Production of Neutron Transmutation Doped Germanium Thermistors for CUORE Reina Maryama for the CUORE Collaboration University of Wisconsin, Madison APS Division of Nuclear Physics Fall Meeting October 2008, Oakland, CA

Reina MaruyamaAPS DNP Oct , 2008, Oakland CA 2 CUORE Array of 988 TeO 2 crystals  19 Cuoricino-like towers  4 crystals x 13 levels per tower  5x5x5 cm 3 (750 g each)  130 Te: 33.8% isotope abundance  741 kg TeO 2  204 kg 130 Te APS Neutrino Study 2004 CUORE Other talks: Adam Bryant, EC 3 Nick Scielzo, EC 5 Laura Kogler, HC 4 Karsten Heeger, MC 2 Goal background < 0.01 cnts/keV/kg/y Resolution = 5 keV 5 year sensitivity F 0  > 2.1 x10 26 y m ee < ~ 25 – 130 meV Goal background < 0.01 cnts/keV/kg/y Resolution = 5 keV 5 year sensitivity F 0  > 2.1 x10 26 y m ee < ~ 25 – 130 meV

Reina MaruyamaAPS DNP Oct , 2008, Oakland CA 3 For E = 1 MeV: ΔT = E/C  0.1 mK Signal size: 1 mV Time constant:  = 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-thermistor  100 M  dR/dT  100 k  K) Absorber: TeO 2 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-thermistor  100 M  dR/dT  100 k  K) Absorber: TeO 2 crystal (C  2 nJ/K  1 MeV / 0.1 mK) TeO 2 Bolometer: Source = Detector CUORE Bolometer Single pulse example Time (ms) Amplitude (a.u.)

Reina MaruyamaAPS DNP Oct , 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 variation Reliable, reproducible, and stable Good 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 variation Reliable, reproducible, and stable Good energy resolution 4 Planned or operating in numerous sub-orbital experiments: BOOMERANGCaltechAntarctic balloon CMB instrument SuZIE Stanford S-Z instrument for the CSO MAXIMA UC Berkeley North American balloon CMB instrument BOLOCAM CIT/CU/CardiffBolometer camera for the CSO ACBAR UC Berkeley Antarctic S-Z survey instrument BICEP Caltech CMB polarimeter MAT UPenn CMB experiment for Chile POLATRON Caltech CMB polarimeter for OVRO Archeops CNRS, France CMB balloon experiment BLASTU. PennSubmillimeter balloon experiment Z-SPECCaltechmm-wave spectrometer QUESTStanfordCMB polarimeter PRONAOS IAS, France Submillimeter balloon experiment

Reina MaruyamaAPS DNP Oct , 2008, Oakland CA 5 Doping Process Acceptor 70 Ge (21%) + n → 71 Ge 71 Ge →  EC) 71 Ga Donor 74 Ge (36%) + n → 75 Ge 75 Ge → 75 As +  - Double Donor 76 Ge (7.4%) + n → 77 Ge 77 Ge → 77 As +  - 77 As → 77 Se +  - Resistance: mK, T0 = 3 K Nominal neutron dose: 4x10 18 n/cm 2 Nominal concentrations: Ge: 4.4 x cm -3 Ga: 1 x cm - 3 As: 3 x cm - 3 Se: 2 x cm - 3 Neutron source: reactors Production time: ~1 year for 2 Hz in 9 mm 3 chips (  T = 3.43 bn) (  T = 0.51 bn)(  T = 0.16 bn)

Reina MaruyamaAPS DNP Oct , 2008, Oakland CA 6 Challenges for CUORE Thermistors Temperature (mK) T -1/2 (K -1/2 ) Resistivity (Ohm-cm) q1q1  =  o exp (T o /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 cm -3 (150 times less than in CUORICINO) ⇒ Use reactor with few fast neutrons to minimize activation of long- lived isotopes, e.g. 68 Ge, 65 Zn

Reina MaruyamaAPS DNP Oct , 2008, Oakland CA 7 MIT 4” port (4TH1-3) ‣ Dedicated facility for Silicon NTD ‣ Sufficient flux: fluence per pass: – 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 , 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 T 0 and ρ 0 Ultimate test ~ 10 months of cool down required before count rate of decay to Ga is < 2 Hz for 3x3x1 mm 3 chips  Monitor foils fast check, compare with nominal CUORICINO sub-% relative measurement possible e.g. 59 Co(n,γ) 60 Co (T 1/2 = 5.3 yrs), 58 Fe(n,γ) 59 Fe (T 1/2 = 45 days), 94 Zr(n,γ) 95 Zr (T 1/2 = 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 , 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 , 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 , 2008, Oakland CA 11 NTD Ge Wafers and Holders 65 mm

Reina MaruyamaAPS DNP Oct , 2008, Oakland CA 12 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 test Old New CUORICINO 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 , 2008, Oakland CA 13 CUORE Collaboration Laboratori Nazionali del Gran Sasso M. Balata, C. Bucci, S. Nisi Universita’ di Firenze e INFN, Firenze M. Barucci, L. Risegari, G. Ventura University of Zaragoza S. 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 Legnaro V. Palmieri Universita di Roma F. 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. Ardito 1, 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 Milano G. Maier University of California at Berkeley A. Bryant, M.P. Decowski 2, M.J. Dolinski 3, E. Guardincerri, S.J. Freedman 2, L. Kogler, Yu.G. Kolomensky 2, E.E. Haller 2 ( 2 also at LBNL, 3 also at LLNL) University of South Carolina D.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 Laboratory K. Kazkaz, E.B. Norman, N. Scielzo University of California, Los Angeles H. Huang, C. Whitten Jr. University of Wisconsin, Madison L.M. Ejzak, K.M. Heeger, R.H. Maruyama California Polytechnic State University T.D. Gutierrez 13