Water drop to metal and water drop to water drop corona discharges

ABSTRACT Water drop corona has been identified by many authors as a major cause of deterioration of silicone rubber high voltage insulation but at this stage there have been no thorough studies made of this phenomenon. In this paper fundamental observations are presented of electrical discharges from water drops, movement of drops, and drop coalescence in the presence of 50 Hz alternating electric fields. Measurements are made both with water drops on metal electrodes and with water drops on the surface of silicone rubber insulation. Comparisons are made of current pulses and atomic emission spectra from previous work by the authors on dry point-plane discharges to provide information about the main types of active species which may cause insulator surface degradation. Visual images of wet electrodes show how water drops can play a part in encouraging flashover. The first reproducible visual images of water drop corona at the triple junction of water air and rubber insulation are presented. The current measurements were captured with a digital oscilloscope sampling at 200 MHz. The time constant of the measuring circuitry was approximately 14 nanoseconds

Fusion and Quasifission in Superheavy Element Synthesis

In the 1960s, quite soon after the recognition of the role of quantum shells in providing extra stability to nuclei, an “island of stability” of spherical superheavy nuclei was predicted. It was expected to be centered on proton number Z = 114 and neutron number N = 184, the next magic numbers predicted above Z = 82 and N = 126, which give nuclei around 208Pb their enhanced stability. Since then, intensive experimental efforts have been made to synthesize these superheavy elements, usually defined as those with atomic number 104 or more.This work has been supported by several Australian Research Council Grants (DP140101337, DP160101254, DP170102318, DE140100784, FT120100760, and FL110100098) and accelerator operations support from the Australian Federal Government NCRIS program

Probing quantum many-body dynamics in nuclear systems

Quantum many-body nuclear dynamics is treated at the mean-field level with the time-dependent Hartree-Fock (TDHF) theory. Low-lying and high-lying nuclear vibrations are studied using the linear response theory. The fusion mechanism is also described fo

Disentangling effects of nuclear structure in heavy element formation

Forming the same heavy compound nucleus with different isotopes of the projectile and target elements allows nuclear structure effects in the entrance channel (resulting in static deformation) and in the dinuclear system to be disentangled. Using three isotopes of Ti and W, forming 232Cm, with measurement spanning the capture barrier energies, alignment of the heavy prolate deformed nucleus is shown to be the main reason for the broadening of the mass distribution of the quasifission fragments as the beam energy is reduced. The complex, consistently evolving mass-angle correlations that are observed carry more information than the integrated mass or angular distributions, and should severely test models of quasifission

How the Pauli exclusion principle affects fusion of atomic nuclei

The Pauli exclusion principle induces a repulsion between composite systems of identical fermions such as colliding atomic nuclei. Our goal is to study how heavy-ion fusion is impacted by this "Pauli repulsion." We propose a new microscopic approach, the density-constrained frozen Hartree-Fock method, to compute the bare potential including the Pauli exclusion principle exactly. Pauli repulsion is shown to be important inside the barrier radius and increases with the charge product of the nuclei. Its main effect is to reduce tunneling probability. Pauli repulsion is part of the solution to the long-standing deep sub-barrier fusion hindrance proble

Reconstructing breakup at sub-barrier energies

Using a position sensitive detector array, back-angle coincidence measurements of breakup fragments at sub-barrier energies has enabled the complete characterisation of the breakup processes in the reactions of 6,7Li with 208Pb. Breakup processes and the

Microscopic study of the effect of intrinsic degrees of freedom on fusion

usion cross-sections are computed for the 40Ca+40Ca system over a wide energy range with two microscopic approaches where the only phenomenological input is the Skyrme energy density functional. The first method is based on the coupled-channels formalism, using the bare nucleus-nucleus potential calculated with the frozen Hartree-Fock technique and the deformation parameters of vibrational states computed with the time-dependent Hartree-Fock (TDHF) approach. The second method is based on the density-constrained TDHF method to generate nucleus-nucleus potentials from TDHF evolution. Both approaches incorporate the effect of couplings to internal degrees of freedoms in different ways. The predictions are in relatively good agreement with experimental dat

Designing neural networks for manufacturing process control systems

The design of neural networks for the control of discrete manufacturing processes is addressed. Rather than treating the networks as adaptive black boxes, an architecture that links the weights associated with the nodes and thus allows the relationships and internal structure to be tightly constrained is introduced. The constrained search space gives greater confidence in the internal representations that have been induced by the training set and therefore about the correct behavior of the network between the given limits. The method is illustrated by applying it to the dispensing of adhesive