Underground nuclear astrophysics
This presentation is the property of its rightful owner.
Sponsored Links
1 / 24

Underground Nuclear Astrophysics PowerPoint PPT Presentation


  • 106 Views
  • Uploaded on
  • Presentation posted in: General

L aboratory U nderground N uclear A strophysics. Underground Nuclear Astrophysics. Heide Costantini INFN, Genova, Italy University of Notre Dame, IN, USA. Outline. Reaction rate for H-burning. Why going underground ?. The LUNA project:. - Main nuclear reactions studied.

Download Presentation

Underground Nuclear Astrophysics

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Underground nuclear astrophysics

LaboratoryUndergroundNuclearAstrophysics

Underground Nuclear Astrophysics

Heide Costantini

INFN, Genova, Italy

University of Notre Dame, IN, USA


Underground nuclear astrophysics

Outline

  • Reaction rate for H-burning

  • Why going underground ?

  • The LUNA project:

- Main nuclear reactions studied

  • Experimental techniques:

  • - detectors

    • targets

    • bck sources

  • Outlook


Underground nuclear astrophysics

Hydrogen burning

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

produces energy for most of the life of the stars

4p  4He + 2e+ + 2e + 26.73 MeV


Underground nuclear astrophysics

Reaction rate for charged particles

Z1Z2e2

tunneling probability

KT <<

RN

EG

E

dE

S(E)

exp

<v> =

E

KT

0

E0

3He(3He,2p)4He 22 keV

8

1



d(p,)3He 7 keV

(KT)3/2

14N(p,)15O 27 keV

(E) = S(E)·exp(-(EG/E)1/2)


Underground nuclear astrophysics

Reaction rate in the laboratory

Rlab= ··Ip··Nav/A

e ~ 10 %

IP ~ mA

 ~ mg/cm2

pb < s < nb

event/month < Rlab < event/day

(E) = S(E)·exp(-(EG/E)1/2)

Extrapolation is needed !!


Underground nuclear astrophysics

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)

3MeV < Eg < 8MeV 0.0002 Counts/s

3MeV < Eg < 8MeV: 0.5 Counts/s

HpGe

GOING

UNDERGROUND

Cross section measurement requirements

Rlab> Bcosm+ Benv+Bbeaminduced


Luna site

Laboratory forUnderground

Nuclear Astrophysics

LUNA 1

(1992-2001)

50 kV

LUNA 2

(2000…)

400 kV

LUNA site

LNGS

(shielding  4000 m w.e.)


Underground nuclear astrophysics

Measurements @ LUNA

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

3He(3He,2p)4He

50 KV

3He(4He,)7Be

400 KV

d(p,)3He

14N(p,)15O

400 KV

50 KV


Underground nuclear astrophysics

50 kV: LUNAI

Energy spread:

20 eV

keV/h


Underground nuclear astrophysics

3He(3He,2p)4He

Cosmic background suppression

in silicon detector

beam induced background

3He(d,p)4He.

Coincidence between two Si detectors

  • Lowest energy: 2cts/month

  • Lowest cross section: 0.02 pbarn

  • Background < 4*10-2 cts/d in ROI

windowless gas target


Underground nuclear astrophysics

LUNA II

U = 50 – 400 kV

I  500 A for protons

I  250 A for alphas

Energy spread  70eV

Long term stability: 5 eV/h


Underground nuclear astrophysics

14N(p,)15O

p,

12C

13N

-

p,

Bottle neck of

CNO cycle

15N

13C

p,

+

15O

14N

p,

Determination age of globular clusters

Determination of CNO neutrino fluxes

Turn-off

luminosity

Dredge-up efficiency

in AGB stars

F. Herwig and S. M. Austin. Astrophys. J., 612:L73, 2004.


Underground nuclear astrophysics

14N+p

7556

278

1/2 +

7297

7/2 +

7276

6859

5/2 +

-21

6793

3/2 +

3/2 -

- 504

6176

Q = 7.3 MeV

5/2 +

5241

Angulo et al 2000

1/2 +

5183

factor 20 !

15O

1/2 -

0

Stot(0) = 3.2  1.77 keV b

2 goals for underground measurement

Single -transitions cross

section contributions

(high resolution)

Total cross section

at energies close to Gamow window

(high efficiency)

METHOD

METHOD

Solid target + HPGe detector

Gas target + BGO summing crystal


Underground nuclear astrophysics

High resolution measurement

6.17

6.79

5.18

DC/0

126 %

  • purity and stability of solid targets  TiN deposited on Ta backing

  • Careful determination of summing effect due to close detector geometry

  • HpGe efficiency ~ 1%

Emin=120 KeV


Underground nuclear astrophysics

High efficiency measurement

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

  • windowless 14N gas target

gas target

beam

  • Ip~500 A  the beam heats the gas changing the local density

  • BGO efficiency in the ROI ~ 65%

Emin= 70 KeV


Underground nuclear astrophysics

Q = 9277 C

t = 49.12 days

Reaction Rate = 10.95  0.83 counts/day

Background rate = 21.14  0.75 counts/day

Elab=80 keV


Results

Results

Both results confirm the low reaction rate

GC age increases of 0.7-1 Gyr

  • CNO neutrino flux decreases a factor  2


Underground nuclear astrophysics

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

The 3He(,)7Be cross section is the major nuclear physics uncertainty in the determination of the 8B-neutrinos flux

p + p d + e+ + ne

d + p 3He + g

pp chain

84.7 %

13.8 %

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

Pb

The production of 7Li in BBN is very sensitive to 3He(,)7Be cross section.

3He +3He a + 2p

3He +4He 7Be+g

Cu

0.02 %

Det

13.78 %

7Be+e- 7Li+g +ne

7Be +p 8B+g

7Li +p a + a

8B 2a + e++ ne

Ongoing experiment

3He(,)7Be

Q = 1.6 MeV

Environmental radioactivity is present underground (Rn)

BUT underground passive shielding is more effective since  flux, that create secondary s in the shield, is suppressed.


Underground nuclear astrophysics

Q = 1.6 MeV

Ecm

J

Ex(keV)

1586

DC

3He+

3He(a,g)7Be

7Be+e7Li*(g)+e

429

1/2-

3/2-

0

7Be

Eg=1586 keV + Ecm (DC  0);

Eg= 1157 keV + Ecm (DC  429)

Eg= 429 keV

Eg = 478 keV

1/2-

478

EC

0

3/2-

7Li

Cross sections measurements were performed:

detecting the prompt  from -capture reaction

detecting delayed  coming from 7Be decay

The results from the two techniques show a 9% discrepancy

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


Underground nuclear astrophysics

Si monitor

Activation method

Online- method

  • 3He recirculating system

  • 135% HpGe detector in close geometry to target

  • 0.3 m3 Pb-Cu shield

  • suppression of natural bck: 10+5

  • chamber in OFC to reduce background on

  • detector

  • 7Be nuclei collected on the beam stop

  • during online -measurement

  • 125% HpGe detector

  • Pb-Cu shield in low activity lab in LNGS

  • suppression of natural bck: 10+5

7Be- decay from activation

measurement at E=350 keV

On line -measurement

E=400 keV

T=4.5 d

I=280 A

7Be+e7Li*()+e

T=2 days

3He(,)7Be

See poster by G. Gyürki on Thursday


Underground nuclear astrophysics

ECM (keV)

Ex (keV)

J

25Mg(p,)26Al

solid

target

1”x1”NaI(Tl)

Cooling trap

Motivations

  • Nucleosynthesis of the elements

    24<A<27

  • Astronomical interest of

    1809 keV 26Al decay -line

4 BGO Detector

5+(4+)

190

6496

Novae explosive

Burning (T9>0.1)

130

6436

4-

108

6414

0+

93

6399

2-

AGB or W-R

Stars (T9~0.05)

6364

3+

58

4-

37

6343

Q = 6306 keV

25Mg+p

6280

3+

-26

Astronomical interest:

T9<0.2 EG<220 keV

26Alm

228

0+

0

5+

26Al0


Underground nuclear astrophysics

A working group inside LUNA is preparing

a new proposal for the new LUNA phase

Spokesperson: Carlo Broggini [email protected]

What else can be done with LUNA II (400kV) ?

maybe a new accelerator for He-burning key reactions?


Underground nuclear astrophysics

ALNA

Idea of a new underground accelerator facility inside the DUSELlaboratory (Homestake (SD) or Henderson Mine (CO))

Focused mainly on study of He-burning and C-burning reactions

  • 1st phase:

installation of a light ion (2 MV terminal Voltage) accelerator to study (,n) and (,) reactions in forward kinematics

  • 2nd phase:

heavy ion accelerator for inverse kinematics studies

Notre Dame Recoil

Mass separator

See J. Görres’ talk tomorrow!!


Underground nuclear astrophysics

LUNA

ATOMKI : Debrecen

INFN: Genova, Gran Sasso, Milano, Napoli, Padova, Torino

Univ. Bochum

Univ. Lisboa


  • Login