilibrium)

Stefano Pirro, IDEA Meeting –Milano November 10 2006

Future developmentsCdWO4 crystals are good (apart 113Cd) and extremely radiopure

We plan to make a “pilot experiment” with an array of 4 crystals within 2007.

Regarding Mo is more complicated….

Molybdates crystal are not so developed

Molybdates crystal are not so clean

We found a different CaMoO4 supplier and wehave a new large sample (97 g)

From HPGE measurements we know thatthe radiopurity is a factor 3.3 better withTespect to the 17.4 g sample

This new crystal will be tested in the next CUORE R&D run

This kind of research is funded by INFN for 2007-2008, OUTSIDE (parallel to) CUORE