The LUNA experiment - PowerPoint Presentation

Slide1

The LUNA experiment Laboratory for Underground Nuclear Astrophysics

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et Rayons Cosmiques

Slide2

Why studying nuclear fusion reaction cross sections?

-

Stars

are powered by nuclear reactions They determine:stellar evolution and dynamicselements origin and abundances neutrino production

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Slide3

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 neutrinosHeavy elements nucleosynthesis

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Slide4

Holy Grail of Nuclear Astrophysics

Oxygen-16

Most

important

reaction

in

He-

burning

phase

Determines

Carbon

-Oxygen

abundance

in

the

universe

Influences

late

stellar

evolution

nucleosynthesis

of

heavy

elementsCarbon/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)

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3

12

C(

,)

16

O

Slide5

nucleosynthesis of heavy elements

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et Rayons Cosmiques 413C(a,n)16O 22Ne(a,n)25Mg

Heavy elements are produced in neutron capture processes

neutron sources

Slide6

Neutrino production in the Sun

Neutrino flux from the Sun

can be used to study:

Solar interior compositionNeutrino properties

ONLY if the cross sections of the involved reactions are accurately knownONLY if the cross sections of the involved reactions are accurately known

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p + p



d + e

+

+

n

e

d + p



3

He +

g

3

He +

3

He



a

+ 2p

3

He +4He  7Be

+ g

7Be+e- 7Li + g +ne 7Be + p 

8B

+

g

7

Li +

p



a

+

a

8

B



2

a

+ e

+

+

n

e

84.7 %

13.8 %

13.78 %

0.02 %

pp

chain

Slide7

Extremely low measured reaction rate

Why going in an underground laboratory?

It is mandatory to have very low background

7Perform measurements 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!!

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C(

a,g

)

16

O

Surface

Underground

Slide8

LUNA site

LUNA 1

(1992-2001)50 kV

LUNA 2

(2000…)400 kV

L

aboratory for Underground

Nuclear Astrophysics

Radiation

LNGS/surface

Muons

Neutrons

10

-6

10

-3

LNGS (1400

m rock shielding



4000 m w.e.)

LUNA MV

(

2018->...)

3.5 MV

8

7

Slide9

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)15

O: determination of age of the globular clusters (age of the universe) 3He(4

He,g)7Be: precise determination of 8

B and 7Be neutrino flux d(4He,g)7Li: Li –problem in BBNLUNA 2 accelerator : 400 kVLUNA 1 accelerator: 50 kV

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At the moment unique accelerator facility underground

Slide10

LUNA MV

The scientific program

: 3He(4He,g

)7Be: solar neutrinos13C(a,n)16O:

22Ne(a,n)25Mg12C(a,g)16O: C/O ratio in the universe SN Type II, Type Ia…Heavy elements nucleosynthesis3.5 MV accelerator

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existing meas

.

existing meas

.

LUNA-MV

LUNA-MV

Slide11

Experimental challenges12C(a,g)16O : - extremely pure (10-7) and stable solid carbon target - high efficiency, high resolution and bck-free gamma-detector13C(a,n)16O, 22Ne(a,n)25Mg : - dense and pure 22Ne gas target - high efficiency and

bck-free neutron detector

Carbon target

(

CSNSM-Orsay)Sidonie implanter at CSNSM: consolidated expertise in high pure implanted targetsNeutron detector (CPPM)Expertise in :detector simulation and characterization - low background environmentProximity of neutron facility (C

adarache) good occasion to develop new expertise (neutron detection)

(Possible) French contribution

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Slide12

Status of the LUNA-MV projectFebruary 2013 the “Starting up the LUNA MV Collaboration” workshop was organized at the LNGSSeptember 2013: different WG were formedNeutron 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:AcceleratorSite preparationShieldings

Beam-lines

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Slide13

2014-2015 Site definition -Tender for the accelerator- Beam lines and detectors R&D2016 beginning of Site preparation - Infrastructures2017 Accelerator arrival at LNGS – Shielding – beam lines construction2018 Calibration of the apparatus and first beam on targetSchedule

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et Rayons Cosmiques 13A USA project (CASPAR) is aiming to install a 1 MV machine at the SURF lab (Homestake): time schedule similar to LUNA-MVCollaboration has started with CASPAR project

Competitive project

Slide14

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 2015-2020LUNA-MV looks for collaboratorsConnected to the Cosmology, Astrophysics and Particle physicsSmall 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)

Slide15

BACKUP slides

Slide16

Cross section and astrophysical S factor

Gamow energy region

Astrophysical factor

Cross section of the order of pb!

Gamow factor

event/month < Rate

lab

< event/day

e

~ 10 %

I

P

~ mA



~

m

g/cm

2

Rate

lab

=

 ·  · I

p

·  · N

av

/A

Reaction rate in the lab

Extrapolation is needed !!

16

IPHC 29

th

November

2013

Slide17

Ratelab > Bkgcosm+ Bkg

env

+ Bkg

beam induced

Cross section measurement requirements

Impurities in beam, targets, apertures

mainly U-

Th

chains

Passive shielding

cnts/hour

mainly muons

Going underground

10

3

reduction at E



>4 MeV

17

IPHC 29

th

November

2013

Slide18

12C(,)

16

O: status of the art and requirements

Needs angular distribution measurements (E1 and E2)

High beam currents (>500 µA)Ultraclean Vacuum < 10-8mbarHigh target density (~2 1018 at/cm2)

13C depletion level <10-6 (ideal 10-7:

could be measured using 13C(p,)14N 1.75 MeV resonance)Detection Efficiency 100 times higher prev.

exp (HPGe or Scintillator ball)

Need and requirements:

18

Slide19

Reaction-rate prediction

Summing peak detection

Single angle detection

Conditions:

target areal density: 2 1018 at/cm2I=500 µA

19

Slide20

13C(a,n)16O: status of the art

Big uncertainties in

R-matrix extrapolations

Heil 2008

Needs and requirements:

High detection efficiency Low neutron production (LNGS constraints) Possibly some energy resolution to signal/background identification Neutron shield to decrease natural background

E

n

>2.2 MeV

20

IPHC 29

th

November

2013

Slide21

22Ne(a,n)25Mg: status of the art

Unmeasured resonance at E=635 keV



big uncertainties in the reaction rate.

Jaeger 2001Needs and requirements

: High detection efficiency Low neutron production (LNGS constraints) Possibly some energy resolution to signal/background identification

Neutron shield to decrease natural background - Extremely pure target

0.1 MeV <E

n

< 0.45 MeV

21

IPHC 29

th

November

2013

Slide22

13C(a,n)16O :Expected rate

efficiency ~ 10%

Lowest data

Feasible at the 400 kV acc. too

22

Conditions:

target areal density: 1 10

18

at/cm

2

I=100 µA

IPHC 29

th

November

2013

Slide23

22Ne(a,n

)

25Mg :Expected rate

efficiency ~ 10%

23

Conditions:

target areal density: 1 10

18 at/cm2I=100 µA

Lowest data

IPHC 29

th

November

2013

Slide24

Current measurement: 2H(a,g)6Li

[F. Hammache et al., Phys. Rev. C 82, 065803 (2010)]

Direct

measurements:Robertson et al.: E > 1 MeVMohr et al. :0.7

MeV resonance

Indirect

measurements:Kiener et al

Hammache

et al.

upper

limits

with

high

energy

Coulomb break-

up

At

LUNA

direct

measurements

at

the

energies of astrophysical interest

Discrepancy between observed and predicted

6

Li from BBN

2

H(

a,g

)

6

Li produces almost all

6

Li during BBN

24

Slide25

Motivations for 3He(,)7Be

B depends on nuclear physics and astrophysics inputs 

B= B (SSM) · s

33-0.43 s34 0.84 s171 se7-1 spp-2.7 · com1.4 opa2.6 dif 0.34 lum7.2 These give flux variation with respect to the SSM calculation when the input X is changed by x = X/X(SSM) .Can learn astrophysics if nuclear physics is known well enough.

Source

D

X/X (1s)

DF

B

/F

B

(

1s)

S33

0.06

0.03

S34

0.09

0.08

S17

0.05 ?

0.05

Se7

0.02

0.02

Spp

0.02

0.05

Com

0.06

0.08

Opa

0.02

0.05

Dif

0.10

0.03

Lum

0.004

0.03

Nuclear physics uncertainties, particularly on S

34

, dominate over the present observational accuracy



B

/



B

=3.5%

from SNO and SuperKamiokande experiments

Slide26

Physics cases of LUNA MVDavide Trezzi (for the LUNA collaboration) @ LNGS, March 19th, 2013

3He(

α,γ)7Be: Experimental status of the art

A NEW MEASUREMENT IS NECESSARY

Even if only the modern datasets are considered there is a significant scatter among the experimental data points. The datasets are statistically consistent taking into account the respective uncertainties, but the resulting final uncertainty is higher than what is needed for the solar models.