MAREMAREMicrocalorimeterArrays for aRheniumExperiment

A DETECTOR OVERVIEWA DETECTOR OVERVIEW

Andrea Giuliani, University of Insubria, Como, and INFN Milano

on behalf of the MARE collaboration

The physics case: importance of direct m measurement

Methods: spectrometers and microcalorimeters

Status of microcalorimeters and prospects

MARE-1: techniques, detectors and sensitivity

MARE-2: new detector technologies

Conclusions

Outline of the talkOutline of the talk

The physics case: importance of direct m measurement

Methods: spectrometers and microcalorimeters

Status of microcalorimeters and prospects

MARE-1: techniques, detectors and sensitivity

MARE-2: new detector technologies

Conclusions

Outline of the talkOutline of the talk

Tools for the investigation of the Tools for the investigation of the mass scale mass scale

0.7 - 1 eV

0.5 eV

2.2 eV

0.1 eV

0.05 eV

0.2 eV

Presentsensitivity

Future sensitivity

(a few year scale)

Cosmology (CMB + LSS)

Neutrinoless Double Beta Decay

Single Beta Decay

Tools

Model dependentDirect determinationLaboratory measurements

Neutrino oscillations cannot provide information about a crucialparameter in neutrino physics: the absolute neutrino mass scale

Effects of a finite neutrino mass on the beta decayEffects of a finite neutrino mass on the beta decay

The count fraction laying in this range is (MQ)3

low Q are preferred

The modified part of the beta spectrum is over range of the order of [Q – Mc2 , Q]

E – Q [eV]

Tritiumas an example

The physics case: importance of direct m measurement

Methods: spectrometers and microcalorimeters

Status of microcalorimeters and prospects

MARE-1: techniques, detectors and sensitivity

MARE-2: new detector technologies

Conclusions

Outline of the talkOutline of the talk

Source Electron analyzer Electron counter

T2

high activityhigh energy resolution integral spectrum: select Ee > Eth

high efficiency low background

spectrometers spectrometers MAINZ-TROITZK 2.2 eV - KATRIN (2010) 0.2 eV

electron

excitation energies

When in presence of decays toexcited states, the calorimeter

measures both the electron and the de-excitation energy

bolometer high energy resolution differential spectrum: dN/dE

microcalorimeters microcalorimeters MIBETA 15.0 eV

Advantages no backscattering no energy loss in the source no excited final state problem no solid state excitation

Drawback background and systematics induced by pile-up effects

(dN/dE)exp=[(dN/dE)theo+ Ar(dN/dE)theo (dN/dE)theo] R(E)

generates “background” at the end-point

energy [eV]

pure spectrum

pile-up spectrum

Eenergy region relevant

for neutrino mass

Calorimetry: pros and consCalorimetry: pros and cons

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 s 1 s) high reproducibility of the single element possibility of multiplexing

Calorimeter requirementsCalorimeter requirements

A sensitive measurement with the calorimetric method requires:

precise determination of the energy high statistics low pile-up fraction

short pulse-pair resolving time fractionate the whole detector in many independent elements

bound on m (E)1/2 bound on m 1 / (Ncounts)1/4

The physics case: importance of direct m measurement

Methods: spectrometers and microcalorimeters

Status of microcalorimeters and prospects

MARE-1: techniques, detectors and sensitivity

MARE-2: new detector technologies

Conclusions

Outline of the talkOutline of the talk

187Re 187Os + e- + e5/2+ 1/2– unique first forbidden (computable S(Ee))

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

Microcalorimeters for Microcalorimeters for 187187Re spectroscopyRe spectroscopy

Re crystalsensor

heat sink~ 100 mK

beta decays produce very low energy (~ meV) excitations phonons quasiparticles

a proper sensorconvert excitation

number to anelectrical signal

a dilution refrigerator provides the necessary

low temperatures

General structure of a microcalorimeter

coupling coupling

True microcalorimetersTrue microcalorimeters

beta decay

thermal phonons

transmission to a phonon sensor(thermometer)

semiconductor thermistor transition edge sensor (TES)

T

R

100 mK T

R

100 mK

M m

Precursors Precursors 187187Re experimentsRe experiments

MANU MANU (Genoa)

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

single crystal total collected statistics:6. x 106 decays above 420 eV

1 mm

MIBETA MIBETA (Milano/Como)

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 -machining

typically, array of 10 detectorslower pile up & higher statisticstotal collected statistics ~ 365 mg day6.2 x 106 decays above 700 eV

1 mm

MIBETAMIBETA

Kurie plot

Q = 2466.1 0.8 stat 1.5 sys eV

½ = 43.2 0.2 stat 0.1 sys Gy

M 2 = -141 211 stat 90 sys eV2

M15 eV (90% c.l.)

MANUMANU

beta spectrum

Q = 2470 1 stat 4 sys eV

½ = 41.2 0.02 stat 0.11 sys Gy

M 2 = - 462 + 579 - 679 eV2

M26 eV (95% c.l.)

The future of bolometric experiments: MAREThe future of bolometric experiments: MARE

General strategy: push up bolometric technology aiming at: multiplication of number of channels improvement of energy resolution decrease of pulse-pair resolving time

MARE is divided in two phases

MARE-2

TES or magnetic calorimetersor kinetic inductance detectors

~ 50000 elements

0.2 eV m sensitivity

MARE-1

semiconductor thermistors

(Mi/Co)

transition edge sensors (TES)

(Ge)~ 300 elements

2-4 eV m sensitivity

and

Activity/element ~ 0.25 HzTR ~ 100 - 500 sEFWHM ~ 20 eV

Activity/element ~ 1-10 HzTR ~ 1 - 10 sEFWHM ~ 5 eV

Genova

NASA

Heidelberg

Como

Milano

NIST Boulder

ITC-irst

PTB Berlin

Roma

SISSA

Wisconsin

The collaborationThe collaboration

The physics case: importance of direct m measurement

Methods: spectrometers and microcalorimeters

Status of microcalorimeters and prospects

MARE-1: techniques, detectors and sensitivity

MARE-2: new detector technologies

Conclusions

Outline of the talkOutline of the talk

target statistics

Required total statistics (MARE-1)Required total statistics (MARE-1)

On the basis of the analytical approach to pile-up problem and on preliminaryMonte Carlo studies, the sensitivity as a function of the total statistics can be determined, for assumed detector performance in terms of time/energy resolution

MARE-1 / semiconductor thermistorsMARE-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 pixel0.3 0.3 mm

AgReO4

crystals

36 elements

Best energy resolution: 19 eV FWHM @ 1.5 keV

Fastest risetime: 230 s (10%-90%)

MARE-1 / semiconductor - single pixel performanceMARE-1 / semiconductor - single pixel performance

Calibration spectrum obtained at 85 mK

M = 0.4 mg

Very promising for MARE-1 development

Re spectrum

288 elements gradually deployed0.3 decays/s/element

~ 400 s time resolution

~ 50 s time resolution

MARE-1 / semiconductor - prospectsMARE-1 / semiconductor - prospects

MARE-1 / transition edge sensorsMARE-1 / transition edge sensors(Genoa)

Two searches are going on in parallel Ag-Al superconductive hcp phase alloy Ir-Au film

Tc lowered by proximity effect

Ir\Au\Ir multilayer on Si

Resist pattern

Ar Ion etching

Final result

Re crystals

risetime: 160 s

Energy resolution11 eV FWHM@ 5.9 keV

In a few years, the present limit on neutrino mass (2.2 eV) can be approached

MARE-1 / TES - single pixel performanceMARE-1 / TES - single pixel performance

The physics case: importance of direct m measurement

Methods: spectrometers and microcalorimeters

Status of microcalorimeters and prospects

MARE-1: techniques, detectors and sensitivity

MARE-2: new detector technologies

Conclusions

Outline of the talkOutline of the talk

Required total statistics (MARE-2)Required total statistics (MARE-2)

target statistics

guideline for R&D on single pixel: goalsR 1 sEFWHM 5 eV

guideline for R&D on set-up: goals

multiplexing scheme

10000 element array “kit”

development of several “kits”

groups involved in detector developments for future X-ray mission are working for us!

Candidate techniques Candidate techniques for MARE-2for MARE-2

NASA-GSFC, Wisconsin, NIST Boulder

450 m

250 m

Bi absorber

Si3N4 membrane Mo/Cu TES

TES

55Mn

Kirkhoff Institute of Physics, Heidelberg

Magnetic MicroCalorimeter

3.4 eV FWHM

MMC

New available technologyNew available technology

MKID Multiplexed kinetic inductance detectors

A superconductive strip below the critical temperature has a surface inductance proportional to the penetration depth ( ~ 50 nm) of an external magnetic field

Ls = 0

The impedance is Zs = Rs + iLs

Absorption of quasiparticles changes both Rs and Ls

If the strip is part of a resonant circuit, both width and frequency of the resonanceare abruptly changed

Roma, ITC-irst, Cardiff

phase variation signal

Aluminum strip on a Si substrate Equivalent circuit Resonance peak

phase signal induced by absorptionof a single 5.9 keV photon

metallurgic problem:

coupling of the Re crystal to the Al film

MKIDs: resultsMKIDs: results Nature, K. Day et al., 2003

MARE: statistical sensitivityMARE: statistical sensitivity

50000 channels in 5 y10000 detectorsdeployed per year

The physics case: importance of direct m measurement

Methods: spectrometers and microcalorimeters

Status of microcalorimeters and prospects

MARE-1: techniques, detectors and sensitivity

MARE-2: new detector technologies

Conclusions

Outline of the talkOutline of the talk

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