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MARE

MARE. M icrocalorimeter A rrays for a R henium E xperiment. A DETECTOR OVERVIEW. Andrea Giuliani , University of Insubria, Como, and INFN Milano on behalf of the MARE collaboration. Outline of the talk. The physics case: importance of direct m n measurement

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MARE

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  1. MARE Microcalorimeter Arrays for a Rhenium Experiment A DETECTOR OVERVIEW Andrea Giuliani, University of Insubria, Como, and INFN Milano on behalf of the MARE collaboration

  2. Outline of the talk • The physics case: importance of direct mn measurement • Methods: spectrometers and microcalorimeters • Status of microcalorimeters and prospects • MARE-1: techniques, detectors and sensitivity • MARE-2: new detector technologies • Conclusions

  3. Outline of the talk • The physics case: importance of direct mn measurement • Methods: spectrometers and microcalorimeters • Status of microcalorimeters and prospects • MARE-1: techniques, detectors and sensitivity • MARE-2: new detector technologies • Conclusions

  4. Tools for the investigation of the n mass scale Future sensitivity (a few year scale) Present sensitivity Tools Cosmology (CMB + LSS) 0.7 - 1 eV 0.1 eV Neutrinoless Double Beta Decay 0.5 eV 0.05 eV Single Beta Decay 2.2 eV 0.2 eV Model dependent Direct determination Laboratory measurements Neutrino oscillations cannot provide information about a crucial parameter in neutrino physics: the absolute neutrino mass scale

  5. The modified part of the beta spectrum is over range of the order of [Q – Mnc2 , Q] The count fraction laying in this range is  (Mn/Q)3 low Q are preferred Tritium as an example E – Q [eV] Effects of a finite neutrino mass on the beta decay

  6. Outline of the talk • The physics case: importance of direct mn measurement • Methods: spectrometers and microcalorimeters • Status of microcalorimeters and prospects • MARE-1: techniques, detectors and sensitivity • MARE-2: new detector technologies • Conclusions

  7. Electron analyzer Electron counter Source n T2 b excitation energies electron high activity • high efficiency • low background • high energy resolution • integral spectrum: select Ee > Eth spectrometers MAINZ-TROITZK 2.2 eV - KATRIN (2010)  0.2 eV microcalorimeters MIBETA  15.0 eV • high energy resolution • differential spectrum: dN/dE bolometer When in presence of decays to excited states, the calorimeter measures both the electron and the de-excitation energy

  8. Calorimetry: pros and cons pure b spectrum pile-up spectrum energy [eV] energy region relevant for neutrino mass DE • Drawback • background and systematics induced by pile-up effects • Advantages • no backscattering • no energy loss in the source • no excited final state problem • no solid state excitation (dN/dE)exp=[(dN/dE)theo+ Atr(dN/dE)theo(dN/dE)theo]  R(E) generates “background” at the end-point

  9. Calorimeter requirements A sensitive measurement with the calorimetric method requires: • precise determination of the b energy • high statistics • low pile-up fraction • short pulse-pair resolving time • fractionate the whole detector in many independent elements bound on mn 1 / (Ncounts)1/4 bound on mn (DE)1/2 In terms of detector technology: development of a single element with these features • extremely high energy resolution in the keV range (1 ‰) • very fast risetime (100 ms 1 ms) • high reproducibility of the single element • possibility of multiplexing

  10. Outline of the talk • The physics case: importance of direct mn measurement • Methods: spectrometers and microcalorimeters • Status of microcalorimeters and prospects • MARE-1: techniques, detectors and sensitivity • MARE-2: new detector technologies • Conclusions

  11. Microcalorimeters for 187Re spectroscopy • Calorimeters measure the entire spectrum at once • use low Q beta decaying isotopes to achieve enough statistic close to Q • best choice: 187Re – Q = 2.47 keV - 1 mg natural Re  1 Bq vs. 3x10-10 for T beta spectrum event fraction in the last 10 eV: 1.3x10-7 5/2+ 1/2– unique first forbidden (computable S(Ee)) 187Re 187Os + e- + ne General structure of a microcalorimeter Re crystal coupling coupling heat sink ~ 100 mK sensor a proper sensor convert excitation number to an electrical signal • beta decays produce very low • energy (~ meV) excitations • phonons • quasiparticles a dilution refrigerator provides the necessary low temperatures

  12. True microcalorimeters beta decay thermal phonons transmission to a phonon sensor (thermometer) semiconductor thermistor transition edge sensor (TES) R R MW mW W T T 100 mK 100 mK

  13. MANU (Genoa) MIBETA (Milano/Como) 1 mm 1 mm Energy absorbers • AgReO4 single crystals • 187Re activity  0.54 Hz/mg • M  0.25 mg  A  0.13 Hz Phonon sensors • Si-implanted thermistors • high reproducibility  array • possibility of m-machining • Energy absorber • Metalllic Re single crystals • M  1.5 mg  A  1.5 Hz • Phonon sensor • NTD Ge thermistors • size = 0.1 x 0.1 x 0.23 mm typically, array of 10 detectors lower pile up & higher statistics total collected statistics ~ 365 mg  day 6.2 x 106 decays above 700 eV single crystal total collected statistics: 6. x 106 decays above 420 eV Precursors 187Re experiments

  14. MIBETA MANU Kurie plot beta spectrum Q = 2466.1 0.8 stat  1.5 syseV Q = 2470 1 stat  4 syseV t½ = 43.2 0.2 stat  0.1 sysGy t½ = 41.2  0.02 stat  0.11 sysGy Mb2 = -141  211 stat  90 sys eV2 Mb2 = - 462 + 579 - 679 eV2 Mb< 15 eV (90% c.l.) Mb< 26 eV (95% c.l.)

  15. The future of bolometric experiments: MARE MARE is divided in two phases MARE-2 MARE-1 transition edge sensors (TES) (Ge) semiconductor thermistors (Mi/Co) and TES or magnetic calorimeters or kinetic inductance detectors ~ 50000 elements ~ 300 elements Activity/element ~ 0.25 Hz Activity/element ~ 1-10 Hz TR ~ 100 - 500 ms TR ~ 1 - 10 ms DEFWHM ~ 20 eV DEFWHM ~ 5 eV 0.2 eV mn sensitivity 2-4 eV mn sensitivity • General strategy: push up bolometric technology aiming at: • multiplication of number of channels • improvement of energy resolution • decrease of pulse-pair resolving time

  16. The collaboration Genova NASA Heidelberg Como Milano NIST Boulder ITC-irst PTB Berlin Roma SISSA Wisconsin

  17. Outline of the talk • The physics case: importance of direct mn measurement • Methods: spectrometers and microcalorimeters • Status of microcalorimeters and prospects • MARE-1: techniques, detectors and sensitivity • MARE-2: new detector technologies • Conclusions

  18. Required total statistics (MARE-1) On the basis of the analytical approach to pile-up problem and on preliminary Monte Carlo studies, the sensitivity as a function of the total statistics can be determined, for assumed detector performance in terms of time/energy resolution target statistics

  19. MARE-1 / semiconductor thermistors(Milano / Como) Three options in parallel, in all cases micromachined arrays: Si doped thermistors realized by NASA/Wisconsin collaboration Si doped thermistors realized by irst-ITC, Trento NTD Ge thermistors (LBL, Berkeley) on Si3N4 membranes single pixel 0.3  0.3 mm AgReO4 crystals 36 elements

  20. MARE-1 / semiconductor - single pixel performance Best energy resolution: 19 eV FWHM @ 1.5 keV Fastest risetime: 230 ms (10%-90%) Calibration spectrum obtained at 85 mK M = 0.4 mg Re spectrum Very promising for MARE-1 development

  21. MARE-1 / semiconductor - prospects ~ 400 ms time resolution  ~ 50 ms time resolution 288 elements gradually deployed 0.3 decays/s/element

  22. MARE-1 / transition edge sensors(Genoa) Tc lowered by proximity effect • Two searches are going on in parallel • Ag-Al superconductive hcp d-phase alloy • Ir-Au film Ir\Au\Ir multilayer on Si Resist pattern Ar Ion etching Final result Re crystals

  23. MARE-1 / TES - single pixel performance Energy resolution 11 eV FWHM @ 5.9 keV risetime: 160 ms In a few years, the present limit on neutrino mass (2.2 eV) can be approached

  24. Outline of the talk • The physics case: importance of direct mn measurement • Methods: spectrometers and microcalorimeters • Status of microcalorimeters and prospects • MARE-1: techniques, detectors and sensitivity • MARE-2: new detector technologies • Conclusions

  25. Required total statistics (MARE-2) groups involved in detector developments for future X-ray mission are working for us! tR 1 ms guideline for R&D on single pixel: goals DEFWHM  5 eV multiplexing scheme 10000 element array “kit” guideline for R&D on set-up: goals development of several “kits” target statistics

  26. Candidate techniques for MARE-2 MMC TES NASA-GSFC, Wisconsin, NIST Boulder Kirkhoff Institute of Physics, Heidelberg 450 mm Bi absorber 250 mm Magnetic MicroCalorimeter Mo/Cu TES Si3N4 membrane 55Mn 3.4 eV FWHM

  27. A superconductive strip below the critical temperature has a surface inductance proportional to the penetration depth l ( ~ 50 nm) of an external magnetic field Ls= m0l Zs = Rs + iwLs The impedance is Absorption of quasiparticles changes both Rs and Ls If the strip is part of a resonant circuit, both width and frequency of the resonance are abruptly changed phase variation signal New available technology MKID Multiplexed kinetic inductance detectors Roma, ITC-irst, Cardiff

  28. MKIDs: results Nature, K. Day et al., 2003 Resonance peak Aluminum strip on a Si substrate Equivalent circuit phase signal induced by absorption of a single 5.9 keV photon metallurgic problem: coupling of the Re crystal to the Al film

  29. MARE: statistical sensitivity 10000 detectors deployed per year 50000 channels in 5 y

  30. Outline of the talk • The physics case: importance of direct mn measurement • Methods: spectrometers and microcalorimeters • Status of microcalorimeters and prospects • MARE-1: techniques, detectors and sensitivity • MARE-2: new detector technologies • Conclusions

  31. Neutrino is at the frontier of particle physics Its properties have strong relevance in cosmology and astrophysics • Absolute mass scale, a crucial parameter, is not accessible via flavor oscillations • Direct measurement through single beta decay is the only genuine model independent method to investigate the neutrino mass scale • KATRIN is the only funded next generation experiment (0.2 eV) • Low temperature microcalorimeters can provide an alternate path to the sub-eV region • Microcalorimeters will develop in two phases: MARE-1 - technology already established - 2 eV in 5 y scale MARE-2 - new technologies are required - 0.2 eV in 10 y scale • Unlike spectrometers, microcalorimeter technology can be expanded further

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