Nuclear Astrophysics at the Gran Sasso Underground … · Gas target + BGO summing ... 12C 13N p,γ...
Transcript of Nuclear Astrophysics at the Gran Sasso Underground … · Gas target + BGO summing ... 12C 13N p,γ...
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
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