R. S. Wang

SπRIT: A time-projection chamber for symmetry-energy studies

A time-projection chamber (TPC) called the SAMURAI Pion-Reconstruction and Ion-Tracker (S pi RIT) has recently been constructed at Michigan State University as part of an international effort to constrain the symmetry-energy term in the nuclear Equation of State (EoS). The S pi RIT TPC will be used in conjunction with the SAMURAI spectrometer at the Radioactive Isotope Beam Factory (RIBF) at RIKEN to measure yield ratios for pions and other light isospin multiplets produced in central collisions of neutron-rich heavy ions, such as Sn-132+Sn-124. The S pi RIT TPC can function both as a TPC detector and as an active target. It has a vertical drift length of 50 cm, parallel to the magnetic field. Gas multiplication is achieved through the use of a multi-wire anode plane. Image charges, produced in the 12096 pads, are read out with the recently developed Generic Electronics for TPCs

Competition between Coulomb and symmetry potential in semi-peripheral heavy ion collisions

The anisotropy of angular distributions of emitted nucleons and light charged particles for the asymmetric reaction system,

Prototype studies on the forward MWDC tracking array of the external target experiment at HIRFL-CSR

^{40}

Non-uniformity effects of the inter-foil distance on GEM detector performance

Ar+

High-spin structures in the139Pr nucleus

^{197}

Long-time drift of the isospin degree of freedom in heavy ion collisions

Au, at b=6fm and

Time-dependent isospin composition of particles emitted in fission events following Ar-40+Au-197 at 35 MeV/u

E_{beam}

Reinvestigation of the collective band structures in odd-odd 138Pm nucleus

=35, 50 and 100MeV/u, are investigated by using the Improved Quantum Molecular Dynamics model. The competition between the symmetry potential and Coulomb potential shows large impacts on the nucleons and light charged particles emission in projectile and target region. As a result of this competition, the angular distribution anisotropy of coalescence invariant Y(n)/Y(p) ratio at forward regions shows sensitivity to the stiffness of symmetry energy as well as the value of Y(n)/Y(p). This observable can be further checked against experimental data to understand the reaction mechanism and to extract information about the symmetry energy at subsaturation densities.

High-spin structures in the Xe-129 nucleus

A prototype of the forward tracking array consisting of three multiwire drift chambers (MWDC) for the external target experiment (CEE) at the Heavy Ion Research Facility at the Lanzhou -Cooling Storage Ring (HIRFL-CSR) has been assembled and tested using cosmic rays. The signals from the anode wires are amplified and fed to a Flash-ADC to deliver the drift time and charge integration. The performances of the array prototype are investigated under various high voltages. For the tracking performances, after the space-time relation (STR) calibration and the detector displacement correction, the standard deviation of 223 μm of the residue is obtained. The performances of the forward MWDCs tracking array meets the requirements of CEE in design.

Collective band structures in the Tc-99 nucleus

The non-uniformity effect of the inter-foil distance has been studied using a gaseous electron multiplication (GEM) detector with sensitive area of 50mm × 50mm. A gradient of the inter-foil distance is introduced by using spacers with different heights at the two ends of the foil gap. While the cluster size and the intrinsic spatial resolution show insignificant dependence on the inter-foil distance, the gain exhibits an approximately linear dependence on the inter-foil distance. From the slope, a quantitative relationship between the change of the inter-foil distance and the change of the gain is derived, which can be used as a method to evaluate the non-uniformity of the foil gap in the application of large-area GEM detectors.