Production of Neutron Transmutation Doped Germanium Thermistors for CUORE

Reina Maryama for the CUORE CollaborationUniversity of Wisconsin, Madison

APS Division of Nuclear Physics Fall Meeting23 - 26 October 2008, Oakland, CA

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 2

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CUORE

Array of 988 TeO2 crystals 19 Cuoricino-like towers 4 crystals x 13 levels per tower

5x5x5 cm3 (750 g each)

130Te: 33.8% isotope abundance 741 kg TeO2 ⇒ 204 kg 130Te

APS Neutrino Study 2004

CUORE

Other talks:Adam Bryant, EC 3Nick Scielzo, EC 5Laura Kogler, HC 4Karsten Heeger, MC 2

Goal

background < 0.01 cnts/keV/kg/y

Resolution = 5 keV

5 year sensitivity

F0ν > 2.1 x1026 y

mee < ~ 25 – 130 meV

Goal

background < 0.01 cnts/keV/kg/y

Resolution = 5 keV

5 year sensitivity

F0ν > 2.1 x1026 y

mee < ~ 25 – 130 meV

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 3

For E = 1 MeV:ΔT = E/C ≅ 0.1 mK

Signal size: 1 mVTime constant:

τ = C/G = 0.5 s

Energy resolution (FWHM): ~ 5-10 keV at 2.5 MeV

Heat sink: Cu structure (8 mK)Thermal coupling: Teflon (G = 4 pW/mK)Thermometer: NTD Ge-thermistor100 MΩdR/dT ≅ 100 kΩμK)Absorber: TeO2 crystal (C ≅ 2 nJ/K ≅ 1 MeV / 0.1 mK)

Heat sink: Cu structure (8 mK)Thermal coupling: Teflon (G = 4 pW/mK)Thermometer: NTD Ge-thermistor100 MΩdR/dT ≅ 100 kΩμK)Absorber: TeO2 crystal (C ≅ 2 nJ/K ≅ 1 MeV / 0.1 mK)

TeO2 Bolometer: Source = DetectorTeO2 Bolometer: Source = Detector

CUORE Bolometer

Single pulse example

Time (ms)

A

mpl

itude

(a.

u.)

1000 2000 3000 4000

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 4

NTD Ge Thermistors

Neutron Transmutation Doped Ge Thermistors •Developed at Berkeley by E.E. Haller (material science)Ge doped with Ga & As by neutron irradiation•provides very uniform doping•Few % variation in doping results in performance variationReliable, reproducible, and stableGood energy resolution

Neutron Transmutation Doped Ge Thermistors •Developed at Berkeley by E.E. Haller (material science)Ge doped with Ga & As by neutron irradiation•provides very uniform doping•Few % variation in doping results in performance variationReliable, reproducible, and stableGood energy resolution

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Planned or operating in numerous sub-orbital experiments:

BOOMERANG Caltech Antarctic balloon CMB instrumentSuZIE Stanford S-Z instrument for the CSOMAXIMA UC Berkeley North American balloon CMB instrumentBOLOCAM CIT/CU/Cardiff Bolometer camera for the CSOACBAR UC Berkeley Antarctic S-Z survey instrumentBICEP Caltech CMB polarimeterMAT UPenn CMB experiment for ChilePOLATRON Caltech CMB polarimeter for OVROArcheops CNRS, France CMB balloon experimentBLAST U. Penn Submillimeter balloon experimentZ-SPEC Caltech mm-wave spectrometerQUEST Stanford CMB polarimeterPRONAOS IAS, France Submillimeter balloon experiment

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 5

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Doping ProcessAcceptor 70Ge (21%) + n → 71Ge

71Ge →EC) 71GaDonor74Ge (36%) + n → 75Ge

75Ge → 75As + β-

Double Donor76Ge (7.4%) + n → 77Ge

77Ge → 77As + β-

77As → 77Se + β-

Resistance: 10 MΩ-cm @ 10 mK, T0 = 3 K Nominal neutron dose: 4x1018 n/cm2

Nominal concentrations: Ge: 4.4 x 1022 cm-3

Ga: 1 x 1017 cm-3

As: 3 x 1016 cm-3

Se: 2 x 1015 cm-3

Neutron source: reactorsProduction time: ~1 year for 2 Hz in 9 mm3 chips

Ge70Ge71Ge72Ge73Ge74Ge75Ge76Ge7711.4dGa71As75As77Se7711.3 hr39 hrβECββ1.38hr

(σT = 3.43 bn) (σT = 0.51 bn) (σT = 0.16 bn)

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Challenges for CUORE Thermistors

Temperature (mK)

T-1/2 (K-1/2)

Res

istiv

ity (

Ohm

-cm

)

q1

ρ = ρo exp (To/T)1/2ρ = ρo exp (To/T)1/2

• Reproduce CUORICINO doping⇒Need to obtain neutron fluence to within 1%⇒BUT fluence known only to ~ 5%• 1250 thermistors necessary:⇒1 thermistor/crystal + extras for monitoring + spares =

1250• Must meet the low background materials requirement⇒electrically active impurities in Ge: 5 x 1010 cm-3 (150 times less than in CUORICINO)⇒Use reactor with few fast neutronsto minimize activation of

long-lived isotopes, e.g. 68Ge, 65Zn

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 7

MIT 4” port (4TH1-3)

‣ Dedicated facility for Silicon NTD‣ Sufficient flux: fluence per pass: 1017 – 1018 cm-2

‣ Sample rotated for uniform irradiation‣ Sample speed adjusted by feedback with monitors‣ Large ports to accommodate 65 mm wafers‣ We have determined that:

- MIT has 1/1000 fast neutrons than MURR- fluence per pass reliable to 3%

Cons:‣Different neutron energy spectrum

- may contribute to different Ga:As:Se ratio

- Cold test necessary in any case

CUORICINO used University of Missouri Research Reactor (MURR)

CUORE: MIT Nuclear Reactor Laboratory was chosen:

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 8

Doping Procedure and Diagnostics• Reach 1% accuracy by multiple passes

e.g. 3% accuracy of 10% of total dose -> 0.3%

• Irradiate four sets at different doses to cover uncertainty in absolute dose

• Three diagnostic tools-Cold test: measure T0 and ρ0

• Ultimate test• ~ 10 months of cool down required before count rate of decay to Ga is < 2 Hz

for 3x3x1 mm3 chips

-Monitor foils • fast check, compare with nominal CUORICINO• sub-% relative measurement possible• e.g. 59Co(n,γ)60Co (T1/2 = 5.3 yrs), 58Fe(n,γ)59Fe (T1/2 = 45 days), 94Zr(n,γ)95Zr (T1/2 = 64 days)

-Neutron Activation Analysis (NAA)• Direct comparison with CUORICINO thermistors by activating Ga & As • quicker turn around than cold test• 2.5% accuracy achieved (some interferences from neighboring lines &

reactions)

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 9

Neutron Activation Analysis• Reactions:

• Interference:

• Activated at McClellan, counted on-site & at LBL

Dolinski, Smith, Norman

(14 hrs)(1.1 day)

(11.3 hrs)

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 10

Neutron Fluence Monitors

• Fe & Zr foils, standard pottery used

• 3 monitors replaced between each pass

• 1 monitor stay with wafers for all passes for cross check

• Monitors counted at LBL low background counting facility

• 7 passes at MIT indicates that they can aim for 3% run-to-run consistency

Fe & Zr

Standard Pottery

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 11

NTD Ge Wafers and Holders

65 mm

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Neutron Fluence vs. Cold Test• Cold tests done in Florence and Milan

- absolute temperature calibration is different, but show good relative agreement

• 9 small sets irradiated earlier at Missouri- Monitors used to measure neutron fluence

- Show some inconsistencies with cold testOld

NewCUORICINO

• 4 new sets for CUORE have been irradiated and cold tested. NAA in agreement.

• Unfortunately NTD-40 A/B are over-doped

• NTD-39 A/B top-off is underway (two different doses)

• Two more sets to start

Reina MaruyamaAPS DNP Oct 23 - 26, 2008, Oakland CA 13

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CUORE Collaboration

Laboratori Nazionali del Gran Sasso M. Balata, C. Bucci, S. Nisi

Universita’ di Firenze e INFN, FirenzeM. Barucci, L. Risegari, G. Ventura

University of ZaragozaS. Cebrian, P. Gorla, I.G. Irastorza

Universita’ dell’Insubria e Sezione di Milano dell’INFN, Como

A. Giuliani, M. Pedretti, S. Sangiorgio

Universita di Genova S. Cuneo, S. Didomizio, A. Giachero, M. Olcese,

P. Ottonello, M. Pallavicini

Laboratori Nazionali di LegnaroV. Palmieri

Universita di RomaF. Bellini, C. Cosmelli, I. Dafinei, M. Diemoz, F. Ferroni,

C. Gargiulo, E. Longo, S. Morganti, M. Vignati

Universita’ di Milano-Bicocca - INFN Sezione di Milano F. Alessandria, R. Ardito1 , C. Arnaboldi, C. Brofferio, S. Capelli, L.

Carbone, M. Clemenza, O. Cremonesi, E. Fiorini, C. Nones, A. Nucciotti, M. Pavan, G. Pessina, S. Pirro, E. Previtali, M.

Sisti, L. Torres, L. Zanotti

Politecnico de MilanoG. Maier

University of California at BerkeleyA. Bryant, M.P. Decowski2 , M.J. Dolinski3 , E. Guardincerri,

S.J. Freedman2, L. Kogler, Yu.G. Kolomensky2, E.E. Haller2 (2also at LBNL, 3also at LLNL)

University of South CarolinaD.R. Artusa, F.T. Avignone III, I. Bandac, R. J. Creswick,

H.A. Farach, C. Rosenfeld

Lawrence Berkeley National Laboratory J.W. Beeman, R.W. Kadel, A.R. Smith, N. Xu

Lawrence Livermore National LaboratoryK. Kazkaz, E.B. Norman, N. Scielzo

University of California, Los AngelesH. Huang, C. Whitten Jr.

University of Wisconsin, MadisonL.M. Ejzak, K.M. Heeger, R.H. Maruyama

California Polytechnic State University T.D. Gutierrez

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