S - IPN

ipnweb.in2p3.fr

S - IPN

Laboratory

Underground

Nuclear

Astrophysics

Recent results and status of the

LUNA experiment

Heide Costantini

Dipartimento di Fisica and INFN, Genova (Italy)


the abundance of the elements in the Universe

relative abundance

10 10

10 8

10 6

10 4

10 2

1

the ambitious task of

Nuclear Astrophysics

is to explain the origin

and relative abudance

of the elements

in the Universe

10 -2

0 10 20 30 40 50 60 70 80 90

Atomic number

elements are produced inside stars during their life


0

M < 8 M

star switches off

(white →black dwarf)

M > 8 M

star explodes

(supernova)

H burning → He

He burning → C, O, Ne

C/O … Si burning → Fe

explosive burning

relative abundance


Hydrogen burning

produces energy for most of the life of the stars

pp chain

p

p

+

+

p

p

→ d

d

+

+

e

e + +

+

ν

ν e e

CNO cycle

p,γ

12

C

13

N

d

d

+

+

p

p

→ 3 He 3 He

+

+

γ

γ

84.7 % 13.8 %

15

N

p,α

β - 13

C

3

He 3

He

+

+ 3 He 3 He

→α

→α

+

+

2p 3

2p

He 3

He

+

+ 4 He 4 He

→ 7 Be 7 Be

+

+

γ

γ

13.78 %

0.02 %

7

Be+e 7

Be+e - → - 7 Li 7 Li

+

+

γ

γ

+ν 7

+ν e Be 7

e

Be

+

+

p

p

→ 8 B+γ 8 B+γ

β +

15

O

p,γ

p,γ

14

N

7

Li 7

Li

+

+

p

p

→ α

α

+

+

α 8

α

B→ 8

B→



+

+

e

e + + +

ν

ν e e

4p → 4He + 2e+ + 2ν e + 26.73 MeV


Maxw. energy distribution function (KT ~ keV)

KT


The astrophysical S-factor

σ(E) = S(E)·exp(-2πη) /E

S(E) = E·σ(E)·exp(2πη)

?

2πη = 31.29 Z 1 Z 2 (µ/E) 0.5

extrapolation is needed….


ut…

S(E) factor

??

sometimes extrapolation fails !!


Background reduction in LNGS

(shielding ≡ 4000 m w.e.)

Cosmic shower

Radiation

Muons

Neutrons

Photons

LNGS/surface

10 -6

10 -3

10 -1

Gran Sasso

underground halls


7 Li

7

+ p → α + α 8 B→

8

2α + e + + ν e

Laboratory for Underground

Nuclear

LUNA site

uclear Astrophysics

LUNA 1

992-2001)

50 kV

LUNA 2

(2000…)

400 kV

pp chain

p + p → d + e

p + p → d + + e + ν

+ e

ν e

d + p →

d + p → 3 He 3 + γ

He + γ

84.7 % 13.8 %

3 He 3 +

He + 3 He 3 →α + 2p

He →α + 2p

3 He 3 +

He + 4 He 4 →

He → 7 Be 7 + γ

Be + γ

13.78 %

0.02 %

7 Be+e 7 Be+e - → - → 7 Li 7 + γ +ν

Li + γ +ν 7 e Be 7

+ p →

e

Be + p → 8 B+γ

8 B+γ


400 kV accelerator



U max

= 50 – 400 kV

Energy spread : 72eV

I ∼ 500 µA for protons

Total uncertainty is ±300 eV

I ∼ 250 µA for alphas

between Ep = 100 ÷ 400keV


14

N(p,γ) 15 O

Determines neutrino flux from CNO cycle

CNO cycle

p,γ

12

C

13

N

p,α

β - 13

C

15

N

15

O

β +

p,γ

p,γ

14

N

Φ ν ( 15 O) ∝σ 1,14

1

Φ ν ( 13 N) ∝σ 1,14

0.85


Globular Clusters and 14 N(p,γ) 15 O reaction rat

S 14,1

/5

S 14,1

x5

Standard CF88

turnoff


14 N(p,γ) 15 O

297

+p

-21

-504

278

7556

7276

6859

6793

6176

1/2 +

7/2 +

5/2 +

3/2 +

3/2 -

Schröder et al. (1987)

Nucl. Phys A

5241

5/2 +

5183

1/2 +

0

15 O

1/2 -

Angulo, Descouvement (2001),

Nucl. Phys A

factor 20 !

R/DC → 0

S(0) = 1.55 ± 0.34 keV-b (Schröder)


2 experimental approaches

Solid target + HpGe detector

angular distribution

high density

E b-min = 140 keV

Single γ transitions

Low efficiency

High resolution

Gas target + BGO summing crystal

Pure target

Stable target

total-S(E)

Low resolution

High efficiency


First phase:

HpGe and solid target

126 %



o

( 55 ) ≈1

High density

High stability

High purity

TiN deposited

on Ta


HpGe background

At surface

3MeV < Eγ < 8MeV

0.5 Counts/s

Yield

counts

1,00E+00

1,00E-01

1,00E-02

1,00E-03

1,00E-04

1,00E-05

1,00E-06

0 2000 4000 6000 8000 100

Eγ [keV]

Yield

1,00E+00

1,00E-01

1,00E-02

Underground

counts

1,00E-03

1,00E-04

1,00E-05

1,00E-06

0 2000 4000 6000 8000 10000

Eγ[keV]

3MeV < Eγ < 8MeV

0.0002 Counts/s


Beam induced background

70

60

50

counts

11

B(p,γ) 12 C

14

N(p,γ) 15 O

40

30

11

B(p,γ) 12 C

E beam = 200 keV

20

10

0

3000 5000 7000 9000 11000

30

E γ

[keV]

counts

E beam = 140 keV

25

20

E γ

15

10

11

B(p,γ) 12 C

14

N(p,γ) 15 O

11

B(p,γ) 12 C

5

0

3000 5000 7000 9000 11000

E γ

[keV


The experimental spectrum

counts

DC/6.79

DC/6.17

E p = 250 ke

Q = 41.2 C

T = 20 h

I =570 µA

DC/5.18

6.17

6.79

5.18

DC/0

E γ

[keV]


eam

Angular distribution measurements


2,5

Y

R/DC→0

E lab

= 220 keV

2

1,5

1


=


1

2

+ a1 P1

( ϑ)

+ a2P

( ϑ)

+

0,5

0

cos 2 (θ)

-0,01 0,19 0,39 0,59 0,79 0,99

Y R/DC→6.79 Y R/DC→6.18 Y R/DC→5.18

cos 2 (θ)

-0,01 0,19 0,39 0,59 0,79 0,99

1,4

1,2

1

0,8

0,6

0,4

0,2

cos 2 (θ)

0

-0,01 0,19 0,39 0,59 0,79 0,99

1,6

1,4

1,2

1

0,8

0,6

0,4

0,2

cos 2 (θ)

0

-0,01 0,19 0,39 0,59 0,79 0,9

Y 5.18→0 Y 6.18→0 Y 6.79→0

0

-0,01 0,19 0,39 0,59 0,79 0,99 -0,01 0,19 0,39 0,59 0,79 0,99

1,2

1

1,2

1

0,8

0,8

0,6

0,6

0,4

0,4

0,2

0,2

cos 2 (θ) cos 2 (θ) cos 2 (θ)

1,4

0

-0,01 0,19 0,39 0,59 0,79 0,9


Ground state results

. . . . . . . a = 5 fm

• present data

Schröder (corr. for

summing)

a = 5.5 fm

a = 6 fm

S 0 gs

gs = 0.25 ± 0.06 keV b


R/DC→6.79 results

• present data

Schröder

. . . . . . .

a = 5 fm

a = 5.5 fm

a = 6 fm

S 0

6.79

.79 = 1.35 ± 0.05 keV b


Schröder(‘87)

[kev-b]

3.2 ± 0.5

Angulo (’01)

[kev-b]

1.8 ± 0.2

S 0 tot

tot = 1.7 ± 0.1 ± 0.2 keV b

GC age increases of 0.7-1 Gyr

CNO neutrino flux decreases a

factor ≈ 2


R/DC→0

LENA -LUNA

C. Angulo, , A. E. Champagne, H.P. Trautvetter

Poster @ NIC8 (July 2004)

R/DC→6.79

R/DC→6.18

Good agreement !!


Second phase:

BGO and gas target

gas target

beam current

calorimeter

beam


Gas target scheme

BGO

Calorimete

10 -7 mbar 10 -6 mbar 10 -4 mbar

0.5-2 mbar

Windowless gas-target

Max 10 mbar


Target Chamber

Beam Axis

Calorimeter


BGO detector

etection Efficiency ≈ 65 %

Natural background

(6500-8000 keV)

Length : 28 cm

Int. hall diam.: 6 cm

Thickness : 7 cm

20 c/day

Beam induced background

E beam =210 keV

E beam = 130 keV

19

F(p,αγ) 16 O

11

B(p,γ) 12 C

13

C(p,γ) 14 N

D(p,γ) 3 He

13

C(p,γ) 14 N


Beam heating effect measurement

The particle beam heats the gas

changing the local density.

Movable Lead Shielded NaI detector (1” x 1”)

The 278 keV 14 N(p,γ) 15 O

resonance is positioned

in front of the detector.

The beam energy loss is

proportional to

the gas density.


Pressure (mbar)

Pressure profile


Conclusions for the 14 N(p,γ) 15 O measurement

N(p,γ) 15 O has been studied with a solid target

set-up down to E cm =135 keV

14 N(p,

Present work improves the experimental

information especially concerning the

R/DC → 0 transition

Using a gas target set-up the 14 N(p,γ) 15 O total

cross-section has been studied at LUNA

down to

E cm

cm =71 keV


Work in progress @LUNA

pp chain

p

p

+

+

p

p

→ d

d

+

+

e

e + +

+

ν

ν e e

d

d

+

+

p

p

→ 3 He 3 He

+

+

γ

γ

84.7 % 13.8 %

3 He 3 He

+

+ 3 He 3 He

→α

→α

+

+

2p

2p

3 He 3 He

+

+ 4 He 4 He

→ 7 Be 7 Be

+

+

γ

γ

13.78 %

0.02 %

7

Be+e 7

Be+e - → - 7 Li 7 Li

+

+

γ

γ

+ν 7

+ν e Be 7

e

Be

+

+

p

p

→ 8 B+γ 8 B+γ

7 Li 7 Li

+

+

p

p

→ α

α

+

+

α

α

8 B→ 8 B→



+

+

e

e + + +

ν

ν e e


4 He( 3 He,γ) 7 Be

Mainly 3 γ:

Eγ =1585 keV + E cm

Eγ = 1157 keV + E cm

cm (DC→0)

0);

and Eγ = 429 keV

cm and

keV (DC→0.429; 0.429 →0)


Motivations

Φ B depends on nuclear physics and astrophysics inputs

Φ B = Φ (SSM) B · s

-0.43

33 s

0.84 34 s

1

17 s

-1

e7 s

-2.7

pp · com 1.4 opa 2.6 dif 0.34 lum 7.2

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.

uclear physics uncertainties,

rticularly on S 34 , dominate

er the present observational

curacy ∆Φ Β /Φ Β =7%.

he foreseeable accuracy

Φ Β /Φ Β =3% could illuminate

out solar physics if a

gnificant improvement on S 34 is

Source

S33

S34

S17

Se7

Spp

Com

Opa

Dif

Lum

∆X/X

(1σ)

0.06

0.09

0.05 ?

0.02

0.02

0.06

0.02

0.10

0.004

(SSM) .

∆Φ Β

/Φ Β

(1σ)

0.03

0.08

0.05

0.02

0.05

0.08

0.05

0.03

0.03


Past measurements

0,8

on-line γ-measurements

activation measurements

0,7

Hilgemeier et. al.

1988

0,6

0,5

Nagatani et. al.

1969

Osborne et. al.

1982

Hilgemeier et. al.

1988

on-line γ -meas.

average

Osborne et. al.

1982

Robertson et. al.

1983

Volk et. al.

1983

M. Hass

NIC8

activation

average

0,4

Parker et. al.

1963

Kräwinkel et. al.

1982

Alexander et. al.

1984

0,3


Target chamber design

Target chamber design

55 o

Internal lead shield to

be independent to angular

HPGe

distribution effects

135%

Expected attenuation for

1.6 MeV γs: 10 -5 -10 -6

Lead shield


Gas target scheme

3 He purification & recirculation


Experimental schedule

‣ Autumn 2004- Spring 2005:

set-up mounting, tests, preliminary measurements

(background, density profile, beam heating, ecc.)

‣ Summer- End 2005:

runs down to E cm = 100 keV ( prompt γs) and 2-32

3 runs

for 7 Be delayed counting

‣ Summer- End 2006:

low energy runs (prompt γs s only)

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