George A. Souliotis Collaborators:

M. Veselsky, G. Chubarian, L. Trache, A. Keksis, E. Martin, D.V. Shetty, S.J. Yennello

Recent research results presented at:

I The International Conference of Nucleon-Nucleon Collisions (NN03), Moscow, June 17-22, 2003, and The Institute of Nuclear Physics of NCSR ‘Demokritos’, Athens, Greece, June 24, 2003

a) Neutron-Rich Rare Isotope Production in the Fermi Energy Domain (Slides:1-12) b) Heavy Residue Properties, Isoscaling and N/Z Equilibration (Slides: 13-29)

   Production of Neutron-Rich Nuclides (methods):  target, projectile fission     cold projectile fragmentation (medium to high energy)  

 deep inelastic collisions (low to medium energies)   multinucleon transfer reactions (around Vb)  

Present work: deep inelastic collisions at Fermi energies:   86Kr(25MeV/nucleon) + 64Ni, ( PLB 543 163 (2002)   86Kr + 124Sn, 112Sn (PRL in press , nucl-ex 0302011)   Heavy-Residue Yield Scaling (nucl-ex 0305027)

Findings:  Enhanced production of neutron-rich species, neutron skin effect  Heavy-Residue Yield Ratios probing N/Z equilibration

Applications with RIB from TAMU upgrade and RIA

Introduction

MARS Recoil Separator and Setup

PPAC2 Stop T Silicon Telescope:ΔE1, X,Y (Strips)ΔE2, Eresidual

PPAC1 Start T X,Y

Production Target

D1D2

D3

WienFilter

Q1Q2Q3

Q4Q5

Dispersive Image

FinalAchromatic Image

Rotatable ArmReaction Angle: 0-12o (selectable)

MARS Acceptances:Anglular: 9 msrMomentum: 4 %

Beam angle set to: 0o (1.0-3.0o) for Kr+Ni (gr = 3.5o)

4o (2.5-5.5o) for Kr+Sn (gr = 6.5o)

Extracted physical quantities:

Velocity, Energy loss, Total Energy Mass-to-charge ratio: A/Q B ~ A/Q Atomic Number Z Z ~ ΔE1/2 Ionic charge Q Q ~ f(E, ) Mass number A A = Qint A/Q

  Yield distribution (Z,A,υ)  

Reactions studied: 86Kr 22+ (25 MeV/u, 1-5 pnA) + 64Ni (4 mg/cm2) PLFs in 1.0-3.0o (gr= 3.5o)

86Kr 22+ (25 MeV/u, 1-5 pnA) + 124,112Sn (2 mg/cm2) PLFs in 2.5-5.5o (gr= 6.5o)

Measured quantities: ΔE1, ΔΕ2, Εr , (x,y) strips

time of flight (START-STOP) x-position at First Image (Bρ information)

Experimental Details:

Gross Distributions: 86Kr (25 MeV/u) + 64Ni

 ----- DIT/GEMINI

- - - DIT/GEMINI (filtered)

DIT: L. Tassan-Got and C. Stephan, Nucl. Phys. A524 121 (1991)GEMINI: R. Chariy et al., Nucl. Phys. A483 391 (1988)EPAX: K. Summerer and B. Blank, Phys. Rev. C61 034607 (2000).

Isobaric YieldDistribution

Z - A Distribution

(relatice to Z)

Velocity - A Distribution

References:

Gross Distributions: 86Kr (25 MeV/u) + 124Sn

-- DIT/GEMINI

-- DIT/GEMINI

filtered (θ,Bρ)

-- EPAX2

DIT: L. Tassan-Got and C. Stephan, Nucl. Phys. A524 121 (1991)GEMINI: R. Chariy et al., Nucl. Phys. A483 391 (1988)EPAX2: K. Summerer and B. Blank, Phys. Rev. C61 034607 (2000).

Isobaric YieldDistribution

Z - A Distribution

(relatice to Z)

Velocity - A Distribution

References:

Data Data Corrected (θ, Bρ)

Resolutions (FWHM) : ΔZ = 0.5 ΔQ = 0.4 ΔA = 0.5

Z, Q, Α spectra (one run): 86Kr (25 MeV/u) + 64Ni

Mass distribution of Ge (Z=32) isotopes

- 4p

- 4p+1n

- 4p+2n

86Kr (25 MeV/u) + 64Ni

Mass distributions: 86Kr (25 MeV/u) + 64Ni*

Data---- EPAX DIT/GEMINI

- 3p+1n+2n+3n

-2p+1n+2n+3n+4n

-1p+1n+2n+3n+4n

-4p+1n+2n

-5p+1n -6p

Largercross sectionsw.r.t. DIT/GEMINIor EPAX(Z=35-31)

Cross sectionssimilar to DIT/GEMINIor EPAX(Z 30)

Br Se

As

ZnGa

Ge

* G.A. Souliotis et al., Phys. Lett. B 543, 163 (2002)

Mass distributions (cont.): 86Kr (25 MeV/u) + 64Ni

Measured cross sections are similar to DIT/GEMINIand EPAX

Data

---- EPAX

DIT/GEMINI

Cu

Fe

Mn Cr

Ni

Co

Mass distributions : 124Sn (20 MeV/u) + 124Sn

Measured cross sections agree with DIT/GEMINI

They are 10-100 larger than

EPAX predictions

Data

---- EPAX

DIT/GEMINI

Cu

Fe

Mn Cr

Ni

Co

?

Estimates of Production Rates: 86Kr+64Ni

 

86Kr beam (25MeV/u) 100 pnA 64Ni target (20 mg/cm2)

*

Use cross sections of this work, assume:

* GSI data: M. Weber et al . Nucl. Phys. A 578 (1994) 659

Mass distributions: 86Kr (25 MeV/u) + 124Sn, 112Sn*

86Kr +124Sn 86Kr +112Sn

----- EPAX

- 3p

-2p-1p

-4p

-5p

Largercross sectionswith the n-rich 124Sn target(Z=35-30)

Se

As

ZnGa

Ge

* G.A. Souliotis et al., Phys. Rev. Lett. in press, nucl-ex/0302011

Br

Neutron-Proton Density Calculations for 124Sn, 112Sn

Thomas-Fermi : V.M. Kolomietz, A.I. Sanzhur et al., PRC 64, 024315 (2001)

------- Skyrme-Hartree-Fock: J. Friedrich, P. Reinhard, PRC 33, 335 (1986)

neutronskin

n

n

p

p

Mass Distribution of Germanium from 86Kr(25MeV/u) + 124Sn,112Sn, 64Ni

Ge

Data usingtargets:

124Sn 112Sn 64Ni

------ EPAX2

Target N/Z Valley of stability 124Sn 1.48 n-rich 118Sn

112Sn 1.24 n-poor 64Ni 1.29 n-rich 60Ni

Comparison: Data, Calculations: 86Kr (25 MeV/u) + 124Sn, 112Sn*

Data DIT/GEMINI (standard) DIT/GEMINI with (r) EPAX

Calculation withneutron “skin”appears to accountfor the largercross sectionswith the n-rich 64Ni, 124Sn targets

* G.A. Souliotis et al., Phys. Rev. Lett. in press, nucl-ex/0302011

Comparison: Data/EPAX : 86Kr (25 MeV/u) + 64Ni, 124Sn

For near-projectilefragments and above the projectile N/Z,the cross sectionsare larger.

DIC between massive n-rich nuclei appear to beadvantageousfor very high N/Z RIB production

Velocity vs Z correlation

• 86Kr + 124Sn

• 86Kr + 112Sn

• 86Kr + 64Ni

• 86Kr + 58Ni

min E*/A = 2.2 MeV

T = 5.3 MeV

min

N/Z vs Z correlation

• 86Kr + 124Sn

• 86Kr + 112Sn

• 86Kr + 64Ni

• 86Kr + 58Ni

EAL: evaporation attractor line *

SL: stability line

* R. Charity, Phys. Rev. C 58, 1073 (1998)

86Kr: 1.39124Sn: 1.44112Sn: 1.24

64Ni: 1.2958Ni: 1.07

N/Z

N/Z ~ constant

Scaling of Yield Ratios :

•86Kr+124Sn,112Sn

R21 (N,Z) = Y2/Y1

R21 = C exp ( N )

R21 = C´ exp ( Z )

Scaling of Yield Ratios :

•86Kr+64Ni,58Ni

R21 (N,Z) = Y2/Y1

R21 = C exp ( N )

R21 = C´ exp ( Z )

Isoscaling Parameters: ,

• 86Kr+64Ni,58Ni

R21 = C exp ( N )

R21 = C´ exp ( Z )

• 86Kr+124Sn,112Sn

=0.43

=0.27

= – 0.34

= – 0.51

Origin of Isotopic Scaling:

Grand Canonical Ensemble (equilibrium limit): Fragment Yield: *

Y(N,Z) = F(N,Z) exp{B(N,Z)/T} exp { (Nn+Zp)/T }

R21 (N,Z) = Y2(N,Z) / Y1(N,Z) = C exp ( N + Z) (Isoscaling)

with: = n/T = p/T n Sn

p Sp

= 4 Csym/T ( (Z1/A1)2 – (Z2/A2)2

)

* J. Randrup and S. Koonin, Nucl. Phys. A 356, 223 (1981) M. B. Tsang et al. Phys. Rev. C 64, 054615 (2001) A.S. Botvina et al. Phys. Rev. C 65, 044610 (2002)

Extracted Parameters:

Heavy Residue Isoscaling and N/Z equilibration

R21 ~ exp ( N ) N/Z86Kr+124Sn => [210Rn] 1.4486Kr+112Sn => [198Rn] 1.30

(N/Z) = 0.14N/Z equilibratedquasi-projectile

= 4 Csym/T ( (Z1/A1)2 – (Z2/A2)2

) *

= 8 Csym/T (Z/A)3ave (N/Z)

* M. B. Tsang et al. Phys. Rev. C 64, 054615 (2001) A.S. Botvina et al. Phys. Rev. C 65, 044610 (2002)

• 86Kr+124Sn,112Sn

Evolution towards N/Z equilibration of quasi-projectile**

** G.A. Souliotis et al., nucl-ex/0305004, Phys. Rev. C submitted

Velocity and E* vs mass correlations

• 86Kr + 124Sn

• 86Kr + 112Sn

min E*/A = 2.2 MeV

T = 5.3 MeV

E*/A maxobserved

Isobaric Scaling of Yield Ratios : R21(N,Z) = Y2/Y1

R21 = C exp ( N + Z) Rearrange with ´= ( +)/2 * ´= ( -)/2R21 = C exp {´A + ´(N Z)} = C exp (´A + 2´tz )

86Kr+124Sn,112Sn data

=0.47

* A.S. Botvina et al. Phys. Rev. C 65, 044610 (2002)

= 0.47

Heavy Residue Isobaric Scaling and N/Z equilibration

R21 ~ exp{ (NZ)} N/Z86Kr+124Sn => [210Rn] 1.4486Kr+112Sn => [198Rn] 1.30 = 4Csym/T (Z/A)2

ave (N/Z)qp **

86Kr+124Sn,112Sn Isobaric approach Isotopic approach

Evolution towards N/Z equilibration of quasi-projectile**

(N/Z) = 0.14N/Z equilibratedquasi-projectile

N/Z equilibration : continuous process strongly correlated with E*

Intermediate Energy: S.J. Yennello et al, Phys. Lett. B 321, 15 (1994)(IMF yield ratios) B.A. Lee and S.J. Yennello, Phys. Rev. C 52, 1746 (1995) H. Johnston et al., Phys. Lett. B 371, 186 (1996)

** G.A. Souliotis et al., nucl-ex/0305027, Phys. Lett. B, submitted

Early N/Z equilibration studies

N/Z equilibratedquasi-projectiles

Evolution towards N/Z equilibration

58Ni,64Ni (8.5MeV/u) + 238U (2)

92Mo(15MeV/u) + 238U, 154Sm (1)

N/Z

N/Z58Ni measured derived64Ni measured derived

Derived from datausing evap. code

(1) M. Petrovici et al. , Nucl. Phys. A 477, 277 (1988)(2) R. Planeta et al., Phys. Rev. C 38, 195 (1988)

DIC Model(Randrup)

Measured charge, mass, velocity distributions of residues from: 86Kr (25 MeV/u) + 64Ni, 124Sn, 112Sn, Studies inside gr

Reaction simulations: DIT/Gemini: reasonable description, Effect of the Neutron Skin (very n-rich products)

Scaling of Heavy-Residue Yields: N/Z Equilibration

Plans for future work : Investigate reactions with heavier targets: 208Pb, 238U (look ~ gr )

Study the process of N/Z equilibration, E/A dependence

* TAMU Cyclotron White Paper in : http://cyclotron.tamu.edu

Tools at Texas A&M: Superconducting Solenoid Rare Isotope Line (Large Acceptance) MARS Line (High Resolution) Future: Re-accelerated beams via a Gas-Cell based ISOL concept*

Summary and Outlook

Application in studies using high-N/Z beams from RIA