150 Nd activities at TUM

21. October 2004 IDEA DBD Meeting, Heidelberg

150Nd activities at TUM V. Lazarev1, E. Nolte1, L. Oberauer1, F. Pröbst2

1 - Technische Universität München, E152 - Max Planck-Institut für Physik, München

with help of

J. Doncev2, V. Kochurichin3, L. Nagorna4, D. Kovalev5, S. Schönert6, M. Stark1

3 - General Physics Institute, Coherent and Nonlinear Optics Department, Russia4 - Institute for Single Crystals, Ukraine5 - Technische Universität München, E166 - MPI, Heidelberg, Germany


emitters

Isotope Q, keV T 2, 1019 a

T 0 for <m>=50 meV, 1026 a

(T2/ T0

, 10-7)

48Ca 4271 4 4.2 1.2 12.7

(0.33) 35 (0.1) 10 (0.4)

76Ge 2040 1 13 10 6.8 (19) 71 (2) 56 (2.3) 9.3 (14) 12.8 (10)

14.4 (9)

82Se 2995 6 9.2 1.0 2.3 (4) 9.6 (1) 22 (0.4) 2.4 (4) 3.2 (3) 6 (1.5)

100Mo 3034 6 0.8 0.06 5 (0.2) 1.2 (0.7) 16

(0.05)

116Cd 2802 4 3.2 0.3 1.9 (1.7) 3.1 (1) 18.8 (0.2)

130Te 2533 4 270 10 0.6

(450) 23 (12)

2.8 (100)

2 (135) 3.6 (75) 3.4 (80)

136Xe 2479 8 >81 48.4 8.8 21.2 7.2

150Nd 3367 2 0.7 + 1.2 – 0.3 0.1 (7) 0.2 (3.5)

A. Staudt A. Faessler

150Nd:• the shortest half-time for neutrinoless 0 decay• the second largest Q-value• low 2 background


Tungstates and scintillation

Almost all tungstates scintillate.The best known scintillators are:CdWO4, PbWO4, CaWO4

The reason is the structure of WO4

From: Williams R.T., Y.C. Zhang, Y. Abraham, and N.A.W. HolzwarthElectronic structure of pure and defective PbWO4, CaWO4, and CdWO4

Invited paper presented by R.T. Williams at the SCINT99 conference in Moscow, Aug. 1999


Crystal scintillators• Tungstates are often scintillators: CaWO4, CdWO4, PbWO4

• Measurements with CdWO4 are done with low background: 0.03 counts/(keV kg a) (Danevich F.A. et al. Phys. Rev. C62:044501 (2000))• Crystals of CaWO4 can have good resolution: 5% at 1332 keV (F. Pröbst)

Crystal of Nd2(WO4)3 is probably a scintillator

Detector resolution could be %31332

05.0 Q

keV

1%64.5503

280 44

M

kg

T

ameVm With |M0|2 from Staudt,


Current state of the investigationWe need highly enriched neodymium (Russia!):

1%852005

45 44

M

kg

T

ameVm

• A process of Nd2(WO4)3 growing was investigated. • Sample crystals were grown using Czochralski method (V. Kochurichin, Moscow).


Crystals

Successful crystals of CaWO4



1%852005

45 44

M

kg

T

ameVm

• A process of Nd2(WO4)3 growing was investigated. • Sample crystals were grown using Czochralski method (V. Kochurichin, Moscow). • 3 small crystals (about 1 cm3 each) were delivered to Munich


Scintillation

dark box

to electronic

Crystal

PMT, XP3461B

standard source

90Sr, 137Cs

60Co

Jelena Doncev, MPI, München

No clear result!


Spectral characteristics

Nd2(WO4)3 crystal

grid

focusing mirror focusing mirror CCD camera Prinston Instruments GmbH cooled with liquid N2

Monochromator: Special Pro-250, Acton Research Corporation

Sensitivity: 400 (300) – 1000 nm

D. Kovalev, TU München, E16



1%852005

45 44

M

kg

T

ameVm

• A process of Nd2(WO4)3 growing was investigated. • Sample crystals were grown using Czochralski method (V. Kochurichin, Moscow). • 3 small crystals (about 1 cm3 each) were delivered to Munich• The crystals showed no scintillation (J. Doncev, MPI, D. Kovalev, TUM, E16)• A powder of other compositions (e.g. LiNd WO4) showed no roentgen-luminescence (L. Nagorna, Ukraine)


The choice of a detector

Direct counting Other

150Nd is within detector 150Nd is outside detector

Electron hole pairs(Semiconductors)

Production of photonsand photoelectrons

(Scintillators)

Production of phonons(Cryodetectors)

Crystal scintillators

Liquidscintillators

Production of phonons(Cryodetectors)


Cryogenic detectors

Heat capacity of an insulator

3

D

Tc

Heat capacity of a ferromagnet

If there is an energy splitting

2

2

1 T

T

e

eTc

Energy resolution

)(2 TcTkE B

In case of thermalization

Temperature increase

t

eTc

EtT

)()(

Low heat capacity is necessary!

2

3

A

Tkc B


• Particle or light interaction with absorber

• High frequency phonons are produced

• Phonons become ballistic and fill the crystal homogeneously

• In the Al-phonon collector those phonons break up quasiparticles

• Quasi particles diffuse to the Ir/Au-superconducting thermometer and heat it up

• Resistance of the film changes and the resistance of the thermometer

Al-phonon-collector

Ir/Au-thermometer

Cryodetectors at TUM








Al-phonon-collector

Ir/Au-thermometer









Al-phonon-collector

Ir/Au-thermometer









Ecooper-pairs Eprox

aluminum Ir/Au

quasiparticles

phonon









Ecooper-pairs Eprox

aluminum Ir/Au

quasiparticles








• Resistance of the film changes -> this is the signal

R

T



Neodymium cooling

NdGaO3

Thermostat

M. Stark,E15, TUM

• Ir/Au thermometer was glued on the NdGaO3 crystal• Only signals from the thermometer were detected

• Ir/Au thermometer was sputtered on the NdGaO3 crystal• The results are not available yet


Liquid scintillators

A scintillator like CTF could be used

PMTs cover about 20% of the solid angle

penE

E %1323.2

where npe – number of photoelectrons

The energy resolution for CTF

Photoelectron yield of the CTF with100 PMT

MeV

ronsphotoelect300


Liquid scintillatorsWith 400 PMT the energy resolution

keVEE

E160%,8.4

Background at 3.3 MeV

akeVkgB

1109.2 5

Now it is possible to solve about 1 %0 of Nd (S. Schönert, MPI, Heidelberg)


Local tasksIf we assume that everything is perfect and not additional problem arises

1. Preliminary investigation with natural Nd

4

3

44

4 5

0 1051

1601109.2

%1%64.5260

CTFM

kg

T

a

keV

E

akeVkg

BmeVm

This is sufficient to prove the results of Klapdor-Kleingrothaus, m=400 meV

2. The second step with enriched Nd

4

3

44

4 5

0 1053

1601109.2

%1%8550

CTFM

kg

T

a

keV

E

akeVkg

BmeVm

This is sufficient to prove the inverse hierarchy


Summary

• 150Nd is one of the most interesting candidates to detect a neutrinoless double beta decay• There is no established method to measure this decay• Estimations show that it could be possible to build a scintillation detector. However, till now no scintillator with Nd was found. (Maybe because of the properties of Nd).• It is possible to cool Nd-crystal at least down to 60 mK. However, no phonon signal could be measured• A liquid scnitillator with dissolved 150Nd is the most promising idea at the moment

Documents

150 Nd activities at TUM