E432a : Decay of Highly Excited Projectile-like Fragments Formed in dissipative peripheral collisions at intermediate energies 1. Understanding thermodynamic properties as a function of N/Z 2. Studying N/Z equilibration allows us to probe mass and energy transport in heavy-ion collisions at intermediate energies. Indiana University + DEMON + GANIL+ GSI + Daresbury + LNS-INFN M.B. Tsang et al., PRL 92, 260701 (2004) Both these issues are related to the density dependence of the asymmetry term! Creation of more “surface material” (low density nuclear matter that is significantly excited ) 1. L.G. Sobotka et al., PRL 93, 132702 (2004) 2. J. Toke et al, PRC 72 031601 (2005) 3. L.G. Sobotka et al., PRC 73, 014609 (2006) PLF* decay Comparison of PLF* decay (~ 0 ) with mid- rapidity (low )
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E432a: Decay of Highly Excited Projectile-like Fragments Formed in dissipative peripheral collisions at intermediate energies 1.Understanding thermodynamic.
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E432a: Decay of Highly Excited Projectile-like Fragments Formed in dissipative peripheral collisions at intermediate energies
1. Understanding thermodynamic properties as a function of N/Z
2. Studying N/Z equilibration allows us to probe mass and energy transport in heavy-ion collisions at intermediate energies.
Both these issues are related to the density dependence of the
asymmetry term!
Creation of more “surface material” (low density nuclear matter that is significantly excited)
1. L.G. Sobotka et al., PRL 93, 132702 (2004)2. J. Toke et al, PRC 72 031601 (2005)3. L.G. Sobotka et al., PRC 73, 014609 (2006)
PLF* decay
Comparison of PLF* decay (~ 0) with mid-rapidity (low )
Event selection: 15≤Z≤46 in 2≤lab≤4 Nc≥5 in 4
Proof of approach in studying PLF* decay
PLF*
TLF*
Decreasing VPLF*
Increasing E*
R. Yanez et al., PRC68, 011602(2003)
Ability to reach high excitation energy (E*/A~6 MeV) and select it.
114Cd + 92Mo at E/A = 50 MeV
Study particles emitted from surface
YieldSpectraCompositionQuantum states
Thermodynamics of surface with varying
N/Z
114Cd + 92Mo at E/A = 50 MeV
Tidal Effect and Proximity decay
11.35 MeV
3.03 MeV
gr. st.
8Be α + α93 keV
11.44 MeV
3.12 MeV
3.5 MeV
=1.51 MeV
=6.8 eV
• Select 2 particles forward of the PLF (15≤Z≤46)
• construct statistical background with mixed event technique
• Mixed event background in agreement with Monte Carlo simulation
Zsource
Cluster
Transverse Higher Erel
Zsource Zsource
Longitudinal Lower Erel
Short-lived state probes nuclear surface
Zsource
Zsource
β
Zsource
Erel depends on decay angle,
consistent with coulomb tides model
20% effect
11 MeV state only evident for transverse decay
A. B. McIntosh et al., in preparation
This demonstrates the level of resonance spectroscopy possible in
these reactions with FIRST+LASSAAlso intend neutron-fragment resonance spectroscopy!
Keys:1. Good event selection of peripheral
collisions2. High resolution measurement
(angle/energy/isotope) for charged particles
3. Measurement of neutron spectra (DEMON)
FIRST
LASSA
FIRST and LASSA are highly segmented 600 Si channels
ISiS
Measure Z,A,E,Al T. Paduszynski et al., NIM A 547,464 (2005)
Experimental Setup
Data from FIRST commissioning expt.!
FIRST + LASSA at TAMU
Since E432 proposal:
1. Scattering chamber built (thin-wall)2. FIRST concept proved in commissioning expt.3. Publication of initial physics results underway4. ASIC readout successfully used in HiRA experiments5. New electronics (MASE) to facilitate readout of FIRST near completion.6. Integration of VME QDC/TDC into DAQ for DEMON readout.
ElectronicsMASE: Multiplexed
AnalogShaper Electronics
(Readout of FIRST)
512 channels in 2 crate configuration
HiRA ASIC (HINP16C)
(Readout of LASSA)(Preamps, Shaper, Discriminator, TAC)
George L. Engle et al., submitted to NIM
C. J. Metelko et al., in preparation
MRS(low )
QP(normal )
Neutron enrichment of low-density nuclear matter
64Zn + 64Zn at E/A=45 MeV (commissioning expt. for FIRST)
• no initial driving force to N/Z equilibrate
• low density mid-rapidity (MRS) is neutron-rich in comparison to high density (QP).
• Different behavior is observed for the emitted charged particles (large clusterization of N=Z at low density)
• Observation of enrichment above that of the system’s N/Z requires measurement of free neutrons.
12C + 232Th at E/A=16,22 MeV ANL and MSU-NSCL PRC 66,014608 (2002)
Selected publications
Extra slides start here
Proposed measurement
Define emitting source by selecting PLF size (Z) and excitation (velocity damping).
Measure neutrons with DEMON
Measurement with different projectile N/Z
Measurement of different N/Z and mass asymmetry
Measure N/Z of fragments produced in highly aligned breakups
Statistical decay of nuclear matter as a function of N/Z, size, and E*:Isotope yields (e.g. mirror nuclei), spectral shapes (sensitivity to level density), correlation functions (emission timescales), population ratios, etc.
Isospin equilibration/reaction dynamics
Correlation studies of short-lived particle unbound states
W.P. Tan et al., PRC 69, 061304(R) (2004)
FIRST :Forward Indiana Ring Silicon Telescopes
T1 : 200 m Si(IP), S2/ 1mm Si(IP), S2/ 2-3cm CsI(Tl)At 28 cm, = 2.25-7.05 with = 0.1
T2 : 300 m Si(IP), S1/ 2-3cm CsI(Tl) At 19 cm, = 7.37-14.5 with = 0.4
T3 : 300 m Si(IP), S1/ 2-3cm CsI(Tl) At 9 cm, = 15.2-28.5 with = 0.7
Device dedicated to measure the decay of the PLF* :
Limiting temperature Dynamical process PLF* fragmentation ...
Large number of channelsuse of MASE
Design : P.H. Sprunger
5811
6194
6139
6072
5903 5946
1. <M> and Tslope depend linearly on VPLF*
2. E*/A deduced by calorimetry increases monotonically with increasing dissipation reaching a maximum of approximately 6 MeV.
3. <E*> attained is independent of ZPLF, depends on VPLF*
• Select PLF* size by selecting residue Z.• Select excitation by selecting VPLF*
• Vary N/Z by changing (N/Z)proj.,tgt.
FIRST performanceResolution:
• T1: A up to 30 Z up to projectile
• T2: A up to 18• T3: A up to 15
Telescope Case a Case b Case c Case d RejectT1 16 72 0.04 1.2 10.8T2 69 4.7 26.3T3 49 24 27