Collision Dynamics with HRACLES at ISACII

1
Collision Dynamics with HÉRACLES at ISAC-II

• Objective Study the isotopic enhancement from
  isospin effects
• by
• Projectile fragmentation of Na isotopes on light
  targets

2
How? By detecting projectile fragmentation
events with the multidetector HÉRACLES
optimized for such measurements

• - With light projectiles
• - With light targets in reverse kinematics

3
In general, why do we heat a nucleus with heavy
ion collisions?

• For the exploration of extreme states of
• nuclei,
• - to understand the dynamics and
• thermodynamics of these states,
• like the supernovae mechanisms,
• the internal structures of neutron stars.
  
• - to sound the nuclear potential of the matter at
  the origin of our world.
• - and more

4
Presentation

• Collision physics
• The experimental setup
• Calculations AMD
• Manpower

5
Dissipative binary collisions dominate at
intermediate energy (10 MeV/nucleon Eproj
100 MeV/nucleon)
Projectile
Target
QT E
MR
QP E
6
The experimental setup

• HÉRACLES

7
HÉRACLES
8
The HÉRACLES Multidetector

• BaF2
• Si-CsI
• Phoswich
• 11-43
• CsI(Tl)
• View from the target

9
Detectors types, angular ranges and
characteristics

• Detectors Angular Nb.ring ?E thickness
  E thresholds range x
  Nb./ring MeV/nucleon
• - BaF2  2? - 5? 1x5 100 ?m 32S  ? 6.6
• phos. Mount
• - Si CsI 6? - 10? 1x5 50-200 ?m 12C  ?
  3.5
• telescopes
• Phoswich 10.5? - 24? 2x16 100 ?m
  12C  ? 4.6
• scintillators
• CsI(Tl) 24? - 46? 2x13 None p,?  lt 2
  MeV
• - Si CsI 24? - 46? 2 total 50 ?m
  24Mg  ? 4.6
• telescopes

10
Calculations with AMD Antisymmetrized Molecular
Dynamics

• A. Ono et al. Phys. Rev. Lett. 68, 2898 (1992)
• - Microscopic simulations based on
  nucleon-nucleon collision processes incorporated
  into the Antisymmetrized version of Molecular
  Dynamics
• - Can describe quantum-mechanical features such
  as shell effects
• - Fragment formation at the end treatment of
  nuclear cascade decays of the excited fragments
• - Fragment mass distributions are produced,
  easily compared to experimental distributions.
• - Advantages of small systems
• full calculations with a minimum of
  approximations
• possible to reach high statistics (enough events
  to make a realistic comparison)

11
Two different asymmetry terms
12
Standard Gogny
Modified Gogny
13
Isotope distributions two Gogny terms
Standard
Modified
14
Isotope distributions 20Na vs 28Na(---)
20
28
15
Other observables  correlation functions

• A - Velocity correlations between IMFs and
  quasi-spectators
• B - Two-fragment reduced-velocity correlation
  functions
• C - Emission chronology of non-identical particles

16
Activities

• Calculations
• The AMD code (A. Ono) is running on our
  computers.
• Predictions are becoming available.
• Analysis
• The group has already done many different
  analyses on similar data.
• Codes are available, as well as analysis routines
  for extracting different observables from the
  data.

17
In a word

• We want to study complex physics
• in a simple way

18
ManpowerGraduate students

• J. Gauthier Ph.D. Full time (electronics)
• F. Gagnon-Moisan Ph.D.. Full time (detectors)
• M.-O. Frégeau M.Sc. Flull time (stab.w/fibers)
• A. Vallée Ph.D. Full time (calculations)
• J. Moisan Ph.D. Part time (calibration)
• F. Grenier Ph.D. Part time (calc/simul.)
• D. Thériault Ph.D. Part time
  (elect./analysis)
• J.-P. Lavoie Ph.D. Full time ISAC
• F. Labrecque M.Sc. Full time ISAC
• R. Labbé M.Sc. Full time ISAC
• To be confirmed (May 2007) M.Sc. Full time
  (sim.)
• Co-supervision with A. Chbihi, GANIL
• Ph.D. just completed
• R. Moustabchir has just completed his Ph.D. 2005
• (Co-supervision IPN Lyon)
• Collaborators several from GANIL and INDRA
  Collaboration are interested to participate
• - Preliminary and setup runs
• - Main experiments

19
(No Transcript)
20
(No Transcript)
21
(No Transcript)
22
(No Transcript)
23
Yields of different Na isotopes and time required
for a measurement (from nominal measured
intensities)

• Isotopes Yields Acquisition
  Events/hr. Events/day Possibility
• (part./s) events/s (days)
• Na-20 2 x 108 400 1 440 000 34 000 000
  yes (1)
• Na-24 5 x 1010 idem idem idem yes (1)
• Na-26 108 idem idem idem yes (1)
• Na-27 5 x 106 250 900 000 21 600 000
  yes (1)
• Na-28 4 x 105 50 180 000 4 320 000
  yes (4)

24
Beam time required for the complete experimental
measurements with Na beams

• Beam Energy Intensity Number
  Target Cumulative Detection
• (MeV/nucleon) (part./s) of days
  (nb. days)
• Campaign 1 (7 days 1 day stable beams)
• Na-24 8 5 x 107 1 C
  1 charged
• Na-20 8 5 x 107 1 C
  2 charged
• Na-28 8 maximum 4 C 6 charged
• (back-up Na-27)
• H, He, H 8 5 x 107 1 C, Au 7 E
  calibra.
• Na 8 5 x 107 1 C, Au 8 startup
• Campaign 2 (12 days 1 day stable beams)
• Na-20 15 5 x 107 1 C 1 charged
• Na-28 15 maximum 4 C 5
  charged
• Na-26 15 gt5 x 107 4 C 9 chgedntrons
• Na-26 12 5 x 107 2 C, Mg
  11 charged
• H, He, H 12 5 x 107 1 C, Au
  12 E calibra.
• Na 15 5 x 107 1 C, Au 13 startup

25
Results of different simulations
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
Other observables  correlation functions

• A - Velocity correlations between IMFs and
  quasi-spectators
• B - Two-fragment reduced-velocity correlation
  functions
• C - Emission chronology of non-identical particles

30
A - Velocity correlations between IMFs and
quasi-spectators

• IMF Intermediate Mass Fragment
• PLF Projectile-Like Fragment
• TLF Target-Like Fragment
• - IMFPLF and IMFTLF sub-systems
• Vrel(IMF,PLF) and Vrel(IMF,TLF)
• - Relative to the velocities corresponding to
  the Coulomb repulsion given by the Viola
  systematics for asymmetric systems (V. Viola et
  al., Phys. Rev. C31 (1985) 1550).
• VViola 20.755Z1Z2/(A11/3A21/3) 7.3
  MeV/m 1/2
• - Goal determine the time sequence and time
  scale of IMF production processes, as prompt
  emission vs sequential emission.

31
B - Two-fragment reduced-velocity correlation
functions

• - Definition is
• R(vred)1 C Ncorr(vred)/Nuncorr(vred)
• where vred is the reduced velocity between two
  fragments
• vred vrel /(Z1Z2)1/2
• - The functions N should reflect the topology of
  the events at freeze-out.
• - Goal extract information on the space-time
  structure of the emission source.
• E.g., is there a transition from surface to
  volume emission with increasing Ex?
• - A decrease in emission time
• from t 500 fm/c to t 20-50 fm/c
• is observed for Ex from 2.5 to 5 MeV/A.
• - No hypotheses are done information extracted
  directly from experimental data.
• - G.Tabacaru et al., Proc. of Bologna 2000,
  arXivnucl-ex/0102015 (INDRA data) - L.Beaulieu
  et al., Phys. Rev. Lett. 84 (2000) 5971 (ISiS
  data) - D.Durand et al., Nucl. Phys. A630
  (1998) 52c (data systematics for heavy-ion
  induced reactions).

32
C - Emission chronology of non-identical particles

• - Correlation functions gated on the particle
  velocity for two-(non-identical) particles
• C(q) k Ncorr(q)/Nuncorr(q)
• where q m(p1/m1-p2/m2) is the relative
• momentum of the particle pair (m is the reduced
  mass),
• Ncorr(q)is the measured coincidence yield, and
  Nuncorr(q)is the uncorrelated yield constructed
  by singles product of event mixing.
• Goal extract information on the order of
  particle emission, sensitive to reaction
  mechanisms
• No hypotheses information extracted form
  experimental data.
• The deduced emission time sequence is
  model-independent.
• - Results
• - R. Lednicky et al., Phys.Lett. B 373 (1996) 30
  (Method is proposed theoretically).
• - R. Ghetti et al., Phys. Rev.Lett. 87 (2001)
  102701 PRL 91 (2003) 092701 (CHIC Data).
• - D. Gourio et al., Eur. Phys. J. A 7 (2000) 245
  (INDRA Data).
• - R. Kotte and H. W. Barz, Eur. Phys. J. A 6
  (1999) 185.
• - D. Ardouin et al., Phys. Lett. B 446 (1999) 191
  (method applied to K K-).

33
Energy calibration and particle identification
34
Modified Parlog equation
The 5 parameters to ajust are a1,2,3,4 and T. We
take T8A et a36
35
(No Transcript)
36
GEMINIThis program follows the decay chain of a
compound nucleus via sequential binary decays
37
HIPSE event generator

• HIPSE Heavy-Ion Phase-Space Exploration
• Denis Lacroix, Aymeric Van Lauwe, and Dominique
  Durand, Phys. Rev. C 69, 054604 (2004)
• - An event generator dedicated to the description
  of nuclear collisions at intermediate energy
• - Based on the sudden approximation and on simple
  geometrical hypotheses, it can conveniently
  simulate heavy-ion interactions at all impact
  parameters.
• A valuable tool for the understanding of such
• processes as neck emission or multifragmentation
• in peripheral or/and central collisions.
• The reaction is described with help of three
  steps
• (a) The approaching phase of the collision
  ending
• when the two partners are at maximum overlap.
• (b) The partition formation phase This phase
  corresponds to the rearrangement of the nucleons
  into several clusters and light particles
  according
• to the impact parameter of the reaction.
• (c) The exit channel and after-burner phase up to
  the detectors The partition is propagated taking
  into account explicitly reaggregation effects due
  to the strong nuclear and Coulomb interactions
  among the various species of the partition.
  Secondary decays are taken into account by an
  evaporation code.

38
Grazing angles and fusion cross sections for the
different projectile-target systems

• System Lab. Grazing Angle (deg.) sFusion (mb)
• 28Na12C at 8 MeV/nucleon 7.6 700
• 28Na12C at 12 MeV/nucleon 4.7 600
• 28Na12C at 15 MeV/nucleon 3.8 570
• 28Na24Mg at 8 MeV/nucleon 10.1 840
• 28Na24Mg at 12 MeV/nucleon 6.4 722
• 28Na24Mg at 15 MeV/nucleon 5.1 675
• 20Na12C at 8 MeV/nucleon 9.6 560
• 20Na12C at 12 MeV/nucleon 6.2 490
• 20Na12C at 15 MeV/nucleon 4.9 462

39
Setup and bias optimization DIT, GEMINI,
HIPSE, GEANT4 Simulations for facility
optimization DIT Deep Inelastic
Transfer GEMINI statistical binary decay
code HIPSE event generator dedicated to the
description of nuclear collisions Calculations A
MD Antisymmetrized Molecular Dynamics DIT L.
Tassan-Got and C. Stephan, Nucl. Phys.A524 121
(1991) A model of stochastic transfers, using a
Monte Carlo method and accounting for sequential
evaporation. GEMINI R. Chariy et al., Nucl.
Phys. A483 391 (1988) This program follows the
decay chain of a compound nucleus via sequential
binary decays

40
The binding energies
41
At 28.7 MeV per nucleon
42
Modified Gogny
43
Two different asymmetry terms
44
Isotope distributions two Gogny terms
45
Isotope distributions 20Na vs 28Na
46
Mechanisms as an illustration
PLF Projectile-Like Fragment TLF
Target-Like Fragment IMF Intermediate Mass
Fragment
47
Our Z distribution measured at 45 MeV per nucleon
on 64Zn 64Zn
48
Isospin ratios for compound systems of Z 16
and 15

• Ne on 12,13C N/Z Mg on 9Be N/Z
• 17Ne 0,7 20Mg 0,83
  24Ne 1,4 28Mg 1,33
• F on 12,13C N/Z Na on 9Be N/Z
• 17F 0,89 20Na 0,82
• 24F 1,67 28Na 1,55

49
Collision Dynamics with HÉRACLES

• Readiness
• Apparatus
• - The multidetector HÉRACLES is being mounted at
  this moment.
• - Required changes have been made on the
  detectors already existing (CsI(Tl) and plastic
  phoswich detectors).
• - The complete setup of the chamber with pumping
  facility and complete cabling for the
  electronics, and the new detectors, could be
  complete in one year from now.
• Simulations
• - Several simulations have already been
  completed. More will be made to choose the best
  detector configuration according to the physics
  observables most appropriate to extract physics.
• - Other possibilities than DIT-GEMINI are being
  tried to check independently- HIPSE.

50
(No Transcript)
51
(No Transcript)
52
(No Transcript)
53
Two different asymmetry terms

• Standard

Modified