Sviluppi futuri degli esperimenti di astrofisica nucleare in Italia

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V riunione nazionale di astrofisica
nucleare Teramo,  20-22 aprile, 2005 
Sviluppi futuri degli esperimenti di astrofisica
nucleare in Italia
Paolo Prati
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Experimental Nuclear Astrophysics in Italy
In the future experimental groups will
concentrate their activities on facilities at two
INFN National Labs Catania (LNS) Gran Sasso
(LNGS)
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ERNA (present) setup
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Future activities _at_ LNS
A recoil separator, ERNA, will be installed at
the new RIB facility, EXCYT, at LNS
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Future activities _at_ LNS Trojan Horse Method
quasi-free interaction
three body reaction a A ? c C s A
cluster of x ? s To study a x ? c C of
astrophysical interest
if Ea gtgt Ecoul
Coulomb barrier electron screening negligible
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Trojan Horse Method
3-body cross section measured by the coincidences
of c and C
Calculation of the 2-body cross section for bare
nuclei
s astrophysics
s measured
KF kinematic factor
G(Ps)2 momentum distribution of x in A
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3He(d,p)4He
6Li d ? a
The 200 keV resonance, due to the 16.87 MeV level
of 5Li, has been reproduced
11B(p,a0)8Be
d p ? n
The 150 keV resonance, due to the 16.1 MeV level
of 12C, has been reproduced
Courtesy of Claudio Spitaleri, INFN -LNS
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Underground N.A. LUNA _at_ LNGS
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Laboratory for Underground Nuclear Astrophysics
Gran Sasso National Laboratory (LNGS) Cosmic
background reduction g 10-6 n 10-3
3He(3He,2p)4He
d(3He,p)4He
50 KV (1992-2001)
d(p,g)3He
14N(p,g)15O (CNO cycle)
400 KV (2000-2004)
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LUNA400 kV accelerator

• Umax 50 400 kV
• I ? 500 ?A for protons
• I ? 250 ?A for alphas

• Energy spread 72eV
• Total uncertainty is ?300 eV
• between Ep 100 ? 400keV

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Present/next-future program
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Motivations

• FB depends on nuclear physics and astrophysics
  inputs
• FB FB (SSM) s33-0.43 s34 0.84 s171 se7-1
  spp-2.7
• com1.4 opa2.6 dif
  0.34 lum7.2
• 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.

• Nuclear physics uncertainties, particularly on
  S34 , dominate over the present observational
  accuracy DFB/FB 7.
• The foreseeable accuracy DFB/FB3 could
  illuminate about solar physics if a significant
  improvement on S34 is obtained

Courtesy of Gianni Fiorentini, INFN-Ferrara
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SEATTLE 98 S34(0.5720.026) keVb 5
S34(0.5070.016) keVb 3 Adopted S34(0.530
.05) keVb 9
NACRE 99 S34(0.540.09) keVb 16
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A very recent result at the Weizmann Institut
(Israel)
Final result S34(0) 0.53(3)(1-2) keV-b
(experiment) (model)
Courtesy of Michael Hass
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Summary of previous measurements
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Lead shield
1st
2nd
3rd
HPGe
_at_LUNA
Expected attenuation for 1.6 MeV gs
10-5-10-6 (GEANT4 simulations)
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3He(a,g)7Be Target chamber
Movable silicon detector for Ir meas.
_at_LUNA
Removable calorimeter cap for off-line
7Be-activity measurement
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Gas target layout
3He purification recirculation
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Expected counting rate
Gamow peak
Lowest meas. point
LUNA goal a 3 precision on S(E)
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3He(a,g)7Be a new detector E-TOF to measure at
Ecmlt 1.5 MeV
_at_ERNA
Ecm0.4 MeV
Ecm1.2 MeV
Courtesy of Lucio Gialanella, INFN - Napoli
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Next _at_ LUNA
25Mg(p,g)26Al
Radioactive 26Al in the Galaxy
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Motivation for 25Mg(p,g)26Al
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NeNa and MgAl cycle
Slowest reaction of MgAl cycle
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Possible 26Al production sites

• Supernovae
• Novae
• Massive stars AGB, Wolf-Rayet stars

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Level scheme
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25Mg(p,g)26Al RESONANCES
Target pure 25Mg Beam 500 mA
LUNA Limit ?
Iliadis, Phys. Rev.C53 (1996)
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Spettro Totale 70 keV
LUNA best cases (p,g) and (a,g) with Eg gt 5 MeV
r 11 ev/d
Trun 50 d
5 MeV
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Some selected cases at LENA
EXIT from the Ne/Na cycle
OK for LUNA Eg gt 5 MeV, I 250 mA, no
coincidence needed!
Courtesy of Cristian Iliadis, Univ. of North
Carolina
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Some selected cases at LENA
Upper limit
OK for LUNA Eg gt 5 MeV, I 300 mA
Courtesy of Cristian Iliadis, Univ. of North
Carolina
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Another case neutron source(s) for s-process
LUNA range 300 70 keV Ec.m.

• Courtesy of Michael Heil, Forschungszentrum
  Karlsruhe

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Courtesy of Michael Wiescher, Univ. of Notre Dame
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Reaction Mechanism
s(E0) is expected to be dominated by E1
transition due to a broad 1- state (Ex9585 keV,
Ecm2423 keV) and to the high energy tail of the
sub-threshold 1- state (Ex7117 keV, Ecm-45
keV). An E2 transition comes from a 2 state
(Ex6917 keV, Ecm-245 keV). Direct capture also
plays a role. E1 and E2 are expected to be
comparable at E0.
Rolfs Rodney Cauldrons in the cosmos
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12C(a,g)16O S Factor
Ouellet et al. Phy. Rev. C 54 4 (1996) 1982-1998
Lowest energy directly investigated 940 keV c.m.
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Requirements

• Alpha beam Ea 0.2 - 3 MeV
• also for 22Ne(a,g), 22Ne(a,n), 40Ca(a,g)
• I beam 1 mA
• DE/E 10-3 10-4
• Negligible beam induced background

A new underground facility Is it possible?
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News from USA
A workshop to discuss an underground
accelerator for nuclear astrophysics , Tucson
2003-11-27/28
Courtesy of Wick Haxton, Univ. of Washington
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The last idea
A new tunnel under Cashmere peak (Washington) a
granite rock with a cover of 6421 feets ( LNGS)
Data taking from 2013....
Courtesy of Wick Haxton, Univ. of Washington
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Accelerator technology The RFQ
Beam energy is fixed

• The RFQ provides rf longitudinal electric field
  for acceleration and transverse rf electric
  quadrupole field for focusing -ideal for
  acceleration of low-velocity high-current ion
  beams.

Courtesy of Tom Wangler, LANL
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Suggestion Continuous energy variability can be
provided by installing the sectioned RFQ on a DC
HV platform.

• By providing a variable HV platform voltage with
  a maximum value that exceeds the voltage gain of
  the individual RFQ sections, it should be
  possible to dial up any output energy by
• turning off appropriate number of downstream RFQ
  sections
• adjusting the platform HV.
• An RFQ design study should be carried out to
  answer questions such as current limits (10s of
  mA ), energy spread, energy variability, size,
  and AC power for normal-conducting and
  superconducting options.

Courtesy of Tom Wangler, LANL
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At LNGS ?

• Several problems.
• Space required 200 - 400 m2
• Possible background induced to other experiments
• Budget
• .

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FFLEEP 2002
Thanks from the Moon
LUNA ATOMKI (HU) Debrecen INFN (IT) Genova,
Gran Sasso, Milano, Napoli, Padova, Torino Univ.
Bochum (FRG) Univ. Lisboa (PT)