Engineering topics
Xiao, Z. G.
Publications and source records attributed to Xiao, Z. G..
Probing the Symmetry Energy with the Spectral Pion Ratio
Many neutron star (NS) properties, such as the proton fraction within a NS, reflect the symmetry energy contributions to the Equation of State that dominate when neutron and proton densities differ strongly. To constrain these contributions at supra-saturation densities, we measure the spectra of charged pions produced by colliding rare isotope tin (Sn) beams with isotopically enriched Sn targets. Here, using ratios of the charged pion spectra measured at high transverse momenta, we deduce the slope of the symmetry energy to be 42 < $L$ < 117 MeV. This value is slightly lower but consistent with the $L$ values deduced from a recent measurement of the neutron skin thickness of 208 Pb.
Symmetry energy investigation with pion production from Sn+Sn systems
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Coexistence of Reflection Asymmetric and Symmetric Shapes in $^{144}\mathrm{Ba}$
Level structures in the neutron-rich $^{144}\mathrm{Ba}$ nucleus have been reinvestigated by measuring prompt gamma rays in the spontaneous fission of $^{252}\mathrm{Cf}$. The previous $s = +1$ octupole band structure with reflection asymmetric shape has been expanded, and a side quadrupole band structure based on a $3^+$ state with reflection symmetric shape is identified. Thus, the results show the coexistence of reflection asymmetric and symmetric shapes in $^{144}\mathrm{Ba}$. This is a first identification of such a shape coexistence structure in a nuclear structure. Finally, the other structural characteristics are discussed.
A gating grid driver for time projection chambers
A simple but novel driver system has been developed to operate the wire gating grid of a Time Projection Chamber (TPC). This system connects the wires of the gating grid to its driver via low impedance transmission lines. When the gating grid is open, all wires have the same voltage allowing drift electrons, produced by the ionization of the detector gas molecules, to pass through to the anode wires. When the grid is closed, the wires have alternating higher and lower voltages causing the drift electrons to terminate at the more positive wires. Rapid opening of the gating grid with low pickup noise is achieved by quickly shorting the positive and negative wires to attain the average bias potential with N-type and P-type MOSFET switches. The circuit analysis and simulation software SPICE shows that the driver restores the gating grid voltage to 90% of the opening voltage in less than 0.20 µs, for small values of the termination resistors. When tested in the experimental environment of a time projection chamber larger termination resistors were chosen so that the driver opens the gating grid in 0.35 µs. In each case, opening time is basically characterized by the RC constant given by the resistance of the switches and terminating resistors and the capacitance of the gating grid and its transmission line. By adding a second pair of N-type and P-type MOSFET switches, the gating grid is closed by restoring 99% of the original charges to the wires within 3 µs.
Reinvestigation of high spin states and proposed octupole correlations in Ce 147
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Observation of new levels and proposed octupole correlations in neutron-rich 150 Ce
Not Available