Pre-equilibrium emission and its possible relation to α ... · (in total 180+180 for the 2...
Transcript of Pre-equilibrium emission and its possible relation to α ... · (in total 180+180 for the 2...
Pre-equilibrium emission and its possible relation to α-clustering in nuclei
T. Marchi INFN - Laboratori Nazionali di Legnaro
for the Nucl-ex collaboration
W. Von Oertzen et al., Phys. Rep. 432 (2006) 43 M. Freer et al., Rep. Progr. Phys. 70 (2007) 2149
Ebran et al., Nature 487 (2012) 341
Cluster structure appears close to the decay thresholds
The interest in nuclear clustering has been pushed strongly due to the study
of neutron-rich and exotic weakly-bound nuclei
-clusters in light nuclei:
In 1968 Ikeda suggested that -conjugate nuclei are observed as excited states close to decay threshold into clusters. The original idea was introduced by Hafstad and Teller in 1938. The starting point is a quite reasonable observation:
Ikeda diagram
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Presently these structures are mainly described by theory, but must be experimentally verified at the new radioactive beam facilities
Extended Ikeda diagrams
In light nuclei at the neutron drip-line, clustering might be the preferred structural mode Nuclear states built on clusters bound by valence neutrons in their molecular configurations might appear
Extension of the clustering concepts
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
1. Pre-equilibrium processes 2. Coalescence vs Preformation
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
E_beam h Comp E* Detectors
16O + 116Sn 130 MeV 250 MeV
8 AMeV 15.8 AMeV
0.76 132Ce 100 206
GARF FW+ PPAC
16O+116Sn 192 MeV 12 AMeV 0.76 132Ce 155 GARF FW+ PHOSWICH
16O+65Cu 256 MeV 16 AMeV 0.60 81Rb 209 GARF FW+BW+
RCo
19F + 62Ni 304 MeV 16AMeV 0.53 81Rb 240 GARF FW+BW+
RCo
19F + 63Cu 304 MeV 16 AMeV 0.52 82Sr 243 GARF FW+BW+
RCo
Shopping list…
Forward Chamber Backward Chamber 29<q<83 97<q<151
0< f<70 0<f<360
110< f<360
Double stage ΔE-E: Micro Strip Gas Counter (MSGC)+ CsI(Tl) telescopes (in total 180+180 for the 2 chambers)
Only one volume of gas for all sectors
F. Gramegna et al., IEEE Nucl. Sci. Symp. Conf. Proc. 2, 1132 (2004) A.Moroni et al. NIM A556 (2006) 516 M. Bruno et al., EPJ A 49 (2013) 128
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Experimental setup: GARFILED + …
Microstrip Drift Chamber + CsI(Tl)
Experimental results (2002-2003): 16O + 116Sn 130,250 MeV (8, 16 AMeV)
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Light charged particles in coincidence with
Evaporation Residues
A. Corsi et al., PLB 679 (2009) 197
Evaporative (statistical) emission: Statistical decay of a Compound Nucleus is analyzed using modified PACE2 Monte Carlo code,
with level density parametrization [A.V. Ignatyuk et al. Sov. J.Nucl. Phys. 29 (1979) 450], decay
competition probability (n, p, a, g or fission), kinetic energy of emitted particles, binding energy,
transmission coefficients, angular momentum.
Insertion of non-equilibrium stage in the fusion reaction
All the process probabilities are calculated within the Hauser-Feshbach model
Pre-equilibrium emission: The relaxation process in the nuclear system after fusion reaction is described by the Hybrid
exciton model based on Griffin model [J.J.Griffin Phys. Rev. Lett.17 (1966) 478].
The state of nuclear system produced in the collision is determined by the exciton number
n=p+ h, where p is the number of valence particles over the Fermi energy and h the number of
holes located under the Fermi energy, and by excitation energy E*.
The exciton number can be determined from the empirical trend
[N.Cindro et al. Phys. Rev. Lett. 66 (1991) 868; E. Běták Fizika B12 (2003) 11]
“Our“ model: statistical + pre-equilibrium emission
O.V. Fotina et al. Int. Journ. Mod. Phys. E19 (2010) 1134 D.O. Eremenkoet al. Phys Atom. Nucl. 65 (2002) 18 O.V. Fotina et al. Phys. Atom. Nucl. 73 (2010) 1317c
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
n0 = p0 + h0 Number of excitons
k 100 – 800 MeV3
g = 6a/π2 Level density parameter
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16O+116Sn @130 MeV
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-particles
Exp
SIMUL_pre_A
SIMUL_evap_A
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Energy (MeV)
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Exp SIMUL_pre_A SIMUL_evap_A SIMUL_tot_A
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Exp SIMUL_pre_A SIMUL_evap_A SIMUL_tot_A
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16O + 116Sn @130MeV
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EXP
SIMUL_pre_A
SIMUL_evap_A
SIMUL_tot_A
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Comparison with the model (130 MeV)
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Energy (MeV)
16O +116Sn @250 MeV
Dq= 29°-41° protons
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16O+116Sn @250MeV
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Energy (MeV)
16O + 116Sn @ 250 MeV
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-particles
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Energy(MeV)
16O + 116Sn @250MeV Dq=29°-41°
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Comparison with the model (250 MeV)
Evaporative (statistical) emission: Statistical decay of a Compound Nucleus is analyzed using modified PACE2 Monte Carlo code , with level density parametrization [A.V. Ignatyuk et al. Sov. J.Nucl. Phys. 29 (1979) 450], decay competition probability (n, p, a, g or fission), kinetic energy of emitted particles, binding energy, transmission coefficients, angular momentum.
Insertion of non-equilibrium stage in the fusion reaction All the process probabilities are calculated within the Hauser-Feshbach model
Pre-equilibrium emission: The relaxation process in the nuclear system after fusion reaction is described by the Hybrid exciton model based on Griffin model [J.J.Griffin Phys. Rev. Lett.17 (1966) 478]. The state of nuclear system produced in the collision is determined by the exciton number n=p+ h, where p is the number of valence particles over the Fermi energy and h the number of holes located under the Fermi energy, and by excitation energy E*.
The exciton number can be determined from the empirical trend [N.Cindro et al. Phys. Rev. Lett. 66 (1991) 868; E. Běták Fizika B12 (2003) 11]
Clustering: Pre-formation probability of cluster and exciton energies for cluster/light ion induced reactions
[M. Blann et al. Phys Rev. C 62 (2000) 034604]
“Our“ model: statistical + pre-equilibrium emission + CLUSTERING
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
n=4p+0(1)h
nC=12p+0(1)h
nO=16p+0(1)h
Adding -clusters preformation probability to the decay model:
16O 116Sn
16O
e – clusters energy
x – random number
e
e12C
2 possible starting configurations are considered in 16O nucleus
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
250 MeV 16O + 116Sn
--- No -clustering in 16O __ 10% -clustering in 16O __ 50% -clustering in 16O Exp
-particles spectra
Experimental results (2002-2003) – with clustering:
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
“Dynamic Dipole“: GARFIELD (digital) + Phoswich
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
16O + 116Sn Eb = 192 MeV (12 AMeV)
T.o.F. (a.u.)
S. Sambi, Master Thesis, LNL and Univ. Bologna A. Giaz et al., submitted to PRC
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16O+116Sn
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250 MeV_Z1
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192MeV_Z1
192MeV_p
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16O+116Sn
Dq=53°-67° protons
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16O+116Sn
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130MeV_Z1
250MeV_Z1
192MeV_Z1
192MeV_p
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Experimental results (192 MeV):
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16O+116Sn
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192MeV_alpha
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16O+116Sn
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130MeV_Z2
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192MeV_alpha
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Energy (MeV)
16O+116Sn
Dq=67°-82°
-particles
130MeV_Z2
250MeV_Z2
192MeV_Z2
192MeV_alpha
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Experimental results (192 MeV):
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Comparison with the Hybrid Exciton Model - protons (192 MeV):
S. Sambi, Master Thesis, LNL and Univ. Bologna
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Comparison with the Hybrid Exciton Model – -particles (192 MeV):
S. Sambi, Master Thesis, LNL and Univ. Bologna
“ACLUST 2013”: GARFIELD + Rco
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
16O + 65Cu Eb = 256 MeV (16 MeV/u) 19F + 62Ni Eb = 304 MeV (16 MeV/u)
CN 81Rb* E*(16O) = 209 MeV E*(19F) = 240 MeV
Comparing the light charged particles emitted in fusion reactions where an -cluster projectile (16O) and projectile without clusterization (19F) are used.
The two systems have the same projectile velocity.
Unified Code, O.V. Fotina, Moscow State University
50
%
-clu
ste
rin
g in
16O
From Cabrera systematics the pre-equilibrium emission is mainly dependent
on the projectile velocity
[J. Cabrera et al. Phys. Rev. C68 (2003)
034613]
Light Charged Particles Angular distribution an Energy spectra in coincidence with Evaporation Residues:
Ring Counter IC-Si Dq = 8.6° ÷ 17° at P = 25 mbar CF4
ACLUST experiment (2013):
256 MeV 16O + 65Cu qgr =8.2°
304 MeV 19F + 62Ni qgr =7.3°
Rin
g C
ou
nte
r IC
-Si
D
q =
8.6
÷
17
° at
P =
25
mb
ar C
F 4
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Slow (ch)
Fast
(ch
)
p, d,t
3He,
Experimental Proton spectra in Lab
29°- 41° 41°- 53° 53°- 67° 67°- 82°
98°- 113° 113°- 127° 127°- 139° 139°- 151°
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014 Elab (MeV)
___ 16O + 65Cu ___ 19F + 62Ni
Experimental a particles spectra in Lab
139°- 151° 127°- 139° 113°- 127° 98°- 113°
67°- 82° 53°- 67° 41°- 53° 29°- 41°
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
___ 16O + 65Cu ___ 19F + 62Ni
Elab (MeV)
CM Spectra at different angles
Proton in CM
ECM
19F + 62Ni 16O + 65Cu
Alpha in CM
ECM
19F + 62Ni 16O + 65Cu
Very small pre-equilibrium contribution in proton spectra
Larger pre-equilibrium contribution in 19F induced reaction -spectra
with respect to 16O reaction
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Comparison with Hybrid Exciton Model (NO clustering):
16O + 65Cu n0 = 17 16(1) Exp Total Pre-eq Evap PACE
Protons
139°- 151° 127°- 139° 113°- 127°
98°- 113°
67°- 82° 53°- 67° 41°- 53° 29°- 41°
Co
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a.u
.)
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Elab (MeV)
16O + 65Cu n0 = 17 16(1) • Exp Total Pre-eq Evap PACE
- particles
139°- 151° 127°- 139° 113°- 127°
98°- 113°
67°- 82° 53°- 67° 41°- 53° 29°- 41°
Co
un
ts (
a.u
.)
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Comparison with Hybrid Exciton Model (NO clustering):
Elab (MeV)
19F + 62Ni n0 = 20 Protons
139°- 151° 127°- 139° 113°- 127°
98°- 113°
67°- 82° 53°- 67° 41°- 53° 29°- 41°
Co
un
ts (
a.u
.)
• Exp Total Pre-eq Evap PACE
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Comparison with Hybrid Exciton Model (NO clustering):
Elab (MeV)
19F + 62Ni n0 = 20 - particles
139°- 151° 127°- 139° 113°- 127°
98°- 113°
67°- 82° 53°- 67° 41°- 53° 29°- 41°
Co
un
ts (
a.u
.)
• Exp Total Pre-eq Evap PACE
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Comparison with Hybrid Exciton Model (NO clustering):
Elab (MeV)
16O + 65Cu
19F + 62Ni
• Exp n0 = 17 Total Pre-eq n0 = 15 Total Pre-eq n0 = 14 Total Pre-eq
• Exp n0 = 20 Total Pre-eq n0 = 18 Total Pre-eq n0 = 17 Total Pre-eq
67°- 82°
67°- 82°
53°- 67°
53°- 67°
41°- 53°
41°- 53° 29°- 41°
29°- 41°
Elab (MeV)
Elab (MeV)
Co
un
ts (a
.u.)
C
ou
nts
(a.u
.)
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
- particles Comparison with Hybrid Exciton Model:
Comparison with Hybrid Exciton Model:
16O + 65Cu
19F + 62Ni
• Exp n0 = 17 Total Pre-eq n0 = 15 Total Pre-eq n0 = 14 Total Pre-eq
• Exp n0 = 20 Total Pre-eq n0 = 18 Total Pre-eq n0 = 17 Total Pre-eq
67°- 82°
67°- 82°
53°- 67°
53°- 67°
41°- 53°
41°- 53° 29°- 41°
29°- 41°
Elab (MeV)
Elab (MeV)
Co
un
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.u.)
C
ou
nts
(a.u
.)
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Protons
Preliminary results seem NOT to confirm the predicted difference between the two systems (16O+65Cu and 19F+62Ni) due to -clustering effects in 16O induced reactions.
Using the same parameters the Hybrid Exciton Model describes resonably the -particles but strongly overestimates the protons. Cluster preformation has to be considered to take into account the alpha – protons emission competition.
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Summary:
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29°<Dq<41° -particles O_Sn_250MeV_new
F_Ni_304MeV
O_Cu_256MeV
O_Sn_SIMUL_B
O_Cu_SIMUL_B
F_Ni_SIMUL_B
O_Sn_SIMUL_B_n015
O_Cu_SIMUL_B_n015
Elab (MeV)
Analysis is in progress….
• To extract energy spectra for all particles p, d, t, 3He, also for the most forward angles of the Rco where the pre-equilibrium emission and any possible difference are maximized. • To study angular and energy correlations of the emitted particles event-by-event. • To perform more selective coincidences with evaporation residues, as a function of their energies and of the detected angles. • To complete the Hybrid Exciton Model calculations for all particles and for all the measured angles.
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Summary:
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29°<Dq<41° - protons O_Cu_256MeV_sperim
F_Ni_304MeV_sperim
O_Sn_250MeV_sperim
O_Sn_OLGAB_tot
O_Cu_OLGAB_tot
Elab (MeV)
Outlook: SPES
132Sn + 27Al @ 11 AMeV
28 Si 30 Si
27Al
SPES beam intensities are referred to Ep=40 MeV -- Ip=200 mA on Ucx tgt
87Rb 1,6 108
96Rb 2,0 107
94Rb 2,7 108
85Rb
132Sn 2,0 107
116Sn 124Sn 130Sn 1,6 108
114Sn
130-132Sn + 30-28Si @ 11 AMeV
114-116Sn + 30-28Si
94-96Rb + 30-28Si
85-87Rb + 30-28Si
STABLE targets
SPES Day 1 Beams!
(I /40)
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Collaboration
F. Gramegna1, D. Fabris2, T. Marchi1, M. Degerlier3, V.L. Kravchuk4, M. Cinausero1, S. Appannababu1, M. Bruno5, M. D’Agostino5, L. Morelli5, G. Casini6, S. Barlini6, M. Bini6, A. Olmi6, G. Pasquali6, S. Piantelli6, G. Poggi6, S. Valdrè6, O.V. Fotina7, S.A. Goncharov7, D.O. Eremenko7, O.A. Yuminov7, Yu.L. Parfenova7, S.Yu. Platonov7, V.A. Drozdov7, E. Vardaci8
1Laboratori Nazionali di Legnaro, Legnaro (PD), Italy 2INFN sezione di Padova, Padova, Italy 3University of Nevsehir, Science and Art Faculty, Physics Department, Nevsehir, Turkey
4National Research Center “Kurchatov Institute”, Moscow, Russia 5Dipartimento di Fisica, Università di Bologna and INFN sezione di Bologna, Bologna, Italy 6Dipartimento di Fisica, Università di Firenze and INFN sezione di Firenze, Firenze, Italy 7Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, Russia 8 Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Napoli, Italy
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Proton spectra in Lab
ACLUST experiment (2013):
[D. Fabris, IWNDT 2013, Texas A&M University, College Station, Texas]
98°- 113° 113°- 127° 127°- 139° 139°- 151°
29°- 41° 41°- 53° 53°- 67° 67°- 82°
Elab (MeV)
___ 16O + 65Cu ___ 19F + 62Ni
___ 16O + 65Cu PACE ___ 19F + 62Ni PACE
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Alpha spectra in Lab
ACLUST experiment (2013):
[D. Fabris, IWNDT 2013, Texas A&M University, College Station, Texas]
98°- 113° 113°- 127° 127°- 139° 139°- 151°
29°- 41° 41°- 53° 53°- 67° 67°- 82°
Elab (MeV)
___ 16O + 65Cu ___ 19F + 62Ni
___ 16O + 65Cu PACE ___ 19F + 62Ni PACE
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
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Cs8 Settore 1 - protoni O_Cu_256MeV_sperim
F_Ni_304MeV_sperim
O_Sn_250MeV_sperim
O_Sn_OLGAB_tot
O_Cu_OLGAB_tot
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CS5 Settore 1 - protoni
O_Sn_250_sperim O_Cu_256_sperim F_Ni_304_sperim O_Sn_OLGAB_tot O_Cu_OLGAB_tot F_Ni_OLGAB_tot
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
250 MeV 16O + 116Sn
--- No -clustering in 16O __ 10% -clustering in 16O __ 50% -clustering in 16O Exp
proton spectra
Experimental results (2002-2003) – with clustering:
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
Moving source analysis
1) Evaporative (statistical equilibrium) contribution
N2, T2, Vc2 – yield, temperature, Coulomb energy parameter for the evaporative particles
2) Pre-equilibrium contribution
N1, T1, Vc1 – yield, temperature, Coulomb energy parameter for the preequilibrium particles
))(cos1()(4
222
2
22
2
2
2
2
PeVE
T
N
dEd
Nd T
VE
c
c
-=
--
1
1
1)(
22/3
1
11
2T
VE
c
c
eVET
N
dEd
Nd--
-=
Light particle emission mechanisms
T. Marchi – International Workshop on Multi facets of Eos and Clustering – Catania, 6-9 May 2014
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Dq=67°-82° protons
Exp
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Dq=28°-41° protons
Exp
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O_Sn_FOTINA_tot
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CS8 SETTORE 1 ALFA O_Sn_250MeV_new
F_Ni_304MeV
O_Cu_256MeV
O_Sn_SIMUL_B
O_Cu_SIMUL_B
F_Ni_SIMUL_B
O_Sn_SIMUL_B_n015
O_Cu_SIMUL_B_n015