Nuclear Astrophysics at the Gran SassoUnderground Laboratory

Laboratory Underground Nuclear

Astrophysics

Heide Costantini

INFN, Genova, Italy

Outline

• Nuclear fusion reactions in Stars

• Why going underground ?

• The LUNA experiment:

- Main nuclear reactions studied

- Experimental techniques and challenges

• Future perspective in underground nuclear astrophysics

Elements are produced inside stars during their life

H burning → He He burning → C, O, Ne

C/O … Si burning → Fe

explosive burning

12C 15N

13C 14N

13N 15O

(p,γ)

(p,γ)

(p,γ)

(p,α)

e+ν

e+ν

CN

16O

17O

17F

(p,α)

(p,γ)e

+ν

NO

(p,γ) 18O

18F(p,γ)

e+ν

(p,α)

p + p → d + e+ + ne

d + p → 3He + g

3He +3He → a + 2p 3He +4He → 7Be + g

7Be+e-→ 7Li + g +ne7Be + p → 8B + g

7Li + p → a + a 8B→ 2a + e++ ne

84.7 % 13.8 %

13.78 % 0.02 %

pp chain

4p → 4He + 2e+ + 2νe + 26.73 MeV

H burning

event/month < Rlab < event/day

ε ~ 10 %IP ~ mAρ ~ µg/cm2

Rlab= σ·ε·Ip·ρ·Nav/A

pb < σ < nb

Reaction rate for charged particles

In the lab

( )( )

EZZ tp

eE

ESE

µ

!29.31"

=

Rn Rc

Ec

E PROJECTILE T= 15.0 106 KkT ~ 1 keV << EC ≈ MeV

In the Sun:

( )E!

( )ES

3He(αγ)7Be

Extrapolation is needed !!

?

RRlablab >> BBcosmcosm+ + BBenvenv ++ BBbeambeam inducedinduced

Environmental radioactivityhas to be consideredunderground (shielding) andintrinsic detector bck

Beam induced bck fromimpurities in beam & targets →high purity and detectortechniques (coincidence)

Cross section measurement requirements

1,00E-06

1,00E-05

1,00E-04

1,00E-03

1,00E-02

1,00E-01

1,00E+00

0 2000 4000 6000 8000 10000

E![keV]

counts

1,00E-06

1,00E-05

1,00E-04

1,00E-03

1,00E-02

1,00E-01

1,00E+00

0 2000 4000 6000 8000 10000

E! [keV]

counts

3MeV < E3MeV < Eγ γ < 8MeV: < 8MeV: 0.5 Counts/s 3MeV < E3MeV < Eγ γ < 8MeV < 8MeV 0.0002 Counts/s

GOINGUNDERGROUND

HpGeHpGe

LUNA site

LUNA 150 kV

(1992-2001)

LUNA 2400 kV

(20002013)

LLaboratory foraboratory for UUndergroundnderground

NNuclear uclear AAstrophysicsstrophysics

10-6

10-3

MuonsNeutrons

LNGS/surfaceRadiation

LABORATORI NAZIONALI DEL GRAN SASSO

(shielding ≡ 3800 m w.e.)

p + p → d + e+ + ne

d + p d + p →→ 33He + He + γγ

33He +He +33He He →→ αα+ 2p+ 2p 33He +He +44He He →→ 77BeBe + + γγ

7Be+e-→ 7Li + g +ne7Be + p → 8B + g

7Li + p → a + a 8B→ 2a + e++ ne

84.7 % 13.8 %

13.78 % 0.02 %

pp chainH-burning measurements at LUNA

CN-NO cycle50 kV50 kV

400 kV400 kV

Ongoing experimentOngoing experiment@ 400 kV@ 400 kV

12C 1515NN

13C 1414NN

13N 1515OO

(p,γ)

(p,γ)

(p,(p,γ) γ)

(p,α)e

+ν

e+ν

1616OO

17O

17F

(p,α)

(p,γ)e

+ν

(p,(p,γ)γ)18O

18F(p,γ)

e+ν

(p,α)

24Mg

(p,γ)

27Al(p,α)

27Si

(p,γ)

e+ ν4 s

2626AlAl

26Mg

(p,γ)e +ν

6 s

2525MgMg

25Al(p,γ)

e +ν7 sMg-Al cycle

(p,γ)

(p,γ)

See Benedetta Limata’s talkThis afternoon in the Nuclear Astrophysicssession:HK 50.7

See Daniel Bemmerer’s posterHK 67.64: Poster session onThursday

Mg-Al cycle

400 kV: LUNAII400 kV: LUNAII

Umax= 50 – 400 kV

I ∼ 500 µA for protons

I ∼ 250 µA for alphas

Energy spread : 72eV

Total uncertainty is ±300 eV

between Ep = 100 ÷ 400keV

Bottle neck ofCNO cycle

Solid target + Solid target + HPGeHPGe detector detector

2 goals for underground measurement

Single γ-transitions cross section contributions

(high resolution)

METHODMETHOD

Total cross sectionat energies close to Gamow window

(high efficiency)

METHODMETHOD

Gas target + BGO summing crystalGas target + BGO summing crystal

14N(p,γ)15O12C 13N

p,γ

β-

13C

14N

p,γ

15O

β+

15N

p,α

p,γ

Determination age of globularclusters

Turn-off luminosity

Q = 7.3 MeV

- 504

-21

27872977297

7556

72766859

6793

6176

5241

5183

0

1/2 +7/2 +

5/2 +

3/2 +

3/2 -

5/2 +

1/2 +

1/2 -1515OO

1414N+pN+p

factor 20 !Angulo et al 2000

High resolution measurement

126 %

( ) 155 !"

o

d

d#

DC/0DC/0

6.796.796.176.17

5.185.18

•• purity and stability of solid targets purity and stability of solid targets ⇒⇒ TiNTiN deposited on Ta backing deposited on Ta backing

•• Careful determination of summing effect due to close detector geometry Careful determination of summing effect due to close detector geometry

•• HpGeHpGe efficiency ~ 1% efficiency ~ 1%

EEminmin=120 =120 KeVKeV

High efficiency measurement

gas target

beam

•• BGO efficiency in the ROI ~ 65% BGO efficiency in the ROI ~ 65%

•• I Ipp~500 ~500 µµA A →→ the beam heats the gas changing the local density the beam heats the gas changing the local density

EEminmin= 70 = 70 KeVKeV

•• windowless windowless 1414N gas targetN gas target

•• All the All the γγ cascades are summed together to a peak at E cascades are summed together to a peak at Eγγ==Q+EcmQ+Ecm

GC age increases of 0.7-1 Gyr

CNO neutrino flux decreases a factor ≈ 2

Both results confirm the low reaction rate

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

0 50 100 150 200 250 300 350 400 450

E [keV]

S-f

ac

tor

[ke

V b

]

Stot (keV b)

gas target

gs

6.79

6.17

5.24

5.18

S0tot(LUNA) = 1.61 ± 0.08 keV b

R-matrix extrapolation is needed: Clover detector measurement

• TiN target + clover detector

• Measurement of the RC→0 transition

• E=318,334,353 keV

• negligible summing correction

LUNA (2004)LUNA (2004)LENA (2005)LENA (2005)

LUNA LUNA ––CLOVER (2008)CLOVER (2008)Schroeder (1987)Schroeder (1987)

High energy region (E>300 High energy region (E>300 keVkeV) is important for R-matrix extrapolation) is important for R-matrix extrapolation

See talk of See talk of Michele MartaMichele Marta: this afternoon , : this afternoon , Nuclear astrophysics session: HK 50.3Nuclear astrophysics session: HK 50.3

If the Q-value of the nuclear reaction is < 3MeV, is it useless to gounderground ?

Environmental radioactivity is present underground (Rn)

Detectors can be shielded passively with proper Pb-Cushield as on surface

Pb

CuDet

µ

BUT underground passive shielding is moreeffective since µ flux, that createsecondary γs in the shield, is suppressed.

p + p → d + e+ + νe

d + p → 3He + γ

3He +3He → α + 2p 3He +4He → 7Be + γ

7Be+e-→ 7Li + γ +νe7Be + p → 8B + γ

7Li + p → α + α 8B→ 2α + e++ νe

84.7 % 13.8 %

13.78%

0.02%

pp chainThe 33He(He(αα,,γγ))77Be Be cross section is the majornuclear physics uncertainty in thedetermination of the 8B-neutrinos flux

ΔΦB/ΦB=3.5 % from SuperKamiokandeexperiment

Can learn astrophysics if nuclear physicsis known well enough.

Q = 1.6 MeV33He(He(αα,,γγ))77BeBe

The results from the two techniques show a 9% discrepancy

Cross sections measurements were performed:

detecting the prompt γ from α-capture reaction

detecting delayed γ coming from 7Be decay

GOAL GOAL AT AT LUNA:LUNA: MEASUREMENT MEASUREMENT WITH WITH BOTH METHODS AND WITH ACCURACY ~ 4-5 %BOTH METHODS AND WITH ACCURACY ~ 4-5 %

Eγ = 478 keV

33He(He(αα,,γγ))77BeBe 77Be+eBe+e77Li*(Li*(γγ)+)+ννee

Eγ =1586 keV + Ecm (DC 0);Eγ = 1157 keV + Ecm (DC 429)Eγ = 429 keV

Q = 1.6 MeV

Si-detector

Experimental Setup• 3He recirculating gas target

• HpGe detector in close geometry for online γ detection

• Removable calorimeter cap for offline 7Be counting (with separated HPGe

Detector)

• Si-monitor for target density measurements (beam heating effect)

• 0.3 m3 Pb-Cu shield around detector

• chamber in OFC to reduce background on the detector

Low activity materials (Oxygen free copper)

Radon box

105 Reduction Eγ< 2 MeV

22 days

Results from activation and prompt measurements

Our data Promptactivation

Our dataS(0)=0.567±0.018±0.004 keV b

Brown et al. Brown et al. ‘‘0707

Singh. et al Singh. et al ‘‘0404

New Measurement with ERNA ΔE=0.7-3.2 MeVSee talk Antonino di Leva

This afternoon: Nuclear Astrophysicssession: HK 50.6

Improvements could come fromfull-energy range experiment to

determine S-factor energydependence: 0.1-2 MeV

What else can be done withLUNA2 400kV accelerator?

Proposal Approved by INFN (2008-2013)

1.478.8

11.7

8.0

5.6

12.13

Q-value

(MeV)

700(direct)50(indirect)

250

240

143

300

130

Lowest meas.Energy (keV)

50-30050-300

100-200

50-200

35-260

10-300

Gamowenergy (keV)

5068

138

89

65

50

LUNAlimit

22Ne(p,γ)23NaD(α,γ)6Li

reaction

23Na(p,γ)24Mg

18O(p,γ)19F

17O(p,γ)18F

15N(p,γ)16O

CNO cycle

Ne-Na cycle

BBN

OngoingOngoingexperimentexperiment

In preparationIn preparation

TiN 15N enriched targets1st phase: measurement with solid target + Ge detector in collaboration with

Notre Dame University; Ecm=120-1700 keV → complete R-matrix fit

2nd phase: measurement with solid target + BGO detector : Ecm =<100 keV-400 keV

DATA ANALYSIS ISONGOING!

DATA TAKING IS ONGOING!

15N(p,γ)16O

STATUS OF THE ART

Hammache et al.

LUNA?

Observed primordial 6Liabundance is unexpectedlylarge in respect to BBNpredictions

D(α,γ)6Li is a key reaction in 6Li primordialproduction

D(α,γ)6Li

New possibleexperiment at LUNAwith α beam and D2target using similar

setup of 3He(α,γ)7Be…

Q=1.47 MeV

LOILOI to LNGSLNGS for a new accelerator for He-burning key reactions

3.5 MV accelerator

13C(α,n)16O22Ne(α,n)25Mg

12C(α,γ)16O

The “Holy Grail”

LUNA Future?

n-sources for weak s-processn-sources for weak s-process

Other projects for underground nuclearastrophysics

• Homestake Mine, SD USA: The DIANA project(Dakota Ion Accelerator for Nuclear astrophysics) inthe framework of the DUSEL laboratory.

• Boulby Mine (Institute of Underground Science) UK:A proposal for an underground accelerator has beensubmitted.

• Laboratorio Subterraneo de Canfranc, Spain: Aproposal for an underground accelerator has beensubmitted.

Conclusions

• LUNA has proved that for many nuclearreactions of astrophysical importance, there is agreat advantage of an underground study

• New underground facilities are foreseen in thefuture around the world→ new challenges toimprove accelerator, target and detectortechnologies should be faced

HK 50.7 HK 50.7

LUNA CollaborationLaboratori Nazionali del Gran Sasso, INFN, ASSERGI: A.Formicola, C.Gustavino, M.Junker Forschungszentrum Dresden-Rossendorf, GermanyD. Bemmerer, M.Marta INFN, Padova, ItalyC. Broggini, A. Caciolli, R.Menegazzo, C. Rossi Alvarez Institute of Nuclear Research (ATOMKI), Debrecen, HungaryZ.Elekes, Zs.Fülöp, Gy. Gyurky, E.Somorjai Osservatorio Astronomico di Collurania, Teramo, and INFN, Napoli, ItalyO. Straniero Ruhr-Universität Bochum, Bochum, GermanyC.Rolfs, F.Strieder, H.P.Trautvetter Seconda Università di Napoli, Caserta, and INFN, Napoli, ItalyF.Terrasi Università di Genova and INFN, Genova, ItalyF. Confortola, P.Corvisiero, H. Costantini, A. Lemut, P.Prati Università di Milano and INFN, Milano, ItalyA.Guglielmetti, C. Mazzocchi Università di Napoli ''Federico II'', and INFN, Napoli, ItalyG.Imbriani,B. Limata, V.Roca Università di Torino and INFN, Torino, ItalyG.Gervino

Laboratory Underground Nuclear

Astrophysics