nucleus-nucleus 2012san antonio (tx) 18 f+p 15 o + @ crib 1
TRANSCRIPT
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Trojan Horse method and radioactive ion beams:
study of 18F(p,a)15O reaction at astrophysical energies
Nucleus-Nucleus 2012San Antonio (TX)
MARISA GULINO
INFN,LNS, CATANIA, ITALY
UNIVERSITÀ DI ENNA “KORE”, ENNA, ITALY
18F+p 15O + @ CRIB
Astrophysical motivations
Gamma-ray emission of energy 511 keV from novae is dominated by the positron annihilation following the b+ decay of unstable nuclei
18F is especially important because It is produced relatively abundantly
Its lifetime of 158 min is well matched ∼to the timescale for nova ejecta to become transparent to -g ray emission
IT IS IMPORTANT TO STUDY THE REACTIONS PRODUCING AND DESTROYING 1 8F
as 1 8F(p,a)1 5O
The 18F(p,a)15O reaction influence the 15O production considered as a key isotope for the escape from the hot- CNO cycle to the rp-process
AX
b+
(p,g)
(p,a)
18F
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18F(p,a)15OAstrophysical factor is dominated by several resonances in 19Ne
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Astrophysical motivations
A. Coc, M. Hernanz, J. José, and J.-P. Thibaud Astron. Astrophys. 357, 561–571 (2000)
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Nucleus-Nucleus 2012San Antonio (TX)
State of Art
ARGONNE
LLN
ORNL
TRIUMF GANIL- SPIRALRIKEN – CRIB
TAMU
Most recent references:
D. J. Mountford et al PHYSICAL REVIEW C 85, 022801(R) (2012) “Resonances in 19Ne with relevance to the astrophysically important 18F( p,α)15O reaction.”
A. S. Adekola et al. PHYSICAL REVIEW C 83, 052801(R) (2011) “First proton-transfer study of 18F + p resonances relevant for novae”
C. E. Beer et al. PHYSICAL REVIEW C 83, 042801(R) (2011) “Direct measurement of the 18F( p,α)15O reaction at nova temperatures”
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5Nucleus-Nucleus 2012San Antonio (TX)
State of Art
C. E. Beer et al. PHYSICAL REVIEW C 83, 042801(R) (2011)
D. J. Mountford et al PHYSICAL REVIEW C 85, 022801(R) (2012)
DIRECT EXPERIMENT
DIRECT EXPERIMENT
A. S. Adekola et al. PHYSICAL REVIEW C 83, 052801(R) (2011)
TRANSFER REACTION
New measurement @ CRIB by using the Trojan Horse Method
d
p
n
18F
15O
a
Trojan Horse
nucleus
EBA > ECEC
xS x
x
x
SA= nuclear
field
EBA= A-B relative energy
EC= A-B Coulomb Barrier
B
C
DEBx
= ECD – Q2Body
(pcp)
A (x+s) + B C + D + S B + x C + D
18F + d 15O + a + n
18F + p 15O + a
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Reazione a tre corpiDecadimento
virtuale
Reazione Virtuale (Half off - Shell)(processo astrofisico)
A
B
S
C
D
x =A
x
S x
B
C
D
IMPLEMENTAZIONE DELL’IDEA…
Assumendo che il contributo QF sia dominante si può rappresentare ilprocesso con un diagramma di Feynman del tipo:
(EBx= ECD- Q2body)
misurata
ad alta energia
d3σ
dΩC dΩD dECKF· |Φ (Ps)|
2
Calcolatae.g.
Montecarlo
dσN
dΩ
Dedotta
= x
In PWIA:
TURNING THE IDEA INTO PRACTICE
Assuming the QF mechanism is dominant the process can be represented in Feynman diagrams
Three body reaction Virtual decay Virtual reaction Half off-shell
(astrophysical process)
Measured
at high energy
Calculated DeducedNeed direct data for
normalization
✚
α
CRIB set-up
BEAM PRODUCTION
18O+8 @ 4.5-5 MeV/Afrom AVF cyclotron
gas target2H
Wien filter
Dou
ble-
achr
omati
c m
agne
tic
sepa
rato
r18O(p,n)18F
Scattering chamber
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Test fascioYear BTU type Prod.Target
typePeak
intensity
2006 Beam dev Room temp. ~105
2007 Thick target experiment Liquid N cooled 5x105
2008 Trojan Horse experiment Liquid N cooled > 106
Primary beam: 18O 8+, 4.5-5 MeVA
Production target: H2
Production reaction: 18O(p,n)18F
18F beam development
BEAM PURITY > 98%
Ebeam = 48.7 MeV
s = 0.8 MeVNucleus-Nucleus 2012
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188 mg/cm2
PPAC MCP
CD2 2
TARGET
DPSSDarray
Front view of DPSSD array
DSSSD
0.5 m 15 cm
28.7 cm
Safety disk
Beam @PPAC2.4 106 pps48.7 + 0.8 MeV
0.107 m
EXPERIMENTAL SETUP(other than CRIB.....)
ASTRHO:Array of Silicons for TRojan HOrse
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BEAM TRACKER
PPACtarget
MCP
Beam track reconstruction event by event
z
x
mm mm mm
mm mm
mm
y
q1
q2
DPSSD
DSSiSD
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CUTS:
• Event multiplicity = 2
•
• E1 > 20 MeV
T2 T1 0
Q-VALUE SPECTRUM18F+d 15N+a+p q = 4.194 MeV
18F+d 18O+p+p q = 0.213 MeV 18F+d 18F+p+n q = -2.225 MeV
1 + 2 + 3
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18F+d 15O+a+n q = 0.658 MeV
EVENT SELECTION
Red : 18F + d 15N + a + pBlack: 18F + d 15O + a + nBlue: 18F + d 18F + p + n Green: 18F + d 18O + p + p “1”+“2”+“3”
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• Correlation E13 - E12
• Correlation E1 - q1
Q-VALUE SPECTRUM
CUTS:
• Event multiplicity = 2
•
• E1 > 20 MeV
T2 T1 0
GOOD AGREEMENT with q-value expected position (0.658 MeV) and beam profile (exp. Sigma 0.8 MeV)
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HINTS FOR QF MECHANISMIf the quasi-free mechanism is predominant
d3d 15O
ddE
KF ps 2dd
N
Hulten function
Minumum of ps
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BARE NUCLEUS CROSS SECTION
38 keV
PRELIMINARY
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First TH exp. with RIB
BARE
NUCL
EUS
NU
CLEA
R CRO
SS SE
CTIO
N
THM was successfully applied to radioactive ion beam induced reaction
the beam is tracked event by event and the kinematical variables were consequently reconstructed
the preliminary results showed the possibility to study the cross section of the 18F(p,a)15O reaction and extract complementary information on S(E) factor (work in progress)
To do: Increase statistics and confirm the results with a second experimental run
Explore the possibility to measure the 18F(n,a)15N reaction
Conclusions and Perspective
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S. Cherubini, M. Gulino, M. La Cognata, L. Lamia, G. G. Rapisarda, C. Spitaleri, S. Kubono, H. Yamaguchi, S. Hayakawa, Y. Wakabayashi,‡, N. Iwasa§, S. Kato ¶, H. Komatsubara k, T. Teranishi ††,A. Coc‡‡, N. De Séréville§§ and F. Hammache§§
Dipartimento di Fisica ed Astronomia, Università di Catania and INFN-LNS, Catania, Italy†INFN-LNS, Catania, Italy and UniKORE, Enna, ItalyCenter for Nuclear Study, The University of Tokyo, Japan‡Present address KEK, Japan§Department of Physics, Tohoku University, Sendai, Japan¶Department of Physics, Yamagata University, Yamagata, JapankDepartment of Physics, Tsukuba University, Tsukuba, Japan††Department of Physics, Kyushu University, Fukuoka, Japan‡‡Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, IN2P3, F-91405 Orsay, France§§Institut de Physique Nucléaire, IN2P3, F-91405 Orsay, France
Nucleus-Nucleus 2012
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THANK YOU FOR YOUR ATTENTION !
THANK YOU TO ALL THE COLLABORATION !
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BARE NUCLEUS CROSS SECTION
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Trojan Horse for Resonance Reactions
HALF OFF-SHELL ON-SHELL
PENETRABILITY
Indipendent from spectroscopic factor value
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BEAM position on PPAC and MCP
DREB 2012 - Direct Reactions with Exotic Beams
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CUTS
DREB 2012 - Direct Reactions with Exotic Beams
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State of Art
Many experiments performed using 18F beam @ ARGONNE - ATLASLLNORNLTRIUMFGANIL- SPIRALRIKEN – CRIBTAMUDirect measurements thick target method
Indirect measurement (d,p) (d,n) stripping reaction
Most recent references:
D. J. Mountford et al PHYSICAL REVIEW C 85, 022801(R) (2012) “Resonances in 19Ne with relevance to the astrophysically important 18F( p,α)15O reaction.”
A. S. Adekola et al. PHYSICAL REVIEW C 83, 052801(R) (2011) “First proton-transfer study of 18F + p resonances relevant for novae”
C. E. Beer et al. PHYSICAL REVIEW C 83, 042801(R) (2011) “Direct measurement of the 18F( p,α)15O reaction at nova temperatures”
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Summary
Astrophysical motivations & State of Art
Indirect measurement by Trojan Horse Method
Experimental set-up new apparatus for RIB application
Data Analysis and preliminary results
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“Plus” of the TH methods1) Typical QF process cross sections (mbarn/sr) though
measuring astrophysical ones
2) The TH cross sections is the purely NUCLEAR one: no Coulomb barrier effects
3) No electron screening effects: an INDEPENDENT piece of information can be obtained on the electron screening potential Ue by comparison to direct data
4) Can be extended to use QFR for studying NEUTRON induced reactions (VNM Virtual Neutron Method)
“Minus” of the TH methods
1) Competition between QF and other reaction mechanisms: identification of the convenient kinematical conditions may need more than one experiment run
2) Some dependence on theoretical models
3) Need of direct data at higher energies for normalization
S. Cherubini et al., ApJ 457 (1996) 855