ALNA- Accelerator Laboratory for NuclearAstrophysics Underground

Heide Costantini

University of Notre Dame, IN, USAINFN, Genova, Italy

Outline:Outline:

• LUNA:LUNA:- - an example of experimental nuclear astrophysics an example of experimental nuclear astrophysics

laboratory UNDERGROUND laboratory UNDERGROUND

• ALNA: ALNA: - goalgoal- methodsmethods- experimental techniquesexperimental techniques

• Nuclear astrophysics:Nuclear astrophysics: - main reactions - main reactions - experimental problems- experimental problems

the abundance of the elements in the Universe

0 10 20 30 40 50 60 70 80 90

10-2

102

104

106

108

1010

1

Atomic number

rela

tive

ab

un

dan

ce

the ambitious task ofNuclear Astrophysics

is to explain the originand relative abundance

of the elements in the Universe

elements are produced inside stars during their life

n-capture, -decay,…N-ToF, RIA

Charged particlesFusion reactions

Fe

p + p d + e+ + ep + p d + e+ + e

d + p 3He + d + p 3He +

3He +3He + 2p3He +3He + 2p 3He +4He 7Be +

3He +4He 7Be +

7Be+e- 7Li + +e7Be+e- 7Li + +e 7Be + p 8B +

7Be + p 8B +

7Li + p + 7Li + p + 8B 2+ e++ e

8B 2+ e++ e

84.7 % 13.8 %

13.78 % 0.02 %

pp chain

12C 13Np,

-

13C

14N

p,

15O

+

15N

p,

p,

CNO cycle

produces energy for most of the life of the stars

4p 4He + 2e+ + 2e + 26.73 MeV

Hydrogen burning

Two questions remain relevant: Energy production and timescale:

4He(2,)12C(,)16O(,)20Ne

Neutron production for weak s-process:

14N(,)18F(+)18O(,)22Ne(,n) 22Ne(,)

Neutron production for fast s-process:

13C(,n)

1212C(C(,,))1616OO

Triple Triple

4He

16O12C

4He

20Ne

1616O(O(,,))2020NeNe

4He

Helium burning

The extrapolation problem

?

extrapolation is needed….

??S(E

)

fact

or

S(E) = E·(E)·exp(2)

(E) = S(E)·exp(-2) /E

2 = 31.29 Z1 Z2 (/E)0.5

sometimes extrapolation fails !!

RRlablab >> B Bcosmcosm+ + BBenvenv ++ BBbeambeam inducedinduced

Environmental radioactivity has to be considered underground (shielding) and intrinsic detector bck

Beam induced bck from impurities in beam & targets high purity and detector techniques (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]

coun

ts

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]

coun

ts

3MeV < E3MeV < E< 8MeV: < 8MeV: 0.5 0.5 Counts/sCounts/s

3MeV < E3MeV < E< 8MeV < 8MeV 0.0002 Counts/s

GOINGUNDERGROUND

HpGeHpGe

LUNA site

LUNA 1(1992-2001)

50 kV

LUNA 2(2000…)

400 kV

LLaboratory foraboratory for UUndergroundnderground

NNuclear uclear AAstrophysicsstrophysics

Radiation

LNGS/surface

MuonsNeutron

sPhotons

10-6

10-3

10-1

LNGS(shielding 4000 m w.e.)

Measurements @ LUNA

12C 13Np,

-

13C

14N

p,

15O

+

15N

p,

p,

CNO cycle

p + p d + e+ + ep + p d + e+ + e

d + p 3He + d + p 3He +

3He +3He + 2p3He +3He + 2p 3He +4He 7Be +

3He +4He 7Be +

7Be+e- 7Li + +e7Be+e- 7Li + +e 7Be + p 8B +

7Be + p 8B +

7Li + p + 7Li + p + 8B 2+ e++ e

8B 2+ e++ e

84.7 % 13.8 %

13.78 % 0.02 %

pp chain

3He(4He,)7Be14N(p,)15Od(p,)3He

3He(3He,2p)4He

Energy spread 70eV

Long term stability: 5 eV/h

U = 50 – 400 kVI 500 A for protonsI 250 A for alphas

LUNA II

Q = 7.3 MeV

- 504

-21

278

1414N+pN+p72977297

7556

7276

6859

6793

6176

5241

5183

0

1/2 +

7/2 +

5/2 +

3/2 +

3/2 -

5/2 +

1/2 +

1/2 -

1515OO

1414N(p,N(p,))1515OO

gas target

beam

Reaction Rate = 10.95 0.83 c/dBackground rate = 21.14 0.75 c/d

t = 49.12 days

Q = 9277 C

Spectrum 70 keVSpectrum 70 keV

BGO summingcrystal

LUNA main results

High beam current

Event identification

High efficiency detector

Pure gas target

full advantage Underground lab

• Lowest energy: 2cts/month

• Lowest cross section: 0.02

pbarn

• Background < 4*10-2 cts/d in

ROI

3He(3He,2p)4He1414N(p,N(p,))1515

OO

Low cosmic background

Goal at ALNA:• systematic study of reactions relevant for the understanding of He-burningHe-burning and C-C-burningburning in red giants, AGB stars and late evolutionary stages

Accelerators:

installation of a small (2 MV terminal Voltage) accelerator to study (,n) and (,) reactions in forward kinematics

•1st phase:

heavy ion accelerator for inverse kinematics studies (M. Couder’s talk)(M. Couder’s talk)

•2nd phase:

• energy calibration: < 0.1%

• Energy resolution: < 0.1%

• long-term stability: > days to months

• beam intensity: I > 100 A

• Energy range: 100kV-2MV

• Beam: p,

• Count rate limitation of 1 ev/day > 0.2 nbarn

Accelerator Requirements1st phase

• high efficiency increase counting rate

• Low intrinsic activity

• Passive shielding

• event identification

• active shielding decrease beam-induced background

decrease environmental background

Detector facility requirements1st phase

Example: 19F(p,-)16O background reduction by Q-value gating for 19F(p,)20Ne

counts

E

counts

E

Facility requirements

• Depth shielding 4000 (mwe)

• Space 15X10X5 (m3) accelerator 15x10x5 (m3) (target

room 1st phase) 15X20X5 (m3) (target room 2nd phase)

• Electrical power 50 kW (1st phase)200 kW (2nd phase)

•Additional facilities machine shoppower supply

low level countingDI water systemcompressed airLN25 ton crane in target area

Contributors and collaborators:

A. Champagne University of North Carolina

R. Clark LBNL

M. Couder University of Notre Dame

M. Cromaz LBNL

A. Garcia University of Washington

J. Görres University of Notre Dame

U. Greife Colorado School of Mines

C. Iliadis University of North Carolina

D. Leitner LBNL

P. Parker Yale University

K. Snover University of Washington

P. Vetter LBNL

M Wiescher University of Notre Dame