HOLMES - The Electron Capture Decay of 163Ho to Measure the

HOLMES - The Electron Capture Decay of 163Ho to Measure
the Electron Neutrino Mass with sub-eV sensitivity
ERC - Advanced Grant 2013
PI: Prof. S. Ragazzi
Host Institution: Istituto Nazionale di Fisica Nucleare (INFN)
Additional Beneficiary: Università di Milano-Bicocca (Resp. Sci.: A. Nucciotti)
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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The HOLMES experiment is aimed at directly measuring the electron neutrino mass using the electron
capture (EC) decay of 163Ho.
A measurement fixing the value of the absolute neutrino mass represents a major breakthrough with
profound consequences in particle physics and cosmology. In fact, due to their abundance as big-bang
relics, massive neutrinos strongly affect the large-scale structure and dynamics of the universe. In
addition, the knowledge of the scale of neutrino masses, together with their hierarchy pattern, is
invaluable to clarify the origin of fermion masses beyond the Higgs mechanism.
The innovation of HOLMES lies in the calorimetric measurement of the energy released in the decay of
163
Ho. This allows to measure all the atomic de-excitation energy, except the fraction carried away by
the neutrino. A finite neutrino mass mν causes a deformation of the energy spectrum which is truncated
at Q-mν, where Q is the EC transition energy. The sensitivity depends on Q - the lower the Q, the higher
the sensitivity - and 163Ho is an ideal isotope with a Q around 2.5keV. The direct measurement exploits
only energy and momentum conservation and is therefore completely model-independent. At the same
time, the calorimetric measurement eliminates systematic uncertainties arising from the use of external
beta sources, as in experiments with beta spectrometers, and minimizes the effect of the atomic deexcitation process uncertainties.
HOLMES will deploy a large array of low temperature microcalorimeters with implanted 163Ho nuclei.
The resulting mass sensitivity will be as low as 0.4eV. HOLMES will be an important step forward in the
direct neutrino mass measurement with a calorimetric approach as an alternative to spectrometry. It will
also establish the potential of this approach to extend the sensitivity down to 0.1eV.
The cutting edge detection techniques developed for HOLMES will also have an impact in many
frontier fields like astrophysics, material analysis, nuclear safety and diagnostic, archaeometry, and
quantum communication.
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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●
●
HOLMES è il coronamento di quasi 20 anni di ricerca nel campo
● della misura diretta della massa del neutrino
● dello sviluppo di rivelatori a bassa temperatura
HOLMES sfrutta le risorse e le competenze presenti nel
Laboratorio Criostati, realizzato presso il Dipartimento di Fisica
in collaborazione con l'INFN
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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Neutrino open questions
mass scale: i.e. mass of the lightest ν
◼ degenerate (m 1 ≈ m 2 ≈ m 3 ) or hierarchical masses
◼
▶
mass hierarchy: m 1 < m 2 ≪ m 3 or m 3 ≪ m 1 ≈ m 2 ?
◼
ν = ν ? i.e. Dirac or Majorana particle?
◼
CP violation in the lepton sector
normal
hierarchy
inverted
hierarchy
mass
scale
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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Direct neutrino mass measurements
kinematics of weak decays with ν emission
▶ low Q nuclear beta decays (3H, 187Re...)
▶ only energy and momentum conservation
▶ no further assumptions
◼ 2 approaches with different systematics:
▶ spectrometry:
spectrometry the β source is outside the
detector
▶ calorimetry:
calorimetry the β source is contained in the
detector which measures all the energy
released except the ν energy
◼
m ν= 0
ΔE=0
m ν> 0
Q-mν
Q
∝ √(Q−E)2−m2ν
electron kinetic energy
≈5 mm
KATRIN
large MAC-E filter
spectrometer with 3H
MARE/ECHO/HOLMES
array of low temperature
microcalorimeters
with 187Re or 163Ho
AgReO4
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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thermometer
T  V
particle absorber
E  T
T = E/C
electro-thermal
link G
temperature
Calorimetry with low temperature detectors
 = C/G
tim
1 mg of Re @ 100 e
mK
C ~ T 3 (Debye) → C ~ 10-13 J/K
→ ΔErms ~ 1 eV
6 keV x-ray
→ ΔT ~ 10 mK
G ~ 10-11 W/K →  = C / G ~ 10 ms
▷
complete energy thermalization
(ionization, excitation → heat) → calorimetry
 T = E/C with C total thermal capacity (phonons, electrons, spins...)
phonons: C ~ T 3 (Debye law) in dielectrics or superconductors below Tc
→ low T (i.e. T≪1K)
▷
Erms = (kB T 2 C)1/2 due statistical fluctuations of internal energy E
▷
T(t) = E/C e-t/ with  = C/G and G thermal conductance
▷
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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HOLMES (ERC-Advanced Grant n. 340321)
http://artico.mib.infn.it/nucriomib/experiments/holmes
goal
●
neutrino mass measurement: mν statistical sensitivity as low as 0.4 eV
●
prove technique potential and scalability:
▶
▶
assess EC Q-value
assess systematic errors
baseline
● Transition Edge Sensors (TES) with 163Ho implanted Au absorbers
●
▶
6.5x1013 nuclei per detector → 300 dec/sec
▶
ΔE≈1eV and τR≈1μs
1000 channel array
▶
▶
6.5x1016 163Ho nuclei → ≈18μg
3x1013 events in 3 years
→ Project Start: 1 Feb 2014
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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Electron capture end-point experiment
Ho + e– → 163Dy* + e
163
electron capture from shell  M1
A. De Rujula and M. Lusignoli, Phys. Lett. B 118 (1982) 429
● calorimetric measurement of Dy atomic de-excitations (mostly non-radiative)
● rate at end-point and ν mass sensitivity depend on Q
keV Recommended: Q = 2.555 keV
► Measured: QEC = 2.22.8 keV.
● ½ ≈4570 years → few active nuclei are needed
O
N
2
N
1
QEC = 2.20
keV
Q
= 2.55
EC
keV
M
2
m = 0
eV
m = 5
eV
m
 = 10
M
1
eV
pile-up
QEC = 2.555 keV
Nev=1014; fpp=10-6; EFWHM=2eV
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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HOLMES tasks
Ho isotope production INFN-Ge
○ 163
Ho isotope embedding in detector INFN-Ge
○ 163
○
single TES optimization and testing INFN-Ge + INFN-MiB/UniMiB
○
TES array design, engineering and testing INFN-Ge + INFN-MiB/UniMiB
○
multiplexed SQUID read-out optimization and testing INFN-MiB/UniMiB
○
room temperature signal processing and in-line analysis INFN-MiB/UniMiB
○
cryogenic set-up INFN-MiB/UniMiB
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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Ho production by neutron activation
163
Er (n,γ) 163Er
162
Er → 163Ho + νe
163
σthermal ≈ 20b
τ½EC ≈ 75min
only few experimental data for almost all cross sections involved
◼ possibly high yield
▶ ≈3⨯1012 163Ho nuclei/mg(162Er)/h for a thermal neutron flux of 1013 n/cm2/s
◼ 163Ho(n,γ)164Ho (burn-up)?
◼ 165Ho(n,γ) (from Ho contaminations or 164Er(n,γ)) → 166mHo, β τ½=1200y
◼
◼
◼
analyse 163Ho content in MARE-RD activated samples → ICPMS
requires enrichement and oxide chemical form (Er2O3)
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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HOLMES detectors
Transition Edge Sensors (TES) with Au absorber
▷ hot electron microcalorimeters with
electro-thermal feedback
▷ 2 μm thick electrodeposited Au for full absorbtion
●
MoAu or MoCu proximity TES → Tc≈100mK
●
on Si2N3 membrane
τd≈30
μs
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
NASA/GSFC
●
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HOLMES detector array fabrication
●
single pixel development @Genova
▷
▷
●
●
array design @Genova
subcontract array fabrication
▷
●
optimize design for speed and resolution
define process for 163Ho implantation
subcontractor fabricates array with 1 μm Au absorber
Genova completes array fabrication
▷
Genova implants
▷
Genova covers implant with 1 μm Au absorber
▷
Genova completes array fabrication (Si2N3 release)
163
163
Ho at shallow depth (≈100Å)
Ho
Ge
A. →
Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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HOLMES detector array and multiplexed read-out
NIST
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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ERC Synergy 2012 (prima call Synergy...)
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●
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NEXHO
PI: S. Ragazzi, F. Gatti, A. Nucciotti
HI: INFN
STEP 1: valutato B (Ranking range : 25-34%)
miglior risultato per i Synergy 2012 proposti dall'INFN
Ground-breaking Group added value Methodology PIs Quality PIs Commitment
referee 1
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referee 2
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referee 3
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referee 4
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FG e AN non sono piaciuti
Non abbiamo capito
cos'è un Synergy...
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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ERC Advanced 2013
NEXHO → HOLMES
● PI: S. Ragazzi
● HI: INFN (Additional beneficiary: Univ. Milano-Bicocca)
Milano-Bicocca
● stesso progetto ma budget ridotto da 9.3M a 3.5M
● migliorie:
● CV del PI
● abstract e synopsis (B1): keywords (ground-breaking, …)
● inglese (con l'aiuto di un collaboratore americano)
STEP 2: valutato A (Ranking range : 1-43%)
budget ridotto di altri 0.5M...
●
●
●
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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Riflessioni
●
●
il PI giusto (prestigio personale vs. opportunità di finanziamento)*
● CV: usare le giuste keywords
● e la HI?
la proposta scritta nel modo giusto
● capire meccanismi di valutazione dell'ERC
● B1 vs. B2
● B1: scritto per non esperti del settore, con tutte le risposte alle possibili critiche
● imparare il linguaggio della commissione: keywords
● importanza dell'autovalutazione
● imparare dai referti (anche di altri progetti...)
● migliorarsi attraverso sottomissioni ripetute (cambiando PI...) *
●
●
●
●
“... These restrictions are designed to allow unsuccessful
Principal Investigators the time to develop a stronger proposal. ...”
approfittare dei servizi di supporto e consulenza
● UniMiB: Area della Ricerca
● INFN: CSTF - Common Strategic Task Force
condizioni al contorno: comunità scientifica amichevole, momento giusto
molta fortuna
* contrario ai principi dell'ERC
A. Nucciotti - Giornata FET e ERC presso UNIMIB - 12 marzo 2014
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