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The low background laboratory at the Gran Sasso National Laboratories
Dr. Matthias LaubensteinLaboratori Nazionali del Gran Sasso
ITALY
Synergies in Low Background Radiation TechniquesUniversity of MinnesotaMinneapolis MN, USA
July 25th, 2005
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Introduction
• Many fundamental experiments aim to detect very weak signals. They have to fight against background of different origin.– cosmic radiation– particles of nuclear decays– intrinsic natural radioactivity⇒ low background α and γ spectroscopy @
L.N.G.S.
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LNGS
In 1979 A. Zichichi makes a proposal to the Italian Parliament for building a large underground laboratory inside the highway tunnel underneath the Gran Sasso, at that time under construction.
In 1982 the Parliament approves theconstruction, then completed in 1987.
In 1989 the first underground experiment, MACRO, is starting data taking.
The EAS-TOP experiment, on Campo Imperatore, already started working from 1987 on.
The birth
QuickTime™ and aPhoto - JPEG decompressor
are needed to see this picture.
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Some very deep underground laboratories
CanfrancSpain
BoulbyUK Modane
France
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Underground laboratories
HALL C
HALL B
HALL A
Borexino
OPERA
LVD
ICARUS
CRESST2
CUORICINO
LBL-2
HDMS
GENIUS-TF
DAMAGerda
LBL-1
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LNGS and the ILIAS EU initiative
ILIAS=
Integrated Large Infrastructures forAstroparticle Science
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ILIAS was proposed under the coordination and review of APPEC (AstroParticle Physics European Coordination)
ILIAS is an initiative supported by the EU VI Framework Programmewith the aim to support the EU Large infrastructures operating in the
astroparticle physics sector
France : Commissariat a l’Energie Atomique, CNRSItaly: Istituto Nazionale di Fisica Nucleare, Istituto di Fotonica e Nanotecnologie Trento,
European Gravitational Observatory
Germany: Max-Planck-Institut für Kernphysik Heidelberg, Technische Universität München, Max-Planck-Institut für Physik München, Eberhardt-Karls-Universität Tübingen
Spain: Zaragoza UniversityUK: Universities of Sheffield, Glasgow, and LondonCzech Rep.: Czech Technical Univ. in PragueDenmark: University of Southern Denmark Netherland: Leiden UniversityFinland: University of Jyväskylä Slovakia: Comelius University BratislavaGreece: Aristotle University of Thessaloniki
Participants
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The ILIAS project is based on three main groups of activities
• Networking activitiesaim: favour the contacts/collaborations among researchers working on
the same fields in different EU countriessupport: organisation of workshops, visits, specific activities
• Transnational Access activitiesaim : support access of EU researchers to major research infrastructuressupport: subsistence and travel costs for host researchers
costs of technical support for the hosting institution
• Joint research activitiesaim : support specific R&D activities conducted jointlysupport: travel costs
personnelequipment and consumables
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Laboratoire Souterrainde Modane, France
Institute of UndergroundScience in Boulby mine,
UK
Laboratorio Subterraneode Canfranc, Spain
LSC
IUS
Laboratori Nazionali delGran Sasso, Italy
LNGS
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A1 : TARI-DUSLTransnational Access to the EU Deep Underground Science Laboratories
N2 : EUNet-DUSLEuropean Network of the Deep
Underground Science Laboratories
J1 : LBT-DUSLow Background Techniques for Deep
Underground Science
Activities of the Deep Underground Laboratories in ILIAS
Joint R&D for the improvement of the strengthening of the low background facilities and know-how of the UG labs
Coordination and networking to support the management of common issues relevant in the operation of the UG Labs
Activity
Support for the transnational access ofresearch teams to the EU underground labs with priority to researchers from less favoured countries
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J1 : Low background techniques for deepUnderground science
MotivationsMotivations ::
Extremely low-level background techniques and instrumentation are an essential requirement for a number of topics in astroparticle physics, f.i.:
v Search for bb decayv Search for Dark matterv Detection of low-energy neutrinos (solar, geo)
Fundamental topics common to most experiments are:- Selection of radiopure materials- Techniques for shielding against environmental backgrounds- Purification techniques
This is the main motivation to carry on a Joint Research Activity onLow Background Techniques coordinated by the 4 UG Labs within ILIAS
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Key Key R&D R&D topicstopics::
v Development and strenthening of the ultra-low background facilitiesand instrumentation in the UG labs
v Measurement and monitoring of the background components in the underground Labs – Development of background simulation codes
v Application of low background techniques to interdisciplinary fields
v R&D on radiopurity of materials and purification techniques.
EUEU Support to Support to LNGS :LNGS :
v Personnel (2 post-docs + 1 technician)v Travel moneyv Contribution to equipment and consumables for selected specific activities
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A1 : Transnational Access
The key objective of the Transnational Access is to offer free access to the
deep Underground labs for EU research teams to carry out short or medium-term
projects using the underground environment and facilities offered by the labs
projects are selected by a User Selection Panel (USP) which meets periodically
EUEU Support to Support to LNGS :LNGS :
v Travel and subsistence money for the host researchersv Contribution to management costs
LNGS was already supported for Transnational Access since December 2001Within contract HPRI-CT-2001-00149 (to be competed in December 2004)
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N2 : Network of the EU Deep Undergr. Labs
Objectives Objectives ::
• Scientific coordination and public communicationseveral specific activities ongoing (R. Antolini)
- open days at the underground labs- preparation of booklet on underground science for general
public- dedicated web pages
• Safety problems and accident preventionExchange of information, visits of experts, ….
• Service Improvement, coordination and extension of deep underground laboratories
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Rock properties
• composition:
Ca 26 %, Si 1 %, Mg 9 %, O 51.5 %,C 12.5 %
<ρ> = (2.71 ± 0.05) g cm-3
<Z> = 11.4
<Z2/A> = 5.7
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Rock properties
radioactivity (in Bq kg-1):
100-20005-5040K
30-3004.5226Ra
80-5005238U
≈900.25-0.5232Th
Mt BlancGran Sasso
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Characteristics
lat. 42o 27’ Nlong. 13o 34’ E
mean depth:3800 m.w.e.
min. depth:3000 m.w.e.
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Muons
muon fluence:≈ 1 µ/(m2⋅h), Eµ>1 TeV
(106 reduction with respect to surface)
LNGS
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Neutrons
neutron flux:e.g. @ L.N.G.S.
fission and (α,n)Φth ≈ 3×10-6 cm-2 s-1
Φfc < 0.3×10-6 cm-2 s-1
(103 reduction)
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Low background counting laboratory
8 (+3) HPGe detectors working
1.9102%413GeMPI p-type
2.04×96%4×225GeMulti p-type
2.0120%465GeCris p-type
2.0113%518GePaolo p-type
1.996%414GsOr p-type
1.891%363GePV p-type
1.986%403GeMi p-type
2.056%235GeBer n-type
FWHM [keV]rel. efficiencyvolume [cm3]type
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Collaboration of European Low-LevelUnderground Laboratories
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University ofIceland
IAEA-MEL
ARCS
LNGS
IRMM
LSCE
VKTA
MPI-K
PTB
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To promote higher quality and sensitivity in ultra low-level radioactivity measurements for the improvement of crisis management, environment, health and consumer protection standards of Europe.
Mission
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Partners:Partners:
(m w.e. = meter water equivalent, the height of water equivalent to that of the actual shielding material)
(~ 1750 m(~ 1750 m ≅≅ 4800 m w.e.4800 m w.e.))LSCE LSCE -- FranceFrance
(~ 1400 m(~ 1400 m ≅≅ 3800 m w.e.3800 m w.e.))LNGS LNGS -- ItalyItaly
(~ 925 m(~ 925 m ≅≅ 2100 m w.e.2100 m w.e.))PTB PTB -- GermanyGermany
(~ 225 m(~ 225 m ≅≅ 500 m w.e.500 m w.e.))IRMM IRMM -- EU EU -- BelgiumBelgium
(~ 165 m(~ 165 m ≅≅ 350 m w.e.350 m w.e.))University of IcelandUniversity of Iceland
(~ 50 m(~ 50 m ≅≅ 110 m w.e.110 m w.e.))VKTA VKTA -- GermanyGermany
(~ 14 m(~ 14 m ≅≅ 30 m w.e.30 m w.e.))IAEAIAEA--MEL MEL -- MonacoMonaco
(~ 8 m(~ 8 m ≅≅ 15 m w.e.15 m w.e.))MPIMPI--Heidelberg Heidelberg -- GermanyGermany
(above ground, (above ground, ~~ 3 m w.e.3 m w.e.))ARC Seibersdorf ARC Seibersdorf -- AustriaAustria
+ 1 associated partner (+ 1 associated partner (NPL NPL -- UKUK))
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What is ULGS?
Ultra Low-level Gamma Spectrometry
i.e. low-level γ-spectrometry with additional background reduction by using active shields, material selection and/or underground laboratories
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Sensitivity
10-11ULGS + NAA
primordial parents
10-10 - 10-7ICP-MS (destructive)
primordial parents
10-8 - 10-7ULGS (non-destructive)
γ emitters
Detection limit for
U and Th [Bq/kg]
Method
1 Bq 238U/kg ≅ ≅ ≅ ≅ 81 x 10-9 g/g1 Bq 232Th/kg ≅ ≅ ≅ ≅ 246 x 10-9 g/g1 Bq 40K/kg ≅ ≅ ≅ ≅ 32 x 10-6 g/g
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e.m. showers are only partially attenuated
Neutron thermalization produces photons through (n,γ) captureInteraction of high energy particles with shielding induces secondary background
γext
High energy muons are not stopped
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e.m. showers are attenuated
Neutron thermalization produces photons through (n,γ) captureInteraction of high energy particles with shielding induces secondary background
γext
high energy muons are reduced by overburden and/or active shield
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100
101
102
103
104
105
106N
orm
alis
ed c
ount
ing
rate
[d-1
kg-1
]
Depth [m w.e.]
0 300100 200 400 500
Muo
n fl
uenc
e ra
te [
a.u.
]
600 700
above ground
VKTA Rossendorf
JRC-IRMM
ARC Seibersdorf
MPI-K-HD
IAEA-MEL
active + passive shieldonly passive shield
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Rn
high energy muons are reduced further deep underground(factor >10-6 reduction @ LSCE & LNGS)
Neutrons now induced from natural radioactivity ((α,n) & fission)(factor 10-3 reduction @ LNGS)
γext
γ's now from natural radioactivity inside shielding and detector components
gas radon becomes important
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BUT … !!!
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10-1
100
101
102
103
104
105
106
Nor
mal
ised
cou
ntin
g ra
te [
d-1kg
-1]
10-2
Depth [m w.e.]
0 30001000 2000 4000 5000
Muo
n fl
uenc
e ra
te [
a.u.
]
LSCE
LNGS
PTBJRC-IRMM
VKTA Rossendorf
above ground
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10-1
100
101
102
103
104
105
106N
orm
alis
ed c
ount
ing
rate
[d-1
kg-1
]
10-2
Depth [m w.e.]
0 30001000 2000 4000 5000
Muo
n fl
uenc
e ra
te [
a.u.
]
199319961997
LNGS
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10-4
10-3
10-2
10-1
100
101
102
103
Nor
mal
ised
cou
ntin
g ra
te [
d-1ke
V-1
kg-1
]
Energy [keV]0 1500500 1000 2000 2500 3000
above groundARC SeibersdorfVKTA RossendorfJRC-IRMMLNGS
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HPGe detectors
shielding:20 cm low activity lead (210Pb < 20 Bq kg-1)
5 cm OFHC copper
5 cm acrylic and Cd foil on the bottom
Rn-suppression:1 cm acrylic cover with continuous N2 flow
material selection:highly radiopure, (almost) no activation
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plus continuous contribution of Ge intrinsic cosmogenics
ANG2 LNGS, no shieldHeidelberg Moscowplot from O. Chkvorets
β+
40K137Cs
ThU60Co
60Co
207Bi
0νββ
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HPGe detectors
0.24 ± 0.03< 0.06< 0.0730 ± 2GeMPI
0.88 ± 0.22< 0.130.29 ± 0.2277 ± 2GeCris
1461 keV583 keV352 keV40-2700 keV
1.8 ± 0.20.31 ± 0.161.1 ± 0.3222 ± 2GePaolo
4.2 ± 0.50.76 ± 0.352.0 ± 0.5442 ± 5GsOr
3.2 ± 0.41.8 ± 0.42.6 ± 0.7498 ± 5GePV
6.1 ± 0.81.4 ± 0.54.1 ± 1.0555 ± 7GeMi
total and peak background count rate [d-1 kg-1Ge] detector
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GeMPIOperated at
LNGS
(3800 m w.e.)
G. HeusserB. Prokosch H. Neder
M. Laubenstein
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effective volume of sample chamber ~ 15 l(e.g. 125 kg Cu or 157 kg Pb)
High purity copper directly placed underground after electrolysis
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OUTLOOK
further improvements possible:
- neutron shield- material selection improved- active shield- going deeper underground- storage of construction material underground- multisegmented crystals or multiple crystals- collaboration with producers
γext
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INFN LNGS, Assergi, ItalyA.Di Vacri, M. Junker, M. Laubenstein, C. Tomei, L. Pandola
JINR Dubna, RussiaS. Belogurov,V. Brudanin, V. Egorov, K. Gusev, S. Katulina,
A. Klimenko, O. Kochetov, I. Nemchenok, V. Sandukovsky, A. Smolnikov, J. Yurkowski, S. Vasiliev,
MPIK, Heidelberg, GermanyC. Bauer, O. Chkvorets, W. Hampel, G. Heusser, W.
Hofmann, J. Kiko, K.T. Knöpfle, P. Peiffer, S. Schönert, J. Schreiner, B. Schwingenheuer, H. Simgen, G. Zuzel
Univ. Köln, GermanyJ. Eberth, D. Weisshaar
Jagiellonian University, Krakow, PolandM.Wojcik
Univ. di Milano Bicocca e INFN, Milano, ItalyE. Bellotti, C. Cattadori
INR, Moscow, RussiaI. Barabanov, L. Bezrukov, A. Gangapshev, V. Gurentsov, V. Kusminov, E. Yanovich
ITEP Physics, Moscow, RussiaV.P. Bolotsky, E. Demidova, I.V. Kirpichnikov, A.A. Vasenko, V.N. Kornoukhov
Kurchatov Institute, Moscow, RussiaA.M. Bakalyarov, S.T. Belyaev, M.V. Chirchenko, G.Y. Grigoriev, L.V. Inzhechik, V.I. Lebedev, A.V. Tikhomirov, S.V. Zhukov
MPI Physik, München, GermanyI. Abt, M. Altmann, C. Bűttner. A. Caldwell, R. Kotthaus, X. Liu, H.-G. Moser, R.H. Richter
Univ. di Padova e INFN, Padova, ItalyA. Bettini, E. Farnea, C. Rossi Alvarez, C.A. Ur
Univ. Tübingen, GermanyM. Bauer, H. Clement, J. Jochum, S. Scholl, K. Rottler
71 physicists / 12 institutions / 4 countries Spokesperson: Stefan Schönert, MPIK Heidelberg
GERDAThe GERmanium Detector Array for the search
of neutrinoless double beta decay of 76Ge
53Ø 4.0 mØ 9.4 m
Ø 3.8 m
h c
a 5
m
8.3
m
2 x 10 cm Pb
1.5 mstainless steel
Vespel or similar
concrete
8x106
Ra-226
1x107
Th-228
9x107
K-40
radio-activity [µµµµBq/kg]
copper
<<<< 20
<<<< 26
<<<< 88
Ge
<<<< 1x10-3
<<<< 1x10-4
<<<< 1x10-2
10 cm Pb
water shield
instrumented with PMT‘s as cosmic veto
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ANG2 LNGS, no shieldHeidelberg Moscowplot from O. Chkvorets
2.039 MeV
envisioned levelfor Gerda
also next step for screening at nBq/kg level
exiting to see what comes up at this level
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Measurements
measurements of direct physics interest:
- 42Ar in natural liquid argon: 42Ar/40Ar ≤10-18
- double beta decay of 96Zr and 150Nd:
T½(96Zr) > 3 × 1019 a
T½(150Nd) > 1 × 1020 a
- Roman Pb (age > 2000 a): 210Pb <1.3 Bq/kg
− β-decay of 115In to 115Sn*: (3.73 ±0.98) × 1020 a
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Cu of Norddeutsche Affinerie (Hamburg, Germany)
NOSV quality
99.9975% (1-4 ppm O2)
anodes 97-99 % + 2000 ppm O2
+...
Ni: % IN ORE < 1-2 ppm
Co: about 5 ppm < 1 ppm40K: 7.5 ±±±± 1.0 mBq/kg < 0.088 mBq/kg226Ra: 1.8 ±±±± 0.4 mBq/kg < 0.020 mBq/kg228Th: < 0.44 mBq/kg < 0.023 mBq/kg
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125 kg NOSV Cu for LENS measured with GeMPIG. Heusser
M. Laubenstein
< 19< 201.91 a228Th (Th)
455 ± 12044.5 d59Fe
53 ± 1883.79 d46Sc
110 ± 4015.97 d48V
primordial
< 16< 351600 a226Ra (U)
unexposedexposed (270 d)cosmogenic
< 88< 1201.277 × 109 a40K
215 ± 21312.15 d54Mn
activity [µBq/kg]halfliferadionuclide
< 102100 ± 1905.27 a60Co
1650 ± 9070.86 d58Co
1800 ± 400271.83 d57Co
230 ± 3077.31 d56Co
Cosmogenic* and primordial radioactivity concentrations in Cu
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Development and strengthening of the ultra low-level background facilities (LNGS)
Ø Extension of the Low Level Laboratory at LNGSØ Development of new generation of HP-Ge detectors for Ultra-low level applicationsØ Set-up of ultra low-level scintillation counter systemsØ Ultra low-level gas counting (GNO low counting lab)
GNO Ultra low-level gas countingUltra low-level HPGe detector @ LNGS
Other activites
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Measurement and monitoring of the background componentsunderground
- Development of detectors for determination of neutron and gamma flux and spectrum
- Coordinated measurement and comparison of neutron and gamma spectra in all 4 UGlabs
- Set-up of Rn monitoring systems in air and water inside all 4 UG labs
New measurement and monitoringof n spectrum (INFN Pv)
γ-ray mapping in the LNGS
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v Application of low backgroundtechniques to interdisciplinary fields
- low-level environmental radioactivity measurement and monitoring
- Radiodating laboratory
- Geophysics
v Radiopurity of materials andpurification techniques
- Set-up a database containing relevant information on radiopurity of materials commonly used for low background applications. Setting up an efficient database is not a trivialjob.
- Measurement of poorely known radiopurity ofmaterials with possible applcations within ultra-low background esperiments
- Cross-check of measuring methods available at the different labs.
W.Plastino, L. Kaihola
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