Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

150Nd Project

• High Temperature Thermistors

• News about NdGaO3

• Scintillating Bolometers

• Conclusions & Prospect

• Results on NdGaO3

• Neodymium Garnet

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

High temperature thermistors

Since the optimum operation temperature for the Nd bolometers is not predictable a priori, several NTD (Neutron Transmutation Doped) thermistors with different sensitivities and therefore optimized for different operation temperatures were prepared (thanks to the collaboration with E. Haller, LBL, and co-workers).

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

NdGaO3

We tested this compound several times during 2004 & 2005

We succeed to reach “low temperatures” (~ 17 mK)

However the assembled bolometer showed a “strange” behavior

We was able to see thermal injected power

We wasn’t able to recognize Particle pulses

Down-conversions of ballistic phonons to thermal phonons is suppressed/trapped

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

Phonon opacity….?

Interaction between phonons and nuclear magnetic moments could explain this behavior.

It is not easy to evaluate the mean free path of a ballistic phonon in the NdGaO3 crystal because the spin-phonon interaction depends crucially on fine-structure parameters that needs to be measured.

The only way to avoid this interaction, and to effectively test the theory, is to eliminate in the crystal the isotopes with nuclear spins, i.e. 143Nd (12%) and 145Nd (8%) through a suitable enrichment in 150Nd.

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

NdGaO3- thin sample

The Idea is to try to evaluate roughly the enrichment needed to avoid this effect.

We assembled a very small NdGaO3 bolometer by cutting the small sample

13x13x2 mm3 NdGaO3 (2.5 g)

ThermistorHeater

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

NdGaO3- thin sample-results 1

After 3 weeks the temperature of the bolometer is ~ 13 mK

The detector is presently running @ LNGS

The detector works as bolometer

We are able to see ~ 70 keV ofthermal injected power

However…….

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

NdGaO3- thin sample-results 2

Heater pulse

Particle Pulse

There are several classes of pulses

The heater pulses are the fastest

Structure ?

238U 710-7 g/g

232Th 310-8 g/g

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

Neodymium garnet

Neodymium garnet (Nd3Ga5O12) is somehow “similar” to neodymium gallate but easier to grow

18 mm height x 13 mm diameter Nd-Garnet

The detector is presently running @ LNGS

After 3 weeks the temperature of the bolometer is ~ 33 mK

No pulses are observed

We will test a new Nd compound ( NaNd(MoO4)2 ) within the next run in the Hall C cryostat

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

Innovative Techniques

Several tests were made in the R&D cryostat @LNGS during the lasts months

The idea is to move towards a active background rejection

Double readout heat - light

Nuclei with Q-Value above the 208Tl - line

100Mo 3034 keV

48Ca 4271 keV

116Cd 2802 keV

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

First “LARGE” mass high RESOLUTION scintillating

bolometer for DBD

A very impressive result was indeed obtained as a by-product.

The idea was to measure the thermal neutrons flux inside the CUORE R&D cryostat using a CdWO4 crystal, via the (113Cd,n) reaction.

3x3x2 cm3 CdWO4

(140g)

6.6 cm dia 1 mm thick Ge

Q(116Cd)=2802 keV

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

Setup

Mixing Chamber

Stainless steel wire

First damping mass(Roman Lead)

Cuore Radioctivitytest run

(II Damping stage)

Light Detectors

Very “un-clean” setup”

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

Calibration results

0.9 % FWHM @ 2615 keV

3 % FWHM @ 2615 keV

232Th + 56Co Calibration

HeatScitillation

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

Background measurement

During April a background measurement was performed with the RAD detector

The measure was optimized for the TeO2 crystals

417 h live time measurement

arXiv:nucl-ex/0510074

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

Actual Energy resolutionAt the end of the radioactive run we recognized that there were an error in the electronic setup of Cd

We therefore performed a short calibration optimizing the CdWO4 bolometer.

0.24 % FWHM

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

New Run4x4x3 cm3 LiF Crystal

3x3x2 cm3 CdWO4 crystal2 cm height 2 cm dia ZnSe crystal

Preliminary results

EFWHM LD =25 eV

Light Detector

ZnSe shows large Scintillation light

Stefano Pirro, IDEA Meeting -Zaragoza November 7 , 2005

Conclusions

• Neodimuim-based Detectors/Bolometers shows clearly the difficulties of this compound

• The Nd enrichment could be, maybe, not achievable within the needed level• The “new” implementation of scintillating bolometers clearly shows the easy feasibility of a “new” powerful experiment

• Lot of effort is needed in order to identify a suitable scintillating compound