MANU2: status report Maria Ribeiro Gomes* for the Genoa Group IAP, 14-Nov-05 * pos-doc under TRN HPRN-CT

Objectives Micro-calorimetric neutrino mass direct measurement Investigate Re-187 beta 1 eV/c 2 region Requirements Stable TES sensors (Ir-Au or  Al-Ag) Required energy resolution 5-10 eV 6 keV no-SQUID readout electronics 300  calorimeters with Re single crystal absorber Second generation experiment IAP, 14-Nov-05

TES R&D -Stable SC intermetallic alloy (instead of bilayer) -SC  -phase from phase diagram IAP, 14-Nov-05 Al-Ag alloy X-ray diffraction pattern from film growth by e-beam evaporation of Al and Ag onto Si(110) substrate T C of the alloy depends on the material stoichoimetry: mK Advantages: Easy preparation Freedom on T C choice Shorter pulse

TES R&D (cont.) Ir-Au multilayer Stable/reproducible performance PLD on Si substrate and subsequently patterned by ion sputtering Ir-Au-Ir on Si Photo-resist pattern Ar ion-etching Final result Pulsed Laser Deposition Laser frequency: 2-10 Hz Starting pressure: 6.5 × 10 −9 mbar Plasma pressure: 1.2 × 10 −7 mbar Substrate temperature: 350 o C Laser energy: 500 mJ/pulse Ablation rate: 0.1 – 0.4 Å/shot IAP, 14-Nov-05 balance Linear sample feed-through laser

Au target Sample holder Si substrate wafer Laser beam Nd:YAG 1064 nm Plasma plume Target carrousel Ir target

S-N phase transition i=0.4mA R=200 m 82.9 mK  =T/R (  R/  T) ~ 9100 Ir-Au TES IAP, 14-Nov-05

Detector performance comparison Calorimeter Sensor  c#18 Ge-NTD  c#28  c#31  c#35  c#55 Ir-Au TES Re (  g) C Re (pJ/K) C sensor (pJ/K) R sensor (  ) 4.9M6.0M7.8M6.6M1 V noise (mV) cal Baseline noise (mV) 4.5(.2)4.05.4(.2)4.6(.2)650 pA  E(eV) cal. keV  E(eV) meas. keV IAP, 14-Nov-05

Transformer readout electronics Trans-resistance amplifier coupled via transformer Low temperature operating transformer (100 mK) Transformer core material selected over:  -metal, ferrite, metallic amorphous, spin glasses Low noise RT JFET amplifier: present noise 0.9 nV/√Hz Integrating stage in order to flat the transfer function IAP, 14-Nov-05 5pf 270pf 1K R b = H 5H 3.6H ∫ 1.6

Cold transformer and bias circuit Measured noise: 14 1 kHz, < kHz There is space of parameters for optimal matching: I(thermal noise)=√ (4kT 2 aI/G eq ) ~ T √ (4k) √(a/R) Signal to noise is proportional to √R Setting a proper value of the TES resistance it possible move the current equivalent thermal noise to level in the range of the current equivalent electronics input noise a= K -1, R=1W-> I(thermal noise) ~ pA/√Hz Further improvement can be done with new JFET (0.3 nV/Hz, 10 fA/Hz) and a slight higher mutual inductance transformer Further improvement can be done with new JFET (0.3 nV/ √ Hz, 10 fA/ √ Hz) and a slight higher mutual inductance transformer IAP, 14-Nov-05

Input Current transformer V out Integrated Output Transfer function IAP, 14-Nov-05

Single pixel results Ir-Au TES on high-purity Si 70 mK Re crystal absorber with (400x470x54)  m 3  0.2 decay/s Tested bandwidth (1-1000) Hz and readout by DC-SQUID pulse-height=2560 mV rise time 160  s pileup discrimination time 80  s RMS noise 1.2 mV Energy resolution at 6 keV IAP, 14-Nov-05

Statistical Sensitivity IAP, 14-Nov-05 MANU MANU2

Under progress… testing 1 single disc: 20 readout channels 16 mg  3 months  1.2 x 10 8 counts 200 channels in measurement by Mars 2006 In 1 yr of data taking 9x10 9 counts (MANU: single 1.5 mg Re crystal, Ge-NTD sensor and 3 months  7x10 6 counts ) Number of channels ~ 300 Total Re mass ~ 250 mg Expected count-rate ~ 300 counts/s Expected sensitivity between 1.5 and 1.7 eV IAP, 14-Nov  m/disc 10 discs  180