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P. Corvisiero (INFN – Italy) on behalf of LUNA collaboration. LUNA: an underground nuclear astrophysics laboratory: recent results and future perspectives. the ambitious task of Nuclear Astrophysics is to explain the origin and relative abudance of the elements in the Universe. 10 10.

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slide1

P. Corvisiero (INFN – Italy)

on behalf of LUNA collaboration

LUNA: an underground nuclear astrophysics laboratory:

recent results and future perspectives

slide2

the ambitious task of

Nuclear Astrophysics

is to explain the origin

and relative abudance

of the elements

in the Universe

1010

108

106

relative abundance

104

102

1

10-2

0 10 20 30 40 50 60 70 80 90

Atomic number

the abundance of the elements in the Universe

elements are produced inside stars during their life

slide3

A<60

M < 8 M

star switches off

(white black dwarf)

M > 8 M

star explodes

(supernova)

Hburning  He

relative abundance

He burning  C, O, Ne

C/O … Si burning  Fe

explosive burning

Atomic number

slide4

p,

12C

13N

p + p d + e+ + ne

-

p,

d + p 3He + g

pp chain

CNO cycle

84.7 %

13.8 %

15N

13C

3He +3He a + 2p

3He +4He 7Be+g

p,

+

0.02 %

13.78 %

15O

14N

7Be+e- 7Li+g +ne

7Be +p 8B+g

p,

7Li +p a + a

8B 2a + e++ ne

Hydrogen burning

produces energy for most of the life of the stars

4p  4He + 2e+ + 2e + 26.73 MeV

slide5

Maxw. energy distribution function (KT ~ keV)

Z1Z2e2

tunneling probability

KT <<

RN

<v> =

b

E

E1/2

KT

3He(3He,2p)4He

3He(,)7Be

14N(p,)15O

20 < E0 < 26 keV

8

1

S(E)

exp

dE



(KT)3/2

0

E0

the Gamow peak….

slide6

(E) = S(E)·exp(-2) /E

S(E) = E·(E)·exp(2)

?

2 = 31.29 Z1 Z2 (/E)0.5

The astrophysical S-factor…

extrapolation is needed….

slide7

but…

sometimes extrapolation fails !!

S(E) factor

?

?

slide8

Screening effect of atomic electrons

interaction not between “bare” nuclei

in the lab: atoms and/or ions interact

in the stars: plasma electrons

r < Ra: electr = cost  -Z1e/Ra

tot = n + electr = Z1e/r - Z1e/Ra

for r > Ra: Frepuls=0

Eeff = Z1Z2e2/Rn - Z1Z2e2/Ra

Rn/Ra 10-5: negligible correction

but if: RC > Ra barrier thickness dramatically changes.

the electron screening….

slide9

measured:

Ue=219 eV

3He(d,p)4He

Adiab. limit:

Ue=119 eV

measured:

Ue=109 eV

d(3He,p)4He

Adiab. limit:

Ue=54 eV

slide10

how to overcome

these

experimental problems

??

slide11

Indirect methods

Direct methods

different approaches

Coulomb dissociation

ANC method (Asymptotic Normalization Coefficient)

Trojan Horse method

Recoil separator technique (ERNA)

(Ecm > EG , but very precise measurement  better extrapolation)

Underground experiments (LUNA)

slide12

spectator s

A

participant x

c

a

C

A

VFm

a

x

s

Vrel=Va-VFm~ 0

Eax0 astrophysical energies

Trojan Horse Method

Quasi-free Mechanism

3-body Reaction

a + A  c + C + s

A cluster x  s

to study a + x  c + C

of astrophisical interest

If: Ea >> Ecoul

Coulombeffects

(barrier + el. screen)

are negligible

slide13

Trojan Horse Method

3-body cross section measured through coincidence detection c and C

“bare” nucleus 2-body cross section

of astrophysicalinterest

astrophysical 

measured 

KF= kinematical factor

|G(Ps)|2= momentum distribution of s inside A

slide14

6Li(d,a)4He  6Li(6Li,a a)4He

6Li =d a

Ue=340±51 eV

Uth=186 eV

(Engstler S. et al.: 1992, Z. Phys., A342, 471)

• C.Spitaleri et al.: 2000, sottoposto Phys. Rev. C.)

7Li(p,a)4He  7Li(d,a a)n

d =p  n

Ue=350 eV

Uth=186 eV

(Engstler S. et al.: 1992, Z. Phys., A342, 471)

•(Spitaleri C. et al.: 1999, Phys. Rev., C60, 055802)

slide15

coincidence

Requirements

Advantages

Disadvantages

  • inverse kinematics (gas target)
  • beam purification (Ycont<<Yreac)
  • 100% transmission for the

selected charge state

  • well defined recoil charge state

(evtl post stripping)

  • high suppression of the incident beam (Yrec/Yleaky=1, Fsuppr=sNt, no coinc.),

e.g. F ~10-15 for s~ 10-9 b

  • gas target
  • low background
  • high detection efficiency: e=F(qrec)
  • measure stot
  • background free g-ray spectra
  • difficult to do

Recoil Mass Separator

Cn+

B

A

detection

A

C

purification

detection

separation

slide16

on source

Dynamitron tandem accelerator

recoil

transport

Magnetic quadrupole multipletts

beam purification

g - raydetection

gastarget

DE-E

Detector

Wien filter

Wien

filter

recoilseparation

60° dipole

magnet

ERNA setup

12 c a 16 o

16O recoils

SuppressionR~8*10-12

“leaky” beam

12C(a,)16O

Ecm=2.5 MeV

slide18

12C(a,)16O

  • Astrophysical motivation:
  • The cross section at the relevant Gamow-energy, Eo = 0.3 MeV, determines:

evolution and nucleosynthesis of massive stars;

  • dynamics of supernovae;
  • kind of remnants after supernova explosions.
slide19

12C(a,)16O: present situation

2+ (2.68 MeV)

 (relative units)

1- (2.4 MeV)

Ecm [MeV]

shower on lngs
Shower on LNGS

GranSasso

underground halls

Background reduction in LNGS

(shielding  4000 m w.e.)

Cosmic shower

luna logo

LUNA logo

Luna logo

LaboratoryUndergroundNuclearAstrophysics

" Some people are so crazy that they actually venture into deep mines to observe

the stars in the sky ".

(Naturalis Historia - Plinio, 23-79 B.C.)

luna site

LUNA 1

50 kV

LUNA 2

400 kV

LUNA underground Laboratories

LUNA site
slide24

p + p d + e+ + ne

d + p 3He + g

pp chain

84.7 %

13.8 %

3He +3He a + 2p

3He +4He 7Be+g

0.02 %

13.78 %

7Be+e- 7Li+g +ne

7Be +p 8B+g

7Li +p a + a

8B 2a + e++ ne

LUNA results

slide26

p + p d + e+ + ne

d + p 3He + g

pp chain

84.7 %

13.8 %

3He +3He a + 2p

3He +4He 7Be+g

0.02 %

13.78 %

7Be+e- 7Li+g +ne

7Be +p 8B+g

7Li +p a + a

8B 2a + e++ ne

LUNA results

slide28

----- IA

IA + … + 

sizeable effect of non nucleonic degrees of freedom

Viviani et al.: PRC61 (2000) 064001

luna ii foto

allowed beams : protons, alphas

Vmax = 50 - 400kV

Imax = 650 A

Energy spread : 72eV

  • Total uncertainty
  • 300 eV between

Ep=100400 keV

precise knowledge of the energy

calibration of the accelerator

LUNA II Foto

LUNA 400 kV at LNGS:

slide30

experimental program in progress

Emin~140 keV: published

14N(p,)15O

Emin~70 keV: coming soon…

Short term program

4He(3He,)7Be

25Mg(p, )26Al

Long term program

new scientific proposal

new machine (?)

slide31

p,

12C

13N

-

p,

CNO cycle

15N

13C

p,

+

15O

14N

p,

(15O) 1,141

(13N) 1,140.85

14N(p,)15O

Determines neutrino flux from CNO cycle

slide32

S 14,1 /5

S 14,1 x5

Standard CF88

CNO

pp-chain

14N(p,)15O

Turn Off luminosity

The onset of the CNO

slide33

+

Solid target

HpGe detector

  • single transitions
  • angular distribution
  • low efficiency
  • high density- pointlike
  • high resolution

Gas target +

BGO summingcrystal

  • total S(E)

target purity

  • low resolution
  • target stability
  • high efficiency

2 experimental approaches

Emin~140 keV

Emin ~ 70 keV

slide34

earth surface

Yield

3MeV < Eg < 8MeV

0.5 Counts/s

Yield

Underground

3MeV < Eg < 8MeV

0.0002 Counts/s

410-8 counts/s/keV

HpGe background

slide35

ECM (keV)

Ex (keV)

893

3/2+

8284

259

7556

1/2+

Q = 7297

6790

-507

6176

-1121

5180

-2117

0

0+

15O

14N(p,g)15O is the bottleneck of the CNO cycle and regulates the release of energy and the H consumption.

slide36

Level structure of 15O

Ep [keV]

Ex [keV]

Jp

8284

3/2+

1058

278

7556

1/2+

7276

7/2+

7297

14N+p

6793

3/2+

-504

6176

3/2-

5183

1/2+

0

1/2-

slide42

S0tot = 1.7 ± 0.1 keV b

LUNA (’04)

(Phys. Letter B)

GC age increased by 0.7-1 Gyr

  • CNOneutrino flux
  • reduced by a factor  2

Conclusions from the first phase

of the experiment

slide44

beam current

calorimeter

gas target

beam

Second phase:

BGO and gas target

slide46

Gas target results (preliminary)

four orders of magnitude !!

LUNA gas target

LUNA solid target

  • gas target data
  • solid target data

Schroeder

PRELIMINARY

71 keV

slide48

p,

12C

13N

p + p d + e+ + ne

-

p,

d + p 3He + g

pp chain

CNO cycle

84.7 %

13.8 %

15N

13C

3He +3He a + 2p

3He +4He 7Be+g

p,

+

0.02 %

13.78 %

15O

14N

7Be+e- 7Li+g +ne

7Be +p 8B+g

p,

7Li +p a + a

8B 2a + e++ ne

future program @ LUNA

slide49

Eg =1585 keV + Ecm (DC  0);

Eg = 1157 keV + Ecm (C  0.429)

Eg = 429 keV

E = 478 keV

3He(a,)7Be(e,n)7Li*()

slide50

3He(a,)7Be(e,n)7Li*()

SEATTLE 98

S34=(0.572±0.026) keV·b [5%]

S34=(0.507±0.016) keV·b [3%]

Adopted

S34=(0.53±0.05) keV·b [9%]

NACRE 99

S34=(0.54±0.09) keV·b [16%]

slide51

Target chamber design

Movable silicon detector for I* meas.

Removable calorimeter cap for off-line 7Be-activity measurement

slide53

P = 1 mbar; I = 200 A

1.6 MeV

counts/day

1.2 MeV

BCK HpGe

Ecm [keV]

Expected counting rate

Gamow peak

slide54

what else might be studied underground?

12C(a,g), 16O(a,g)

Supernovae ~ He burning

14N(a,g)

18O(a,g)

22Ne(a,g)

AGB stars ~ s process

14N(p,g)

17O(p,g)

17O(p,a)

Red giants ~ CNO cycle

22Ne(p,g)

23Na(p,a)

24Mg(p,g)

Globular clusters ~ Ne/Mg/Na cycles

Supernova nucleosynthesis

20Ne, 24Mg, 28Si, 32S, 36Ar, 40Ca(a,g)

[J.C. Blackmon, Physics Division, ORNL ]

Future plans…

slide57

Temperature trend along the target

0.5 mbar

1 mbar

2 mbar

Temperature (K)

Position (cm)

slide58

Experimental setup

LN2

LN2

Target chamber

7 mm

10 mm

beam

HpGe

55o

wobbeling

units

target

High density

High stability

High purity

TiN deposited

on Ta

slide59

Solid Target features

TiN

14N(p,)15O ER=278 keV

Target profile

(thickness, homogeneity)

D = 115keV

Target stability

typical: 25 C/day

slide60

The experimental spectrum

DC/6.17

Ep = 250 keV

Q = 41.2 C

T = 20 h

I =570 mA

counts

DC/6.79

6.17

6.79

DC/5.18

5.18

DC/0

E [keV]

slide61

R/DC0

cos2()

Y

Elab = 220 keV

Y

R/DC6.79

Y

R/DC6.18

Y

R/DC5.18

cos2()

cos2()

cos2()

Y

5.180

Y

6.180

Y

6.790

cos2()

cos2()

cos2()

slide62

Data Analysis (1)

Epinc

Eginc

Epi

Eg

x

DEpi

beam

s

E

slide63

s

Data Analysis (2)

Ep

x

Ep

E

slide64

Imax 400mA

Calorimeter

BGO

DE < 100 eV

10-7 mbar

10-6 mbar

10-4 mbar

HV 50-400 kV

0.5-2 mbar

Windowless gas-target

Max 10 mbar

Beam: p, He

Gas target set-up

slide65

----- IA

IA + … + 

sizeable effect of non nucleonic degrees of freedom

Viviani et al.: PRC61 (2000) 064001

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