Introduction to Underground Physics

Dr. Matthias Laubenstein Laboratori Nazionali del Gran Sasso ITALY

Scientific Fair at GSSI L’Aquila, Italy November 3rd, 2015 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 ⇒ underground experiments

November 3rd, 2015 Science Fair @ GSSI 2 Some very deep underground laboratories

Boulby SURF UK Modane SD, USA France

Canfranc CJPL Spain China

November 3rd, 2015 Science Fair @ GSSI 3 IUS

Institute of Underground Science in Boulby mine, UK Laboratoire Souterrain de Modane, France

LNGS

LSC Laboratori Nazionali del Laboratorio Subterraneo Gran Sasso, Italy de NovemberCanfranc, 3rd, Spain 2015 Science Fair @ GSSI 4 The birth

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 the construction, 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.

November 3rd, 2015 Science Fair @ GSSI 5 November 3rd, 2015 Science Fair @ GSSI 6 November 3rd, 2015 Science Fair @ GSSI 7 November 3rd, 2015 Science Fair @ GSSI 8 November 3rd, 2015 Science Fair @ GSSI 9 November 3rd, 2015 Science Fair @ GSSI 10 Underground laboratories

Lucifer HALL B

Borexino HALL C

LVD Darkside LUNA Xenon1T OPERA Gerda DAMA VIP STELLA CRESST Cobra CUORE

HALL A

November 3rd, 2015 Science Fair @ GSSI 11 Low background techniques for deep Underground science

Motivations :

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 decay v Search for Dark matter v 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

November 3rd, 2015 Science Fair @ GSSI 12 Rock properties

• composition: Ca 26 %, Si 1 %, Mg 9 %, O 51.5 %, C 12.5 %

<ρ> = (2.71 ± 0.05) g cm-3 = 11.4 = 5.7

November 3rd, 2015 Science Fair @ GSSI 13 Rock properties

radioactivity (in Bq kg-1): Gran Sasso Mt Blanc 232Th 0.25-0.5 ≈90 238U 5 80-500 226Ra 4.5 30-300 40K 5-50 100-2000

November 3rd, 2015 Science Fair @ GSSI 14 Characteristics lat. 42o 27’ N long. 13o 34’ E mean depth: 3800 m.w.e. min. depth: 3000 m.w.e.

November 3rd, 2015 Science Fair @ GSSI 15 Muons

2 muon fluence: ≈ 1 µ/(m ⋅h), Eµ>1 TeV (106 reduction with respect to surface)

November 3rd, 2015 Science Fair @ GSSI 16 Neutrons neutron flux: e.g. @ L.N.G.S. fission and (α,n) -6 -2 -1 Φth ≈ 3×10 cm s -6 -2 -1 Φfc < 0.3×10 cm s (103 reduction)

November 3rd, 2015 Science Fair @ GSSI 17 November 3rd, 2015 Science Fair @ GSSI 18 November 3rd, 2015 Science Fair @ GSSI 19 CELLAR Collaboration of European Low-level underground LAboRatories

November 3rd, 2015 Science Fair @ GSSI 20 IRMM University of PTB Iceland

VKTA LSCE MPI-K IRSN

IFIN-HH IAEA-MEL LNGS University of SL Insubria

November 3rd, 2015 Science Fair @ GSSI 21 Mission 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.

November 3rd, 2015 Science Fair @ GSSI 22 Some of the partner laboratories:

Seibersdorf Laboratories- Austria (above ground, ~ 3 m w.e.) MPI-Heidelberg - Germany (~ 8 m ≅ 15 m w.e.) IAEA-MEL - Monaco (~ 14 m ≅ 30 m w.e.) VKTA - Germany (~ 50 m ≅ 110 m w.e.) University of Iceland (~ 165 m ≅ 350 m w.e.) IRMM - EU - Belgium (~ 225 m ≅ 500 m w.e.) PTB - Germany (~ 925 m ≅ 2100 m w.e.) LNGS - Italy (~ 1400 m ≅ 3800 m w.e.) LSCE - France (~ 1750 m ≅ 4800 m w.e.)

(m. w.e. = meter water equivalent, the height of water equivalent to that of the actual shielding material)

November 3rd, 2015 Science Fair @ GSSI 23 γext

High energy muons are not stopped

e.m. showers are only partially attenuated

Neutron thermalization produces photons through (n,γ) capture Interaction of high energy particles with shielding induces secondary background November 3rd, 2015 Science Fair @ GSSI 24 November 3rd, 2015 Science Fair @ GSSI 25 106

above ground

] 5

-1 10

ARC Seibersdorf kg -1 104 MPI-K-HD VKTA Rossendorf 103

IAEA-MEL JRC-IRMM 102 Muon fluence rate [a.u.] rate Muon fluence 101

Normalised counting rate [d counting Normalised rate active + passive shield only passive shield 100 0 100 200 300 400 500 600 700 Depth [m w.e.]

November 3rd, 2015 Science Fair @ GSSI 26 γext

high energy muons are reduced by overburden and/or active shield

e.m. showers are attenuated

Neutron thermalization produces photons through (n,γ) capture Interaction of high energy particles with shielding induces secondary background November 3rd, 2015 Science Fair @ GSSI 27 106

105 above ground ] -1 4

kg 10 -1 VKTA Rossendorf 103 PTB LSCE JRC-IRMM 2 10 LNGS 101

0 10 [a.u.] rate Muon fluence

Normalised counting rate [d counting Normalised rate 10-1

10-2 0 1000 2000 3000 4000 5000 Depth [m w.e.] November 3rd, 2015 Science Fair @ GSSI 28 gas radon becomes important γext 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) γ's now from natural radioactivity inside shielding and detector components November 3rd, 2015 Science Fair @ GSSI 29 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

November 3rd, 2015 Science Fair @ GSSI 30 106

105

] -1 4

kg 10 -1

103 LNGS

2 1993 10 1996 1 1997 10 2005 0 10 [a.u.] rate Muon fluence

Normalised counting rate [d counting Normalised rate 10-1

10-2 0 1000 2000 3000 4000 5000 Depth [m w.e.] November 3rd, 2015 Science Fair @ GSSI 31 103 above ground ARC Seibersdorf

VKTA Rossendorf

] 2 10 JRC-IRMM -1 LNGS kg -1 101 keV -1 100

10-1

10-2

10-3 Normalised counting rate [d counting Normalised rate 10-4 0 500 1000 1500 2000 2500 3000

November 3rd, 2015 Science EnergyFair @ GSSI [keV ] 32 ANG2 LNGS, no shield Heidelberg Moscow plot from O. Chkvorets

β+ 137Cs 40K 60Co U

207Bi Th

0νββ 60Co

plus continuous contribution of Ge intrinsic cosmogenics

November 3rd, 2015 Science Fair @ GSSI 33 γext 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

November 3rd, 2015 Science Fair @ GSSI 34