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Isospin Diffusion Experiment(s) at RIKEN

Betty TsangAugust 22, 2012

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Outline

• Introduction – MSU expeirment• Experimental Setup in RIKEN• Status of RIKEN isospin expeirments• Proposed reaction 132Sn+112Sn, 124Sn

HIC constraints on symmetry energy

Current constraints from HIC weigh heavily on isospin diffusion. (The n/p ratios are more for consistency checks due to large error bars at high nucleon energy.

Isospin Diffusion with Neck Fragments

This can be described by the isoscaling parameters and :

)ZNexp(C

Z,NYZ,NY

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Liu et al.PRC 76, 034603 (2007).

Ri(α)=Ri(d) assuming d=mα+bd (residue asymmetry)α (isoscaling parameter)

BBAA

BBAAABi xx

xxxR

2/)(2

Confirm the assumed Linearity of α on δ

• α depends linearly on the asymmetry according to statistical and dynamic models.

• Experimentally verified in central collisions.

• Measure 118Sn on 118Sn to add a data point to 112Sn + 112Sn and 124Sn + 124Sn.

BBAA

BBAAABi xx

xxxR

2/)(2

Ri(α)=Ri(d) assuming d=mα+bd (residue asymmetry, BUU)α (isoscaling parameter, expt)

Isospin Transport in Residues

• Different amount of isospin diffusion for heavy residues.

• provide another isospin observable and impact parameter selection

iiksym SSE

0

3/2

0)(

Experiment 07038: Precision Measurement of Isospin Diffusion

• Investigates the density-dependence of the nuclear symmetry energy• 112,118,124Sn+ 112,118,124Sn Collisions• Combines the MSU Miniball, the LASSA Array, and the S800 Spectrograph

Incoming Beam, 70 MeV/u

Beam-like fragments 10<Z<50

J.R. Winkelbauer,7

Experiment 07038: Precision Measurement of Isospin Diffusion

Motions:1. Targets2. Downstream

scintillator/degrader (deflect beam away from focal plane)

Detectors3. miniball—b selection4. LASSA – detect Z<85. S800 – detect

residues 20<Z<45

J.R. Winkelbauer,8

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1. Introduction1.1 Data taken at MSU (Ex07038)

• 112,118,124Sn + 112,118,124Sn • ~5 mg/cm2 Targets• 70 MeV/u beam energy• Event rates 200-300/s• Beam Rate 2*107/s to 6*107/s• Millions of events:

BeamTarget

112Sn 118Sn 124Sn

112Sn / 43hr 11.4M/11.2hr x 8.7M/11.3hr118Sn / 43hr 3.8M/2.8hr 10.7M/8.4hr x124Sn / 43 hr 12.3M/10.6hr 10.1M/9.5hr 15.2M/10hr

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1.2 RIKEN Experiment

• 108Sn + 112Sn • 108Sn + 124Sn • 112Sn + 112Sn (referenced to MSU) • 112Sn + 124Sn (referenced to MSU)

Primary beam: 124Xe (10-30 pnA)No 124Sn beam because there is no 132Xe primary beam124Sn Beam is not availableProposed beams : 108Sn and 112SnProposed reactions:

Calculations use beam intensities in the proposal based on 100 pnA of 124Xe beams

Microball from WU

2. Proposed Experimental Set up

Chamber from RIKEN

Scintillator & degrader foil ladder

12Fast Plastic Scintillator with a hole in the center: Polystyrene ,C8H8, 1.06g/cm3, 125 micron

Target Thickness ( mg/cm2)

112Sn 50124Sn 50

Beam Energy ( MeV/u)

Intensity (pps)

108Sn 73 6e+5112Sn 73 1e+6124Sn 73 6e+5

Experimental Setup

BigRIPSZero Degree Spectrometer

TargetSlits

(It turns out that the beam intensity is only 20% of what is written in the proposal and here)

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6. Beam Charge States Measurement

Beam Brho(Tm) F9 slit (mm) Charge states

108Sn 2.64 -75 ~ 75 50+ , 49+ , 48+

112Sn 2.74 -75 ~ 75 50+ , 49+ , 48+

(With target, With Fast Plastic hole)

108Sn: 112Sn:

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3. Brho “Safe” Region

(In current setting, the same fragments from different reactions have the similar Brho. )

I. Avoid the beamII. Consider different reactions at the same time.

beam target Brho without plastic

Brho with plastic

108Sn 112Sn <2.58 <2.52124Sn <2.58 <2.52

112Sn 112Sn <2.68 <2.62124Sn <2.68 <2.62

124Sn 112Sn <2.995 <2.935124Sn <2.995 <2.935

Conclusion: choose the Brho region smaller than 2.58.

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7. Al Degrader (For Plan A)

Use the Al to replace the target to tune the beam into the fragments Brho region.

Beam Brho(Tm) F9 slit (mm) Al thickness (mg/cm2)

108Sn 2.505 -75 ~ 75 70.7 (7 layer)

112Sn 2.505 -75 ~ 75 101 ( 10 layer)

108Sn: 112Sn:

(No target, No Fast Plastic)

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5.2* Summary of the measured isotopes (for Plan B)

Zn(Z=30) Br(Z=35) Zr(Z=40) Rh(Z=45)

108Sn+112Sn (62?),63,64 73,74,75 83,84,85,86 93,94,95,96,97

108Sn+124Sn (62?),63,64 73,74,75 83,84,85,86 93,94,95,96,97

112Sn+112Sn (62?),63,64 73,74,75 83,84,85,86 93,94,95,96,97,98

112Sn+124Sn (62?),63,64 73,74,75 83,84,85,86 93,94,95,96,97,98

112Sn+112Sn(MSU)

61 ~ 66 72 ~ 77 83 ~ 89 93 ~ 101

112Sn+124Sn(MSU)

61 ~ 66 71 ~ 77 82 ~ 89 93 ~ 101

Press here to directly go back to Slide 16

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Status• Xe beam cancelled for December, 2012• Rachel Hodges will travel to RIKEN in week of Sept 10

and work on the chamber design & beam calculations.• Transport microball to RIKEN in Dec (Betty?)• Pursuing a separate set of electronics (loan from ORNL?)• Propose 132Sn+ 112, 124Sn; 124Sn+124Sn (match to MSU) to

Dec PAC• Run the proposed experiment as a campaign to the

108,112Sn + 112, 124Sn isospin diffusion expt.