Laboratory for Underground Nuclear Astrophysics The LUNA experiment Laboratory for Underground Nuclear Astrophysics Reunion prospective: Univers et Rayons Cosmiques

Why studying nuclear fusion reaction cross sections? - Stars are powered by nuclear reactions They determine: stellar evolution and dynamics elements origin and abundances neutrino production Reunion prospective: Univers et Rayons Cosmiques 1

Heavy elements nucleosynthesis LUNA MV The scientific program: 12C(a,g)16O: Carbon/Oxygen in the universe SN Type II, Type Ia… 13C(a,n)16O: 22Ne(a,n)25Mg: 3He(4He,g)7Be: Solar neutrinos Heavy elements nucleosynthesis Reunion prospective: Univers et Rayons Cosmiques 2

12C(,)16O Holy Grail of Nuclear Astrophysics Oxygen-16 12C(,)16O Most important reaction in He-burning phase Determines Carbon-Oxygen abundance in the universe Influences late stellar evolution nucleosynthesis of heavy elements Carbon/Oxygen determines: dynamics of SN type II end of heavy stars (Black Hole, Neutron star) peak-luminosity and shape of SN type Ia (standard candles in measurements of cosmological distances) Reunion prospective: Univers et Rayons Cosmiques 3

nucleosynthesis of heavy elements Heavy elements are produced in neutron capture processes 13C(a,n)16O neutron sources 22Ne(a,n)25Mg Reunion prospective: Univers et Rayons Cosmiques 4

Neutrino production in the Sun p + p  d + e+ + ne d + p  3He + g 3He +3He  a + 2p 3He +4He  7Be + g 7Be+e- 7Li + g +ne 7Be + p  8B + g 7Li + p  a + a 8B 2a + e++ ne 84.7 % 13.8 % 13.78 % 0.02 % pp chain ONLY if the cross sections of the involved reactions are accurately known Neutrino flux from the Sun can be used to study: Solar interior composition Neutrino properties ONLY if the cross sections of the involved reactions are accurately known Reunion prospective: Univers et Rayons Cosmiques 6

Why going in an underground laboratory? Energy range in stars ~ kTstar ( ~ 10 keV for H-burning ; ~ 100 keV for He-burning) Due to Coulomb barrier, cross section ~ pbarn-fbarn …even less!! Extremely low measured reaction rate 12C(a,g)16O It is mandatory to have very low background Surface Underground Perform measurements in an underground laboratory Reunion prospective: Univers et Rayons Cosmiques 7

Laboratory for Underground Nuclear Astrophysics LUNA site LNGS (1400 m rock shielding  4000 m w.e.) LUNA MV (2018->...) 3.5 MV LUNA 1 (1992-2001) 50 kV LUNA 2 (2000…) 400 kV Radiation LNGS/surface Muons Neutrons 10-6 10-3 7

Key nuclear reactions studied with LUNA1, LUNA2 LUNA 1: 3He(3He,2p)4He ; first direct measurement at solar energies (neutrino problem) LUNA 2: 14N(p,g)15O: determination of age of the globular clusters (age of the universe) 3He(4He,g)7Be: precise determination of 8B and 7Be neutrino flux d(4He,g)7Li: Li –problem in BBN LUNA 1 accelerator: 50 kV LUNA 2 accelerator : 400 kV At the moment unique accelerator facility underground Reunion prospective: Univers et Rayons Cosmiques 9

Heavy elements nucleosynthesis LUNA MV The scientific program: 3He(4He,g)7Be: solar neutrinos 13C(a,n)16O: 22Ne(a,n)25Mg 12C(a,g)16O: C/O ratio in the universe SN Type II, Type Ia… Heavy elements nucleosynthesis 3.5 MV accelerator LUNA-MV LUNA-MV existing meas. existing meas. Reunion prospective: Univers et Rayons Cosmiques 10

Experimental challenges 12C(a,g)16O : - extremely pure (10-7) and stable solid carbon target - high efficiency, high resolution and bck-free gamma-detector 13C(a,n)16O, 22Ne(a,n)25Mg : - dense and pure 22Ne gas target - high efficiency and bck-free neutron detector (Possible) French contribution Carbon target (CSNSM-Orsay) Sidonie implanter at CSNSM: consolidated expertise in high pure implanted targets Neutron detector (CPPM) Expertise in : detector simulation and characterization - low background environment Proximity of neutron facility (Cadarache) good occasion to develop new expertise (neutron detection) Reunion prospective: Univers et Rayons Cosmiques 11

Status of the LUNA-MV project February 2013 the “Starting up the LUNA MV Collaboration” workshop was organized at the LNGS September 2013: different WG were formed Neutron detector (F. Cassol) Solid carbon targets (A. Formicola) Gamma detector (R. Menegazzo) LUNA-MV has been financed with a total of 5.3 Meuro by Italian Research Ministry: Accelerator Site preparation Shieldings Beam-lines Reunion prospective: Univers et Rayons Cosmiques 12

Schedule 2014-2015 Site definition -Tender for the accelerator- Beam lines and detectors R&D 2016 beginning of Site preparation - Infrastructures 2017 Accelerator arrival at LNGS – Shielding – beam lines construction 2018 Calibration of the apparatus and first beam on target Competitive project A USA project (CASPAR) is aiming to install a 1 MV machine at the SURF lab (Homestake): time schedule similar to LUNA-MV Collaboration has started with CASPAR project Reunion prospective: Univers et Rayons Cosmiques 13

“ We are made of star-stuff” Interested people at CPPM: J. Busto, F. Cassol, H. Costantini preliminary work: Feb. 2013-Dic. 2013 present status: frozen participation due to: 2 years delay of the project (change of location at LNGS) at present no French critical mass (CPPM, CSNSM only) ...... Something to keep in mind for 2015-2020 LUNA-MV looks for collaborators Connected to the Cosmology, Astrophysics and Particle physics Small scale experiment: small investment for good quality physics Short time needed for physics results Ideal experiment for students (from experimental work to data analysis and astrophysical implications) “ We are made of star-stuff” (Carl Sagan 1973)