This book contains information on atomic, molecular and optical physics. Topics covered include: muon-catalyzed fusion and cooperative effects in atomic physics.

Advances in Atomic, Molecular, and Optical Physics

The physics of gas discharge lamps is reviewed, with particular emphasis on new developments in the field. In addition to the most important light sources (fluorescent and high-pressure discharge lamps), a number of less common sources are also discussed. The review covers not only the physics of the discharges themselves, but also their interactions with lamp materials and external driving circuits. Important historical steps in lamp product development are described and special sections are devoted to the properties of light, diagnostics, and modeling of the discharges. A detailed, but not exhaustive, review of the published literature is provided and some possible future directions for research in the subject are discussed.

The physics of discharge lamps

The formation of an axisymmetric vortex ring by forcing uid impulsively through a pipe is examined. An idealized model of the circulation, impulse and energy provided by the injected plug is developed, and these quantities are equated to the corresponding properties of the class of rings with finite cores described by Norbury (1973). It is shown that, as the length-to-diameter aspect ratio L/D of the plug increases, the size of the core increases in comparison with all the fluid carried along with the ring, until the limiting case of Hill's spherical vortex is reached. For aspect ratios larger than a certain value it is not possible to produce a single ring while conserving circulation, impulse, volume and energy. This implies that the limiting vortex is ‘optimal’ in the sense that it has maximum impulse, circulation and volume for a given energy input. While this matching calculation makes the physical mechanism clear, the L/D ratio that can be achieved in practice is more appropriately taken from the direct experimental measurements of Gharib et al. (1998) who concluded that the limiting value is L/D = 4. This is close to the value found in our calculation.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112000002263

The formation of optimal vortex rings, and the efficiency of propulsion devices

An analysis is presented of the motion of a turbulent thermal in an unstratified environment. Although based upon the entrainment hypothesis introduced by G. I. Taylor (see Morton, Taylor & Turner 1956), the analysis differs from previous work in that it is not limited to small density differences between the thermal and its surroundings. Also, the influence of the virtual mass of the unsteadily moving fluid, ignored by previous investigators, is included and shown to be of significance for any density difference.Calculations of the temporal variations of size, velocity and density are presented in non-dimensional form for thermals with initial density ratios covering the practically attainable range. It is shown a posteriori that losses of momentum and buoyancy to a wake are probably of negligible influence in any real case.

On the motion of turbulent thermals

A method for measuring the density of mercury in high intensity discharge (HID) lamps using x‐ray absorption is described. The method is suitable for use with lamps with any outer envelopes. Time dependent values of absolute density and cold spot temperature were obtained for a variety of HID lamp types during the period following the extinguishing of the arc. Values for the time dependent mercury mass per unit area at various locations in the lamp were obtained during the warming up of the lamps.

Timothy Fohl

Papers

X‐ray measurements of mercury density in arc discharge lamps during warm‐up and following extinction

Turbulent Effects in the Formation of Buoyant Vortex Rings

The Creation of Vortex Rings by Impulsive Acceleration of a Sphere of Fluid